European Plastic Pipes Market (The)

Rapra Industry Analysis Report Series The European Plastic Pipes Market Trevor Stafford Europe’s leading plastics and...

Author: T Stafford

136 downloads 2704 Views 1MB Size Report

This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site. Start by pressing the button below!
Report copyright / DMCA form

DOWNLOAD PDF

Rapra Industry Analysis Report Series

The European Plastic Pipes Market

Trevor Stafford

Europe’s leading plastics and rubber consultancy with over 80 years of experience providing industry with technology, information and products


A Rapra Industry Analysis Report

By

Trevor Stafford Plasticpipes

January 2001

Rapra Technology Limited Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK Tel: +44 (0)1939 250383

Fax: +44 (0)1939 251118

http://www.rapra.net

The right of Trevor Stafford to be identified as the author of this work has been asserted by him in accordance with Sections 77 and 78 of the Copyright, Designs and Patents Act 1988.

Cover photographs reproduced with permission from: top, Wavin Plastics Limited; middle and bottom, Plasticpipes, © Trevor Stafford, 1998.

© Rapra Technology Limited 2001 ISBN: 1-85957-237-5 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means – electronic, mechanical, photocopying, recording or otherwise – without the prior permission of the publisher, Rapra Technology Limited, Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK.


Contents 1 INTRODUCTION............................................................................................................ 1 1.1 Overview.................................................................................................................. 1 1.2 Report Structure ...................................................................................................... 2 1.3 Politico-Economic Factors ....................................................................................... 3 2 THE POLYMER PIPE SUPPLY INDUSTRY................................................................... 7 2.1 Material Selection Criteria for Pipe Applications....................................................... 7 2.1.1 Basic Property Requirements............................................................................ 7 2.1.2 Effects of Internal Fluid ..................................................................................... 9 2.1.3 Effects of External Environment ...................................................................... 10 2.1.4 Installation Requirements................................................................................ 12 2.1.5 Costing............................................................................................................ 13 2.2 Historic Developments ........................................................................................... 14 2.2.1 Why Evolution of Technology is Important ...................................................... 14 2.2.2 Early Developments - The 1940s and 1950s................................................... 14 2.2.3 Establishing a Mainstream Technology - The 1960s and 1970s...................... 15 2.2.4 A Mature Industry, the 1980s and 1990s and The Current Situation ............... 15 2.2.5 Perceiving Trends in Supply............................................................................ 16 2.3 Current Polymer Usage ......................................................................................... 19 2.3.1 Overview ......................................................................................................... 19 2.3.2 Polyvinyl Chloride (PVC) and its Variants ........................................................ 19 2.3.3 Polyethylene (PE) and its Variants .................................................................. 23 2.3.4 Polypropylene (PP) and its Variants ................................................................ 25 2.3.5 Polybutylene (PB)............................................................................................ 26 2.3.6 Acrylonitrile Butadiene Styrene (ABS) ............................................................. 26 2.3.7 Polyketones..................................................................................................... 27 2.3.8 Polyamides...................................................................................................... 27 2.3.9 All Other Polymers .......................................................................................... 27 2.4 The Major Resin Suppliers..................................................................................... 28 2.4.1 Petrochemical Technology Background .......................................................... 28 2.4.2 Polymer Capacity of The Oil and Petrochemical Industry................................ 30 2.4.3 Price Sensitivity of Polymers ........................................................................... 31 2.4.4 Niche Markets ................................................................................................. 32 3 PIPE SYSTEMS MARKET ........................................................................................... 33 3.1 Application Sectors and Major Users ..................................................................... 33 3.1.1 Water Drainage and Control............................................................................ 33 3.1.2 Agricultural Purposes ...................................................................................... 35 3.1.3 Potable Water Supply ..................................................................................... 37 3.1.4 Sewerage ........................................................................................................ 41 3.1.5 Gas and Fuel Supply....................................................................................... 42 3.1.6 Hot Water Systems ......................................................................................... 49 3.1.7 Industrial Piping............................................................................................... 51 Contents


3.1.8 Smaller Pipe/Tubing - ‘Plumbing’ and Sanitation .............................................52 3.1.9 Non-Fluids Pipes - Cable Ducting and Telecommunications............................53 3.2 Scales of Demand and Historic Development ........................................................54 3.2.1 Overview - Who Purchases Pipes?..................................................................54 3.3 Trends in Demand..................................................................................................55 4 PIPE MANUFACTURE AND THE SUPPLY CHAIN ......................................................57 4.1 Production Technologies........................................................................................57 4.1.1 Extrusion and its Development ........................................................................57 4.1.2 Co-extrusion and Multi-Wall Pipes ...................................................................60 4.1.3 Conex ..............................................................................................................61 4.1.4 Polymer Orientation Control.............................................................................62 4.1.5 Structured Pipewalls and Foam Core Walls.....................................................64 4.1.6 Composite and Reinforced Pipe Production Techniques .................................66 4.1.6.1 Thermosets –‘GRP Pipes’ .........................................................................66 4.1.6.2 Reinforced Thermoplastic Pipes (RTP) .....................................................67 4.1.7 Extruder Equipment Supply .............................................................................70 4.1.8 Associated Production Equipment ...................................................................70 4.2 The Pipe Manufacturers .........................................................................................72 4.2.1 Present Situation - Major Companies in Europe ..............................................72 4.2.2 Globalisation and Consolidation.......................................................................74 4.3 Economic Trends in Supply....................................................................................75 4.3.1 Description of Supply Chain Patterns...............................................................75 4.3.2 Supply Chain Practicalities...............................................................................76 4.3.3 Future Development Possibilities .....................................................................76 5 PIPE FITTINGS MARKET ............................................................................................77 5.1 Introduction ............................................................................................................77 5.2 Technologies and Production Routes.....................................................................78 5.3 Scale of Industry and Major Suppliers ....................................................................79 6 PIPELINE CONSTRUCTION ........................................................................................81 6.1 Installation Technologies........................................................................................81 6.1.2 Pressure Testing..............................................................................................83 6.1.3 Linings for Steel Pipe.......................................................................................83 6.2 On-Site Jointing Technologies................................................................................84 6.3 Equipment Suppliers ..............................................................................................87 6.4 Construction Industry .............................................................................................87 7 QUALITY CONTROL AND RESEARCH.......................................................................89 7.1 Plastics Pipe Supply...............................................................................................89 7.2 Governing Standards and Authorities.....................................................................90 7.2.2 European (CEN) Pipe Standards .....................................................................90 7.2.3 International (ISO) Pipe Standards ..................................................................95 8 DIRECTORY ..............................................................................................................105 Resin Suppliers ..........................................................................................................105 Extrusion Equipment Suppliers ..................................................................................111 Contents


Pipe and Fittings Manufacturers and Suppliers.......................................................... 113 Pipe Installation Equipment Suppliers........................................................................ 119 Pipeline Constructors................................................................................................. 122 Pipe Design and Consultants..................................................................................... 126 Pipe Test and Technical Centres............................................................................... 128 Industry Representative Bodies ................................................................................. 131 References ................................................................................................................ 135 Abbreviations............................................................................................................. 140

Contents


Contents


1 INTRODUCTION 1.1 Overview The sources of information for participants in the plastic pipe industry are many and varied for it has become one of the great industries of the world. Pipelines and tubing are vital to the infrastructure and economic activity of all countries from the poorest of the third world to the richest developed nations. Plastics have progressively displaced longer established materials through four decades and extruded pipe constitutes a major area of application for polymeric materials. Worldwide, the tonnage of plastics consumed in pipe is around 9 million tonnes out of a total polymer production of around 100 million tonnes. The pipes market is therefore about 8 billion dollars in polymer value which is probably doubled as product turnover when conversion and distribution costs are taken into account. The European market constitutes about one-quarter of the world total being currently around 2.5 million tonnes. The significance of this market in relation to the general use of polymeric materials is shown by Table 1.1 which indicates that pipes are one of the major areas of application. The market is dominated by one polymer, polyvinyl chloride (PVC), and, as shown in Table 1.2, PVC piping in building and construction is perhaps the largest single polymer application, constituting 5% of all plastic used. Table 1.1 Principal Uses of Thermoplastics in Western Europe Products Quantities Percentages of ’000 Tonnes Total Injection Moulded Products 5,337 21 Films 4,709 18 Blow Mouldings 3,074 12 Bags 2,666 10 Pipes 2,285 9 Thermoformed Sheet 1,556 6 Cable 930 4 Forms 720 3 Window Profile 700 3 Extrusion Coatings 395 1.5 Others 3,285 13 Total 25,654 Source: TN Sofres Consulting for APME

The pipes market also involves a very large pipe fittings production and supply sector. The use of polymers in fittings, creates higher added value per unit mass than the bulk material extruded as pipe. Fittings production mostly involves injection moulding and total value is on a similar scale to the sale of pipe itself. Growing with the plastics pipe industry are the building and construction industry sectors specifically related to pipe installation technology. These are usually contracted services with many smaller companies operating within individual countries. The supply of equipment for pipe installation is however increasingly developing a multi-national character. Although the original approach to pipeline construction in plastics was simply to adopt the technologies already in place for metallic systems, there have been new technologies introduced that exploit polymer properties. For instance the trenchless technologies that greatly reduce pipe laying costs are highly dependent on the flexibility and ductility of polyethylene (PE) pipes and jointing by fusion welding also exploits the 1


thermal characteristics of polyethylene. The turnover of the industries associated with installation of plastic pipes is hard to assess but must be many times the figure quoted previously for pipe production value. Clearly the plastic pipe production and construction industries represent a major component of economic activity and are vital to infrastructure development worldwide. Table 1.2 Main Segments in Plastics Processors Consumption (1997) (These ten segments make a total of almost 9 m tonnes which is one-third of total consumption) Market Segment Quantity Percentage ‘000 tonnes of Total PVC Pipes – for buildings 1,435 5.1 LDPE Film – distribution 1,187 4.2 PET Bottles – food 985 3.5 PVC Profile – buildings 957 3.4 LDPE Bags – food 836 3.0 PS Thermoform Sheet – food 815 2.9 HDPE Blow Moulding – detergent/pharmaceutical 755 2.7 LDPE Bags – distribution 706 2.5 PP Injection – furniture 670 2.4 LDPE Film - food 604 2.2 Total 8,950 32 Source: TN Sofres Consulting for APME PET: Polyethylene terephthalate LDPE: Low density PE PS: Polystyrene HDPE: High density PE LDPE: Low density PE

A full understanding of the plastic pipe industry requires far greater analytical coverage than is offered by typical market surveys. Market surveys generally provide good coverage of the status quo in terms of supply and demand volumes and prices on a regional basis. By contrast, in this Rapra Industry Analysis Report we have attempted to probe more widely, using the many and varied information sources to reveal fundamental influences on supply and demand technology that ultimately control price, performance and market trends. For example, perhaps the biggest single question facing the long-term future of the plastic pipe market is, can PVC maintain its great dominance or will it eventually become outpaced by growth of PE and polypropylene (PP) or newer materials? This question might be raised by an analysis of volume and price trends but any form of answer requires a fuller picture of technological trends through the polymer supply, pipe production, installation technology and applications development areas.

1.2 Report Structure This Rapra Industry Analysis Report has the objective of bringing together information from a broad spectrum of polymer and pipe supply technology and relating it to the regional and demographic trends of the demand side. It is hoped that this approach will enable readers to view their own more detailed market information within a broader context and consequently gain a more complete understanding of long-term trends. 2


1.3 Politico-Economic Factors Supply and demand balances of market forces depend crucially on political, economic and demographic factors. Following the turbulent history of the twentieth century, at the beginning of a new Millennium, with the notable exception of the Balkan states and some former Soviet republics, there is currently a climate of peace, giving encouragement of trade and investment. The European Union (EU) has become an economic powerhouse and the global economy, led by the USA, promises growth opportunities that will spread eastwards and southwards, from the well-established market economies of Western and Northern Europe. To assist in interpreting these opportunities, it is useful at the outset to present a summary of the size and economic statistics of the nation states that presently constitute the European continent (see Tables 1.3 and 1.4). Of course some of the states bordering the Mediterranean sea, such as Israel, Egypt, and the North African states might almost be regarded as part of a European economic area of influence but for the purpose of this analysis, Europe is defined by traditional geographic boundaries.

Country

Austria Belgium Denmark Finland France Germany Greece Iceland Ireland Italy Luxembourg Netherlands Norway Portugal Spain Sweden Switzerland UK Totals/Averages Principal Sources:

Table 1.3 Demographics, Western Europe Approx. Number Average GDP GDP/Head Population of Homes Occupancy ($bn) ($000) (m) (m) 8 10 5 5 58 81 10 0.3 3.5 57 0.4 15 4 10 39 9 7 58

3.3 3.9 2.3 2.1 24 35 3.6 0.1 1.0 24 0.15 6.2 1.8 3.5 16 3.9 2.9 23

2.4 2.6 2.2 2.4 2.4 2.3 2.8 2.5 3.5 2.4 2.6 2.4 2.2 2.9 2.4 2.3 2.4 2.5

200 230 150 100 1,400 1,900 85 7 55 1,100 1.2 350 115 75 500 220 280 1,100

25 23 30 20 24 23.5 8.5 25 16 19 30 23 29 7.5 13 24 40 19

Homes with Mains Water (%) >99 >99 98 >99 >99 >99 80 >99 >99 >99 >99 >99 >99 87 90 99 >99 >99

375

156.75

2.5

7,800

21

99

International Database US Bureau of Census UN/OECD Statistics ‘The Economist’ – Book of World Vital Statistics GDP: Gross domestic product UN: United Nations OECD: Organisation for Economic Co-operation and Development

The significance of demographic statistics is that they point to potential opportunities for basic commodities, such as pipes, given that there is sufficient investment incentive. Investment potential depends on gross domestic product (GDP) growth and sometimes on political decisions in other countries. Generally the potential for GDP growth can be high in countries starting from a lower level of economic activity provided there is a stable 3


political economic state and provided the country can be drawn into capital markets. This has been the case for the more recent entrants to the EU from southern Europe and could well hold for Eastern expansion of the EU in coming years. The statistics illustrate some of the differences in relative wealth, particularly between the former Eastern Bloc states and capital driven markets of the West. However, it is important to remember that although growth was restricted by war then by communist central planning, the East European states do have an industrial base and an educated and skilled population. Given sufficient investment they are capable of rapid economic growth without the long-term development of very basic education and industrial cultures required in poorer countries elsewhere in the world.

Country

Albania Belarus Bosnia Bulgaria Croatia Czech Republic Estonia Georgia Hungary Latvia Lithuania Macedonia Moldova Poland Romania Russia Slovakia Slovenia Turkey Ukraine Serbia Totals/Averages Principal Sources:

Table 1.4 Demographics, East and Central Europe Approx. Number Average GDP GDP/Head Population of Homes Occupancy $bn $000 (m) (m) 3 10 3 9 4 10 1.5 5 10 2.5 4 2 4 38 23 150 5 2 60 52 10 408

1 3 0.7 3.3 0.8 3.3 0.4 1.2 4 0.6 1 1 11.4 7.7 52 1.8 14 8.8 3 119

3 3.3 4.3 3 5 3 3.7 4.2 2.6 4.2 4 4 3.3 3 2.9 2.8 4.3 5.9 3.3 3.3

7 18 36 2.6 38 20 36 95 36 700 13 15 135 128 1,279.6

0.8 4.5 3.6 1.7 3.8 8 9 2.5 1.6 47 2.6 7.5 2.3 2.5 4.6

% Homes with Mains Water 72 80 97 84 55 84 83 41 92 99 85

International Database US Bureau of Census UN/OECD Statistics ‘The Economist’ – Book of World Vital Statistics

The era of central planning in Eastern European economies facilitated some major investments in infrastructural necessities such as energy, transport and irrigation. For instance, Russia possesses by far the largest gas supply company - inherited from Soviet intentions to exploit their huge reserves of natural gas. A pipeline industry therefore exists but like many other basic economic features it was for many years starved of technology and investment linked to multi-national companies. The opportunities in Eastern Europe involve decisions to renovate large, ill-maintained systems or to invest in new installations.

4


The important feature of statistics for water drainage, water supply and sewerage pipelines is the number of dwelling houses and rate of new construction. In Eastern Europe there is still scope for addition to water supply grids and even more opportunity for connection of houses to sewerage schemes. The opportunities for piping of fuel gas depend on the availability of natural gas supplies and the economic competition from other fuels. Eastern Europe has the potential to become a major consumer of natural gas from Russia but requires external investment and local cultural adjustment to the realistic charges of fuel delivery. In summary, Eastern and Central Europe offers considerable opportunity for new business from rapid economic growth but the pipe industry will continue to be dominated by the high level of economic activity and investment capability of Western Europe.

5


6


2 THE POLYMER PIPE SUPPLY INDUSTRY

2.1 Material Selection Criteria for Pipe Applications

2.1.1 Basic Property Requirements In considering why certain polymers are chosen for pipe construction we will start with the idealistic supposition that the material selection is part of the design process for pipeline construction. In practice the design process for pipeline engineers involves a balance of considerations, with materials selection being but one aspect. In most situations the dominant consideration is a cost constraint - most commonly a short-term budget; nevertheless good engineers will be concerned to optimise any investments against the criterion of minimised whole life cost. A true balance of the costs: raw materials, pipe and fitting production, pipeline installation and in-service maintenance is complex, but common to any design solution is the importance of achieving long asset life and avoiding premature failure as a result of not anticipating factors affecting long-term durability. Relatively arbitrary ‘design factors’ are often introduced to create a safety margin beyond design calculations, but improved knowledge of the long-term performance of plastic pipes is now permitting a reduction from previous over-generous factors, resulting in savings on material costs. Careful material selection is hence more critical to durability. The life of a pipeline is largely determined by the interaction of three things: • • •

Basic mechanical properties Pipe geometry Environmental conditions

Most design problems and solutions can be seen to involve any two of these, or all three together. This analysis is further illustrated for pipes in Figure 1. Basic properties, e.g., mechanical strength, are derived from the molecular structure and are controllable only by specification of chemical production. Pipe geometry is design dependent, for example, pipe dimensions as well as installation features such as bend radii and jointing method. Environmental conditions are largely outside the designer’s control, involving the given features such as fluid environment, operating temperature and the external loads. A pipeline designer can make initial calculations of flow conditions and pipe sizing with no regard for the pipe material. Except for smoothness of the pipe wall, the flow properties are simply determined by diameter. The pipe material must ultimately be considered for its mechanical properties of resisting internal and external loading and its chemical resistance in long term use. Consideration of basic material properties involves the relationship between those properties that are intrinsic to the material such as strength, stiffness, and toughness and those related to the application, such as environmental stress cracking (ESC) resistance, rapid crack propagation (RCP) resistance, and fatigue resistance. All of these properties fundamentally derive from the polymer microstructure, which can be characterised at a molecular level and at a higher level where crystalline structures mingle with the amorphous regions between them. It is the variations in such structures that differentiate the available grades of each polymer. Additionally, particularly in the case of PVC, it is necessary to consider the property variations due to modifying additives such as low 7


molecular weight plasticisers, reinforcing fillers and alloying polymers. Going beyond the intrinsic properties of base resin and additives it is important to be aware that the extrusion processing conditions can also markedly alter the properties and lifetime characteristics of a pipe product.

Figure 1 Pipe Design Factors From this analysis we can see how it is possible to define requirements for material properties appropriate to pipeline construction and translate these into terms understandable to the chemical engineering technology of polymer production. Indeed the technologies of polymer production and pipeline utilisation have developed in tandem over several decades to a point where we can now select from a proven range of material types with even wider options emerging for the future. The practicalities of material selection for a pipe design engineer are usually a question of obtaining appropriate properties at a minimum cost. One common misconception in selecting using cost information is to look at mechanical properties and polymer prices in isolation. Bulk polymer prices are usually given in cost per mass, e.g., $ per tonne or $ 8


per kilo, but properties (such as tensile strength) are measured on standard sample shapes which have constant volume. The key parameter in evaluating relative performance should therefore be a ratio between the property of interest and the cost per volume, e.g., $ per cubic metre. This can make a significant difference between the relative merits of polymers with differing densities. The effect is illustrated for typical property data for a number of pipe polymers in Table 2.1. Table 2.1 Properties and Prices of Some Pipe Polymers Polymer

uPVC LDPE MDPE/HDPE UHMWPE PP PA 11 ABS PVDF PTFE

Densit y 3 T/m

Cost $/T

Cost 3 $/m

Strength: Cost Ratio

Stiffness: Cost Ratio

0.06 >1.06 0.15 >1.06 0.07 0.05 0.2 0.18

Strain to Yield % 3.5 19 12 25 10 20 1.9 9.5

1.4 0.92 0.94 0.95 0.905 1.04 1.06 1.76

1.70 0.3 1.4 0.4 1.7 0.13 0.96 0.05

0.16

70

2.1

1.2

0.03

200 110

0.03 0.7

4 7.5

1.33 1.2

1,700 920 940 2,400 900 7,200 2,500 31,00 0 20,00 0 4,000 4,800

26.5 11 32 15 36.6 7.4 16 1.1

400

1,200 1,000 1,000 2,500 1,000 7,000 2,400 18,00 0 14,00 0 3,000 4,000

12 13.5

0.6 0.6

Short Term Tensile Strength MPa 45 10 30 35 33 52 47 35

Flex Modulus GPa

Elongation at Break %

Notched Izod Impact

2.9 0.3 1.3 0.8 1.5 0.9 2.7 1.7

50 400 100 500 150 320 8 50

25

0.6

PET 50 2.3 PC 65 2.8 Source: Plascams, Rapra Technology Ltd. UPVC: Unplasticised PVC MDPE: Medium density PE UHMWPE: Ultra high molecular weight PE PA 11: Polyamide 11 ABS: Acrylonitrile-butadiene-styrene PVDF: Polyvinylidene fluoride PTFE: Polytetrafluoroethylene PC: Polycarbonate

2.1.2 Effects of Internal Fluid The internal fluid is the reason for the existence of a pipe. It creates a physical stress on the pipe (as pressure) and may have chemical effects such as corrosion or solvation. The function of the pipe is to maintain containment of the fluid and provide a flow path for the required life. The designer must therefore address the mechanical design in terms of long-term viscoelastic response to continuous stress. Creep rupture is the first level of anticipated long-term failure. To avoid premature failure requires a wall thickness appropriate to the pipe strength. Pipe failure should ultimately, or even prematurely, always involve a ductile failure mode, allowing gradual loss of pressure rather than sudden brittle failure that could release stored energy, leading to additional dangers. The chemical effects of the internal fluid can lead to degradation of mechanical strength and promote early failure. Polymers do not suffer galvanic corrosion like metals. Fluid action is more likely to involve solvent action, where slow permeation of fluid reduces pipe wall strength or chemical degradation whereby the polymer chain structure is broken with resulting loss of strength. Polymer chemical resistance tables exist but certain ‘rules of thumb’ apply to the commodity polymers. PVC, which has an electrically polar molecular structure (because of the chlorine atom in the polymer repeat unit), is solvated by polar solvents such as aromatic hydrocarbons and ketones. PE has a non-polar polymer structure and is therefore not softened by polar solvents. It can however be slowly softened by non-polar low molecular weight fluids such as paraffinic hydrocarbons in 9


fuels, oils and greases. The general trends in chemical resistance of pipe polymers are shown in Table 2.2. More detailed and specific data are available from pipe manufacturers and polymer suppliers and they should be consulted for information on specific product grades. Table 2.2 Pipe Polymers – Chemical Resistance Acids (Concentrates)

Acids (Dilute)

Alkalis

Alcohols

Aromatic Hydrocarbons

Paraffinics, Oils, Greases

Fair Good Good Good Good Good Good Good

Poor Poor Poor Fair Poor Poor Fair Good

Fair Poor Poor Fair Good Fair Good Good

UPVC Fair Good Good LDPE Fair Good Good M/HDPE Good Good Good PP Fair Good Good CPVC Good Good Good ABS Poor Fair Good PVDF Good Good Good PTFE Good Good Good Source: Plascams, Rapra Technology Ltd CPVC: Chlorinated PVC

Polar Solvents (e.g., Ketones) Poor Good Good Good Poor Poor Poor Good

A more subtle effect of fluids coming into contact with polymers for long periods is ESC [1]. This occurs when a contacting fluid causes the rapid acceleration of slow crack growth in stressed areas. This effect is very important for pressure pipe designers since their pipes are continuously stressed. ESC can lead to brittle failure ahead of anticipated long term ductile bursting. As the term environmental stress cracking infers, the rate of slow crack growth is dependent upon the nature of the surrounding fluid. The microstructural causes of this dependency have not been fully elucidated but considerable experimental evidence of the effects of various fluids on a range of polymers has been accumulated. The presumption by most recent authors is that those agents that promote stress cracking do so by weakening the oriented polymer chains being drawn at the very tip of the crack. In some cases the cracking process can be accelerated greatly. For example, hydrocarbons such as fuels, oil-based paints and cleaning fluids can cause severe cracking and crazing of polycarbonates (PC). Problems have also been experienced with PVC pipes carrying gas with aromatic hydrocarbon components and PE pipes are at greatest threat from surface active, detergent type materials. Although aliphatic and aromatic hydrocarbons soften and weaken PE, they do not appear to act as aggressive stress cracking agents, perhaps because they soften material around the crack to an extent where blunting of the crack tip relieves the stress concentration. For practical purposes, the significance of the environmental effects is not only in terms of the fluid carried, but also, in the nature of the chemicals that the outer pipe surface may meet. It is generally accepted that there is no major difference between most soil conditions and the clean water used in hydrostatic testing. Long- and short-term hydrostatic pressure testing in water tanks has become the main technique for assessing the quality of pipe materials in relation to their service in below ground conditions.

2.1.3 Effects of External Environment Whilst some pipe users take pressure containment as their primary design criterion, others, notably the installers of large diameter pipes intended for low pressure drainage and sewerage, are far more concerned with design against failure by collapse or buckling 10


caused by ground loading. Particular interest and expertise in developing such design rules has evolved in Scandinavia and Germany. The long experience and results of many years of experimental study on Scandinavian pipe systems have been reported by Janson and Molin in many reports and two text books [2, 3]. Flexible plastic pipes are able to deform to accommodate surrounding soil movement without necessarily experiencing excessive pipe wall stress. This can have the advantageous effect of transferring vertical loads into the supporting earth. On the other hand rigid pipes, such as metal, clay or concrete, must carry any external ground loads within their own structure. In response to vertical crushing forces from the overburden plus any vehicle axle loads, the reaction forces within a rigid pipe wall generate force moments and these can potentially induce fracture. A less stiff plastic pipe deforms, translating the vertical load into a lateral movement that generates reaction forces in the soil fill around the pipe sides which then oppose further movement and prevent pipe collapse (see Figure 2). The flexibility and ductility of plastic pipes also confers greater tolerance to large-scale ground movement, as might occur in landslips or earthquakes.

Figure 2 Effects of Ground Loading on Flexible Pipe Reproduced with permission from T. Stafford, Plastics in Pressure Pipes, Rapra, Review Report, 1998, 9, 6. © 1998, Rapra Technology Limited.

The effect of ground loads on pipes can be described by equations that involve the primary geometric and material property variables. Various analytical approaches have been adopted and there has been some disagreement between different national codes. The analyses are usually based on techniques first described by Spangler to calculate deflection of highway culverts. In the UK equations devised by the Transport and Road Research Laboratory (TRRL) [4] have been used. The German and Scandinavian codes have become widely used in Europe but in future it is likely that computer-interpreted 11


versions developed from accepted CEN standards will be used. A recent survey of the technical status has been given by Alferink, Bjorklund and Kallionen [5]. By way of example the equation below is that attributed to Spangler who developed it in the late 1940s to aid highway culvert design and it has been the basis of most subsequent expressions. This equation has the form: 6 D Where:

=

K (DL PB + PS) x DR 3 8EI/D + 0.06ES

= = = = = =

Deflection Pipe Diameter Deflection ‘Lag Factor’ (Allows for compaction) Re-rounding Factor due to Internal Pressure Vertical Pressure of Backfill Vertical Pressure of Surcharge Load

EI/D

=

Pipe Ring Stiffness

E ES I t K

= = = = =

Pipe Material Modulus Soil Modulus Moment of Inertia Pipe Wall Thickness Bedding Constant (= 0.1 for sand)

6 D DL DR PB PS 3

=

3

Et 3 12D

The most significant feature of such equations is the very high dependence of pipe stiffness (and deflection) on the diameter to wall thickness ratio, usually termed the standard dimensional ratio (SDR). Because pipe stiffness depends on the reciprocal of 3 (SDR) this means that pipe geometry changes are relatively more important than material modulus differences. The implication is that if the pipe design is not determined by an internal pressure criterion, and if the designer is able to reduce costs by adopting a thin pipe wall, then it may be necessary to control the surrounding soil modulus properties by selection of a backfill material and ensure uniformity by careful and thorough compaction. The long-term response of plastic pipes to intermittent external loads caused by vehicle axle loads causes concern for designers when pipes are laid below roadways. This subject has been extensively investigated by authors associated with the Wavin pipe company [6]. For many years they have conducted pipe profile measurements by drawing sled based instruments through pipes which have remained in service. These studies all tend towards a conclusion that most pipe deformation takes place during and shortly after initial installation. Thereafter, there continues to be some further deformation for a period of about two years and very little movement occurs in subsequent years. The suggestion is made that dynamic loading from heavy traffic speeds up the process of consolidation but does not add to the long-term deformation. It is also inferred that pipe deflection is more associated with early soil compaction than long-term pipe material creep.

2.1.4 Installation Requirements Pipe material suitability may be a key aspect of fitness for purpose in terms of ease and costs of installation. The most obvious example of this is the preferred selection of PE pipes over PVC pipes when coiled pipe installation may be most important. Because of its 12


higher stiffness PVC can only be coiled when used in thin wall, small diameters. PE, as MDPE or HDPE, can be coiled in large diameters. PE therefore is selected for ‘no-dig’ applications or when the number of joints has to be minimised. PE materials are also far more easily welded than PVC and most other polymers. PE is therefore suited to allwelded forms of construction which can give great assurance of long-term pipe integrity and this has been a major factor in its adoption for gas distribution. PVC installations tend to exploit simpler, low cost jointing methods which involve little or no additional tools and equipment and are less demanding of operative skills. It is therefore generally quicker and easier to introduce PVC pipe installation methods when the labour force has previously only experienced construction with metallic or clay pipes. Table 2.3 Cost Comparison for Different Pipe Types and Sizes Polymer type

Pipe Function

Diameter mm

Thickness mm

Cross Section Area 2 m 0.0084 0.0078 0.0069 0.1028 0.0090 0.0079 0.1964 0.0090 0.0075 0.0064 0.0047 0.0841 0.0075

Nominal Pressure PN MPa 0.6 1.0 1.6 1.0 N/A N/A N/A N/A 0.6 1.0 1.6 1.0 0.6

uPVC Pressure 110 3.2 uPVC Pressure 110 5.3 uPVC Pressure 110 8.2 uPVC Pressure 400 19.1 uPVC Sewer 110 N/A uPVC Corrugated OD 120 ID 100 uPVC Corrugated OD 575 ID 500 uPVC Drain/Coil 110 N/A PP-H Pressure 110 6.3 PP-H Pressure 110 10 PP-H Pressure 110 16.2 PP-H Pressure 400 36.4 MDPEPressure 110 6.3 80 MDPEPressure 110 10 0.0064 1.0 80 MDPEPressure 400 36.4 0.0841 0.8 80 HDPEPressure 110 6.3 0.0075 1.0 100 HDPEPressure 110 10 0.0064 1.6 100 HDPEPressure 400 22.7 0.0988 1.0 100 HDPE Drain/Coil 110 N/A 0.0085 N/A N/S HDPE Ducting 63 3.7 0.0024 N/A N/S ABS Industrial 114 6.7 0.0080 0.9 ABS Industrial 114 10.6 0.0068 1.5 CPVC Chemical 114 6 0.0082 1.5 CPVC Chemical 114 8.6 0.0074 2.2 PVDF Chem. Hot 110 3.4 0.0084 1.0 PVDF Chem. Hot 110 5.3 0.0078 1.6 PVDF Chem. Hot 400 12.2 0.1108 1.0 ECTFE Hi-Purity 110 5.3 0.0078 1.0 OD: Outer diameter ID: Internal diameter N/A: Not applicable PP-H: Polypropylene – homopolymer Hi-purity: High purity applications such as semi-conductor production ECTFE: Ethylene chlorotrifluoroethylene

Price per Metre $/m 12 18 27 240 5 3.5 80 1.6 14 22 30 280 13

Mass per Metre kg/m 1.6 2.6 3.9 31.7 1.2 1 25 1.1 2 3 4.3 40 2.06

Price per Mass $/kg 7.5 6.92 6.92 7.57 4.17 3.5 3.20 1.45 7.0 7.33 6.98 7.0 6.31

Price per Capacity 2 $/(PN)m

Price per Area 2 $/m

237.16 231.86 245.15 233.35 N/A N/A N/A N/A 313.04 345.68 396.29 332.86 290.68

1423.0 2318.6 3922.4 2333.5 555.6 443.0 407.3 177.8 1878.2 3456.8 6340.6 3328.6 1744.1

20

3.13

6.39

314.25

3142.5

260

41.2

6.31

386.36

3090.9

14

2.08

6.73

187.82

1878.2

21

3.15

6.67

206.23

3299.7

180

27.2

6.62

182.19

1821.9

1.6

1.1

1.45

N/A

188.2

2.7

0.75

3.6

N/A

1111.6

32 42 55 75 160 250 2100 375

2.5 3.76 3.34 4.63 2.2 3.32 28 3.14

12.8 11.17 16.47 16.20 72.73 75.30 75 119.43

447.14 413.81 448.55 463.05 1912.04 2012.72 1894.54 4830.52

4025.3 6207.1 6728.2 10187.0 19120.4 32203.5 18945.4 48305.2

2.1.5 Costing In perhaps the majority of pipe selection situations the initial purchase price of the pipe, for a given size, is a decisive factor in material selection. The selling price set by the 13


manufacturer is determined by the combination of production costs, purchasing arrangements and competitive pressures. Production costs include pipe resin costs as a basic factor, extrusion costs (which depend greatly on scale and duration of production run), and the costs of quality control and proof testing for high specification materials. The purchase arrangements greatly affect the price agreement. Where a manufacturer issues a stock catalogue the prices asked are relatively high because these are prices for small quantities of products which are maintained in stock and such sales carry the highest overheads. A contract purchase by a user or installer of relatively large quantities, who is likely to become a long-term customer, results in very large discounts from catalogue prices. Competitive pressures and the desire to maintain market share in the larger, more profitable markets, such as pressure pipe utilities also forces prices down and generally keeps the bulk pipe markets at a fairly low level of profitability. Cost comparisons for a variety of pipe types and sizes are given in Table 2.3 but it is always important to keep a broad view of costs and to consider in detail the additional costs of fittings, installation techniques and cost of ‘lifetime ownership’ in the case of buried utilities. Table 2.3 is an analysis of pipe cost factors. It illustrates the effect of material type and size in terms of diameter and wall thickness. For pressure pipes a ‘cost per capacity’ term is evaluated which is the cost per unit length divided by flow area multiplied by pressure. This is not relevant to pipes not specified for pressure uses and so a ‘cost per area’ term is also included which is the cost per unit length divided by the flow area. This type of analysis represents a step beyond the material property-cost relationship shown in Table 2.1 since the pipe prices include processing costs. It is therefore interesting to note that for pipes of differing size there are similar costs per unit mass for each material. The analysis represents a way for pipeline designers and planners to view the relative value of their decisions on pipe material types and pipe sizing. The numerical values in Table 2.3 are given for example only. They have been drawn from various sources at various times and are therefore not intended for current commercial comparisons. Potential purchasers should therefore obtain up-to-date prices directly from sales organisations to conduct their own detailed cost studies.

2.2 Historic Developments

2.2.1 Why Evolution of Technology is Important It is not possible to comprehend the true nature of a major industry by simply looking at its current structure and performance. To properly understand why certain forms of organisation exist and what factors determine performance figures it is vital to appreciate the evolution of the industry. The decisions and standards adopted in response to factors pertaining many years ago often result in consequences that continue to influence current technologies. In addition an appreciation of where the industry came from assists in the perception of where it is going next. Therefore we will briefly review the history of plastic pipe production and supply.

2.2.2 Early Developments - The 1940s and 1950s A reduction in cost and growth in supplies of thermoplastics came about mainly as a result of massive investment in oil refining and chemical process plant both during and 14


after the Second World War. Three bulk commodity polymers became available - PVC, LDPE, and PS. PVC, with its better combination of strength, stiffness and toughness was the first to be used for major pipe applications. The techniques for extrusion of PVC pipe were proven by IG Farben in Germany in the late 1930s and developed in the early 1940s, under wartime pressures to find pipework materials for chemical plants [7]. By the late 1940s, the investment power of the USA had developed a market for non-pressure pipe-work, e.g., for rainwater drainage, and research was progressing on measuring the properties of various polymers which could be used in low pressure applications such as potable water and gas supply. The plastic pipe manufacturers found that these markets were highly critical of engineering performance and so improvements in the materials were necessary. The improvement in properties such as low temperature toughness in PVC and strength and stiffness in PE was achieved via the introduction of new grades of polymer. Perhaps the most notable was the more crystalline HDPE in the mid-1950s, produced thanks to the introduction of catalysts. Reconstruction of European towns and cities that had suffered wartime destruction constituted massive infrastructure investment and boosted demand for construction materials including utility pipelines. Although iron and steel continued to be the dominant pipe materials the increasing availability of plastics at reducing prices prompted much technical development that created many of the plastic pipe production and application technologies used today.

2.2.3 Establishing a Mainstream Technology - The 1960s and 1970s The 1960s saw the opening up of newer markets. In particular, the rapid investment in natural gas supplies by the Netherlands and the UK, brought demands for replacement and extension of ageing iron gas pipe systems. The Dutch gas industry initially made considerable use of unplasticised PVC (uPVC). The preference by British Gas for PE and its specification for materials with long-term durability [8] had a stimulating effect on the development and improvement of MDPE. This material has now achieved a dominant worldwide position for gas supply pipes in preference to the basic grades of HDPE. Two major advantages of the PE based materials for pipeline applications are that they can be laid from long coils and can be fusion welded to provide strong high integrity pipe joints. In contrast, PVC pipes are not normally coiled or fusion welded. They are laid in straight lengths and joined either by solvent welding or by mechanical joints with rubber seals. The UK water industry experienced quality problems with uPVC pipes in the early 1970s and, as a result, introduced more stringent tests for fracture toughness which greatly improved compounding and processing standards. The 1960s and early 1970s was a period of economic growth in Europe, the USA and Japan with correspondingly high investment in polymer production and pipe processing technology. Oil price increases from Organisation of Petroleum Exporting Countries (OPEC) and political strife in the Middle East subsequently created supply uncertainties and price inflation but plastic pipe demand continued to grow and investment in production plant was maintained. Essentially by the 1970s plastic pipe technology was well established and was recognisably the same as it is today.

2.2.4 A Mature Industry, the 1980s and 1990s and The Current Situation Probably because of a well-established price advantages for pipe in preferred pressure ratings, uPVC continued to dominate water industry applications throughout most of the world. However, a newer grade of HDPE (PE100), which possesses a good combination 15


of strength and durability under stress, whilst preserving the flexibility and jointing advantages of PE has been developed [9]. Originally intended to meet gas industry requirements it now offers a viable and attractive alternative to uPVC for water pressure piping. PP is also proving to be a growing competitor for PVC in lower pressure drainage pipe and for general industrial use. In order to defend its share of the pipe market in the advanced economies of Western Europe, uPVC has had to offer the possibility of improved mechanical performance [10]. Improvement of low temperature toughness was achieved by alloying it with other polymers. Greater pressure containment strength was achieved by molecular orientation in the pipe wall and higher temperature rating was achieved by post-polymerisation chlorination. One special form of PE that has extended its market range is the cross-linked version (PE-X), whose advantage is that it remains pressure resistant and durable at hot water temperatures of around 90 °C. This advantage alone has been responsible for increasing sales for both domestic and commercial hot water applications and PE-X piping usage grew significantly across the whole of continental Europe [11]. Today the pipe applications of PVC, PE and PP have become a major consideration in the global consumption of polymeric materials. By comparison, other polymers that were market contenders for pipe products developed little and now consume small tonnages in what may be regarded as specialist applications. Nevertheless piping may still constitute an important market for these other plastics in relation to their total consumption. For instance extrusion of pipe is significant in the markets for polybutadiene (PB), acrylonitrile-butadiene-styrene (ABS) and polyvinylidene fluoride (PVDF).

2.2.5 Perceiving Trends in Supply A number of quantitative market surveys of the plastic pipe markets in European countries have been conducted in recent years. There are problems in teasing out and distilling the long-term trends from surveys that differ in depth of coverage and in composition of countries covered. The interested reader might be best advised to analyse for their own purposes the results of several surveys, such as those by Townsend-Tarnell, IAL, and AMI [12, 13, 14]. To analyse current trends in an historic context perhaps the longest continuous set of data is that published each year by Modern Plastics International [15]. Contained within that extensive survey are pipe consumption figures for PVC, HDPE, LDPE (including linear LDPE; LLDPE) and ABS. The figures available for PP are for overall extrusion and are not specific to pipe production. Extracting the details of pipe application from the Modern Plastics International data over three decades provides the curves shown in Figure 3. Taken over such a long period of time the total growth in plastic pipe usage is most impressive and certain trends become very obvious. The static state of the ABS and LDPE markets has reduced their relative importance. PVC has dominated by early and continuous growth from the 1960s, and indeed the pipe application has grown faster than most other PVC uses, except for building profiles, such as window frames. Pipeline applications are therefore very important to the PVC industry and are responsible for around 40% of resin use. HDPE growth started later but is on a higher and more consistent growth pattern than PVC. HDPE growth overtook LDPE in the early 1980s and surged away as it became the preferred material for many pressure pipe applications. Other surveys indicate that PP, from a much lower level, also has a high growth rate. The 16


most intriguing aspect of these comparisons, with importance for predicting future usage is in the figures for PVC use in recent years. The growth rate appears to have slowed and this may herald an inevitable demand plateau. PVC has been able to maintain its growth rate over the three decades by extending into new markets and, by extending into larger pipe sizes. Larger pipes with thicker walls consume relatively large amounts of polymer and so the usage of PVC could continue to grow, even as other polymers eroded its use in the smaller diameter markets. The future threats to PVC growth come not only from HDPE and PP as alternative polymers but also from more efficient usage of PVC polymer itself in large pipe applications, such as sewerage, which increasingly utilises structured wall technology. For non-pressure, gravity driven drainage, corrugated pipes and foam core pipes provide large diameters but consume significantly less polymer than solid wall pipe. An understanding of overall trends must also take account of geographic and demographic growth patterns. The most likely markets to show early plateaux of demand are those of Northern Europe where plastics already have a major share of pipe applications. Other markets in Southern, Central and Eastern Europe lag in depth of penetration and can be expected to provide continuing growth opportunities for many years. Comment on the qualitative factors affecting market trends has been given by Denning [16]. He illustrated the rapid growth of the PVC pipe market from 1965 to 1975, replacing traditional materials and establishing a dominance with continued growth in the 1980s despite the introduction of competitive materials and attacks based on environmental issues. Denning traced the rapid growth of MDPE and HDPE from 1980 onwards to their development as pressure pipe for the gas market and subsequent application for water supply. With regard to new opportunities, he placed significance on the growth of Eastern European markets and the need for higher pressure capability in plastics systems to challenge the present steel pipe markets. He foresaw no immediate alternative to the established plastic materials for low pressure piping. Given the historic pattern of the data in Figure 3, to which results of other surveys may be added, it is possible to speculate on how the trends may continue. The extrapolations of Figure 4 are offered merely to stimulate discussion. Only the results of the real interplay of market forces and new technologies can determine future events.

17


1600

1400

1200

'000 Tonnes

1000

PVC LDPE

800

HDPE ABS

600

400

200

99

97

95

93

91

89

87

85

83

81

79

77

75

73

71

69

67

65

0

Year

Figure 3 Western European Plastics Consumption in Pipes

18


Ten Year Trends 1600

1400

1200

'000 Tonnes

1000 PVC LDPE

800

HDPE ABS

600

400

200

99 20 01 20 03 20 05 20 07 20 09

97

95

93

91

89

87

85

83

81

79

77

75

73

71

69

67

65

0

Year

Figure 4 Forward Projection of Long-Term Trends in Polymer Usage for Pipes

2.3 Current Polymer Usage

2.3.1 Overview Allowing for some variation in estimates of European consumption of polymers in Pipe applications it is generally observed that around 1.5 million tonnes of PVC are used annually and around 500 thousand tonnes of HDPE are used. PP use in various forms constitutes probably around 150 thousand tonnes. These are the dominant materials that also constitute greatest growth potential in tonnage terms. There is however scope for smaller, but profitable opportunities in speciality markets.

2.3.2 Polyvinyl Chloride (PVC) and its Variants PVC was one of the earliest polymers. It was produced in the laboratory as early as 1872 but methods of production were not patented until 1912 by Klatte in Germany and Ostromislensky in Russia, working independently. Commercial production began in Germany and the USA in the 1930s where PVC began to be used in rigid and plasticised forms. As discussed previously, extruded pipe use began in the late 1930s and was stimulated by wartime shortages of the 1940s. The PVC supply industry grew rapidly in the 1950s and 1960s. Applications were then mainly in plasticised form as a flexible sheet material. The development of the rigid forms (uPVC) was held back by processing difficulties and poor service performance associated with thermo-oxidative degradation. Plasticised PVC, a blend of the polymer with a compatible viscous liquid (such as a phthalate ester), can be processed at lower temperatures where degradation is less severe but the product has limited strength and low elastic modulus. The development of improved processing and compounding ingredients which could resist degradation led to the use of uPVC in thicker walled 19


products including large diameter pipes. This opened the way for great expansion of its use in pressure pipes. The world capacity for PVC is now around 25 million tonnes of which European capacity is 6 million tonnes. Much of the growth of capacity in recent years has been in the AsiaPacific region. European capacity has grown only slowly in the past 20 years with mature market demand in many sectors. As a result, developments have largely been directed at cost reduction and rationalisation of production plant. The trading and merging of assets between major petrochemical companies is a feature of the current supply industry. PVC production has historically been dependent on three differing technologies, suspension, emulsion and bulk processes. These produce a polymer of similar molecular structure but of differing particulate nature. These variations in particulate assembly affect some of the basic properties of PVC but mechanical property differences become masked by additional compounding with additives that are a significant element in the composition and properties of any final product. The ability to modify PVC by formulation with low molecular weight additives, liquid or solid, and its compatibility with other polymers has led to a great variety in the potential range of properties available. Due to the low level of crystallinity and the polar nature of its molecular structure, PVC can be compounded with a large range of fillers, plasticisers and compatible polymers that are used to modify the physical properties, ease processing and reduce cost. This high degree of variability within materials classified as PVC has, in the past, created a number of problems, resulting in the poor performance of some pipes during service life. Liquid plasticisers can be added to increase flexibility and reinforcing fillers can be added to increase stiffness. For applications where high strength is not needed PVC will tolerate relatively high loadings of low cost filler such as calcium carbonate. PVC was one of the earliest thermoplastics to be used in pipes and is still, by far, the most widely used polymer for pipeline construction. The rigid, unplasticised form (uPVC) provides a good balance of properties with acceptable whole life costs. As pipe material, PVC is probably at its most attractive when perceived simply as a substitute for metallic or ceramic pipe products. It is stronger and harder than PE and, for most applications, equally good in terms of chemical and corrosion resistance. However strength and hardness can be less attractive features if they are associated with a greater tendency to brittle failure modes or notch sensitivity and if they do not permit the pipe to be coiled or be ‘squeezed-off’. Within the generic class of PVC there are a number of variants in both material type and performance. The main objective of such polymer material variation is to improve upon the fracture toughness of ordinary PVC resins. The tendency to embrittle has been perceived as a problem, particularly during installation when the pipe is vulnerable to external damage and may also be exposed to low ambient temperatures. Historically some suppliers, seeking to minimise product cost (and not subject to specifications that would ensure long-term durability) produced pipe of inadequate quality. For example, early applications of uPVC, in the UK and Holland, for pressurised water distribution resulted in unacceptable, premature brittle failures. These failures stimulated support for studies into the causes and nature of brittle failure and methods for improving the fracture toughness. The development of appropriate test methods and related specifications, based upon the fracture mechanics approach, did much to bring higher quality materials on to the market. In addition to the modifications achieved by blending with other polymers, the processing of the basic PVC resin was improved to optimise its strength and toughness. The better understanding of the potential failure mechanisms coupled with improvements in quality control methods has overcome durability problems and in recent years, those pipe producers whose market 20


share was under threat from new grades of HDPE have also introduced new products based upon modified versions of PVC. These include PVC toughened by blending with chlorinated PE and other resins, and PVC pipes given a higher burst strength by creating molecular level orientation that reacts against the pipe wall hoop stresses. This molecular orientation can be induced by a secondary processing stage that involves the controlled expansion of the pipe to a larger diameter than the original extruded diameter. The process and pipe properties has been described by Uponor and North East Water [17]. More recently the Wavin company has introduced an oriented PVC pipe produced by simultaneously drawing and expanding the pipe at the mouth of the extruder [18]. Uponor and Vinidex have also collaborated to produce a new technology for continuous production of molecular oriented pipe [19]. Because of the potentially great importance of these types of product to future development of PVC in pressure pipes, the topic will be discussed in greater depth in Section 4.1.4. Ironically, the more efficient use of the polymer achieved by oriented pipe technology may mean that sales of PVC resin are not helped. As discussed previously, the quest for ideal mechanical properties in pipe materials is usually directed at achieving an appropriate combination of long-term strength, stiffness, and fracture toughness. This can, in effect, mean sacrificing some of the strength and hardness attributes in order to minimise the potential of a brittle failure mode. Blends of PVC with elastomeric polymers have been used to produce toughened PVC [20]. These appear to function by creating a crack arresting two-phase microstructure. Two of the current commercial examples of this approach are the PVC-PE-acrylic alloy produced by Hepworths [21] and the PVC-chlorinated PE compound produced by EVC [22]. Perhaps the most successful of the blended polymers has been chlorinated PE (CPE). CPE polymers are formed by the post-polymerisation chlorination of PE. In itself CPE is a low strength polymer with no significant application as a production thermoplastic. However in combination with PVC it produces a product with far better resistance to low temperature embrittlement. Raw PVC polymer has a particulate structure with size and shape determined by the polymerisation conditions. During processes, such as pipe extrusion, sufficient heat and work, as shear mixing, must be applied to the molten polymer to break down and then fully fuse the particle structure. This heat and work must be limited to a level which does not breakdown the polymer structure nor degrade the physical properties. PVC processing must therefore be carefully controlled within optimum conditions with the addition of appropriate additives to protect the polymer chain from thermal and oxidative degradation. PVC polymer selection for pipe extrusion is usually guided by the choice of a high ‘Kvalue’ resin. The K value in this context refers to a molecular weight related parameter determined by solution viscosity measurements as defined in ISO 1628-2:1988. A minimum ISO ‘K’ value of 65 is recommended for pipe applications. Extrusion technology is well developed with twin-screw extruders being the norm. Extruder barrel temperatures of around 180 °C are usual. PVC has a largely amorphous, glassy microstructure with a glass transition temperature (Tg), of about 20 °C but its small crystalline content, around 5%, has a significant residual effect on the polymer chain forces, up to the crystalline melting temperature (Tm) of 212 °C. However processing cannot be raised to this temperature without causing chain scission and reducing the molecular weight. As a result of pipe failures that were identified as having inadequate ‘gelation’, or fusion of the polymer particle structure, a simple test involving the immersion of a sample in methylene chloride was introduced. The solvent action quickly breaks down an inadequately processed sample by destroying the interface between sintered particles. If 21


the particles are fully fused to form a continuous entangled polymer network, then the methylene chloride only produces a swollen gel structure. Although this test can pick out inadequately processed materials it cannot identify a material which has been degraded by excessive heat and shear. These two factors can adversely affect both strength and toughness. Studies by Holloway and Naaktgeboren [23], showed that to optimise uPVC processing conditions, it is best to specify a combination of tests of adequate gelation using resistance to methylene chloride, and measurement of yield strength and fracture toughness. By far the greatest part of PVC production across the world is now made by the ‘suspension’ process. Vinyl chloride monomer (derived from a reaction between ethylene (derived from oil) and chlorine (derived from common salt) is dispersed in deionised water with the help of small quantities of chemical dispersants and polymerisation initiators (typically peroxide compounds). At moderately raised temperature (50 °C) and pressure (0.7 MPa) polymerisation proceeds and the polymer can be removed from the resulting slurry by de-watering and steam stripping the unconverted vinyl chloride monomer. Widespread concern about the dangers to health of vinyl chloride monomer has had a major effect on production plant design and construction in the last 20 years. The general aspects of environmental acceptability of PVC has been a contentious topic perceived as a potential market threat and has stimulated much action and comment from the major producers. The environmental ‘scares’ concerning use of PVC can be viewed as a consequence of its success and ubiquity. All synthetic products utilised on such a wide scale inevitably have environmental impact from their production, use and disposal. Three concerns have been expressed with respect to PVC; carcinogenic effects of vinyl chloride monomer released in production, hormone mimicking effects of some plasticisers and dioxin release from low temperature combustion. The PVC industry has responded collectively and thoroughly to improve its practices where necessary and to defend itself against illinformed criticism. The Association of Plastics Manufacturers in Europe (APME) and the European Council of Vinyl Manufacturers (ECVM) have reported extensively on the environmental issues. ECVM has charters of good practice for limiting environmental emissions in production and is developing a policy on waste management and disposal. The European Plastics Pipes and Fittings Association (TEPPFA) represents the pipes industry on environmental matters of collective interest. Although the environmental issues have been perceived as a general threat to confidence in the very large markets for PVC, particularly food packaging and toys, there appears to have been little real effect on pipe demand in most countries. A variation on PVC that is important for some pipe applications is ‘Chlorinated PVC’ (CPVC). This is manufactured by chlorination at a post-polymerisation stage. The modified polymer which carries additional chlorine atoms has a stiffer polymer chain resulting in better high temperature performance than PVC. CPVC has therefore been used for piping hot water and industrial chemicals where it continues to be used in competition with PP and crosslinked PE. The mechanical properties and chemical resistance characteristics of CPVC are similar to PVC. Polyvinylidene chloride (PVDC) is worthy of mention as a pipe material in an historic context. It was, along with PVC, one of the earliest of pipe polymers. It was marketed in the USA as early as the 1950s under the name ‘Saran’. The material proved to have unacceptably brittle failure modes and has fallen into disuse as a pipe polymer. However PVDC remains important as a coating or lining material or as a co-extrusion layering material for other pipe polymers. This is because PVDC has a much lower permeation 22


coefficient than the major pipe materials. It can therefore be used as a barrier layer to greatly reduce the through-wall transmission of oxygen or hydrocarbon vapours.

2.3.3 Polyethylene (PE) and its Variants The early grades of PE, first commercialised in the 1940s, using the ICI high-pressure process, were characterised by their highly branched polymer molecular structure. The high degree of branching interfered with the polymer chain alignments necessary for crystallisation and so the material had relatively low density. This material, termed LDPE, is tough and flexible but is relatively soft and has relatively poor resistance to chemicals and ESC. It is used in general purpose small diameter tubing and became extensively adopted for water service pipes up to 32 mm diameter but has no significance in the larger pipe market. In the mid-1950s, the discovery of Ziegler catalysts made it possible to polymerise ethylene gas at lower pressures to produce linear growth of the carbon-carbon backbone chain and very few PE side branches. This polymer could crystallise by chain folding (crystallites) to form a HDPE, which proved to be considerably stronger and harder than LDPE. HDPE was quickly developed for pipe purposes, notably by Hoechst in Germany. It had the requisite strength, stiffness, and chemical resistance, could be coiled (up to 180 mm size) and was amenable to heat fusion jointing. The pressure testing and accelerated ageing tests conducted by Hoechst, and other early suppliers, showed that HDPE pipes might suffer early failures by ESC. This became a limiting factor when trying to design for in-ground product lifetimes of at least 50 years [24]. It was noted in the early experimental studies that higher molecular weight polymers, i.e., high melt viscosity, low melt flow rate (MFR), were to be preferred for long-term durability. When it became recognised that poor ESC behaviour of HDPE was associated with slow crack growth between the large crystallites, PE grades with alternative molecular structures were sought. In the mid-1960s, DuPont and Phillips in the USA both developed copolymers of ethylene with small quantities of higher olefins such as hexene and octene. These produced a linear carbon-carbon chain polymer which also had a few short side branches distributed along it. The presence of the short branches served to limit the growth of crystallinity and resulted in a MDPE but, more importantly the long chains became incorporated and locked into several crystallites (tie-molecules) thereby inhibiting cracks forming along crystal boundaries. Such polymers gave excellent long term ESC resistance but still reasonably good mechanical strength. Because of its assured longterm properties, MDPE became widely adopted for gas pipe and with such a premium quality market available, resin quality, maintained by specified high levels of quality control, improved progressively. The Ultra High Molecular Weight (UHMW-PE) polymer developed in the USA by Phillips and in Europe by Hoechst also proved to have exceptionally good properties because molecular entanglements restricted crystallite size and encouraged tie-molecule formation. The material found a large outlet for high quality pipe requirements (such as the gas industry) in the USA but it is generally restricted to high performance demands, such as aggressive chemical process plant, in Europe. The UHMW-PE grades are difficult and slow to process as pipe, because conventional extrusion processes cannot cope with the extremely high viscosity of the melt. Ram extrusion has to be used resulting in high pipe extrusion costs. The next most significant development of PE materials came in the 1980s, in response to gas industry, and in particular British Gas (25) demands for improved resistance to RCP 23


in larger gas pipes operating at higher pressures. The Solvay company developed a HDPE material that, for the first time, had high resistance to RCP yet maintained an ESC resistance similar to the MDPE grades. This combination of preferred properties was achieved by further process plant developments, which could give a bi-modal molecular weight distribution of the polymer. A sequential polymerisation process was developed to produce a reactor blend of two separate molecular weight products (bi-modal). Reactor changes enabled the side branches to be distributed preferentially on the higher molecular weight fraction. Tie-molecules were on the longer chains where they could be most effective. The lower molecular weight fraction with few side branches could crystallise easily leading to a reasonable density. A combination of both effects markedly improved the RCP resistance [26]. The bi-modal type of HDPE is now available from various manufacturers. It should be noted that both the bi-modal and the original, ‘first generation’, HDPE grades are available commercially but they offer widely different performances. The potential for specification confusion, which could have serious consequences, especially for gas pipe design, further encouraged the ISO/CEN standards bodies to establish new and more precise performance standards for gas and water pipes. Firstly, the PE strengths were classified, e.g., PE80 and PE100. The number part of the code, divided by 10, is the minimum long-term circumferential stress (MPa) capability for 50 years continuous operation. For example, an SDR 11 wall thickness PE 100 class of pipe is capable of withstanding an internal pressure of 2 MPa (no safety factor included). Secondly, appropriate gas and water pipe standards were introduced that ensured sufficient ESC and RCP performance for each of the three PE materials. Also minimum safety factors of 2 for gas and 1.3 for water were defined. The higher performance pipes made from PE100 are proving to be popular with the water utilities since this class of PE is able to offer substantial cost savings because pipe wall thickness can be reduced. The original pressure ratings using PE80 with the thicker SDR 11 pipe can now be replaced with the thinner SDR 17 pipes using PE100 operating at the same or similar pressures. The late 1990s have seen the development within several companies of polymerisation processes assisted by ‘metallocene’ catalysts [27]. The significance of this technology is that it permits a high degree of control over the polymer chemical structure. Polymer chain structures can be designed for specific properties by assembling additional molecular structures into the chain or as side branches at specific intervals in the main chain. It is likely that new grades of polyethylene will be developed for special purposes at a premium price whilst bulk production of a few standardised grades will be maintained at commodity prices. There is a revived and growing interest in cross-linked PE (originally abbreviated XLPE but now standardised by ISO/CEN as PE-X) [28]. These materials have a long history in parallel with conventional PE materials but have become of greater interest as the chemistry and processing techniques improved, enabling the production of larger diameter pipes. Cross-linking of PE is achieved in three possible ways. High energy radiation of PE by electron beam or gamma rays creates chemically active sites within the polymeric structure that cross-link to other polymer chains. Similar effects can be obtained by the vigorous chemical action of small additions of peroxide agents at process temperatures. A variation on this, which delays the cross-linking action to a postprocessing stage, is to deposit silane groups into the polymer chain. These become the cross-linking sites when hydrated by steam permeation, which can be carried out any time after production.

24


PE-X pipes have a particularly good range of properties. The material is extremely tough, being virtually immune to both slow crack (ESC) and fast crack (RCP) problems. Moreover, these properties are maintained over a wide temperature range, from about –40 °C to 110 °C. This has led to major market development for hot water piping in plumbing and underground heating where use of PE-X competes with use of polybutylene products. There is also considerable interest in the use of PE-X pipe for severe environment applications, such as very cold (arctic) or hot (tropics/deserts) areas and where piping is liable to damage, e.g., insertion in old pipes with internal projections or in trenches containing sharp rocks [29].

2.3.4 Polypropylene (PP) and its Variants PP ranks third largest among the pipe polymers but quite a long way behind PVC and PE. PP is used for many applications and is used in almost all pipe application sectors. It has good mechanical performance at low price allowing it to compete with PVC in the price sensitive markets such as rainwater drainage goods. Its high temperature capability and chemical resistance promotes its application in the hot water and industrial sectors. It can be joined by most methods including butt fusion and electrofusion welding. We may ask why PP has not a higher market penetration? Why does its usage not approach the tonnages of PVC and PE? Although use of PP in pipe applications is high it has not yet been used for major utility applications and the pressure pipe markets. The reasons for this may simply be associated with historic precedents. PVC and PE materials have received a high level of technical support and development because they are established as the leading materials in the water and gas pressure pipe markets, where technical developments are concentrated. Premium grade products have evolved from the competition to meet the specifications of these markets. The developments in PP supply have usually been subordinate to other applications such as packaging. The PP suppliers have not focussed consistently on pipe applications and there has been a proliferation of grades and properties that perhaps confuses potential users. Whilst for instance, the differences between LDPE and HDPE or uPVC and ‘impact modified’ PVC are fairly obvious, the PP suppliers offer the more subtle variations in copolymer derived molecular structures. Essentially these fall into three categories, homopolymer (PP-H), random copolymer (PP-R) and block copolymer (PP-B) with different manufacturers offering variations that can differ in properties. The co-monomer to produce the copolymer is commonly ethylene so that the PP molecular chain is disrupted by PE segments, either as short random inclusions or longer blocks (where the PE segment lengths become comparable with PP lengths these are called ethylene-propylene copolymers and would have rubbery qualities). The main objective of including PE segments in the PP chain is to introduce flexibility and toughness at low temperature by lowering the Tg. The PP-H is hard and tough and in thin sheet or film applications such as packaging does not suffer embrittlement. For pipe applications, with thick walls, the loss of toughness below a Tg of around 12 °C can lead to inadequate impact resistance at lower temperatures. PP-H pipes have high strength and stiffness and are used for pressure piping in elevated temperature conditions such as chemical industry pipework where they can be obtained for a lower price than the PE-X or CPVC materials PP-R has lower strength, but greater flexibility, whilst retaining good high temperature capability. The material is used for smaller diameter flexible tubing in hot water internal piping. Here it competes as a lower cost alternative to PE-X and polybutylene. PP-B retains good stiffness, has lower strength than PP-H, but is tougher at 0 °C and below. The copolymer block structure essentially creates a heterophase microstructure 25


comparable with that of ABS or impact modified PVC. Such structures prevent crack growth and release internal stresses that induce brittleness. PP-B is therefore a material suited to the rigours of outdoor, buried pipe applications such as drainage and sewerage. It is a relatively low cost polymer and so competes against PVC in such applications. A higher performance version of PP-B given the trade name ‘XMOD PP-B’, has higher stiffness, impact resistance and strength compared to PP-B resins, it is marketed by PCD Polymere of Austria (30). The product is directed at pressure pipe and thin wall structural pipe, as well as sewerage systems. A further advantage of PP is good abrasion resistance and therefore PP products are suitable for slurry pipe applications.

2.3.5 Polybutylene (PB) PB is classified as a polyolefin along with PE and PP with which it shares some polymeric and microstructural characteristics. Like PE and PP it is semi-crystalline which confers a good combination of strength and toughness. PB pipe has been available for many years and for some time it was thought likely to develop into a mass market application comparable to that of PP or even PE. The biggest single advantage of PB is that it has superior high temperature resistance compared with PE for applications involving hot water transport. The market for PB has however not grown substantially. It has not achieved a performance/price breakthrough that would greatly favour its use over, for instance, PP or PE-X. PB also suffered disastrous marketing setbacks after a series of legal claims in the USA arising from in-service failure of domestic hot water systems. The causes were variously attributed to poor installation technique or ESC by chlorinated water. The net result was loss of reputation and a shift of interest towards PE-X for such applications. The plastic pipe supply industry has generally learned a lesson from this case to more thoroughly test for and consider long-term failure modes and specify with a view to fitness for purpose. In Europe, PB has retained a significant but minority share of the hot water pipe market through the supply of high quality complete pipe and fitting systems supported with good jointing techniques. The market for PB materials may increase if Wavin are successful in gaining market acceptance for their recently introduced domestic plumbing pipe, ‘Osma-Gold’ which is marketed as a complete system for hot and cold water, with easy to fit connectors and a design life of 50 years (31).

2.3.6 Acrylonitrile Butadiene Styrene (ABS) The copolymerised rubbery segments of this polymer create a multiphase microstructure that overcomes the brittle characteristics of PS and results in a tough general purpose plastic. ABS is one of the oldest and most established materials used in pipe production, but it has a relatively low market share. ABS is sometimes described as ‘producer friendly’. It extrudes into pipe, and moulds into fittings, with controllable and predictable flow behaviour at relatively low temperatures. It also has appropriate mechanical properties, with a combination of stiffness, strength and toughness, suitable for most pipe applications. The failure of ABS to capture a large market share is perhaps because it has no major advantages to place it above the competitive resins. Although the mix of characteristics is good for general purposes it fails on the specific design requirements required for major applications. ABS does not have the strength and stiffness of PVC or PP, it does not have the ductility and toughness of HDPE. It has less good chemical resistance and lower effective operating temperature range. It has no price advantage in large-scale production. ABS is therefore likely to continue only as a niche market product, 26


produced in low scale of production for local general industrial pipe-work applications (32).

2.3.7 Polyketones Polyketone polymers are a newly developed range of materials that are worthy of note because of a range of attractive properties for pipe applications. The polyketones are potentially a type of low cost commodity polymer because of their low cost, high availability of their monomeric precursor – olefins, e.g., ethylene, and carbon monoxide. The polymers produced have a semi-crystalline structure conferring a good combination of strength, stiffness, toughness, chemical resistance, wear resistance and high temperature stability. A significant advantage for some uses, such as chemical pipe linings, is low permeation properties, i.e., high resistance to through wall flow of oxygen, hydrocarbons and vapours. BP Chemicals [33], also showed, unusually, the possibility of blending polyketones with both PVC and PE polymers. Polyketones have as yet, not appeared in commercial pipe production and there is great uncertainty over their future market potential because it is understood that both Shell and BP have abandoned commercial development of these materials.

2.3.8 Polyamides The polyamide (‘Nylon’) polymers have potentially very attractive properties for pipe application with high ratings for strength, stiffness and operating temperature range. Toughness is usually good but can be inconsistently poor if incorrectly processed. Polyamide toughness is achieved in the presence of a low moisture content. Totally ‘dry’ Nylon becomes notch sensitive and can fail in brittle fashion. In hot water, Nylon becomes hydrated and properties are degraded. The main reasons for Nylon not becoming a major contender in pipeline usage are probably cost and product confusion. The polymerisation processes for polyamides do not appear to lend themselves to the economies of scale achievable by the simpler molecular structures of PVC and the polyolefins. Despite the fact that high strength means that thin walls can be used in pressure applications, the ‘cost per metre’ is still not competitive. Pipe stiffness is too high to allow installation from coil and although joint welding can be done by solvents, there are potential safety hazards with the chemicals used. The product confusion with polyamide resins is even greater than that with PP materials. There are a series of polymers classified as polyamides, and popularly known as Nylons, that have a variety of performance characteristics. This creates a problem when considering the selection of material for specific pipe duties. One example of this polymer being used for a utility pressure pipe application is the use of Nylon 11 as gas distribution pipe by Australian Gas & Coke Co for the city of Sydney. This large-scale application is virtually unique, although the polymer suppliers have attempted to market their material more widely on the basis of long-term successful use in Sydney.

2.3.9 All Other Polymers Of the fluorinated polymers PVDF and polytetrafluoroethylene (PTFE) are used in pipe applications. PTFE materials are very difficult to process and despite excellent chemical and high temperature resistance, PTFE materials have too low strength and stiffness for practical purposes. PTFE is therefore used more as a lining for metallic pipe systems. PVDF however is an excellent pipe-forming polymer. It is highly crystalline with a high melting point and a high degradation temperature. It has a good combination of strength, 27


stiffness, toughness, high operating temperature, and chemical resistance. The very major drawback with PVDF is its very high cost. At a cost of around $30,000 per tonne it has to be a niche market material rather than a high usage material [34]. Where cost is less important than performance, for instance in high temperature, corrosion resistant pipe for chemical or pharmaceutical plant then PVDF can justify its usage. Another example of its application is in ultra pure water supply pipes for microelectronics manufacturing plant. A number of other polymers are used in pipe form for small markets. Polymethylmethacrylate (PMMA) is popular where high transparency pipe is required for purposes such as demonstration display equipment. PC materials have high strength and stiffness and find some application for short-term pipe-work applications but the material can fail in brittle fashion because of notch sensitivity and crack growth when exposed to hydrocarbons. It therefore finds no long-term, large scale applications.

2.4 The Major Resin Suppliers

2.4.1 Petrochemical Technology Background The output of the plastic pipe industry is totally dominated by a very small number of ‘commodity’ polymers. The origin of this supply-led situation lies in the technology and market structure of the oil and chemical industries. Just as coal and iron were the energy and materials basis for 19th century industrial progress, so oil and petrochemicals have been the economic driving forces for 20th century energy and materials. One distinct difference is that the 19th century industrial giants grew within nation states but the major oil and chemical companies have become truly multi-national organisations operating globally with financial structures greater than many national economies. The oil industry started from small beginnings about a hundred years ago and came to maturity in the two decades prior to the second world war, coinciding with the most inventive period of industrial chemistry that gave us most of the thermoplastics still in common use. The simple imperatives of the oil industry have been to sell every component of crude oil for the best price and, at the same time, to continually expand markets by driving down product prices. Crude oil is fractionated by distillation into, ‘heavy’ tars (used in road building), waxes (used in candles and industrial products), oils (used in lubricants), light oils (used in transport fuels) and gases (used in fuels and chemicals). The chemicals industry grew from the 19th century development of basic chemicals derived from mineral-based raw material commodities such as salt, coal and sulphur. Major industries grew around bulk production of secondary chemicals such as soda, chlorine, sulphuric acid and hydrochloric acid, and their downstream bulk products such as fertilisers. The chemicals industry subsequently became a major market for the oil refinery outputs such as ethylene. In particular, polymeric materials became a massive market from the 1950s onwards because of their applicability to so many consumer products. Polymers could effectively convert large tonnages of oil-derived products into materials with practical uses because they condense large quantities of low molecular weight gases into solids which have useful mechanical and physical properties. The simplest of the major polymers, PE is formed from ethylene gases originally produced alongside the light oil fractions (naphtha). Demand for ethylene grew so much that it had to be produced specifically by catalytic breakdown of oil components. Ethylene gas also became the main production route to PVC where it was polymerised with chlorine obtained from sodium chloride. These polymers were produced by chemical 28


industries that were originally independent of the major oil companies but in modern times their interdependency has led to convergence and consolidation, so that today the downstream petrochemical industry is, in corporate terms, often indistinguishable from the oil and fuels sector. The pressures of worldwide competition encouraged investment in larger scale plant for economies of scale, and had the effect of increasing output and reducing real prices which has, in turn, promoted market growth, creating an economic growth spiral that has fuelled a great expansion in living standards in developed and developing nations alike. Any concerns over limits to growth arising from the dilemma of population expansion and finite fossil fuel stocks are continually pushed into the future, but will eventually emerge later in the 21st century as industry supply and demand matching problems, with consequent effects on prices and production efficiency. The scale of fossil fuel usage has also been recognised as a potential threat to the ecological stability of the global environment. The 21st century will see increasing pressures to control pollution of the land, water, and air environments by legislation to restrict emissions and disposal of waste products from this vast industrial output. The relevance of oil and petrochemical industry economics to the pipe industry is that the commodity plastics are produced at prices that greatly favour their selection and encourage pipe makers to design products around the properties of such plastics. This we can interpret as the ‘push’ of a technology into the market place. Later we will examine the ‘pull’ of applications technology that creates a demand for performance properties and therefore influences the investment in polymer production. It is also important to recognise that the high throughput efficiency of large scale pipe extrusion plants causes pipe product price to be greatly dependent on the price of the polymer used. High quality pipe-work produced from say 95% PVC or PE on high throughput extruders with long production runs is converted so efficiently that input costs of plant use, power, labour, etc., represent perhaps only 20-30% of production cost compared with 70-80% being polymer cost. The commodity polymers PVC, PE and PP are manufactured in highly efficient plants on a vast scale and their price is closely related to the market price of oil. Thus for these materials there is a very direct linkage between pipe product prices and the world oil price. In the mid 1990s the long-term growth of worldwide capacities for oil production, refining, polymer production and pipe production have coincided with slowing short-term economic growth that reduced consumption below expectations. The result was downward pressure on prices at all stages. We can see that the production of pipe for large-scale applications in the building and construction sectors and for utility distribution purposes forms part of our economic foundations traceable to fossil fuel exploitation. The market forces that constrain the profitability of mass-market pipe producers tend to support the trends to converge production into large-scale units and polymer purchase arrangements with close affinity to the petrochemical majors. Table 2.4 Table of Added Values Typical Price ($) per Tonne Crude Oil 150 Naphtha (1st Stage Refining) 250 Ethylene (2nd Stage Refining) 700 Polyethylene (Polymerisation Step) 1,200 PE Pipe (Extrusion Plant) 2,000 PE Pipeline (Installation in Ground) 5,000

29


As an illustration of the nature of wealth creation within this sector of modern economic infrastructure it is instructive to look at added values in a sequence of products as shown in Table 2.4. All prices are approximate for purpose of example only.

2.4.2 Polymer Capacity of The Oil and Petrochemical Industry The structure of the oil industry and its downstream petrochemical production facilities has continually evolved in a climate of global competition and is currently changing by merger and re-alignment of core interests. Major political and financial forces shape these industries but the general trend is to grow markets and increase economies of production scale. The 1990s saw a slump in oil prices and overcapacity in commodity chemicals and plastics. This forced the closure of smaller, inefficient polymer production sites and resulted in a series of mergers between producers to concentrate production on everlarger plant. At the time of writing, the oil price has recovered to an historically high value and has caused the expected knock-on in rising prices of chemicals and commodity plastics. The changing relationships and co-operative ventures between major companies is however still continuing under the need to adapt to new polymerisation technologies, such as catalyst improvements, that are controlled by licence agreements. The changing supply pattern has affected the market in principle pipe polymers, reducing the number of European and US based providers to European pipe makers. At the same time however there are newer entrants to the market in the form of Middle East and Asian companies. Table 2.5 West European PVC Capacity (1999) Companies PVC Capacity ’000 Tonnes EVC 1,320 Solvin 1,250 Elf-Atochem 890 Vinnolit 560 LVM 455 Norsk Hydro 490 Shin-Etsu 420 Vestolit 350 Total 5,735 Source: Harriman Chemsult

Table 2.5 illustrates the supply capacity of a number of companies supplying PVC to the West European markets. As with much of the petrochemical industry there is an on-going history of business re-organisation and production plant consolidation. The largest producer, EVC, based in the Netherlands and Belgium, was originally formed by a merger of ICI and EniChem interests but became independent in 1994. EVC has itself recently become subject to a takeover from its rival Vestolit, an offshoot of Degussa–Hüls, which is owned by financial investment organisations D. George Harris & Associates and Candover Investments plc. EVC has previously been associated with plans to merge with the PVC interests of Norsk Hydro and Vestolit has been expected to link with Vinnolit. Hydro Polymers are expected to be divested from Norsk Hydro. Only Solvay as a producer of both PVC and PE pipe resins appears to be remaining independent at the current time.

30


The Western European supply of PE and PP materials for 1998 is shown in Table 2.6. The Hoechst PE capacity was merged into BASF and this company has recently agreed a ‘mega-merger’ with Shell. BASF and Shell had already formed the Elenac PE company but the more recently announced venture will add to their PP capacity, as Montell (Shell) and Targor (BASF) are added to Elenac to form one polyolefins conglomerate. Borealis which emerged from Neste Chemicals, and is jointly owned by Statoil (Norway), OMV (Austria) and PCD (Abu Dhabi) has become a major force in Polyolefins. BP Chemicals has broadened its interests via the BP/Amoco parent company merger and has formed Appryl (a PP production company) by co-operation with Elf-Atochem. Elf-Atochem itself has merged with Total-Fina which will create a joint PE capacity as ATO-Fina. Polimeri of Italy is a joint venture between Union Carbide and EniChem. Union Carbide (UCC) has merged PE interests with Dow. At the same time UCC has a joint venture with ElfAtochem to produce ‘speciality PE’ grades under the name of Aspell. Table 2.6 West European Polyolefin Capacity (1998) ’000 Tonnes Companies PE PP Borealis 2,000 1,340 DSM 1,150 750 Elenac 1,950 0 Targor 0 1,725 BP-Amoco 1,250 475 Polimeri 1,600 0 Dow 1,375 225 Montell 0 1,500 Exxon 800 160 Repsol 525 375 Elf-Atochem 500 375 Fina 460 375 Solvay 440 375 Aspell 300 0 Polychim 0 200 Totals 12,350 7,500 Source: Borealis

The effect of recent merging of the Elenac, Targor and Montell interests will create a single company capacity for 1.95 m tonnes of PE and 3.225 m tonnes of PP. Until recently it appeared that the major Belgian company Solvay was remaining independent as a supplier of both Polyolefins and PVC. However as this report goes to press, there is news of a merging of the HDPE interests of Solvay and BP-Amoco as a joint venture operating in Europe and the USA. Two other major PVC suppliers are EVC and Hydro. EVC based in The Netherlands and Belgium, was originally a merger of ICI and EniChem interests but became independent in 1994. Hydro Polymers produce PVC as part of the Norsk Hydro Group and as Hydro-Geon which was formerly BFGoodrich.

2.4.3 Price Sensitivity of Polymers The significance of price changes of commodity polymers is that there is an immediate knock-on effect to the costs of large-scale pipe production. Raw material costs are a major factor in the overall cost of extruded pipe. Therefore the selling prices of pipes can 31


be expected to reflect the upward trend in polymer prices. The relatively low polymer prices of the mid-1990s must have benefited the marketing of pipes in volume terms because customers could afford more product for a given investment. Competition however has kept the profitability of bulk pipe producers low and it is uncertain what effect the continued price rises may have. On the one hand price rises may squeeze market volume demand but, on the other hand, rising prices may allow some increase in profit margins. What can be observed is that the pipe supply market has, historically, continued to show healthy growth in both volume and turnover, despite the ups and downs of commodity prices over the years.

2.4.4 Niche Markets The previous discussion applied mainly to that greater part of the pipe industry processing and using the low cost commodity polymers. It would be wrong however to ignore the smaller output of pipe in other polymers or more special grades of the bulk polymers because these sectors of the market can still be of significant size and can be far more profitable. They are therefore important to both large pipe companies and smaller producers with more limited market aspirations. Almost all commercial polymers find a market in pipes; perhaps the most significant exception is PS which finds no significant market even though it is one of the commodity materials. This does make the point that price is not the only criterion of selection. PS has an inadequate combination of toughness and strength and inferior chemical resistance for most pipe requirements. ABS a copolymer styrenic is probably the most significant pipe material after the ‘big three’ and can also be classed with them as a commodity grade since it also has wide use in general plastics manufacturing. It has a number of good allround characteristics as a pipe material and has competed for both pressure and nonpressure applications but it has neither the price nor property advantages to be attractive to the bulk market consumers. ABS maintains its position because of good marketing that exploits a proven reputation in certain lower consumption sectors. The pipe market for other polymers mostly exploits particular property advantages which can carry a price premium. An example is PVDF for which pipe is the principle market but at a price around 20 times that of PE. The production of PVDF is costly and on a relatively small scale but it finds a good market in pipes because of its excellent properties. It has an unusually high degree of crystallinity and relatively high melting point which confers a good combination of strength and stiffness up to continuous service temperatures of 140 °C. It also has excellent chemical resistance. Again, this serves as another reminder that price is not the only pipe material selection criterion. A special property that can be exploited is transparency, for example PMMA is used as an alternative to glass pipe-work where flow visibility is required or is aesthetically appealing. The chemical and pharmaceutical industries use a good deal of piping, often for the transport of aggressive fluids. The design criterion in these circumstances is usually resistance to corrosion or solvation of the pipe wall. These industries will accept high materials cost, for instance stainless steel is commonly used. Plastic materials are therefore used when they have appropriate chemical resistance or perhaps temperature tolerance. Reinforced-plastic pipes in particular are also used in the chemicals sector. In general the so-called ‘engineering polymers’ have not been exploited as pipes even though they have good mechanical properties. The reason for this is probably a combination of high price and difficulty in processing by extrusion. 32


3 PIPE SYSTEMS MARKET

3.1 Application Sectors and Major Users

3.1.1 Water Drainage and Control The degree of control that human communities can exercise over local water flow is one measure of civilisation. The process of urbanisation interferes with rainwater runoff to natural watercourses and artificial means of drainage must be introduced to avoid localised flooding. Since the mid-19th century, piping has been used as the primary method of directing water into larger capacity culverts and channels which are for the most part canalised natural watercourses. For about a hundred years the most widely used material for underground drainage has been fired clay pipes. These still form a significant share of the market though for larger diameters they were superseded by concrete pipes which could be produced more cheaply in larger diameters. In above ground applications or where pipe-work might be subject to impact or higher forces then iron pipe was widely used. All these traditional materials can now be replaced by plastic systems. The drainage pipe market can be divided into different sectors where applications involve variations in traditional technologies and where differing bodies are responsible for pipework selection and purchase. Rainwater drainage can involve: • • •

the built environment roadways open land

Relative quantities of pipe used are shown in Table 3.1. Table 3.1 Main Markets for Plastic Pipes in Europe Application

PVC tonnes

HD/ MDPE tonnes 166,090 249,900 15,400 50,270 106,530 27,950 4,900

LDPE tonnes

PP tonnes

PE-X tonnes

ABS tonnes

PB tonnes

5,700 10,315 89,155 9,730 0 3,100 0

46,960 0 0 8,000 0 30,340 24,995

0 0 0 0 0 0 26,005

6,805 0 0 0 0 3,230 0

0 0 0 0 0 0 5,690

Application Totals tonnes 1,273,905 422,715 159,215 157,580 108,530 79,280 63,090

Polymer Totals 1,373,250 621,040 118,000 Source: Macplas International, 1999, 1, p.26. HD: High density

110,295

26,005

10,035

5,690

2,264,315

Drain/Sewer Potable Water Agriculture Conduit Gas Industry Heating/Plumbing

1,048,350 162,500 54,660 89,580 2,000 14,660 1,500

Initial responsibility for supplying systems to collect and dispose of rainwater falling on buildings and impervious surfaces is usually part of architectural design and implementation is by the builders of the property. This market involves pipe-work and a great variety of associated fittings. The market is large in total but highly fragmented and must respond to the localised requirements from very large numbers of relatively small

33


purchasers. The market is therefore served by a cascade of distributors and builders’ merchants with varying degrees of purchasing power. Almost all drainage systems are gravity driven. Water must be collected, routed in a systematic manner involving final discharge to natural water courses, after passing through a purification plant if necessary. Some idea of the design considerations is given by the example of a calculation that 25 mm of rainwater falling on a paved area of 1 3 hectare amounts to 250 m of water to dispose. If this falls in one hour, the discharge rate is 70 l/s and this could be carried by a 315 mm diameter pipe at a flow speed of 1 m/s, implying a gravity fall of 3 m in 1000 m. The water would need to be collected by a 2 reticulated pipe network. Gulley spacings are typically one per 200 m or 50 per hectare implying 50 branch pipes to the 315 mm main drain. Such calculations are the starting point for drainage pipe system design and companies competing for this market must offer a wide range of fittings to facilitate the engineering and architectural features associated with the paved and built environment [35]. The product transported by drains is essentially water which may have a high proportion of suspended solids such as sand and soil. Burial depths are generally relatively shallow but the main design criterion is pipe wall stiffness. Strength to resist internal pressure is secondary. Traditional drainage construction has been dominated by ceramic materials. Vitreous clay pipes and fittings have a long life and have been used for collection and feeder branches whilst the larger diameters have utilised concrete. Iron pipe and fittings, such as collection gulleys have been used where high loads or impact damage are a consideration. The plastics industry has competed very successfully with steady displacement of the traditional materials. The advent of structured wall pipes with high stiffness and advantages of ease of handling and connecting has accelerated the adoption of plastics drainage for highway systems. Building drainage marries the use of above ground rainwater collection systems, guttering, down pipes and fittings to the underground drain network. Rainwater collection systems have been one of the most successful areas of application for plastics. PVC has mainly met the requirements for many years resulting in the almost total displacement of traditional iron pipe and fittings. Being above ground, the pipes and fittings need to be stabilised against long-term ultra violet light and weathering exposure. Although PVC has been the dominant material in a highly competitive, low cost structure market, there is increasing use of PP materials. Some rainwater drainage products for large buildings and construction products need to be more sophisticated. For instance, rapid discharge of flash storm water from large flat roofs is important to avoid destructive overloading from the weight of water. This can involve pumped or syphoned systems requiring pressure pipes such as HDPE systems. The drainage of rainwater runoff from buildings and paved areas subsequently involves larger mains drainage routes which are normally part of the responsibility of local government. These responsibilities may be expressed as legal requirements and in recent times have become increasingly involved with environmental concerns to protect watercourses from pollution. The main drainage of water is subject to much local variation. Design depends greatly on rainfall patterns, particularly in the capability to absorb flash storm water, often overlapping the need to drain water runoff from highways and to dispose of sewage. The differing demands call for differing pipe technology solutions. Decision making on design and purchasing is typically the responsibility of municipal engineering departments. As large corporate entities they may be able to purchase by tender/contract through major product distributors or even direct from pipe manufacturers. 34


Modern highway engineering pays considerable attention to the efficient drainage of road surfaces for the safety of vehicles travelling at high speed. Roadway gulleys and drainage culverts need to have resistance to occasional entry pollutants such as motor oils and vehicle fuel. The mechanical requirements are for resistance to ground forces and traffic overburden. The construction of new roads also requires consideration of land drainage around and below the route to ensure there is no flooding or undermining of the carriageway during heavy rain. Drainage pipe-work design has therefore become an integral feature of total roadway planning and specification of pipe and fittings is a responsibility of highway engineering departments. An appropriate technology has developed as a variation on general drainage pipe-work. There is increasing use of large diameter corrugated or structured wall pipes in PVC, PP or HDPE materials. Purchase of highway drainage is project-specific, generally following large scale contracts to develop sections of major roadways. Land drainage has a very long history and its requirements are often legally expressed so as to avoid conflict between neighbouring landowners. English case law has established the rights of landowners to drain and discharge water to natural watercourses. Most land drainage schemes involve the supplementing of natural water courses by the cutting of additional open ditches but in the mid-19th century, English landowners pioneered the use of pipe for underground land drains. These were made from short sections of clay pipe laid out in herring-bone or rectangular grid patterns which could absorb water from the soil and transport it down hill slopes to drainage channels in lower ground. This remains an accepted method in most countries but is being progressively displaced by the laying of perforated plastic pipes laid from flexible coils. Land drainage pipes are set out in patterns, such as herringbone or gridiron, with spacing dependent on soil conditions. Heavy clays may require drains spaced at 5 m intervals but in light sandy soils spacing at 25 m may be sufficient. Drainage is normally to nearby watercourses which can also absorb silting. The amount of water runoff can be calculated, as in the earlier drainage example, but the main difference is that land drainage is less immediate, because of the holding capacity of the topsoil. Runoff may occur typically in a 24-hour period after the passage of a storm. The burial of perforated, corrugated PVC or PE pipe coils is assisted, particularly in high labour cost countries, by mechanised pipe laying equipment. In rural areas with no other services laid in the soil it is possible to lay drainage pipes quickly by plough-in techniques, at rates of around 1 kilometre per day. The market for drainage products is population related and variations are determined largely by the activity of the building and construction industry, which in turn depends on regional economic progress and government priorities. At this time the developed Western European economies appear to be expanding and steady market growth can be expected. The East European economies are continuing to re-structure and priorities, particularly under Western investment influence, are directed at infrastructure improvements which include much construction industry work. High growth prospects may therefore be anticipated in Eastern Europe drainage pipe applications.

3.1.2 Agricultural Purposes Drainage of land to extend areas of cultivation and to improve winter accessibility has always been a predominant concern of landowners in Northern Europe. In the drier climates of Southern Europe the greater concern was with maintaining soil moisture levels in the summer months. The increase of agricultural crops yield derived by irrigation from the major rivers was the basis of some of the earliest civilisations. Sophisticated systems 35


of water conservation by damming and its distribution by open cut channels were established over hundreds of years and became the basis of farming in most hot dry countries. As with drainage however the availability of pipes gave new opportunities for controlling the flow of water. The population growth of the last 100 years has required progressive increase in land available for agriculture and an increase in crop yields per unit of land area. Much of this has been achieved by irrigation with the result that many countries now have a very high dependency on man-made water supply systems (Table 3.2). Table 3.2 Agricultural Irrigation in Europe in 1998 Land Area Cultivated % Irrigated ’000 ha Area ’000 ha Albania 2,875 699 48.6 Austria 8,386 1,479 0.0 Belgium 3,310 832 4.8 Bulgaria 11,091 4,511 17.7 Slovakia 7,886 3,333 0.7 Denmark 4,309 2,374 20.1 France 55,150 19,517 10.2 Germany 35,698 12,107 4.0 Greece 13,196 3,941 36.1 Hungary 9,303 5,045 4.2 Italy 30,127 11,030 24.5 Netherlands 4084 941 60 Poland 32,325 14,379 07 Portugal 9,198 2,580 24. Romania 23,839 9843 29.3 Spain 50,599 19,080 19.1 Switzerland 4,129 439 5.7 UK 24,488 6,308 1.7 Former Yugoslavia 25,580 7,204 1.7 Country

Area Irrigated ’000 ha 340 4 40 800 24 476 2,000 485 1,422 210 2,698 565 100 632 2,880 3,640 25 108 119

Source: Food and Agriculture Organisation of the UN (FAO) online databases, www.apps.foa.org

The flexibility and corrosion resistance of plastics makes them very suitable for easy installation in, and over, most types of ground. Although most traditionally irrigated lands depend on channelled water courses the more recent additions have been achieved by piped systems [36]. These may be pressurised systems derived from water mains or may be low-pressure gravity fed systems. Water can be fed directly to soil by pipes or in the case of pressure systems can be sprayed by sprinkler devices. In modern farming, irrigation is no longer confined to the hot dry countries of the Mediterranean. Irrigation and land drainage are seen as methods of achieving optimum growing conditions and freeing farmers from the uncertainty of rainfall patterns. Therefore the market for irrigation equipment extends even to areas with relatively high annual rainfall. Eastern Europe and the former Soviet Union countries developed large-scale irrigation schemes during the period of large-scale collectivisation of farms. Many of these largescale schemes were poorly maintained and fell into disuse. The effect of exposure to more efficient production from the West and World markets has meant abandonment of 36


large tracts of irrigated land and collapse of agricultural output levels. As a part of its programmes to improve agricultural production in East Europe the World Bank had identified a need to invest heavily in renewal of irrigation with improved techniques. Some idea of the scale of investment is given in a World Bank report [37]. The provision of pipe-work for irrigation schemes has been identified as an opportunity to develop appropriate pipe systems. The Wavin company for example has a product range specially for the purpose. Most irrigation pipe-work is however probably distributed by agricultural equipment specialists who have developed irrigation systems by assembly of general-purpose water supply and drainage pipes. The main opportunity for new pipe systems in irrigation derives from moves away from traditional open-course water channels to closed pipe systems. The open channel schemes involve not only high construction costs but also high maintenance costs. Additionally in arid climates there is high evaporative loss. Piped systems may involve high installation costs but thereafter they have long trouble-free life and negligible water loss. Piping also creates provision for pumped water schemes that can open land up to irrigation that was not accessible to gravity-channelled water.

3.1.3 Potable Water Supply Water supply is a basic human need. The earliest human settlements were always by a running water supply and most urbanised communities grew up around rivers. The process of industrialisation also created new demands for continuous water supply. When the development of cities and concentrations of population outstripped local supplies it created a need for transporting water. There has therefore been a long history of technological development dating back to the earliest of civilisations. In the 19th and 20th centuries, water control and pumped supplies developed on a very large scale. Damming of rivers controlled the all-year supply capacity. Large diameter trunk mains supplemented natural watercourses. Local header reservoirs and elevated tanks with pumping stations and valving were built to control the supply to a distribution network feeding individual households, factories and commercial centres. This is the pattern of supply to most cities of the developed world and is the aspiration of the poorest countries of the underdeveloped areas. Yet the stark fact remains that around one billion people still have no direct access to clean drinking water. As a consequence, around 35% of deaths in under developed countries are associated with this lack of a basic requirement for decent life. Surprisingly, freshwater is not as ubiquitous as may be thought. Although 70% of the planet is covered with water, less than 3% of this is freshwater. Much of this is inaccessible because approximately 90% of the world's freshwater is locked up as polar ice caps, glaciers and deep underground water. In fact, only about 0.3% of the world's water is available for consumption from lakes, rivers and underground aquifers. Many countries already have inadequate water capacity and amongst those with adequate supplies there are future threats of limitation by contamination and over-extraction. Increasingly, water is being recognised as a finite commodity that must, like fossil fuels, be depleted on a controlled basis with regard for the needs of future generations [38]. The commercial consequences of this are inevitably, higher valuation of water resources and greater emphasis on conservation and regulation. Pipe systems will undoubtedly be an area of continuing investment for this purpose. The main targets of investment are likely to be renewal and improvement of supply in developed cities, and the provision of low cost clean water in undeveloped countries. The former is characterised by decay of existing infrastructures, typically 50 to 100 years old, with associated large leakage rates and inefficiency of supply. The problems of 37


undeveloped countries are characterised by lack of existing infrastructure, lack of investment, lack of expertise, lack of materials supply chain and lack of construction capacity. Table 3.3 West European Potable Water Usage (Per Year) Domestic per Industrial Domestic Total Domestic per 9 3 3 3 Person (m /y) Dwelling (m /y) Totals (bm3) (10 m /y) Austria 0.63 78 191 0.13 Belgium 0.45 46 115 0.18 Denmark 0.32 64 139 0.095 Finland 0.23 48 109 0.197 France 3.3 57 137 1.3 Germany 4.1 51 117 1.6 Italy 4.5 77 187 1.4 Luxembourg 0.027 67 180 0.013 Netherlands 0.96 64 154 0.22 Spain 1.9 49 119 0.87 Sweden 0.53 59 136 0.26 UK 3.4 59 148 2.0 Totals/Averages 20.35 60 144 8.26 Country

Principle Source: EU Panorama ’95 (Review: Water Supply and Distribution, written by EUREAN)

Within Europe the cities fall into the first category, that is to improve existing resources. The cities already offer water supplies to practically all inhabitants (Table 1.3 and Table 3.3). In rural areas of Eastern and Central Europe there are needs for additional piping systems but the overall need is for improvement and refurbishment of systems constructed of traditional materials that are now failing. Failures may involve lack of capacity to sustain increasing demand but this is exaggerated by tuberculation (calcification growth within pipes) and leakage from joints and broken pipes. Because of the perceived low value of water (it falls freely as rain!) there is a widespread disregard for the cost of water lost by leakage. The reluctance to maintain and repair means that water companies can typically lose 25-30% of their product without regarding it as a financial burden. Commercial factors are beginning to act against this. Water supply economics are changing. The value of water is becoming seen to be its value as a delivered product, rather than its cost at source. So the value includes transportation system costs. The water companies are increasingly being managed on a competitive commercial basis. The UK has led the way by privatisation and regulation. France has established large water companies that act as multinational organisations. These trends are likely to continue, with commercial management replacing established municipal service industry values and restrictions. Although commercial management can result in much tighter budgetary control and pressure to adopt short-term profitability goals, it also releases new investment potential. The pattern set by the privatisation of UK water authorities and the international activities of French and US utilities has dramatically changed the decisionmaking process for UK water investment and similar development patterns are likely to follow in other parts of Europe. The changes involve more critical analysis of water supply networks and reviews of the need for investment to maintain quality and quantity to regulated specifications. Advanced forms of network analysis, coupled with flow monitoring data collection are involved. When a need to renew piping or add new supplies is identified, then investment, at acceptable capital costs, is sought with payback secured by the water supply charges. The resulting effect has been the impetus for the supply chain to develop technologies, often involving plastic pipes laid by more efficient installation methods, that are highly competitive. 38


The traditional pipe materials of the water supply industry have been quite varied. From the mid nineteenth century until the 1930s cast iron water mains were laid extensively and it is this heritage of aged pipe that is progressively failing and requiring replacement. Cast iron pipes corrode and fail brittly with ground movements. Many of the older pies are clogged by corrosion or lime deposits. Joints of older pipes are commonly leaky. The later pipes were laid in ductile iron, steel, asbestos-cement, and reinforced concrete. Each material had some advantage for particular circumstances but their markets have been attacked by plastics systems. Ductile iron has retained a sizeable market in moderately large diameters. Steel retains its advantage at high pressures (above 1.6 MPa) and concrete products are competitive for very large diameters. Substitution by plastics material has progressed steadily, largely determined by perceived price advantage. PVC piping has been used in mains pipes since the 1950s and PE, initially as LDPE, and later as MDPE or HDPE became extensively used for small diameter service pipes. The pace of acceptance of PVC and other polymers for larger mains usage was initially relatively slow and very variable with inconsistent selection criteria between different water companies. Plastics became essentially one of several alternatives. In later years however, the improvements in engineering standards and availability of well designed systems at very competitive prices led to plastics becoming a first choice material. The water industry in the USA and Europe looked to PVC as the dominant material for pressure pipes. However the success of MDPE and HDPE pipe systems in gas distribution pipe networks has brought about a major shift towards PE within the European water sector. The advantages of PE are in construction techniques. It can be laid from coils with reduced jointing, can be joined by fusion welding techniques, and can be ‘squeezed-off’ to stop flow. The gas industry was able to accept higher costs for a highly specified, high quality PE system. The water industry was not initially able to justify these costs but became more interested with the introduction of no-dig pipe laying techniques and the introduction of higher strength, crack resisting PE100 grades of HDPE. These materials could tolerate high-pressure water usage without compromise of stress crack resistance. Confidence in their ductility and resistance to short-term or longterm brittle failure allowed for specifications to adopt lower design safety factors. When allowance is made for the usable strength of PE100 with a reduced design factor, the previously perceived performance/cost advantage in PVC can be greatly reduced or removed altogether. One area of water supply regulation that is taking much technical and market attention at present is the EU directed limit on lead levels in drinking water supply. These progressively onerous levels create a problem for those countries that have made extensive use of lead service pipes. To avoid the leaching of lead compounds into the domestic water, the supply may be treated with phosphate salts, but the longer-term solution will require large investment in replacing the lead pipes or lining them with an inert barrier material. Various polymer linings, including PET [39], MDPE and TPE are currently being proposed. The largest European markets for lead service pipe replacement/renovation are France and the UK. German water suppliers many years ago opted to use mainly steel instead of lead. The high level of interest in reducing lead concentrations also raised some questions about the leaching of lead-based stabiliser compounds from PVC pipe. A number of European pipe manufacturers have already moved to non-lead stabiliser systems and it is likely that such moves will be completed by voluntary action before legislation is introduced [40]. Although the water industry’s usage of plastic pipe-work generally pre-dated that of the gas industry, the engineering specifications for PE pipe developed by the gas industry, to ensure high quality and long life under pressure, were subsequently taken up by the water 39


industry in its own specifications. The initial dominance of PVC within the water market meant that the specifications and material developments for PVC have largely been introduced by water utilities. The result of these two separate pedigrees has resulted in quite different approaches to pipe product specification for PVC and PE materials. The mechanical performance demands on a pressure pipe are similar whether the pressure source is gaseous or liquid though there may be some differences with regard to dynamic pressure fluctuations. In gas pipes the pressure variations tend to be characterised by relatively slow changes in response to demand and the movements of control valves. In water systems rapid changes are far more likely and these are transmitted as pressure waves, this is because a liquid is unable to damp surges in flow caused by pumps and valves. As a result of this, dynamic mechanical and fatigue properties of pipes and fittings are of greater significance to the long-term durability of water pipelines. The greatest practical difference in design philosophy between gas and water pipelines is however associated with the consequences of pipe failure. Leakage of gas can have disastrous results whereas leakage of water is not usually hazardous. For this reason, planners can risk failures in water pipes by operating them closer to their theoretically maximum performance whereas designers of gas pipelines adopt safety conscious, conservative engineering practices. The water industry can be expected to use lower safety factors in calculation and to be quicker to try cost reducing procedures, whilst the gas industry is characterised by a prudent approach with high safety factors in calculations and a slow, proof-testing approach to new materials and methods. As an example, the water industry makes extensive use of ‘push-fit‘ pipe connectors which are quick and easy to install but depend on the long-term sealing performance of elastomeric elements whilst the gas industry prefers to use welded joints wherever possible, avoiding dependence on materials that could have a shorter life than the pipe itself. Potable water is transported to consumers through a network of pipes which consists of mains pipes with a range of sizes and connections to consumer premises by smaller service pipes. In the older industrial cities of Europe, much of the pipeline infrastructure is around 100 years old and iron water pipes and gas pipes are subject to decay by corrosion. Water pipes suffer additionally from internal build up of deposits lining the pipes which eventually interfere excessively with flow capacity. The water supply network of the UK consists of around 300,000 km of pipe-work but has not had an investment boost equivalent to the introduction of natural gas. However following privatisation of the water utilities that are responsible for maintaining the public supply, major renovation and replacement strategies have been developed which involves widespread introduction of plastics. New pipeline systems for new urban developments are now almost entirely constructed in plastics. Most pipelining projects start from a supply concept featuring an objective of satisfying the demands of a series of users with water at specific levels of flow. The operating pressure for the water supply network ranges in practice from about 0.1 to 1.6 MPa with occasional variations due to water flow surges that can create negative or vacuum conditions or peak pressures of up to 2 MPa. When considering the possibility of using plastic pipe, or any other alternative to the long established materials, the planner must ensure that there is no possibility of introducing substances that could taint, colour or contaminate, the drinking water supply. The need to protect the water supply from contamination has led to much consideration of the permeability of plastics materials due to the possibility of migration of low molecular weight particles through the pipe wall from the external environment. Also the range of additives in the polymer compound for colouring, modifying properties or protecting the pipe from degradation is limited to materials that produce no threat to public health in the 40


concentrations that could arise by leaching into the water flow. The high molecular weight polymers, such as PVC and PE do not themselves migrate into the water and therefore present no problem. Interest concentrates on the low molecular weight additives that are added as protection from degradation by heat, UV light, or oxidation. Such materials are often organometallic compounds which do pose questions concerning migration concentration and toxicity level. Studies pertaining to lead stabilisers in PVC are outlined in [40]. Antioxidant migration from PE water pipes is dealt with in [41]. Obtaining approval for pipe and fitting materials that come into contact with drinking water requires a series of costly long-term tests and once a supplier has gained acceptance of a product, there is understandable reluctance to make changes that would necessitate new tests. Following construction of a pipe system, sterilisation procedures are required to ensure that no contamination remains to affect the drinking quality of the water. Colour coding of potable water pipes is becoming standardised as a result of European standardisation with national requirements specifying either all blue or black with blue stripes. These two options are becoming widely used throughout the world.

3.1.4 Sewerage Sewerage pipe-work derives from a human need that is less obvious than fresh drinking water, but nevertheless, disposal of wastewater and its separation from freshwater is an important contributor to civilised and healthy life. For thousands of years the transport of wastewater was in open channels flushed by rainwater runoff. In the 19th century there developed an understanding of the microbial nature of diseases and the major role played by dirty water in the spread of life-threatening infections such as cholera and typhoid. This knowledge was the spur for widespread construction of sewerage networks in most towns and cities of the industrialised world. The connection of households to main sewers was slower than the connection to water pipes but most towns and cities by now have fully connected households. Ownership and maintenance of sewers continues to be a municipal responsibility in most countries but, along with the potable water supply, the UK has placed much of its sewerage system into commercial ownership. Generally, in any area of the country, the same company operates water supply and wastewater removal. The provision of both services has much in common. Water supply and sewage disposal are approximately in balance and are predictable for human communities, being related for instance to population density and the number of persons occupying individual premises. Water demand and sewerage capacity need to be provided with regard to typical lifestyles. With increasing prosperity goes an increasing usage of water. The introduction this century of great improvements in sanitation, bathing facilities, and kitchen appliances for most of the population of modern cities has required continued investment in water supplies and sewerage. The older cities which grew with 19th century industry have major sewerage systems that are around 100 years old and in many cases are becoming decayed and inadequate. In most cities the market for renovation of sewerage systems greatly exceeds the opportunity for new build. Sewerage pipe-work is distinct from general rainfall drainage in that it is intended to carry highly polluted water resulting from the domestic or industrial use of water. As such it is usually subject to more control and regulation and may be the responsibility of different authorities. Sewerage systems like drainage are for the most part gravity operated, but whilst surface water can drain to watercourses, foul water must be separated from freshwater and be treated at a purification plant before return to natural systems. Sewage transport pipe-work may therefore involve the use of pumping stations and some elements of pressurised pipe-work. 41


Sewerage systems can involve deeper pipe burial and the use of very large diameter pipe-work systems or tunnelled watercourses. Final disposal to land-based water courses requires a high degree of purification and in countries such as the UK, with a long coastline, extensive use is made of sea outfall pipes. Concern over coastal water pollution and environmental damage has led to improved levels of purification prior to sea disposal but the use of sea outfall pipes continues to be an important aspect of wastewater disposal. Traditional sewer construction materials have been similar to drainage systems, that is, vitreous clay and concrete with iron pipe extensively used for pump systems. Large tunnelled sewers may be of traditional brick construction with a variety of cross section shapes designed to maintain flow speed in dry weather and yet carry excess water flow in storm conditions. Plastics now form a major sector of the market although there has probably been less use of them compared to drainage and potable water systems. Because of the use of large diameter pipe-work, sewerage projects can utilise large quantities of polymer. For instance the replacement of iron or concrete pipe-work for sea outfalls by large diameter plastic systems is a major opportunity. Outfalls operate in a marine environment which may involve tidal forces and present particular problems of construction and anchorage. The subject has been discussed by Berndtson [42] and design guidance on anchorage and protection against tidal movements is provided by Janson [43]. Sewerage pipes share many of the same design objectives as potable water pipes but additional features are: the use of generally larger diameter pipes, the presence of solids carried in the flow, the greater likelihood of exposure to contaminating materials (such as surface active agents), deeper installations with subsequently higher ground loadings and external water pressures. Abrasion from suspended solids can be a problem for metallic and ceramic sewer materials but polymers are usually more resistant. Because the majority of sewerage pipes form part of gravity flow systems, involving low pressures and large diameters, pipe wall stiffness is usually of greater importance than resistance to internal pressure. Pressure pipes are however used for pumped systems. In most countries the sewerage pipe market is still open to greater penetration by plastics. Existing pipe-work installations often feature a variety of traditional materials. Concrete, clay and iron and steel pipes continue to be extensively used whilst PVC, HDPE, PP and glass reinforced plastic (GRP) compete in various forms. As with other forms of below ground pipe-work much use has been made of clay pipes for small feeder connections. Large-scale mains are often constructed as brickwork tunnels. Iron pipe, particularly ductile iron has been used extensively where pipe is above ground. Larger diameter pipework is now mainly made of concrete. Sewerage has become increasingly recognised as one of the major market opportunities for plastics. The market has been extensively exploited in Scandinavia and is now growing in Western Europe generally [30]. One issue for plastic pipes in water and sewerage applications has been their susceptibility to damage by the high-pressure water jetting apparatus that has become adopted for cleaning out accumulated solids. This potential threat to plastic pipe markets appears to have been resolved by improvements to the control of water jetting pressures so as to avoid damage without impairing cleaning efficiency [43].

3.1.5 Gas and Fuel Supply Although the piping of natural gas (methane) as an energy supply for industrial and domestic heating was established early in this century, as an adjunct of the North American oil industry, the technology took on a wider significance in the 1960s with the 42


exploitation of gas fields in North Africa, the former Soviet Union and the North Sea. The transport and trading of natural gas is now a worldwide industry on a scale almost as important as oil. In many countries, gas has displaced coal as a primary fuel and chemical feedstock. Gas is also becoming important for power generation and is perceived as a means of mitigating air pollution and greenhouse gas emissions by virtue of its cleaner burning characteristics when compared with other fossil fuels. The development of natural gas as a major constituent in the basic energy requirements of European countries has been a highly influential factor in the introduction of plastic pipe systems. Pipeline engineering is the fundamental technology of the oil and gas industries. The technology was principally led by the growth of the oil and natural gas industries of the USA but the discovery of natural gas offshore of Western Europe in the 1960s led to rapid exploitation initially by the concentrated populations of the Netherlands and the UK. The major investment decision to convert the whole of the UK gas distribution network to a unified natural gas grid was far seeing and paved the way for subsequent global exploitation of natural gas resources. The high pressure ‘transmission’ of natural gas utilises welded steel pipes of around 1 m diameter operating at around 8 MPa pressure. The low-pressure networks within towns and cities consuming the gas were originally installed for the distribution of coal derivative ‘town’ gas which was generated and transported at quite low pressure. It was for the replacement and extension of such systems that the Netherlands and the UK made extensive use of plastics. Table 3.4 European Gas Production and Usage Country

Gas Reserve 9 3 10 m

Austria 24 Belgium Denmark 120 Finland France 14 Germany 235 Greece Ireland 6 Italy 265 Netherlands 1,870 Portugal Spain Sweden UK 760 Norway 2,560 Switzerland Algeria 3,000 Russia 47,000 Ukraine 1,100 Hungary 85 Czech Republic 4 Slovakia 14 Poland 154 Source: IGU Statistics (1998).

Annual Production 9 3 10 m

Annual Consumption 9 3 10 m

Use as % Primary Energy

% Households Supplied

1.5 7 2 19 1.5 18 68 90 45 66 490 17 3.5 0.5 0.4 4

8.5 16 13.5 3.6 39 85 3.6 58 43

European Plastic Pipes Market (The)

The Pipes Of Pan

The Pipes Of Pan

Between the Pipes

Between the Pipes

The Pipes of Pan

Indian Pipes

Plastic

Indian Pipes

Plastic

(ss) The Pipes of Pan

The European Labour Market: Regional Dimensions

Robert Reed - Pipes

Robert Reed - Pipes

Pipes [Short stories]

The Plastic Abyss

The Plastic Abyss

Brian Stableford - The Pipes Of Pan

Brian Stableford - The Pipes Of Pan

The Stateless Market: The European Dilemma of Integration and Civilization

Two-phase flow in pipes

Brian Stableford - The Pipes Of Pan

Structural Mechanics of Buried Pipes

Developing Measures and Standards for the European Electronic Signatures Market

De vrouw in plastic

Plastic (Science Explorers)

Practical Plastic Surgery

European Plastic Pipes Market (The)

The Pipes Of Pan

The Pipes Of Pan

Between the Pipes

Between the Pipes

The Pipes of Pan

Indian Pipes

Plastic

Indian Pipes

Plastic

(ss) The Pipes of Pan

The European Labour Market: Regional Dimensions

Robert Reed - Pipes

Robert Reed - Pipes

Pipes [Short stories]

The Plastic Abyss

The Plastic Abyss

Brian Stableford - The Pipes Of Pan

Brian Stableford - The Pipes Of Pan

The Stateless Market: The European Dilemma of Integration and Civilization

Two-phase flow in pipes

Brian Stableford - The Pipes Of Pan

Structural Mechanics of Buried Pipes

Developing Measures and Standards for the European Electronic Signatures Market

De vrouw in plastic

Plastic (Science Explorers)

Practical Plastic Surgery

Recommend Documents