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How To Choose The Right Pipework Material And Jointing Method

Choosing the correct material for your piping requirements is not the only difficult decision you will make when installing a new system. The method you use to connect your pipework can also have a critical influence on the cost, longevity and environmental impact of your project. Naturally, change is important in any industry and new pipework materials and jointing methods have recently been developed which offer new benefits, but of course, are only suitable for certain applications and conditions. Therefore, tried and trusted methods and materials remain very popular and getting this combination right is the key to installing a system that works for you.

Pipework types

There are five popular pipework materials for water, refrigeration/air conditioning and heating systems:

Soft copper – Also known as ductile copper tubing, this is a material that can be bent easily around corners and obstacles. The work hardening and annealing process required to make this tubing soft and workable also means it is more expensive, but it is very popular to use for the refrigerant lines in air conditioning systems and heat pumps.

Rigid copper – As the name suggests, this type of tubing is rigid, bought in lengths of 3 or 6 meters. Although can be bent with special tools it is usually fitted using pre formed elbow fittings and tees to go around corners and obstacles. This means it is slightly more labour intensive to install, but it can be joined by various different methods, so it remains very practical and popular, particularly for water lines.

Mild steel – A very traditional pipework material used for many years in closed-circuit heating, chilled water, sprinkler, solar heating and compressed air systems. Typically, steel pipework has to be joined by screw connections or by welding, both of which can add labour costs, particularly as this type of pipework is heavy and has been superseded by more practical materials.

Carbon steel – The modern improvement on mild steel is carbon steel, which is up to 50% lighter, so installation is easier and this material also offers cost and environmental benefits, particularly for largescale projects where a lot of pipework is required. Furthermore, carbon steel pipework has corrosion resistance qualities which considerably increases its lifespan and effectiveness in closed heating and chilled water systems. However, this only applies if specific manufacturer guidance is followed in terms of storage, handling, installation and commissioning, in order to keep oxygen out and therefore ensure corrosion-resistance. Carbon steel is not recommended for systems where exposure to the elements is likely, hence its suitability for closed circuit systems.

PVC – Plastic pipework is extremely versatile for HVAC applications, but it has its limits. PVC is durable and easy to install, it has good corrosion resistance qualities and is a better insulating material than metal pipework, so is good for both heating and cooling applications. However, there is a limit to how hot, water can be before PVC pipework can become affected. Also, if used extensively in large buildings the cost can add up, although this needs to be factored into long term savings in maintenance and energy efficiency.

Jointing types

Again, there are traditional methods of jointing pipework and also more modern applications which offer cost benefits but are not necessarily suitable for all pipework materials.

Flare connections – A labour-intensive but very reliable method of jointing, which uses a flare tool to open up a tube end into a bell shape so that a male fitting can be joined using a flare nut. Due to the working of the material required using this method, it is only suitable for soft copper pipework.

Soldered/sweat connections – Suitable for both soft and rigid copper pipework, soldered joints are smooth, attractive, strong and long-lasting. Modern building construction still tends to use solder-connected rigid copper for its water supply lines, and other plumbing systems in new buildings also prefer soldered joints as they are much quicker and more cost-effective where many joint connections are being made.

Compression connections – These are formed using a basic compression nut, which squeezes a soft metal or thermoplastic ring onto the pipe to form a join. The seal is quite easy to make but is typically more labour-intensive than forming a solder connection. Also, the seal may need re-tightening over time to stop leaks, and therefore does not have the lifespan of other jointing methods. Compression jointing is still quite popular, however, with both soft and rigid copper.

Crimped/pressed connections – This connection method is quick and simple, using special copper fittings containing sealant, which are deformed using pressure to form a seal on the piping. Popular with soft and rigid copper and carbon steel, this is a long-lasting and very robust jointing solution. The corrosion resistance of carbon steel is greatly enhanced by using pressing connections as they provide a fail-safe leak-testing guarantee, so this method is increasingly popular in modern buildings with newly-installed closed-circuit systems.

Fuse seals – These can be used for plastic pipework whereby a tool heats a fitting and the pipework and creates a seal when pushed together like a butt weld. It can be a difficult technique to master, but is durable and reliable.

Mechanical jointing – Mainly used in plastic pipework, a coupling or sleeve fitting is inserted over one end of the pipework and clamps the two separate pieces of pipework together, as a push-fit application, which provides a good, long-lasting seal and is very low maintenance.

We recommend you take advice before deciding on pipework and jointing requirements as this can considerably influence the cost and lead-time of an installation. At Robinsons we have a team of experienced engineers who can advise on solutions to suit your systems.

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