Hi raab,

Unfortunately for plastic piping same as FRP and GRE Pipes, the material properties varies from Vendor to Vendor, so the recommendation of Michael to get the material properties from your Vendor is advisable. If you're working in EPC company the best work around is to coordinate with your material engineer and procurement people. What I usually do is request our material engineer to include in their requisition the stress analysis and support design of plastic piping. If cost permits, this will be the best way to execute it. You just need to cater man hour on your side to review their stress report. I have done this in one of my project around 2 years ago. The experience I had where I have done a lot of digging information is where I cannot convince the management to give the stress analysis to Vendor so the minimum I ask them is to request from Vendor their catalogue that includes guidelines for stress analysis.

Dave is also correct, ASME B31.3 does not address flexibility calculation of plastic piping. So as a stress engineer your on your own to decide what to do, so the approach that I've done is to use Vendor guidelines for stress analysis (loop sizing, support span, support design guidelines, etc.). I only used the software whenever I have some sensitive equipment to extract forces and moments for comparison purposes. I tweak some numbers and come up with some allowable stress and unofficially put it so that I have something in my stress report where it shows pass, since officially it's not a Code requirement. The official is from Vendor guideline which I recommend to request to your vendor thru your material engineer. In this case, you avoid assuming something which at later stage the official vendor may give different numbers.

You can do it.

Cheers!!!