Bolt Torque Target Stress
Bolt Torque Target Stress
(OP)
Hello,
Many gasket manufactures advertise bolt stress value from 30,000 psi to 60,000 psi for bolt torqueing purposes. Is there any concern that if I torque a stud to 50-60 ksi stress you may actually yield the flange that is being bolted? In other words the high torque value of the studs would actually bend the flange over around the flange perimeter. For reference; an SA-105 flange have minimum yield strength of 36,000 psi
Thanks,
Many gasket manufactures advertise bolt stress value from 30,000 psi to 60,000 psi for bolt torqueing purposes. Is there any concern that if I torque a stud to 50-60 ksi stress you may actually yield the flange that is being bolted? In other words the high torque value of the studs would actually bend the flange over around the flange perimeter. For reference; an SA-105 flange have minimum yield strength of 36,000 psi
Thanks,





RE: Bolt Torque Target Stress
RE: Bolt Torque Target Stress
It's not the individual bolt torque you should consider but the total resultant bolt load (clamping force) generated by the bolting at whatever the required torque value specified.
To properly address your concern, please specify flange size and rating, the type of gasket, flange materials, and applicable code. Operating/Design conditions would also be nice.
Since you mention A105, my first reaction is to consider an ANSI/ASME design, rather than API 6A. 6A specifies 55,000 psi bolt stress for it's flanges, but 6DSS requires the same flanges used subsea to be loaded with 75,000 psi. Go figure.
RE: Bolt Torque Target Stress
There is also a PVP paper (PVP2006-ICPVT-11-93075) which essentially outlines that excessive bolt loading really can not lead to mechanical failure of the flange, assuming fatigue is not a concern.
RE: Bolt Torque Target Stress
RE: Bolt Torque Target Stress
RE: Bolt Torque Target Stress
RE: Bolt Torque Target Stress
Regards
r6155
RE: Bolt Torque Target Stress
RE: Bolt Torque Target Stress