Nominal Bore Pipe

ASK NDE’s TECHNICAL EXPERTS

NDE’s technical team receives enquiries on a daily basis that require input from a stainless steel specialist.

Below is one of the questions that we received this month together with the response from our technical experts.

QandA

     

 

 

Q: What is your opinion on the use of stainless steel grades 304 vs 316 for hot water piping?
      Is there a concern about pitting corrosion for 316?
      This is for a food company where they are circulating hot water to heaters on their pasta lines
      They currently have carbon steel pipes which have corroded and they need to replace them.
      The system pressure and temperature is up to 6 bar (g) and 165° C.
      The water is municipal potable water that is generally of good quality.

 A: Unfortunately there is a problem with both 304L and 316L at these temperatures as they can suffer from stress
      corrosion cracking (SCC).
      As an example, they cannot be used for hot water geysers at 65° C.
      We advise the use of a stainless steel Duplex pipe which is SCC resistant.
      The most readily available is 2205, a Duplex stainless steel which is not only SCC resistant but also has better resistance to pitting corrosion than 316L.