ASME B31.8 Calculations

[Jman69]

Good Afternoon everyone, I am a quality manager at an ASME Section 8 Vessel shop. We have a job in-house that is a small skid with about 8 pipe spools. The job package hit my department and now its my job to adhere to the Code of construction (B31.8). My question is, Are calculations needed on the pipe spools? If so, what would I refer my engineer to? He seems to think that all he needed to do was run the formula in 841.1. Need some direction

 

[zdas04]

The B31.8 calculation that I would expect is MAWP (section 841). The biggest difficulty I have with using B31.8 on a skid is that once the skid is completed you have no control over where the skid is going, so what location class do you use? I design on-skid piping to B31.3 to avoid that problem.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[BigInch]

The requisition should specify the design factor. Skid mounted equipment should always considered to be DF 0.50, or possibly, but rarely it might be specified as 0.40. Using a DF of 0.50 is roughly equivalent to B31.3 anyway. In any case, the contract or the owner should specify the DF. Check the fabrication specification referenced in the purchase requisition, or contact the engineer. They may not want B31.3

Independent events are seldomly independent.

 

[LittleInch]

If the spools are a decent length with bends and supports then you may need to do a stress analysis to 31.8.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way