WHICH PRESSURE??

[B.Beykaee]

IN B31.3, FOR WALL THK. CALCULATION, DESIGN PRESSURE IS USED.
THE QUESTION IS WHY THE PIPE RESIST AGAINST TEST PRESSURE WHICH IS AT LEAST 1.5 X DESIGN PRESSURE.
FOR EXAMPLE , NOW I HAVE A REQUISITION FOR A 24" STRAIGHT PIPE WITH THESE SPECS:
1-DESIGN PRESSURE =28 BARG
2-DESIGN TEMPERATURE= 300 C
**3- TEST PRESSURE = 56.7 BARG
FOR THK. CALCULATION, WHICH PRESSURE WILL BE USED? AND WHY?

 

[XL83NL]

Next time leave caps lock off .
The design pressure is used for determining the wall thickness. The design margin on yield in the stress allowances makes that the pipe won’t go over yield during hydro. There is however usually a provision in the design codes for not going beyond 90% yield during hydro, which under certain circumstances might happen. That is however for gross plastic deformation: local, small yielding (E.g. in welds) is not considered an issue and can be beneficial under most circumstances.

Huub
- You never get what you expect, you only get what you inspect.

 

[LittleInch]

You have a higher design pressure at ambient temperature to take account of the high design temp.

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