High temperature pipework

Published:  12 April, 2007

Q:

Our systems need to convey extremely aggressive chemicals at temperatures up to 50°C, what is the best pipework system to use and how long will it last?

A:

The most suitable pipework material will depend on the specific chemical that will be transported and the working pressure. Thermoplastic pipework systems offer the benefit of being corrosion free, which is a crucial element when conveying chemicals. This makes plastics a superior choice to metallic alternatives, which can be prone to corrosion, resulting in process leaks, flow restrictions and ultimately premature failure.

There are several different plastic materials that cater for different applications. For this request, there are three materials that could match the requirements: PVC-U has become the established material for process chemicals and industrial fluid handling as it is resistant to many concentrated chemicals up to 60°C including acids and alkalis, aliphatic hydrocarbons and saline solutions. PVC-C (Corzan) is ideal for conveying corrosive substances as it offers excellent performance in highly aggressive conditions and has the ability to convey chemicals, under pressure, up to temperatures of 95°C. Polypropylene has greater resistance to aggressive acids and alkalis and its main benefit over other materials is its ability to transport chemicals up to 100°C.

In terms of how long the system will last, as long as the pipework material is fully resistant to the chemical, it is mainly the line pressure that determines the service life. At 50°C thermoplastic systems will have a maximum operating pressure capability in the region of 4 bar and an average life span of 50 years.

Manufacturers should always be contacted before specifying any pipework system, to ensure that the material can safely transport the fluid and the most appropriate system for the specific application requirements is selected.