Galvanised steel & copper piping
For many years, copper and galvanised steel have been popular choices for plumbing compressed air systems.
However, recent advances in materials technology have made thermoplastic pipe a safe and economical alternative to traditional materials.
An advantage of metal pipe, tubing, and fittings is that installers are familiar with them and the techniques for joining them. While galvanised steel can be relatively inexpensive, installation is time consuming and labour intensive. Moreover, threaded joints often serve as a source of leakage. This leads to higher operating costs as compressors must use more power generating additional compressed air to compensate for the leakage. Although connections between copper pipe and fittings are less prone to leakage, copper components are more expensive, and installation, again, is labour intensive especially when large diameters are involved.
But these aren't the only drawbacks to metal piping systems. Interior corrosion can cause scaling and pitting on inside surfaces. As the corrosion combines with moisture and other contaminants, it accumulates on the inner surfaces of the pipe and fittings, increasing their roughness. As the internal diameter becomes rougher, pressure drop though the system increases. Again, this ends up costing money by reducing efficiency of the compressed air system.
Perhaps more importantly, particles can dislodge and clog or damage filtration and end-of-line equipment.
Because of their drawbacks, compressed air system users have been seeking alternatives to traditional metal pipe and tubing. Over the past ten years, industrial plastics have been developed that present an attractive alternative to metal piping.
PVC piping is relatively inexpensive, easy to install, lightweight, and corrosion resistant. However, PVC has one major drawback, it is brittle. An inadvertent impact could cause the piping to shatter, endangering surrounding personnel. For example, many PVC pipe manufacturers warn against using PVC for compressed air service due to potential liability from such failures. In the USA, the Plastic Piping Institute, in their Recommendation B, states that plastic piping used for compressed air transport in above-ground systems should be protected in shatter-proof encasements, unless otherwise recommended by the manufacturer.
Furthermore, in many states, the Occupational Health and Safety Administration (OSHA) has stepped in and regulated against using brittle plastics such as PVC in these applications, and additional states are following suit.