5k Pressure Vessel Bolting Issue 1

[MrGezus]

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

 

[Duwe6]

Significant error: if using the post-2000 ASME Code stress allowables, hydro is at 1.3 x, NOT 1.5x. Need to take a harder look at Sect. VIII.

 

[LittleInch]

Can I see if I've got this right. You have a 5000 psi? vessel, designed to ?? Code. What code is the the two flanges?

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.

 

[GenB]

I believe headcap can be used if the right specification. Cannot easily mfr since head caps socket bolts are dropforgings.so you have to buy them ready made and certified.... I hope you understood Littlelnch s notes. Say something or thank someone. We get exited here...

 

[MrGezus]

Duwe6 - I will check it again at the 1.3x hydro test.

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.

 

[MrGezus]

Significant error: if using the post-2000 ASME Code stress allowables, hydro is at 1.3 x, NOT 1.5x. Need to take a harder look at Sect. VIII.

I will check it again at the 1.3x hydro test.

Can I see if I've got this right. You have a 5000 psi? vessel, designed to ?? Code. What code is the the two flanges?

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.

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.

 

[LittleInch]

Aaaah, now I get you. You're using api6a flanges on An Asme viii vessel and because api isn't listed as a standard like b16.5 you're having to calculate bolt sizes to asme viii?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SnTMan]

MrGezus, you look at SA-354 BD? Should be readily available and can meet fairly low temp impact test if needed.

Regards,

Mike

 

[marty007]

Be careful with SA-354 BD... I tried to go this way earlier this year and they failed the impact tests at +6°F. Because of the high tensile for this material, the impact criteria is not impact energy but rather lateral expansion. In the tests we ran, three consecutive samples failed.

While SA-193 B7 is exempt to -40/-55°F (depends on diameter), SA-193 BD is only exempt to +20°F

 

[Gilmiril]

SA-574 is not listed as an approved bolt material in Section VIII Div 2, so I don't think you'd be able to use it. My gut reaction is that it doesn't have sufficient ductility to be used in pressure vessels.

 

[MrGezus]

Correct.

I am actually have a company quote me out prices on this material right now. He told me he will use 4140, anneal it, heat treat it and test it to ASTM A354-BD. I found this on my own a few hours after originally posting. The vessel in question is only going to be rated to -20°F. The company who can manufacture these bolts say they will test it per that spec. Will that include the impacts you are speaking of?

Thank you. I saw that later in the process. I am still new at this. I was dealing with other welding projects and have been thrust in to this ASME code within the past 4 months or so.

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?

 

[MrGezus]

Well. Not really bolt sizes, but the stresses. I'd rather not have to machine special flanges to put the 1.25" bolt in. It would be easier for me to either stop the code at the butt weld or change bolting material.

 

[SnTMan]

MrGezus, SA-563 DH nuts are specifed in SA-354, don't know about availbility of these.

marty007, I had the opposite experience the one time I used SA-354 studs, probably a crap shoot

Regards,

Mike

 

[LittleInch]

You could always just use flanges to ASME B 16.5 like ASME VIII allows without having to do the calcualtions... There are numerous posts on this forum which point out that the B16.5 flanges fail the stress tests if you calculate them to ASME VIII, but as they are allowed (I believe it is UG-44) without doing them then all our issues just go away.

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.

 

[MrGezus]

I have spoken with him and he seems to think that the fasteners is the way to go. Another reason for us using these flanges is because our owner wanted to go ahead with fabrication before calculations had been completed. Therefor the flanges are already welded to weldolets so we would have to ruin those.

 

[MrGezus]

Where do I find information on required lateral expansion for these bolts as discussed by SnTMan and marty007?

 

[marty007]

See ASME VIII-1 Paragraph UG-84(c)(4)(b). This points you to various sections of paragraph UHT-6.

Good luck,

 

[MrGezus]

Thank you very much! I have read it and will forward it to the company that can manufacture these. Everyone's help is greatly appreciated.

 

[MrGezus]

Be careful with SA-354 BD... I tried to go this way earlier this year and they failed the impact tests at +6°F. Because of the high tensile for this material, the impact criteria is not impact energy but rather lateral expansion. In the tests we ran, three consecutive samples failed.

Question. If my bolts using SA-354 are only 1.125" in diameter, would they not be exempted from impact testing per UCS-66 @ -20°F?

 

[SnTMan]

MrGezus, Fig UCS-66, General Note c) exempts SA-354 BD to +20 F only.

Regards,

Mike