Blind flange hydrostatic test
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I’m seeking help from experienced colleagues: When a 48-inch blind flange made of Q235 material, belonging to the B16.47-B series, was subjected to a hydrostatic test at 28 BAR, bending of 7.5 millimeters occurred on its surface. What could be the cause of this? Does anyone know? Solve. Thank you in advance.
During material processing, relatively high stresses are generated, and these stresses remain unresolved; they are released under pressure during the hydrostatic test—this is just a guess
Do you mean the causes resulting from the processing? Do we not need to consider the test temperature during the testing process? Same solution, thank you.
Deformation caused by overpressure. Additionally, large-diameter blind plates should have “#” ribs welded to their outer surface to enhance their strength and prevent deformation. This blind flange is basically useless now. The key issue is the lack of reinforcing ribs.
Large-diameter blind flanges undergo deformation during pressure testing. The exact structural design of the Q235 blind flange mentioned by the poster is still unclear. Even if it is manufactured according to B16.47 standards, the mechanical properties of Q235 differ significantly from those of the lower-grade materials listed in Table 1 of B16.47 – Q235 is not included in that table; materials such as A515 Gr.70 have much higher strength, with a difference in tensile strength of nearly 25%. Therefore, the suggestion given on page 4 is appropriate: necessary reinforcement ribs should be added. Some finite element analysis can be performed.
It’s deformed under pressure – has it exceeded its tolerance limit?
You mean that if we replace material Q235 with A105, then A105 will have higher mechanical properties, with an increased tensile strength, and thus there will be no need for this reinforcement bar. Can you also withstand this pressure? Can it be understood this way?
It’s just that if we switch to a different material, specifically A105, its mechanical properties are better than those of Q235. Does that mean there’s no need to add this reinforcement bar? Can it withstand this stress test? Same solution, thank you
Thank you for your reply. Could you let me know what the allowable range is? Our deformation is 7.5 millimeters – is this within the allowable range?
I calculated that the yield strength is 250; so what should be the allowable buckling range in millimeters? I would appreciate some guidance from those who are more experienced. Also, could you let me know in which standard this allowable buckling range is specified? For the hydrostatic testing of B-series flanges, do the pressure requirements outlined in ASME 16.47 and ASME 31.3 apply?
I took another look at standard B16.47 just now; it only mentions that system pressure testing is applicable to flange joints, and states that no pressure testing is required for flanges. Isn’t this in contradiction with the water pressure testing we carry out on flanges after production?