Go with the flow

Are plastics pipes the way forward for future plumbing installations or are the traditional metals versions still the best? MEP Middle East examines the changes taking place in the sector.

Nemanja Seslija/ITP.
Nemanja Seslija/ITP.

Pipes are one of the most least visible, but most fundamental, features of a MEP services installation. The choice of product used can have a significant effect on the longevity of a system and the maintenance needed during its operational life. Traditionally, terracotta products and heavy metals materials such as cast iron and steel were used for large-scale pipes, with copper and lead also used within buildings for domestic plumbing. But advances in materials technology and influencing factors such as the fluctuating metals market prices are changing this sector.

A wide range of pipe materials is now available, with plastics and composite multi-layer versions vying for popularity over their all-metal equivalents. But how do these products vary and what type should you be installing in future projects?

The move to plastics piping

"Today, pipes for building use can be categorised into three generations: metal pipes, including galvanised, stainless steel and copper; plastics pipes, including PE (polyethylene), PEX (cross-linked polyethylene), polypropylene, polybutylene and CPVC (chlorinated polyvinyl chloride); and multi-layer pipes," explains Wilhelm Niederhauser, manager, Supertrade.

The use of the latter two categories has risen greatly over the past few years throughout the Middle East, with reasons for this cited as including the rising cost of raw metals and the increased speed of construction. "The main drivers for changing to plastics pipes are cost and speed of installation. World metal prices are very high at the moment, particularly for copper and stainless steel, which makes the use of lower cost plastics or composite piping an increasingly attractive alternative, particularly for the lower pressure applications that are often seen in the plumbing sector," confirms Alastair Mitchell, principal mechanical engineer, Hyder Consulting Middle East.

One of the advantages of plastics pipes is their relative ease of use, which has been attributed to reducing installation times and the amount of skilled labour needed for a project. "Modularisation in design coupled with a lack of availability of skilled personnel is also a major driver to the use of plastics pipe systems," states Paul Winfindale, associate director MEP, Hyder Consulting Middle East. A study undertaken by UK-based Building Services Research and Information Association (BSRIA) on behalf of manufacturer Durapipe has indicated a time saving of over 59% when installing a 6m length of 32mm diameter chilled water pipe using thermoplastics compared to steel products.

"Plastics pipework is now widely used in all areas of heating, ventilating, air conditioning and refrigeration and in many cases this has displaced traditional materials such as copper, steel and glazed ceramics," reports EurIng Tim Dwyer, acting head of department, London South Bank University. To date, their use has been generally confined to certain applications, but a sign of their rising popularity is the increasing number of manufacturers offering plastics products, such as Durapipe, Hepworth Building Products and Cosmoplast, and the arrival of new firms into the market. UK-based Polypipe, for example, established a base in Dubai in January 2007 after exporting to the region for around seven years.

"There is a definite trend in the increased take-up [of plastics pipes] within commercial and other developments," states Winfindale. "The market is changing, but for now polyethylene is generally replacing steel only in the small diameter pipes. With the large diameter pipes, steel is still used due to [overall] cost implications," explains Osama Akkawi, sales and marketing engineer, Emirates Pre-insulated Pipes Industries (EPPI). The district cooling sector is also proving popular for the plastics pipes industry, with products of up to 500mm diameter being regularly installed.

The pros and cons of plastics

The cost of metals aside, what benefits can plastics pipes bring to a project?

"Plastics pipes are normally quicker to install, lighter, have lower friction losses and are less susceptible to corrosion than metal pipe systems," explains Mitchell. The speed of installation is also an important factor due to the fast-track nature of projects in the region and this is one area where plastics are proving their worth reports Mitchell. "Many plastics and composite pipe systems' on-site fabrication cutting and connection methods are much quicker than for metallic equivalents," he explains. "PVC pipe connections are normally glued, composite systems normally use simple crimping or compression arrangements and polyethylene uses electro-fusion techniques; all are simpler and quicker than welding, brazing, screwed, flanges or mechanical couplings required for metal systems," adds Mitchell.

"Steel and copper piping system manufacturers have responded with mechanical and compression jointing systems to reduce installation time, but from experience while these speed up the programme of delivery, costs are commensurate with traditional jointing methods," stresses Winfindale. However, the availability of the equipment to carry out 'welding' of plastics pipes is one of the problems facing the market.


The installation of some plastics and high-density polyethylene (HDPE) pipes requires specialist tools such as butt-welding and electro-fusion machines, which can add considerable costs to a project. "Plastics pipes still need to be welded, it's just a different type of welding from steel - extrusion welding. Steel pipes are better for this technique as you need to use specialist welding equipment for each diameter of plastics pipe, this is true for high density polyethylene pipes, and training is needed to use the equipment," reports Akkawi. "You don't need to be as qualified as steel welders, which require set training courses to be passed; it's the machinery that's the problem with plastics welding, it's not easily available in this market."

Other issues with plastics pipes are their co-efficient of expansion and questions over their lifespan and recyclability. "The expansion [of plastics pipes] is up to ten times more than metal pipes," reports Niederhauser. "Other considerations are the lifespan: in metal pipes the normal operating temperature of up to 95°C does not affect the life of the pipe; with plastics pipes, the life of the material is dependant on three factors, temperature, pressure, and time," adds Niederhauser.

This issue of degradation due to temperatures is being addressed by the industry however and products that can withstand higher pressures and temperatures are becoming available. "The recent breakthrough in polypropylene random co-polymer (CP-R) materials indicates that lifespans of 50 years at 70°C are possible," explains Winfindale.

Maintaining metals markets

Despite rising costs and the emergence of plastics alternatives, the steel pipe market remains buoyant and is likely to for some time. Again, an important sign of the strength of this market is the continued arrival of new manufacturers. One such firm, Ukrainian-based global manufacturer Interpipe opened a representative office in the Middle East in 2007 having previously exported to the region. It has since reported a sales growth of 40% in the Middle East and North Africa in the first half of 2007.

There are several reasons for the continued use of metal pipes in addition to those mentioned above, including their temperature and pressure resistance, plus the ease with which the material can be used. In fire systems particularly, they remain the most popular material: "The NFPA (National Fire Protection Agency) allows the use of alternative pipes to steel...but the obvious temperature resistance of steel makes it somewhat unlikely that alternative pipe materials will be widely adopted for this type of system," stresses Mitchell. "Plastics don't behave well in case of fire, they produce toxic fumes," adds Raj Jhurani, general manager building division, TC Gulf Jhurani.

Developments in the metals pipes available are also contributing to the longevity of the market. "All products have gone through changes, they are not the age-old products that people have in mind. The thickness [of metals pipes] is down 33-40% from that used 20 years ago, this has been compensated by applying epoxy coatings to give a longer life," reports Jhurani.

The popularity of high-rise buildings in the region makes the pressure resistance of the products a particularly important issue. "High-rise buildings normally have high pressures in chilled water, plumbing and fire risers and these pressures can easily exceed the limits of nearly all commercially available PVC or similar materials, so the only practical material of choice is steel for fire and chilled water applications and stainless steel for plumbing risers," states Mitchell. "There are applications for plastics and composite pipe systems within tall buildings, but designers must carefully consider pressure, temperature and the expansion and contraction limitations of their selected material," he adds.

Building pipework solutions

One of the solutions now being applied in the market is to use a combination of metal and a plastics pipe within a project, with metals pipes being used for the main distribution risers and plastics pipes installed within individual building floors.

"Normally in plumbing networks the small diameter pipes are plastics," confirms Jhurani. "Many of our key projects make extensive use of PVC and CPVC piping for applications lower than 5.5 bar for hot and cold water plumbing services. PVC and CPVC are easy and quick to install and are not subject to corrosion problems, they are also cheaper than the alternatives of copper, which is not widely used in UAE; stainless steel or a more expensive composite type piping system," reports Mitchell.

"PVC has been used very widely for drainage systems for many years and this will only change if UAE regulations and consultants change to materials with lower smoke/fume generation properties. Condenser water distribution pipes are commonly made from GRP due to the fact the systems generally operate at relatively low system pressures and water quality can cause problems with steel pipes," he adds.


The benefits of switching to plastics alternatives at this level are primarily speed of installation. "For very small diameters below 100mm plastics pipes come in 100m rolls, so they are easy to install as they can be turned into the system and bent as needed; they are more flexible," explains Akkawi.

There are a number of manufacturers offering products for such applications including Durapipe and Polypipe. "We're promoting PEX or polybutylene pipe systems and we are taking market share from the copper pipes market. We've been successful in changing specifications to PEX pipes mainly due to the cost of copper, which has doubled over the past year," explains Neil McNaught, export manager, Polypipe.

"Polybutylene and PEX systems are not rigid... the wall thickness is thinner, so they are more flexible and can bend around corners, reducing the number of fittings and skilled labour needed," adds McNaught. Polypipe offers a general hot and cold water system, Polyplumb in diameters of 10, 15, 22 and 28mm, which has been specified in several projects throughout the region where metal pipes have been used for the main water supply.

Geberit offers a HDPE system as an alternative to cast iron pipes. "Due to its flexibility, resistance to crushing and impact and its lightweight properties, HDPE is ideal for prefabrication, allowing construction to be carried out off site in a safer, controlled environment," explains Guy Wilson, head of Gulf Region, Geberit. "These properties also make the system ideal in real high-rise applications, where the stresses inherent in drainage stacks as buildings get taller have caused lesser materials to crack and systems to leak. HDPE is unbreakable at room temperature and offers excellent impact resistance, which is important at the base of a 50-storey drainage stack," stresses Wilson.

The move to pre-insulation

A further recent development in the market is the rise in use of pre-insulated piping. Here, both metal and plastics pipes are pre-coated with an insulation off-site in factory conditions. This enables reductions in on site installation time and increased health and safety as the insulation period is effectively removed.

The district cooling industry is cited as one of the main reasons for the uptake of this type of product. "People now prefer to build chiller plants away from buildings: in the past local chiller plants were used, but now many developments are using district cooling for air conditioning, so they need to find a way to carry the chilled water to the building [without temperature loss," explains Akkawi.

Pre-insulated pipes are primarily used on underground distribution systems, however the product is now being used for main chilled water distribution lines within buildings, but here the uptake is slower. "Low labour costs in the UAE still make on site application of insulation the common practice within buildings," explains Mitchell.

Pipes can be pre-insulated in various ways, with several firms including Perma-Pipe opting for a spray-on application. The type of pipe used again varies on the application and preference of the project consultant. "For chilled water the two [most in demand] are steel or fibreglass, the third biggest type used is ABS," reports Soren Kjaer, sales manager MENA, Perma-Pipe Middle East. "The biggest problem with steel is that it will corrode and a lot of people are concerned about this, however we have manufactured for 40 years and our experience is that corrosion is not an issue; it will corrode but the rate is very slow," adds Kjaer.

A certain amount of insulation has to be applied on site as the ends of the pre-insulated pipes must be left free to enable joining. To reduce any issues with this, manufacturers offer a range of products that can be added on site. EPPI for example has introduced RayJoint, a tubular product that is positioned over the pipes before they are joined then heat-shrunk to fit after welding is complete.

The future

Ultimately the future of the pipes market will lie with those specifying the products, and it's likely that the various types available will continue to share the marketplace for the foreseeable future. "The point is to be aware of limitations of all specified materials and if mixing materials within a project to be clear as to the application, limiting pipe sizes, working pressures and temperatures for each material," concludes Mitchell.

Pipe types: the pros and cons

Metals

Advantages: High mechanical strength
Suitable for use with high temperatures
Recyclable
Tried and proven welding methods
Good acoustic performance
Low co-efficient of expansion
Non-combustible and don't propogate fire

Disadvantages

Prone to scale build-up
Qualified welders required
High raw materials cost
Low co-efficient of expansion
Heavy

Plastics

Advantages

Corrosion resistant
Lightweight
Low co-efficient of friction
Easy to handle on site
Fast installation time

Disadvantages

High thermal expansion
Shorter life at high temperatures
Lower availability of fittings
Materials are not biodegradable
Welding equipment can be costly
Can emit toxic fumes on burning

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