Radiography for crynogenic service

[jtseng123]

Dear all,

I have a 1/2" thk, 14' diameter 304 SS horizontal drum at low temp -290deF (-180C). Is it necessary to specify full radiography to check complete long seam in lieu of spot ? Shall I concern crack propagation from low temp to ambient vise verso such that full radiography shall be specified ?

I have seen people using full radiography for low temp, but I do not know how to justify to spend additional money.

 

[MrPDes]

If the vessel is to contain a liquid cryogen, then hydrotest may not be an option as residual frozen water may potentially block vessel internal equipment or connecting pipe work. A pneumatic test is therefore required. Many fabricators require that vessels tested pneumatically receive 100% radiography of at least the long seams to increase safety during the pneumatic test.

 

[Afox88]

The one job that we did in recent memory that was in -355F cryogenic service (liquid o2 one side, liquid n2 other side) had full x-ray but I believe it was a customer requirement and not a code requirement.

We also definitely performed hydrotest and not pneumatic test. Most companies that handle cryogenic fluids do a proper drying before any operating fluids are introduced.

 

[MJCronin]

What is the Code of Record in the purchase specification ?

Where is the the final installation location for this vessel ?





MJCronin
Sr. Process Engineer

 

[r6155]

(OP) "I have seen people using full radiography for low temp, but I do not know how to justify to spend additional money".
How can you detect leaks with thermal insulation?
I suggest full RT and preliminary leak test.

Regards
r6155

 

[jtseng123]

Thanks all, but that still does not constitute the technical reason full radiography shall be used for cryogenic service.
Hydrotest will be performed and then complete dry out, no air test. It has nothing to do with code of record or installation location, and thermal insulation is very common to vessels that does not mean it shall be full radiography.

 

[r6155]

Reasons to full RT in long seam instead of SPOT ?

1) Reduction in thickness from E= 0,85 to E=1 : economical reason
2) See 100% RT for long and circumferential welds in “Cryogenic Handbook”

http://www.tdd.org.cn/upload/2011-12/2011120952442829.pdf

3) Vertical or horizontal pressure vessel ? –wind, seismic ?
4) Vacuum insulation ?
5) Leak test . See “Cryogenic Handbook”
6) Preliminary leak test:. See ASME V . You can use vaccum box as minimun leak test in longitudinal and circunferential welds

Regards
r6155

 

[jtseng123]

r6155, this is just a regular drum (there are at least 10 drums, knock out drums, refrigerant drums, suction drums, etc) in ethylene plant that does not need vacuum insulated dual wall bullet such as in LNG plant. Thickness is not a concern, but to justify if full radiography shall be used. I have done some search these days and found spot was used in some projects. So I will go for spot.