Operating Stress Vs. Allowable Stress (SUS & EXP)

Good day.

I have this result for stress analysis of burried preinsulated piping. ASME B313.3 was used.

* Node 3500

OPERATING STRESS - 58,945 psi (NO CODE STRESS CHECKED)

SUSTAINED STRESS - 1,942.1 psi (ALLOWABLE - 20,000 psi)

EXPANSION STRESS - 45,485.8 psi (ALLOWABLE - 48,712 psi)

Now my question is:
How come the OPERATING STRESS is higher than the SUSTAINED & EXPANSION LOAD CASES.

Thanks.

Read the "sticky" topic near the top of tje Forum titled "Allowable stresses", especially the links to other forum topics.