API 650 Drawoff Sumps
API 650 Drawoff Sumps
(OP)
Can anyone tell me or hypothesize as to what is the controlling factor for the location of drawoff sumps relative to the tank shell per API 650? I have a client who wants to use a 6" draw line with only a 24" diameter sump, and after unsuccessfully trying to convince them to use a larger sump I specified that the sump be located 8'6" away from the tank shell in accordance with table 3-16 for a 6" line. Any thoughts? I think that it may be to avoid the sump being pulled up by the suction of the draw line which would potentially induce a bending stress on the bottom to shell connection. I think that this combination of draw line and sump size would increase the probability of this happening. Am I even remotely on the right track? Thanks in advance.





RE: API 650 Drawoff Sumps
You do develop some hoop stress in the outer part of the floor plate, and I assume you want to hold some minimum clearance on that account. And on a tank with seismic (or wind) uplift that depends on the product weight to help hold it down, you're assume that a certain part of the floor can lift to develop that force. You'd want to maintain weld clearances. Those are the only reasons I can think of for limiting how close the sump is to the shell.
RE: API 650 Drawoff Sumps