Problem:

When including Temperature (T3 = 400 deg C) in the Hydrotest load combination, the stresses are massive. Without it they are tiny. Why?

Example:

Hydrotest Load-case with No Thermal

Hydrotest Load-case with Thermal

Why are the Code combination results for Hydrotest load-case with Thermal added so much more than when Thermal was not considered?

Solution:

From AutoPIPE help on Hydrotest:

Perform a Test to simulate this load combination:

Step #1. Changed all spring hangers to v-stops.

Step #2. Set T3 to 500 C ( 400 x 1.25).

Step #3. Set P3 1.25 N/mm2 (1 x1.25).

Step #4. Crete a new code stress combination, GT3P3.

Step #5. Analyze the model and review the results.

Note, Similar results, both very extreme because of the rigid restraints and thermal growth.