What Hydrostatic test pressure may be used to test a 2000bar pressure vessel?

I am not familiar enough with your apps to address some of your finer points. However, when it comes to code. You are to build to current code revisions. It is your responsibility to do so. If you have agreed to, and I quote, "test per code" then you are obligated to do so.

It sounds to me that the client has presented a testing spec that the original bid did not quote to. This is not good for the manufacturer.

So if a drawing says
1.build to ASME Boiler and Pressure vessel code.

2.Test per code.

and no code is given you are to build to current.

If drawing says:
1.Build to PBV code JJJJJJJ (a prior release)

2.Test to code JJJJJJJ (a prior release)

then you build and test to JJJJJJ

Suspect that helps little if any, but more knowledgeable and currently practicing hands are sure to join soon.

regards,

Charles

Mr.Charles, Thanks, your comments are right on to the point at issue. You echoed my own view on the problem. The more general point I wish to ask all in this field, why at all ASME BPV code guys have come up with this 143% overpressure in 2007 while all along it was 125% only? I do not see any logical justification for 143%; of course, for smaller pressures like 10 bar or 50 bar, 1.5 times is specified and acceptable. Its a vastly different when it comes to a high pressures like 2000bar ! And 125% is a sensible and practical limit for the hydrotest. ASME people have unduly complicated this without providing a rider such as "applicable to pressure levels upto 500 bar " or some such thing.

Thanks

2000 bar is 30,000 PSI, is there an error?

Usually static tests are done with water and the tank is filled with care so that there is zero residual air.

Then a test pressure of 143% of the rated pressure is placed and watched for decrese over time. If the tank is sealed it must hold firm.

I am sure you can find a proper test procedure from the national pressure vessel testing facility of your country. If you do not know, ask your insurance company, they know these things

2000 Bars!!!! Wow.

Are you sure ?

And your company landed this contract

From somebody trying to synthesize diamonds?

It is 2000bar, not 2000psi. And synthesis of diamonds requires even much higher pressures - of the order of 6000bar I think.

ASME testing is typically to 125% of rated capacity. This is the standard to which the walls were designed. To go to 143% without damage may require a redesign and re-fabrication, neither of which were in the original specification (I am guessing). While the customer may WANT 143%, what does the contract say? Typically, the default standard is ASME unless some other standard is explicitly stated in the contract. Unless the customer can show you where they said (on some part of the contract or design notes) you had to test to 143% you are under no obligation to do so. Too, the ASME codes are written such that testing over 125% is not recommended and may damage the vessel. If the customer will sign off their approval to accept a vessel damaged by exceeding the recommended test standards, then any guarantees will be null and void. The vessel was likely not designed for the 143% load. Too, there are component design standards that have limits on individual component stresses. Depending on the application these numbers may be as low as 20% of yield. The requested overpressure may violate the design standards and you could refuse to test on that basis.

To: mrhippo2: Thanks. I find your comments useful and relevant. Please note however that the design of the vessel can take overpressure of 143% too, since there is a built-in safety factor of 2 (on YS). But the question is, when the ASME code as recent as 2005 has specified only 125% max. overpressure, why did the Code come up with 143% in the 2007 revision. This is not clear. The code should provide some sensible limit when it is to be applied to pressure vessels rated for 2000bar. And strictly speaking, since the design was based on 2005 revision of the code, the same revision should be applicable for all aspects including the hydrostatic test.

• According to ASME code, Section VIII, Division 2:

AT-301 Hydrostatic Tests Based on Calculated Pressure

A hydrostatic test based on a calculated pressure may be used by agreement between the user and the Manufacturer. The hydrostatic test pressure at the top of the vessel shall be the minimum of the test pressure calculated by multiplying the basis for calculated test pressure for each pressure element by 1.1⁄4 and reducing this value by the hydrostatic head on that element. The basis for this calculated test pressure is the highest permissible internal pressure, as determined by the design formulas, for each element of the vessel using nominal thicknesses, including corrosion allowance, and the allowable stress intensity values given in Subpart 1 of Section II, Part D for the temperature of the test. When this pressure is used, it shall be as set forth in the Design Report.

• I think the design pressure is 2000 psi not 2000 bar, otherwise you have to use ASME code, Section VIII, Division 3.

Perhaps the reason your customer asking for a 143% hydrotest is that they will sell or use this pressue vessel inside the borders of the European Community as the Pressure Equipment Directive 97/23/EG (PED), which requires a 143% hydrotest from the MAWP is applicable on each code used for design calculations.
If this is the reason take care that the NoBo requires also a PMA of the materials use
for construction of this vessel.

Peter

Ahh! Very interesting point.

Were I the receiving party, for a vessel at this high pressure, I would have insisted on full certifications on all materials, weld procedures, welder qualifications,etc. An air receiver at this pressure level is a very dangerous potential explosion. Were I the fabricator, I would insist on checking the design (with pay) to ensure it is valid. If the vessel fails, every survivor or family of victims will sue all parties, and fabrication of a defective design (furnished by others) is no defense.

Yeah I agree. All the sub-sea couplings and drive units we made reqd all certs throughout - and there was no true safety issue, only cost of failure.

So again I would think - full certs from filler to flanges.

OK, I will echo the need for material certs for all components as well as welding and welder certs. I was responding to the testing issues, and had made that horrendous assumption that the question was only on testing, and not on getting the product out the door with full acceptance. Mea culpa.

Please refer to the Contract Agreement that you made with your Client to fabricate the vessel. Go to the Element where reference of International Code and Specification is made. If that element refers to BPV code, 2005 Edition then contractually you do testing @ 125% of MAWP and would not breach the contract if you do so. If that elements refers to BPV Code, latest Edition, unfortunately you would have to follow 2007 Edition @ 143% of Maximum Allowable Working Pressure. If you do not have any Written Agreement, then verbal instruction of Client would prevail. If you compare the Old Edition and New would reveal the reason for enhancing test pressure. I am sure it is becuase of improvement in material grade.

This vessel must be designed by professional and registered engineer and fabricated by an ASME stamp holder, and the vessel must be certified "U2".

My Authorized inspector (R-stamp for repairs and alterations) would not allow me to use any material including welding electrodes that didn't have material test reports or at least some sort of stamping and a paper trial back to the manuf. and the MTR's of the material. On new vessels we always go to 1.5 mawp. On repairs though it is left up to the A.I. but we generally go 80% of mawp or operating pressure which ever is greatest. Any A.I. that does not require at least an operating pressure hydro on a repair is not thinking very well in my opinion. Most of our vessels are in the 150-1000 psi range though nothing like these high pressures.

pipewelder