U-Stamp Vessel Repair

thank you very much .iam is small qc engineer and i need to have more information about material for example st 37 and astm 36 what is the diference its very difcullt to me i need to understand this point pls .my mail is ramadanshishi@gmail.com and iam is egyptian

Thanks so much for this info.Could you please tell if this is mentioned in any clause in ASME sec VIII

Ajay

Good answer but somewhat misleading:

1. It must be remembered that "U" stamp is a construction symbol. I.e. you can't "lose" U-stamp, it's there once and for all. All a "U" stamp signifies is that the vessel was built by a holder of ASME Certificate of Authorization and that the construction / inspection requirements have been fulfilled. Once the vessel is in-service, "U" stamp is no longer relevant in terms of the repairs etc.

2. How the repairs should be carried out is governed by the jurisdictional requirements only. If for example the vessel is located in Outer Mongolia and the jurisdiction doesn't recognise NBBI or its "R' stamp requirements, the vessel shall be repaired as required by the local regulations.

3. One of the other Codes the vessel could be repaired under is API 510 (which of course makes no mention of the "R" stamp)

The following link is free download for some files in DOC format as a guide to any firm need to hold ASME Certificate of Authorization: Guide_to_hold_ASME_Certificates_of_Authorization.

Sir

But in API 510 NO where it is written about R stamp holding authority has to repair u stamped vessel.

Pl. clarify

Correct! That's what I've tried to point out before. "R" stamp is only one of the options, not a mandatory requirement. API 510 does not stipulate "R" stamp and the jurisdictions usually provide other options often based on the API 510 definition of "repair organization":

3.16 repair organization:

Any one of the following:

a. The holder of a valid ASME Certificate of Authorization

that authorizes the use of an appropriate ASME Code symbol

stamp.

b. An owner or user of pressure vessels who repairs his or her

own equipment in accordance with this inspection code.

c. A contractor whose qualifications are acceptable to the

pressure-vessel owner or user and who makes repairs in

accordance with this inspection code.

d. An individual or organization that is authorized by the

legal jurisdiction.

My dear pipewelder,

Thank you very much for your courtesy compliment, and many thanks for your answer showing an important and necessary welding and inspection details, it is a "Good Answer" too.

After welding is complete then you would cap all connection/nozzles and preform a pressure test (usually water but sometime air) on the vessel as per the NBIC, ASME and your authorized inspector may require.

pipewelder, It has been a while since working in ASME, I believe you would have to preform a hydro-test. on the unit, when you use air, all that does is help find the leak. If there is one that weld well have to be removed and redone completely. and then pass the hydro-test. Unless there is something I am missed, or not updated on? Such as your repair procedure.

phoenix911

"It has been a while since working in ASME, I believe you would have to preform a hydro-test"

Not in all cases you can proceed a hydrotest, a pneumatic test may be used in lieu of the standard hydrostatic test prescribed in UG-99. Please refer to UG-100.

Quote. UG-100 PNEUMATIC TEST (see UW-50)

(a) Subject to the provisions of UG-99(a)(1) and (a)(2), a pneumatic test prescribed in this paragraph may be used in lieu of the standard hydrostatic test prescribed in UG-99 for vessels:

(1) that are so designed and/or supported that they cannot safely be filled with water;

(2) not readily dried, that are to be used in services where traces of the testing liquid cannot be tolerated and the parts of which have, where possible, been previously tested by hydrostatic pressure to the pressure required in UG-99. Unquote

Thank you Abdel Halim Galala, it has been a while for me.

Kindly tell me how can we calculate hydrotest stresses manually.any formulas?While we are using Compress to calculate hydrotest stresses, we will get a list of stresses during test and Allowable test stresses.I want to know the method of calculating that stresses.Allowable stresses can be calculated using Sec VIII Div II but how can we calculate the stresses during test.

The reason I believe that the ASME allows air testing is because sometimes the use of water could contaminate the vessel. It may not be good to use water on an hydraulic oil tank or other vessel where you cannot get all the water out after testing. Also certain air dryer vessels after being repaired cannot have water test because it will shorten the life of desiccant. We nearly always perform air test on natural gas pipes and vessels for this same reason. Although air is more dangerous to test with in case of a failure it is sometimes the best way to go and is safe as long as one is careful and does not exceed the MAWP with the test pressure. I would suggest the use of a safety relief valve on all pressure tests to eliminate over pressure. I was inside a boiler checking for leaks while it was being pressurized with boiler feedwater when the yoke on the feed water control valve broke and wedged wide open. Before the operator could get a back up valve close the pressure went to 1250 psi with me inside standing on the tubes. Needless to say I went for the manway immediately. The boiler feed water is very hot and it started to melt the soles on my shoes before I got out. We always gag the pressure relief valves on our boilers so we do not lift them with water and mess up the seats so there was no way to prevent over pressuring. This was the last time I went into a boiler while it was being brought up to pressure. We do not hydro with feedwater pressure anymore and we also use a cheap removable pressure relief valve on the inlet line during hydro tests.

pipewelder

Replacing a damage flange on a pressure vessel is usually not a big problem some times the nozzle the flange attached to has enough length remove the old and install a new one outside the pressure boundary. If you have to do a complete replacement yes you will need an "R" stamp to do the work also your inspection agency would need to know what procedures you are doing before work is carried out generally the "R" stamp holder will know what procedure needed for the replacement. You can start by looking at the U1 form to see how the nozzle was attached from the manufacture (OEM) and proceed from there.

Good luck on the repairs.

Once I was fabricating a set of NCG(non-condensible gas0 burner control skids in my shop and the owner insisted on supplying the 2 small 316 L stainless steel droplet separator pressure vessels that was needed. I am sure he got a "better" price from some other vendor and was trying to save money rather than let me build them. When the vessels came in they were of very bad workmanship and I had to spend allot of time cleaning weld spatter and passivating/pickling them so as to not make all of my piping and other work look bad. But the worst thing of all is that the vessels came in with 300 lb flanges and all of the pipe in the system was fabricated with 150lb. flanges. Well to make a long story short we had to immediately cut off all the 300 lb flanges from the vessel and replace them with 150 lb. at a pretty good cost. The AI treated this work as an alteration and made us get new calculations. This is the first time I had seen a R-stamp nameplate installed on a brand new vessel before it had ever been used.

pipewelder

Sample of stamps we hold its certificates of authorization:

you can go to www.standardshop.org
there sale a lot of asme aws api standard and so one .can immediately download,and very cheap low price!