Hydrostatic testing of pressure vessels
Hydrostatic testing of pressure vessels
(OP)
What is the real reason for the hydrostatic testing of pressure vessels used in industry. Is it:
1)To Validate the design calculations?
2) To ensure that there is sufficient safety margin in the design?
3)To redistribute the stresses induced into the vessel/structure during the manufacturing process?
Should industry continue with this practice and waste time, money and resource or are there better ways to ensure the integrity of vessels and structures.
1)To Validate the design calculations?
2) To ensure that there is sufficient safety margin in the design?
3)To redistribute the stresses induced into the vessel/structure during the manufacturing process?
Should industry continue with this practice and waste time, money and resource or are there better ways to ensure the integrity of vessels and structures.





RE: Hydrostatic testing of pressure vessels
Normally, it wouldn't validate the design calculations unless the calculations were off by a factor of 3 or so. And it doesn't show the safety margin, exactly- it could be underdesigned and still pass the hydrotest. Redistribution of stresses, if any, I would consider an added benefit, rather than the reason for the test.
Would you go out to the airport, and get on a jet that had never been flown before, because someone's calculations showed that it ought to fly?
RE: Hydrostatic testing of pressure vessels
Over the last 30 years I have probably witnessed pressure tests of 100,000+ vessels. 99.99% have been fine,but there have been several failures. These failures were unkown defects of material or workmanship.
If it saved ONE life it was all worth it!!!!!
RE: Hydrostatic testing of pressure vessels
As you listed above, hydrostatic testing was intended to verify the design of the component (in other words will wall thickness and geometry sustain actual pressure in service) and to look for gross defects or flaws in material used to fabricate the component.
Over the years, as hydrostatic testing evolved, other benefits were discovered like local yielding of material at stress risers or inherent fabrication flaws. The local stress redistribution during a hydrostatic test can result in decreased risk of crack initiation and propagation after the component is placed into service.
Should industry continue with this practice? For new boiler and pressure vessels this is a must, and will probably never be removed. Hydrostatic testing is a means of assuring structural integrity of materials used to fabricate a new pressure retaining item. At this point, we are not using hydrostatic testing to prove previous designs, it is used to assure no gross defects or workmanship. Safety comes first.
RE: Hydrostatic testing of pressure vessels
Nope, Mr. MBA, your superior intelect has finally discovered our secret....us wacky mechanicals insist on hydrotesting pressure vessels and other equipment simply to waste time, materials and resources. All of this time, the worldwide engineering profession has been trying to fool people like you........but you figured us out !!!
You state:
"Should industry continue with this practice and waste time, money and resource or are there better ways to ensure the integrity of vessels and structures ?"
Sure, there is a much better way to ensure pressure vessel integrity.....through the use of lawyers and punative lawsuits. Have you seen these links ?
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In fact, I believe that any PE who is arrogant enough to seal a pressure vessel calculation or drawing recommend hydrotesting should be flogged in public to within an inch of his life...
MJC
RE: Hydrostatic testing of pressure vessels
RE: Hydrostatic testing of pressure vessels
the engineers think it's to test their design,
but the REAL reason is per Mr. METENGR:
to yield local highly stressed regions so that they go into compression & are preloaded under normal operating pressure.
That way they never cause a fatigue problem or crack in service.
RE: Hydrostatic testing of pressure vessels
Good points. I'll point out a minor issue, though. You say that "The ASME Boiler and Pressure Vessel code uses a design by analysis approach."
In fact, this is only partially true. For Section VIII, Division 1 is considered to be a "design by rule" code while Division 2 (and Section III) is considered to be a "design by analysis" code. The new Div 2 will apparently emphasize that even more.
jt