API 650 section 5.4.2

[sme75]

Can anyone provide some background on the requirement of the bottom plate to project a minimum of 2" past the outside of the shell? I earlier editions of API 650 this distance was only required to be 1". Does anyone know the reason for increasing the distance?

 

[IFRs]

I don't believe the distance has been increased. See API 650 5.4.2 and 5.1.5.7 d.

 

[JStephen]

10th Edition, Addendum 3 shows 1" there, Addendum 4 shows 2". So that's when it changed. I don't know why.

 

[IFRs]

One difference is that later editions say 2" past the tank shell, while earlier editions say 1" past the toe of the weld. I'm not sure why the change was made.

 

[JoeTank]

The change was made to simply make the chime requirements for annular plates (2" beyond the shell plate) and sketch plates the same (1" beyond the weld toe). There was no tehnical reason for two differing criteria. Two inches is now used for all.

Joe Tank