I am getting a little confuse durin 1

[UT777]

I am getting a little confuse during the stress analysis of a gas line (my first experience of stress analysis) with ASTM A-106 gr. B pipe. We know that allowable stress for A-106 Gr. B pipe is 20000 psi as per Table A-1 of B31.3. But in report it is showing that allowable stress is 35000 psi for hydro-static load case WW+HP (circled red in below image). Why is it so? Is there any clause in ASME B31.3 regarding this? Can anyone clarify this? Any reference will be appreciated. Thanks in advance.

 

[LittleInch]

You could look at 345.2.1 a) where if test pressure would exceed yield then you reduce the test pressure.

Clearly a test pressure of 1.5 x design pressure will result in a stress greater than the allowable stress, which is itself either 2/3 of yield or 1/3 of UTS, whichever is lower.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DSB123]

UT777,
It would seem you are a little out of your depth and perhaps should not be stress analysing the GAS pipe if you are:
1. unsure about the allowable stress for a hydrotest.
2. do not know of the applicable Code requirements.

How do you know that the model you have does not have errors in it. Think you should either:
a. Employ someone who knows the Code requireemnts or
b. Seek out a mentor in your organisation who can advise you.

 

[UT777]

Dear DSB123,

I really appreciate for your concern. As far as the model is concern I am sure that it is flawless. I have some reports on stress analysis of different pipe systems, which we outsourced earlier. Same are the values there in case of hydro-test.
As I have mentioned earlier that i am in learning stage, and also going through the code study. The purpose of my this thread was to get some guidance from experienced and professional like you who can enlighten me on this and refer me to the respective para in B31.3.

Hope to get some encouraging and informative response from your side.

Thanks in advance.