MAS values Part 2D for used vessels 1

[FDiazM]

Hi guys, I desire to calculate the minimum wall thickness of a used pressure vessel. In order to do this, I must use stress value for new materials given in part 2D?

Thanks for your time

 

[jte]

FDiazM-

You have a used pressure vessel which doesn't have a U form which states the allowable corrosion allowance? So now you're in either fitness-for-service or rerate city. Depending on your jurisdiction and insurance carrier, you can take two approaches:

First (essentially the rerate approach), you will essentially duplicate the original fabrication calc's. Use the allowable stress which was applicable at the time the vessel was fabricated. Use the proper value for E also based on the level of RT involved. Oh, wait, you don't have the U form to give you that... Does the nameplate indicate any RT? Otherwise you're stuck assuming no RT was performed.

The second approach would be a FFS approach in which case more options open up. You may use current allowables as listed in II-D. At areas remote from welds you may use an efficiency (E) of 1 regardless of RT.

For either approach, don't forget external loadings from piping, ladders and platforms, etc. Also wind and seismic.

jt