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roof testing - Monday, January 25, 2010 - esam [753]
Single deck external floating roof full fillet welds lap joints was
visually inspected as per point 8.5 and also tested for leakage using
vacuum box as per point 7.3.7.1 b , the weld was accepted according
to the acceptance criteria as per code , during empting of hydro test
water from the tank & during roof was floating on water the floating
roof was sand blasted , the sand blasting disclosed individual rounded
slag inclusions
1.5-2mm diameter in which slag was entrapped & removed due to the
high pressure of sand blasting 7bar , after slag was removed, pores
previously slag entrapped showed evidence of water leakage only after
sand blasting although it passed both visual & vacuum test before sand
blasting and also passed the floatation test before sand blasting ,
please advise
Re: roof testing - Monday, January 25, 2010 - Lawrence [26]
I think you knew the answer. A leak is a leak, so I would fix the leak. This should be be too difficult.
Re: roof testing - Monday, January 25, 2010 - Lawrence [26]I meant to write
I think you knew the answer to your question. A leak is a leak, so I would fix the leak. This should not be too difficult.
Re: roof testing - Monday, January 25, 2010 - karsadi [652]
……..evidence of water leakage only after sand blasting although it passed both visual & vacuum test before sand blasting and also passed the floatation test before sand blasting ,
It means your tank still leakage?
what do you want ? and what about going to repair? whereupon inspected again
before tank operation?
Re: roof testing - Monday, January 25, 2010 - DavidR@Fast.net [39]
Slag should always be removed before testing the welds. I think you should visually inspect every inch of weld, mark all areas with slag and require the contractor to 1 remove the slag, 2 vacuum box test the welds and 3 observe the next flotation test. If this is the only section of weld with slag, Id fix it, test it and move on.
Re: roof testing - Tuesday, January 26, 2010 - JDM [672]
If you know you are going to blast the floater you should at least blast the seams first then test the welds before continuing the blasting.
Since you have already vacuum tested once. I would at least diesel test the roof before putting the tank back in service and before painting.
If you have already repainted the roof then you are stuck with visual testing and possible hydro testing at least high enough to refloat the roof.
Re: roof testing - Tuesday, January 26, 2010 - BABRTs [53]In addition I spray diesel on the bottom side. I have found leaks doing this that were missed by visual and vacuum.
I do this before the hydro as it seems the pressure of the water on the bottom can push the diesel. However, it is just a roof. If you find a leak, repair it.
Re: roof testing - Tuesday, January 26, 2010 - CNT [492]Not that you need any more, but Ill add in my voice. Unless you want to figure out how to tell your boss why the floating roof sank 3 months after being put into service, you need to reinspect all of the welds. Visual, Vacuum, and maybe even diesel test. Then repair anything that shows up as a leak and anything that you just dont like the look of. Then test those repairs.
In my opinion, this should all be on the contractor to pay for, but even if you have to split the cost or pay for it all on your side, it will be a lot cheaper doing that now than taking the tank out of service to repair a leaking roof or much worse a sunken roof.
Re: roof testing - Tuesday, January 26, 2010 - Tankee [235]One more possibly unnecessary comment. If you found these slag remnants and leaks on the center deck portion of the EFR I would be very, very suspicious of the pontoons where even worse welding could be hidden from obvious view.
