API 650 Bottom plate testing

[ahorita]

I need to Know if it is necessary to re do hydro test after repairing a weld where water leaked during the hydro test.
Is it possible to apply vacuum test in the affected area as defined by chapter 7 point 7.3.3 instead of the hydro test.

 

[IFRs]

Since the hydro is primarily to test the shell, I would not think a repeat hydro is required after bottom repairs as long as the bottom repairs pass per 7.3.3 (which should have been the way the bottom was originally tested). Were the bottom seams lap type tested per 7.3.3?

 

[DSB123]

Doing a vacuum test ensures the weld is leak tight for the vacuum it does not subject the weld to the static head and hence the pressure loading. What if the original failure was due to flexing of the base due to poor sub-surface preparation. Doing a Vacuum test will not guarantee when you fill the tank again that the loading will not cause a weld fracture. Are you willing to chance the next fill to be the Product?

 

[Duwe6]

Typically, if the leak(s) have been easily identified by Vac-Boxing, the Inspector will only require a Vac-Box or Dye Penetrant (PT) test of the repair(s). On the other hand, if the leaks were of an 'odd' nature and not easily identified weld defects, or were difficult to locate, the next thing I would do is to PT the welds on the entire floor, and the corner-weld to the shell. Using water-washable dye and a wet-vac to pick up the mess, this can be done in one day.

Last resort is a rehydro. That test is, as IFRS said, to stress-test the shell. It shouldn't be required to find floor flaws. Did you witness the initial vac-boxing of floor?* It is time-consuming and is brutally hard work. Portions of the floor may have been missed.

* It is hard to expect 100% coverage if we are unwilling to participate, or witness testing.