The rules for determining the test pressure for a hydrostatic test include a temperature correction factor, ensuring that a proper amount of stress is imposed on the cold piping. The rules for a pneumatic test dictate that test pressure shall be 110% of the design pressure. For "hot design" piping, this rule would yield a non-conservative strength test due to the lack of temperature factor. Does anyone have any insight as to why the rules are stated in this way?

I would say the answer is in 345.5.1 first sentence. Bases for the pneumatic test is different. Pneumatic test is basically a leak test. See 345.5.5. You do not want to have any change that the system blows up.

If you have ever seen an outcome of a pipe or vessel failure under pneumatic test then you understand.

I have some concerns about Hydrotest and leak test as below:

1. For Hydrotest, we set up in basic load case like this : W+HP , Stress Type is "HYD" and Hanger Stiffness is "Regid"

I have seen some calculation reports that's different from above like: W+HP, Stress Type is "SUS" and Hanger Stiffness is "As Design"

My question is how's different between these?

2.In stead of Hydrotest, we use leak test on our system.
Could you please tell me how to make this test?
-Is this possible to set up load case W+P2, Stress Type is "SUS" and Hanger Stiffness is "As Design" with P2 is test pressure ( 110% Design pressure P1)?