Torque Values for Pressure Vessel Body Flanges

[ReliaEng2008]

I am trying to find how to calculate bolt stresses and torque values for body flanges (joining a heat exchanger channel to a shell, for example) of ASME BPVC Section VIII Div. 1 pressure vessels. There is not a lot of information out there compared to piping.

Checking ASME BPVC Section VIII Div 1., the bolt stress used in the calculations for flanges in Mandatory Appendix 2 comes from ASME BPVC Section II Part D, Table 3. For a SA-193 B7 bolt, for example, the stress is only 25,000 psi (which results in very low torque values in my opinion). But those calculations (the ones that use 25,000 psi for bolt stress) are only to find the minimum amount of bolting required under the rules (this is stated in Nonmandatory Appendix S, 3rd paragraph).

I got some recommendations from engineers to use bolt stress equals 60% of material yield strength (for SA-193 B7: 105,000 psi at 100F - use 63,000 psi). Someone else mentioned to use "w" from equation (5) in Nonmandatory Appendix 2.

Does anyone have experience with calculating torque values for pressure vessel flanges who can help me out?

 

[r6155]

Are you sure there is not a lot of information in ASME VIII Div.1?
Did you read Appendix S completely?. Please read again (slowly).
Why do you think that 25.000 psi results in very low torque values?.

Regards

 

[SnTMan]

See perhaps ASME PCC-1

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[ReliaEng2008]

r6155: 25,000 psi is not a lot because the yield strength of SA-193 B7 bolts at ambient temperature is 105,000 psi. A bolt stress of 25,000 psi is about 24% of the yield strength. Section O-4 of PCC-1 mentions the minimum value for bolt stress is about 20-40% of the yield strength at ambient temperature, and the maximum about 40-70%. So it is in the lower range for minimum value of bolt stress.

Furthermore, Appendix S mentions that the 25,000 psi bolt stress is used the determine the minimum amount of bolting required under the rules, but the actual bolt stress needed might be different (paragraph 3).

 

[r6155]

@ ReliaEng2008
“I am trying to find how to calculate bolt stresses ……….”
Bolt stress is 25,000 psi in your example, as per ASME VIII Div.1 and ASME II, and nothing to calculate.

ASME PPC-1 is not for design
Rules for design of bolted flanges with ring-type gaskets are covered
in Mandatory Appendix 2 of ASME Boiler and Pressure Vessel Code
(ASME BPVC), Section VIII, Division 1; see also ASME BPVC, Section
VIII, Division 1, Nonmandatory Appendix S for supplementary considerations
for bolted flanges that are helpful to the designer of Appendix 2
flanges.

You are very confused.
Sorry, you must do a training course.

Regards

 

[SnTMan]

Using ~60 ksi as an assembly stress for B7 is actually pretty reasonable. Generally speaking the higher the assembly bolt stress, the less likely the bolting is to be affected by the external loads.

Lots of good discussion on this site, and at Bolt Science

The problem with sloppy work is that the supply FAR EXCEEDS the demand