I have some doubt about the code?
Has B 31.3 included hydro test stress as code stress? Or it is just for checking for extreamly high test pressure? Is there any criteria to justify this?
regards,
Pw

Stress analysis of a piping system in hydrotest case is not for stress check, its to find out loads on pipe supports and connected equipments nozzles hydrotested alongwith the pipe.
Regards,

This test have a higher weight in pipe ands loads in the restraint.
Also higher stress in pipe from pressure and weight.
p(test) is normaly 1,3 times p(design).
This load Case hav a special stress limit.

According to ASME B31.3, the test pressure should be

PT= 1.5 x ST/S


where
PT = test pressure
ST = allowable stress @ test temperature
S = allowable stress @ design temperature

This ratio shall fulfill 1 <= ST/S < 6.5.

In Europe, in accordance with the pressure equipment directive, PT = max of 1.43xPD or 1.25 x ST/SxPD.

with PD = design pressure

A sufficient supported system that passed the sustained stress check will normally not show overstressed nodes during hydrotest. Of course the restraint loads are often higher than in any of the operating cases and must be taken into account when designing the related civil structures.

All the best,
Veit Bockemühl

www.esn-gmbh.com
www.surgeanalysis.com

Mein Herren Bockemühl,

One thing that has not been clarified so far in the discussion is what part the weight of the testing fluid plays in this sytems evaluation. That is a large diameter relatively thin walled pipe filled with a near weightless vapor may pass the B31.3 code sustained stresses yet be overstressed (what is the overstressed numeric??? 1.0Sy at temp?)for a hydrotest.

If this is the case this should be adressed early in the design process. Some solutions for this might be.... 1)added temporary hydrotest only supports or 2)design the system for the fluids weight.

However B31.3 does not specifically adress what the hydrotests sustained stress maximums should be.... (hmm maybe at the next B31.3 meeting I'll add this to our discussion??? (I'll probably get stuck with doing something))

Thanks for all input, the reason I asked because now CAESAR II in hydro test case if you input hydro test pressure it report stress for hydro and also have "code stress check passed" My most update B31.3 is 2002 so not quite sure if it is required.
So basically we refering to para 345 only if the test pressure reduction is needed. And it is acceptable if stress limit is not over yield. I understand that CAESAR II use .9 yield as allowance. But still as code stress is not required to be checked. Correct me if I'm wrong.
best regards,
pw

B31.1 requires hoop test pressure stress check, longitidinal sustained stress from test fluid check, pipe support check with test fluid and transmittal of test loads to structure.
It also requires temporary supports to meet stress as required.
The limits are; 90% yield for hoop and longitidunal stress and 80% yield for supports.

Lou,

Yes you are correct; however B31.3 is the code in question, which does not have a lot to say about it. I'm not sure what CAESAR II's Hydrotest case follows. A brief comparison and citation of each code follows…..


The 2004 ASME B31.1 ref paras are...
101.6 Weight Effects

101.6.3 Test or Cleaning Fluid Load

102.2.4 (B) Allowances for Variation from Normal Operation

102.3.3 Limits of Calculated stresses due to an Occasional Load
102.3.3 (B) During test….
137.2.2 Addition of temporary supports

The 2002 AMSE B31.3 para are…
302.2.6 Limits of Calculated Stresses due to Occasional Loads…
302.2.6(b) Test… Which specifically mentions testing and then states “Stresses due to test are not subject to the limitations in para 302.3…. etc.”
345.5.3.2 Temporary Supports
345.4.2 Test Pressure (up to a maximum hoop of Sy at test temperature)

So B31.3 is silent but if it falls down or splits and you’re the designer you’ll be getting the phone call so use your head!

Dear Mr. Luf,

Of course you are right. These line were not included what I meant with 'normal system', sorry. But those vapour lines you described are often pneumatic tested only, otherwise you have to design massive steel structures for the hydro test only.

Best Regards,
Veit Bockemühl

www.esn-gmbh.com
www.surgeanalysis.com