tell tale holes
tell tale holes
(OP)
Tell tell holes in vessel flange reinforcements are usually 1/4" threaded. What is maximum pneumatic pressure that can be applied?
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RE: tell tale holes
I presume you are referring to reinforcing pads on shells at nozzles. A couple of psi should be enough for a bubble test. The pad is not intended to be a pressure retaining part; Don't overdo the test. The pad exists to provide local strength and rigidity.
See also Thread794-25516 and Thread292-97314
jt
RE: tell tale holes
For small nozzles and heavy wall thicknesses, allowable pressure will usually be higher than you'd want to test at anyway. But for an atmospheric tank, you could have a 36" manway in a 3/16" shell, and pressure there is limited by strength of the plates.
Usually no more than 2-5 PSI should suffice. No reason to use any more pressure there than the vacuum you use in a vacuum box.
RE: tell tale holes
In my experience, you'll frequently be limited not by the plate thickness (unless you have narrow repads) but by the fillet welds at the outer edge. These welds by definition cannot be as strong as the plate, and with the pressure induced deformation of the plate will see not only shear but also bending.
jt
RE: tell tale holes
For pressure vessels the same pressure is usually applied to the repad.
And: don't plug the holes after the test.
Putting Human Factor Back in Engineering
RE: tell tale holes
RE: tell tale holes
But it never hurts to be vigilant when testing flimsy equipment.
Putting Human Factor Back in Engineering
RE: tell tale holes
RE: tell tale holes
3/16" shell- good up through 14" nozzle
1/4 shell- good up through 20" nozzle
5/16" shell- good up through 24" nozzle
3/8" shell- good up through 30" nozzle
1/2" shell- good up through 42" nozzle
5/8" shell- good up through 48" nozzle
If the tank diameter is fairly small, this will be overly conservative, but I know of no better analysis. For larger diameters (ie, field erected tanks), these numbers should be reasonable estimates. Normally, you don't have huge nozzles on thin walls, so the most likely problem area is shell manways.
RE: tell tale holes
The only reason the API 650 was brought up as a reference was because I could not find the requirement in pressure vessel code.
What are we talking about? Atmosheric pressure not more.
Putting Human Factor Back in Engineering