5k Pressure Vessel Bolting Issue
5k Pressure Vessel Bolting Issue
(OP)
I am designing a 5k pressure vessel. The problem I have is that my flanges bolts do not meet. The reason I am using these flanges is because we manufacture API flanges for our core business. They do meet API requirements but not ASME. I can change the bolt sizing from 1.125 to 1.25 but that would cause a huge pain to deal with. I found a different bolt material (SA-574) which would allow me to keep my sizing. The problem with this is that the material spec shows it to be hex cap socket screws. Can I use that type of fastener? Can I have all thread studs made from this material? Any suggestions on a different bolt material or way of going about this that I do not see?
Operating Load
Required Bolt Load
Bolt Load at Hydro
I am using SA-193-B7 bolts
Holes: 8
Bolt Size: 1.125
Qty: 8
Threaded Root Area: .7277
Total Actual Bolt Area: 5.822
Flange Bore Dia.: 2.645
OD: 10.50
Flange Thk: 2.190
Hub: 2.160
Hub Major D: 5.250
Minor Hub D: 3.500
45k Mat
Hub Thk G0: .423
Hub Thk G1: 1.298
Stainless Gasket
P.D. 5.375
Temp: 250F
5k Working
7.5k Hydro
Operating Load
Required Bolt Load
Bolt Load at Hydro
I am using SA-193-B7 bolts
Holes: 8
Bolt Size: 1.125
Qty: 8
Threaded Root Area: .7277
Total Actual Bolt Area: 5.822
Flange Bore Dia.: 2.645
OD: 10.50
Flange Thk: 2.190
Hub: 2.160
Hub Major D: 5.250
Minor Hub D: 3.500
45k Mat
Hub Thk G0: .423
Hub Thk G1: 1.298
Stainless Gasket
P.D. 5.375
Temp: 250F
5k Working
7.5k Hydro





RE: 5k Pressure Vessel Bolting Issue
RE: 5k Pressure Vessel Bolting Issue
Why can't you just buy an identical flange?
Messing around with bolts is bad practice and I would have thought it would struggle to get passed by any inspection authority.
You have supplied a lot about the flange but some crucial details are missing.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: 5k Pressure Vessel Bolting Issue
RE: 5k Pressure Vessel Bolting Issue
LittleInch - The vessel is being designed to ASME Section VIII Div. 2. The flange that is being used is one that we produce for API 6A in house. It would allow us to pull one off the shelf. It meets everything except for the bolt loads. The bolt design would not change, just the material. Any more information I can give you is readily available. I am somewhat new at this and still trying to figure out what I can.
I really appreciate all of your comments.
RE: 5k Pressure Vessel Bolting Issue
The vessel is being designed to ASME Section VIII Div. 2. The flange that is being used is one that we produce for API 6A in house. It would allow us to pull one off the shelf. It meets everything except for the bolt loads. The bolt design would not change, just the material. Any more information I can give you is readily available. I am somewhat new at this and still trying to figure out what I can.
RE: 5k Pressure Vessel Bolting Issue
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: 5k Pressure Vessel Bolting Issue
Regards,
Mike
RE: 5k Pressure Vessel Bolting Issue
While SA-193 B7 is exempt to -40/-55°F (depends on diameter), SA-193 BD is only exempt to +20°F
RE: 5k Pressure Vessel Bolting Issue
RE: 5k Pressure Vessel Bolting Issue
I imagine I need to find a nut to fit the stud at least meeting the minimum stress requirements of my material. I think its 30. Should these be easy enough to come by?
RE: 5k Pressure Vessel Bolting Issue
RE: 5k Pressure Vessel Bolting Issue
marty007, I had the opposite experience the one time I used SA-354 studs, probably a crap shoot :)
Regards,
Mike
RE: 5k Pressure Vessel Bolting Issue
I realise you have API 6A flanges available on the shelf and probably at low cost to you, but you need to balance this against the hassle you are now going under.
In all of this you haven't mentioned the opinion of the appropriate inspector / authority in this. I don't believe you can "stop the code" at the butt weld.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: 5k Pressure Vessel Bolting Issue
RE: 5k Pressure Vessel Bolting Issue
RE: 5k Pressure Vessel Bolting Issue
Good luck,
RE: 5k Pressure Vessel Bolting Issue
RE: 5k Pressure Vessel Bolting Issue
RE: 5k Pressure Vessel Bolting Issue
Regards,
Mike
RE: 5k Pressure Vessel Bolting Issue
RE: 5k Pressure Vessel Bolting Issue