Vessels, Hydrotest Pressure and Design Pressure

Because the allowable stress in design is lower than the yield/tensile according to the allowable stress basis.

(and why are you still referencing an old edition of ASME VIII Div 2 and not the completely rewritten 2007 (2008a Addenda)?)

(and why are you still referencing an old edition of ASME VIII Div 2 and not the completely rewritten 2007 (2008a Addenda)?)

Kinda new to the business of engineering, are you?

Many of us have worked on plants and equipment that are repaired, modified, expanded, inspected, and tested under the design code in use during initial construction.

Actually in some cases work done under a later code year would be considered uninsurable, unless every piece in the plant was brought up to the current code year.

It would be a nightmare for both owners and insuring bodies of these pressure vessels to even consider this scenario.

Fair enough.

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Kinda new to the business of engineering, are you?

No.

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I have just gotten impatient with the incessant questions regarding a project paper, and which I believe is a hypothetical design; where I don't see the value in writing a paper on a design that will be obsolete in a couple months.

Perhaps I was a little terse and/or assumed wrongly.

In either case, (rhetorical question to self) why even bother replying to something that frustrates me?

I am guessing that you replied as guest and that made me think you were more college attendee than a skilled professional.

So, hats off to you, but sometimes even us greybeards need to ask a simple question also.

Yeah, I bounce around between a fair number of computers, and fail/neglect/forget to log-in sometimes. I think it causes a bit of confusion - I should really be more attentive.

Cheers.

Safety factor.

For this reason, in any design calculations, the design code states checking of the stresses at many situations of loadings and/or combined loadings. And hydrotest is one situation which is essential to check the stresses at many locations of vessel, especially at mid-span and at saddles, and in no way the calculated stresses to be more than the allowed by the code.

On new vessels and large alterations only would I do a 1.5 hydro test. On repairs it is left up to the A.I. in charge but most will never require a 1.5 test pressure or on the other hand require less pressure than operating pressure for the test. We use to have 3 very old power boilers where I work that seemed to blow generating and super heat tubes routinely . We always did an 850 hydro test after we plugged a leaking tube until we got a new boiler superintendent and he insisted that we hydro at 1-1/2 times operating pressure. His idea was that we would find weak spots and eliminate bad tubes before they failed and he really did think that a 1.5 hydro pressure was required by the NBIC. If you ever met this guy would could see why he thought this. All he knew was what he learned (or was told) way back and was hard headed enough that no one could make him believe different. Not even the authorized inspector could change his mind on this. For about a year when we would repair these old boilers we would put the 1.5 pressure hydro test on them and then we would proceed to chase leaks for sometimes days before we would get a "dry" hydro test. It didn't take long before we had reduced the capacity of the boilers significantly. Finally the upper management realized that he had ruined the old boilers and decided to retire them after they fired the old man. My point here is that although a 1.5 hydro test pressure is required on new vessels/boilers and on some alterations one should use common since on older vessels/boilers that have lost some of their "safety factor" over the years. Ultimately it should be up to the AI to decide what the test pressure should be and most will take the age of the vessel into consideration but under no circumstances should you test a vessel/boiler at less than normal operating pressure. IMO