Process Piping: Polymers Versus Stainless Steel

choice for pharmaceutical industry process systems. Its high mechanical strength and low coefficient of thermal expansion allow components to be sterilised or sanitised using various mediums and at high temperatures. Concerns about stainless steel systems – such as rouging in high purity water, metallic ion contamination and inner surface finishes – which require post-installation maintenance are often tolerated because of advantages such as durability in long-term use and validation. Chemical passivation is frequently required to remove free ions from the surface and restore the oxide film that gives stainless steel its corrosion resistance (1). The orbital welding techniques utilised with stainless steel piping systems are of particular concern, and can cause rough surfaces that commonly need to be inspected by an outside agency using boroscope technology.