Checking deformation on pressure vessel during hydrotest 1

[yogeshsj2014]

Hi,
Is there any code which dictate to measure the deformation of pressure vessel during the hydrostatic testing and post testing? Testing done against ASME B 31.8 as pressure vessel is associated with pipeline facilities.
Normally we use to measure circumference at start of Hydrotest. Then during the test we check the circumference to confirm how much deformation occurs. At the end of test i.e. after depressurization we take final reading to ensure that there is no permanent deformation. I wish to get some code to support this exercise ? I have gone thru one code "BS 13445-5-2014 Unfired pressure vessels Inspection and testing" which mentioned in 10.2.3.9 " Acceptance criteria -During the proof test the vessel shall show no signs of general plastic yielding. Local deformation which is identified by visual inspection and which is cause for concern shall be referred to the designer for reconciliation against the design specification. During the proof test no leaks are permitted from the pressure envelope"

Can anybody have answer for this.

 

[Gorostidi]

Hello

In BS-13121 (this one deals with GRP vessels above ground) there is a max theoric data defined during the testing process

is this vessel in steel or GRP?

Kind regards

 

[racookpe1978]

To check diameter during the test, you could use a pi tape (on an uninsulated tank) to measure diameter at several points on the centerline axis before, during, and after the test. Temperature needs to be the same before, during, and after for the hydro test and the measurements to be validated, or the exact spill and leakoff volumes known.

 

[wsu1975]

I would caution you to be sure of the terminology being used. While I have not looked at B31.8 in a while, nor have I looked at the British Standard, in ASME B&PVC Section VIII, Div. 1, there is a difference between a "Standard Hydrostatic Test" in UG-99 and a proof test "Proof Test to Establish Maximum Allowable Working Pressure" in UG-101. While I do not know the materials, design, or operational requirements, not having to perform the measurements may be a cost saving and not necessary for a "standard hydrostatic test" of the system.

Best Regards,
WSU1975

 

[r6155]

yogeshsj2014

As mentioned in BS 13445 10.2.3.9 "...... Local deformation which is identified by visual inspection......."
No measure is required.

Regards
r6155

 

[yogeshsj2014]

This vessel is scrapper trap launcher barrel which is used in pipeline facilities and material of construction is API5L/X65 grade.

 

[LittleInch]

The scraper trap should be designed to ASME B 31.8. if you're connecting it to a 31.8 pipeline. The scraper trap is part of the pipeline and should be tested as such.

Pipeline pig traps / scraper traps are NOT PRESSURE VESSELS.

The design code will provide the design pressure and allowable test pressures. Just use that.

I've never ever heard of anyone trying to measure the minute amount of circumferential expansion of a pipe or vessel.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Spoonful]

If you limit your hydro test stress to 90% of yield, there theoretically should not be any permanent deformation caused by hydro.

I have seen deformation measured on tubesheet during and after hydro test.

 

[yogeshsj2014]

Thank you for your advisory answer. But there is one query in my mind what should be test pressure. If consider factor of safety as 1.5 multiply by design pressure or 90 % of SMYS whichever more or less? How it is calculated ?
During hydrotest if deformation of barrel happens beyond elastic limit, what is risk associated with the this barrel if it used for operation due to emergency situation. Normally Barrel is used during the pigging.

 

[LittleInch]

I'm very concerned that you are asking this sort of question about pressurized equipment. Please tell me that you have more experienced and senior engineers checking and approving your work.

The DESIGN CODE you are using (in this case ASME B 31.8) will tell you what the test pressure needs to be based on a factor of either Design pressure, MOP, MAOP and is normally limited to 90-100% of SMYS in the material.

There is no code in existence which would require you to yield the material during test and if you've been doing this you're doing it wrong. If you plastically yield an item you are seriously work hardening it and possibly thinning it in places and it won't have the same properties as it did before. A permanent strain of 2-3% is not a big issue, but anything more than that and you've significantly affected the strength of the item.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.