06. Why are Hydrotest results different using AutoPIPE ASME B31.8 piping code?

	Applies To
	Product(s):	AutoPIPE
	Version(s):	2004, XM, V8i
	Area:	Calculation
	Original Author:	Bentley Technical Support Group
	Date Logged & Current Version	Jan 2015 09.06.01.10

Problem:

I have in the past set up my own load combinations for the Hydrotest case - GR T3 P3 (Functional) and use the Hoop stress values for my reports. This gives me 118.54 MPa. For a change, I thought that I would give the default Hydrotest load case a try and but it gives me a different value of 148.17 MPa. Now when I just do a pure Hoop stress calculation (Pd/2t), it gives me another different result of 134.19 MPa. I am trying to understand why these 3 values are different

Solution:

Please see the following AutoPIPE help section:

Help > Contents> Contents Tab> Reference Information> Code Compliance Calculations> ASME B31.8 Chapter VIII - 2010> for calculations used in AutoPIPE. pay special attention to the hoop stress calculation.

In this case, the Hoop stress hand calculation use Dmean (PDmean/2t) and with the correct values for pressure factor in the Hydrotest load case so all stress values match now.

06. Why are Hydrotest results different using AutoPIPE ASME B31.8 piping code?

Problem:

Solution:

See Also