B7 versus B8 Studs For A Stainless Steel Pipng System
B7 versus B8 Studs For A Stainless Steel Pipng System
(OP)
I heard an argument that it is necessary to use B7 studs instead of B8 studs for ANSI stainless steel flanges. This is due to the recommended torque creating a bolt stress that would exceed the yield stress of the B8 studs.
I've worked offshore previously and have always used B8 studs in stainless systems and have never had any problems with leakage.
Is it okay to continue using B8 studs?
I've worked offshore previously and have always used B8 studs in stainless systems and have never had any problems with leakage.
Is it okay to continue using B8 studs?





RE: B7 versus B8 Studs For A Stainless Steel Pipng System
Use a new gasket, square up the flanges, lubricate the stud or bolt, and go slow on the tightening
RE: B7 versus B8 Studs For A Stainless Steel Pipng System
My rules of thumb for using low strength stainless bolting:
1) Don't, if you don't have to for external corrosion reasons. If you must use stainless bolting, use class 2 strain hardened- but be prepared to pay the price ($$).
2) Select "low stress to seal" gaskets that can be seated with the bolt load available. Do the calculations- don't let a gasket vendor simply tell you that its a "low torque" gasket.
3) Do the calcs and determine the necessary assembly torque, and then use a torque wrench so you don't inadvertantly tighten the bolts above their yield strength. For example, a 1/2 x 13 B8 bolt, lubricated, will yield at less than 30 ft-lb. What are the chances that a mechanic will yield this bolt if not using as torque wrench? Answer- 100% chance
4) Don't re-use stainless steel bolts
Finally, if you're using stainless bolts because your gaskets leak corrosive product onto the bolts- correct the leaky gasket and go back to using high strength, less expensive alloy bolting (B7).
RE: B7 versus B8 Studs For A Stainless Steel Pipng System
RE: B7 versus B8 Studs For A Stainless Steel Pipng System
What Stud Bolts shall be use on Piping Class 150#, Piping Specification?
Cryogenic Process Temperture -325F to 400F: ASTM A320, B8M CL 2 stud, w/ 2 heavy hex nuts ASTM A194, GR8.
Leonard Thill
Lenard@thill.biz
www.thill.biz
RE: B7 versus B8 Studs For A Stainless Steel Pipng System
thanks for any assistance
RE: B7 versus B8 Studs For A Stainless Steel Pipng System
We use thousands of B8 Class 2 Studs with standard B8 nuts. You will find that a Cold Worked Class 2 nut is hard to find and somewhat more expensive.
RE: B7 versus B8 Studs For A Stainless Steel Pipng System
A320-B8M Cl.2 is equivalent to stainless steel type 316. I understand that A320-B8 Cl.2 (equivalent to type 304) also can be used for cryogenic temperature. Please comment.
RE: B7 versus B8 Studs For A Stainless Steel Pipng System
Bolting: Cryogenic Process 304/304L
Cryogenic Process Temperture -325F to 400F:
ASTM A320, B8 CL 2 stud, w/ 2 heavy hex nuts ASTM A194, GR8
Pressure and temperature rating may be limited by certain components permitted by the specification. Refer to manufacturer’s recommended pressure-temperature restrictions.