Hydrostatic Blind Flanges Question
Hydrostatic Blind Flanges Question
(OP)
Hi all,
Is it possible to perform an Hydrostatic test on a SA-240 tp304 pressure vessel using carbon steel blind flanges?
Is there any ASME Code restriction to that?
Best Regards,
Is it possible to perform an Hydrostatic test on a SA-240 tp304 pressure vessel using carbon steel blind flanges?
Is there any ASME Code restriction to that?
Best Regards,





RE: Hydrostatic Blind Flanges Question
RE: Hydrostatic Blind Flanges Question
1. Don't touch the stainless steel surface with the carbon steel cover, you risc contamination.
2. What studs do you use for bolting the carbon steel cover to the stainless steel nozzles, B7's? Wrong, use B8's.
3. What gaskets are you using for the hydrotest, do you risk another contamination?
If you are confident you can control these issues, then the carbon steel covers are ok, otherwise the consequences could offset the saving on nozzles cover.
Cheers,
gr2vessels
RE: Hydrostatic Blind Flanges Question
RE: Hydrostatic Blind Flanges Question
RE: Hydrostatic Blind Flanges Question
Thanks for your answers, it's very appreciated.
Here are some more information about this particular test:
- Blind Flanges are made from SA-516 Gr.70 plate with approved eng. calculations to validate required thickness.
- Inside surface will be painted to avoid SS/CS contamination. (We also thought about using a full faced gasket)
- Gasket will separate SS from CS.
- Bolting being SA-193 Gr. B7, we tought about using SS washers to avoid contact with CS.
This way, I think A.I. should be satisfied. :)
thanks again for your comments.
RE: Hydrostatic Blind Flanges Question
RE: Hydrostatic Blind Flanges Question
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Hydrostatic Blind Flanges Question
To LittleInch: Because flanges are quite large and would cost to much. That's why we're going with plate.
RE: Hydrostatic Blind Flanges Question
Your statement:"B7/2H studs/nuts are COMMONLY used on austenitic stainless steel flanges for temperatures below 800 F where external corrosion conditions are modest- not just for testing, but in service
.... is correct and consistent with the commonly referenced PIP piping standards.
Additionally, the highly regarded NORSOK standards also permit the same B7/2H usage
And regarding the concern over the use of test blinds in lieu of blind flanges, this is mentioned and discussed in ASME B31.1
MJCronin
Sr. Process Engineer
Venture Engineering & Construction
www.VentureEngr.com
RE: Hydrostatic Blind Flanges Question
RE: Hydrostatic Blind Flanges Question
When you torque a lean Cr-Mo steel (B7/2H) stud and nut combination in a flange, there is obviously some risk of carbon steel embedment in the surface of the stainless steel under the nut. But of course, the stud and nut themselves are going to corrode MUCH FASTER than the stainless steel with minor damage to its passive layer- so is this a valid concern? A flange assembly wetted on the exterior is a crevice corrosion nightmare regardless what materials you use, and that has to be taken into account any time a flange assembly is used under conditions of severe external corrosion (i.e. flanges internal to a vessel etc.).