Chapter Five – PE Pipes, Electrofusion Fittings & Automatic Butt Fusion

A.  General

The National Control Study carried out by Bina Runding in the late 80s recommended that active NRW control programmes be carried out throughout the whole country and that NRW control should form part of the overall mains rehabilitation or replacement programmes to ensure that the performance and condition of the distribution systems would be maintained or improved to achieve the expected level of service to the consumers. The subsequent shift in the implementation strategy is most appropriate as the operation of a water supply distribution system at optimum NRW levels does not only consist of measures to reduce leakage but also long-term maintenance which requires strategic planning of investments to rehabilitate parts of the distribution system as they are approaching the end of their economic working life.

The few NRW Control initiatives carried out by Bina Runding revealed that water leakage in the distribution systems was mainly from old Asbestos-Cement (AC) pipes which formed more than 50% of mains in the water supply systems. AC pipes were widely used throughout Malaya since the 1950s. Because of their low cost, these pipes of less than 500mm diameter had been a popular choice for use both as trunk mains and reticulation mains. Their other advantages include rigidity, relatively good corrosion resistance and ease of tapping. The housing booms of the 60s and 70s, including the accelerated implementation of Government’s land development programs of the 70s, saw a big increase in the use of AC pipes in housing estates and land development schemes. However, AC pipes have several limitations. They are susceptible to impact damage during transportation, handling, installing and backfilling.  Generally they have relatively low beam strengths and are susceptible to circumferential failure under transverse loading conditions. They are also permeable to external contaminations especially when empty. The National NRW Control Study also highlighted that the big proportion of water losses in AC pipes was due to defective sleeve/Gibault joints and in particular the defective connections of service pipes, using ferrule and saddle, to public mains. AC pipes are commonly available in sizes of 80 to 600mm nominal diameter and are manufactured in standard lengths of 4 metres. It has therefore a relatively high number of joints/unit length.

In the 60s, 70s and 80s AC pipes were the cheapest pipes to use as reticulation and service mains. The other pipes available were Cast iron (CI), Ductile iron (DI), Steel (S) and Unplasticised polyvinyl chloride (uPVC).

Graph of cost index vs pipe diameter

(Extracted from “Guide to Pipe Materials Section For Water Supply Systems”)

All these years, there were Malaysian Standards (MS) issued by SIRIM Berhad for all available pipe materials in used in Malaysia. Besides these MS, there was no other publication on the proper choice of pipes to be used in pipe replacements by the water authorities and in the new housing development projects, particularly for reticulation mains and service pipes. Cost had always been the main criterion in the choice of the type of pipes to be selected for use by the developers. Also, Malaysian engineers were cautious in using new pipe materials being introduced into the market because of lack of information on the performance of these materials. Under the above circumstances, AC pipes were dominantly used in Malaysia then.

There was an urgent need for a uniform criterion for pipe materials selection. To fulfill this need, the Malaysian Water Association (MWA), established in 1988, produced a Guide to pipe materials selection in 2002 to be used as a reference book by water supply engineers in water supply authorities and consulting engineering firms. I was one of the members in the Committee in drafting the Guide: “Pipe Material Selection For Water Supply Systems”, published in 1992.

The Guide provides a systematic approach on the evaluation and selection of pipe materials under various circumstances. It outlines selection procedures for trunk mains, reticulation mains and services pipes. The information provided in the Guide is sufficient for a water supply engineer to evaluate and select the most suitable pipe material to be used for his water supply project.

Due to high leakage from AC mains, many water authorities in Malaysia abandoned its use for water supply reticulation systems by the end of 1980. To replace the use of AC mains, particularly for water reticulations systems, plastic pipes were chosen because of their low costs compared with metal pipes, such as Stainless Steel, Copper, CI and DI pipes. The plastic pipes available then were uPVC and PE.

However, if due consideration is given to cost of fittings, pipe-jointing and other appurtenances that can provide a better reticulation system in reducing leakage, then PE mains are preferred.

B. PE pipes  

The use of PE pipes in water distribution systems in Malaysia was introduced over three decades ago. It was seen to have significant advantages for the transport of water to solve the problems of high leakage in AC, corrosion and encrustation in conventional GI, CI and steel pipelines. Its advantages over other pipes have become a major material choice of the water industry in Malaysia for new pipelines and rehabilitation of old pipelines. The use of PE pipes has grown rapidly since the early 80s. However, the rapid increase in its usage let to a proliferation in the use of “recycle” and unapproved raw materials resulting in producing PE pipes of poor quality. This combined with inconsistent installation practices had resulted in increased system failures.

The main factors that led to the poor quality of the PE pipe systems installed then were the lack of appropriate specifications for pipes and fittings, installation methods and jointing procedures.

Polyethylene is a generic name of a group of products, used in a variety of applications, such as packaging film, bottles, injection molded articles, tanks, drums and ducts. Each of these applications requires different grades of polyethylene and compound. For PE pipes, the correct grade of material and its compound must be selected to ensure fitness for pressure pipe applications.

To meet the requirements for PE pipes to be used for water supply distribution systems, Polyethylene Malaysia Sdn. Bhd., a joint venture between BP Chemicals and Petronas, was formed to locally manufacture high quality compounds for PE pipes. The products are certified by SIRIM QAS and comply with International water pipe standards e.g. ISO4427, now MS 1058: Part 2: 2002.

Through improvements in standardisation and requirements imposed by the authorities, it is now mandatory for both the raw material and pipe producers to be certified to the Malaysian Standard by an accredited certification body. It is now imperative that PE pipe for water supply systems should only be used which is marked with both MS 1058: 2002 and the pipe producer’s SIRM QAS License number.

Also, a Tender Specification, “JKR Tender Specification for PE Pipe System for Water Supply, No 20200-0053-99”, was produced by the Water Supply Branch, PWD. This document provides the necessary information and specification to ensure the correct usage and installation of PE pipe systems.

PE pipe is currently available in diameters up to 1600mm and, due to its flexibility; pipe up to 125mm can be coiled and supplied in long lengths, thus reducing the use of joints and fittings. Long lengths can be pulled through holes below ground bore by mechanical moles, avoiding the need for open cut trenches. Its flexibility and low weight also results in cost saving in installation.

PE pipes can be pre-welded on the surface and its installation requires only the digging of open narrow trenches.

Most significantly, the ability to joint PE pipes by fusion welding is a major factor in the high reliability of leak free water supply systems. The two principle fusion jointing methods are butt-fusion and electro-fusion. Mechanical fittings jointing systems are available and used for connecting to existing non PE pipelines and valves. In addition, electro-fusion tapings or fusion saddles are available for service pipe connections.

Comparing Lengths & Proportion of AC & PE Pipes in all States

(Note: The data are extracted from Malaysia Water Industry Guides)

From the above, the following can be noted during the last decade:

• The states of Sarawak, Johor and Selangor are increasing the usage of AC pipes.

• Currently, the states of Johor, Selangor and N. Sembilan have less than 5% of PE pipes in their states’ water supply distribution systems.

• The use of PE pipes in Malaysia commenced only in the early 1990s.

• Sarawak, Perak and Kedah are the only three states that have more PE than AC pipes.

•  Only about 3,000km of AC pipes have been replaced out of a maximum of 45,000km. At this rate, it would take more than ten decades for water supply distribution systems in Malaysia to be rid of AC pipes!

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