DESIGN

I don't design for a living, so my apologies if this seems like a basic question. I'm trying to determine the first step in design, and it seems to me that the desired operating pressure has to be known before anything else. In looking at the ASME section 1 formula for wall thickness, the two key unknowns are the material and the pressure. If you use 200 psi in the formula with a certain material, then this is the MAWP.

The other question is: Is there an acceptable means to work backward to determine the MAWP? In other words, if MAWP is not known, is it acceptable to rate a pipe at say 200 psi if it has a successful hydrostatic test at 300 psi? By the book it doesn't seem proper to me to work backward, but if there is no documentation or marking on the pipe how is the safe operating pressure determined?

Thank you. Received on Tue Mar 18 07:38:00 2003