Alternate to static hydrotesting of API tanks
Alternate to static hydrotesting of API tanks
(OP)
Although I have designed and purchased storage tanks on and off since 1998, I have not heard of the possiblity of not doing a static hydro test as the final leak testing of a NEW tank. In the last 2 years, I have seen odd specification to perform fracture mechanics analysis to determine critical surface flaw size per API579 in lieu of hydrotesting. I can buy into doing this for existing tanks but I cannot accept this as a replacement for hydrotesting.
Can someone enlighten me on this issue? Is this acceptable alternative to the API650? How is this done? Is this done often now?
Thanks.
Can someone enlighten me on this issue? Is this acceptable alternative to the API650? How is this done? Is this done often now?
Thanks.





RE: Alternate to static hydrotesting of API tanks
Frankly, I don't see how anyone would use this approach (API 579 FFS) for substituting a hydrostatic test for a new construction tank. After all, the purpose of a hydrostatic test is twofold - check for leaks from workmanship and to assure structural integrity. In other words, the tank will hold the specified fluid without collapse.
Using your alternative approach, what would fracture mechanics provide? It would only provide the maximum flaw that could be tolerated without unstable crack growth (aka brittle fracture). You can still have a gross defect or subsequent leak caused by poor workmanship regardless of using fracture mechanics analysis.
So, my point is this, hydrostatic testing is required for a new vessel fabricated under API 650. One alternative that I could possibly entertain in lieu of hydrostatic testing is comprehensive NDT of all shell and floor plate long seam and girth welds.
RE: Alternate to static hydrotesting of API tanks
I totally agree with what you said. My thinking is exactly the same as yours. I too don't see this as a alternate specified in API650. What troubles me is I've seen this "alternate" in a company spec requesting this "to be considered".
I would like to know if this is something that is being used on recent projects.
RE: Alternate to static hydrotesting of API tanks
RE: Alternate to static hydrotesting of API tanks
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I see no way to exempt a newly constructed tank from a hydrotest The last two large tanks, a SS and a CS, I was involved with both had several leaks. The SS had 2 leaks on the T-joint due lack of fusion on a poorly prepared joint.
RE: Alternate to static hydrotesting of API tanks
RE: Alternate to static hydrotesting of API tanks
I took a quick look at the paper you linked to and it is a discussion of API579. It is plausible to use that as an alternative for hydrotest for repair in an existing tank, but I don't see how someone could possibly think it can be stretched to use it as an alternative for a NEW tank.
Anyhow, I'm convinced that I cannot accept the proposal in the specs that I'm reviewing. Thanks.
RE: Alternate to static hydrotesting of API tanks
I should have stated that the misinformation probably came from an article such as this. In today's environment there is no way I would accept a site built tank without the proper hydro. If I was forced to my objections would be covered all walls at the site and probably a little graffiti on the tank.
As I stated in my previous post the last two tanks I was involved with both leaked.
RE: Alternate to static hydrotesting of API tanks
For API 650 tanks, the hydrostatic test if for control of foundation too.
Regards
r6155
RE: Alternate to static hydrotesting of API tanks
RE: Alternate to static hydrotesting of API tanks
In our case we had we had a in process product that had a SG of 1.34. We designed the whole tank for the fill line pressure and to test we added a standpipe to the center vapor nozzle.
RE: Alternate to static hydrotesting of API tanks
I would be confortable with this for large shop built tanks (>1000 BBL). I have also seen it done on tanks as large as (40' dia x 60' high). Sometimes a clean source of water isn't availible for a hydrotest and other options need to be looked at.