Actual Torque; Bolt vs. Flange

[subvanpatent]

I have been searching and searching and I am not sure I have the correct answer. So here are the conditions:

Flange matl: SA-105 Integral flange, Wall matl: SA-516-70
We are using B7M (100% Hardess tested bolts) 80000 psi.
68 bolts X 1" 8 UNC

Flange dimensions (in)appendix 2 nomemclature)

A = 74
B = 66.13
C = 70.38
g0 = 0.875
g1 = 2.125
t = 3
P = 150 psig
T = 700 F
m = 2
y = 2500
No corrosion allowance
there is a groove depth on one of the flanges of 0.08

When I calculate this all out, my W for gasket seating is 680800 psi and for operating is 612200. My understanding from all my research is that my clamping force for gasket seating should be 10012 lbs/bolt. This would in turn give me an allowed stress per bolt of 18170 psi (using an ab of 0.551).

Of course this is no where near the 30, 45 or 60 ksi forces that I can use on the bolts to acheive my torque.

Am I correct in saying from this information that the highest torque I should use to prevent flange deformation (with a K=0.117) would be about 150 ft-lbs.

Thanks in advance for the help!

Subvanpatent

 

[1969grad]

Gasket seating stress looks extremely high. What type of gasket are you using?

 

[subvanpatent]

Flexitallic Flexpro Kammprofile. I got the m and Y values from the web site.

Subvanpatent

 

[jte]

Subvan-

See thread378-138163.

I agree with 1969grad: Your Wm2 (gasket seating) load (pounds, not psi) looks really high. I ran your numbers and it looks as though you are an order of magnitude off. Make sure you didn't enter 25,000 psi as your gasket seating stress!

Your Wm1 (operating) load looks about right. My numbers came out to 598,000 pounds which is close enough considering my rounding of your dimensions. In my case, the bolt stress came out to 14 ksi, again, close enough. I'd recommend a torque of about 140 ft-lbs for a bolt stress of 25 ksi.

We'd go higher with other gaskets, but the kammpro's and Graphonics types are giving us good sealing at lower stresses compared to double jacketed or spiral wound. So we don't feel the need to go to 50 ksi "just because" like we used to.

jt

 

[subvanpatent]

I appreciate both your comments. PSI was a tired typo. I used X-calcs to run the calcs with the dimensions from the fab drawing and the results were Wm1 = 612.2 klbs and Wm2 = 353.7 klbs, but later in the results section the W for operating is 612.2 klbs and the W for gasket seating is shown to be 680.8 klbs?

My main concern is how does my bolt stress (say 45000 psi) affect my flange that has an allowable operating stress of 17200 psi and gasket seating of 20000 psi. I don't want to recommend a torque where I consider bolt stress only, if I could damage my flange.

Subvanpatent

 

[jte]

Subvanpatent-

I'm not familiar with X-calcs so I can't help you there.

I think you'll find your answer in Div. 1 Appendix S. Simply put, don't worry about it.

jt

 

[subvanpatent]

Thanks jt,

So it sounds like that if my J factors are both less than 1 I can probably torgue to 45000 or 60000 psi given all other conditions are amenable.



Subvanpatent

 

[1969grad]

Beware! Bolt torques vary with the type of thread lubricant to get the same bolt load.

 

[subvanpatent]

Thanks 1969grad,

I have learned alot about the bolts and torqueing. Lubricant, washers, torque wrenches, hydraulic tensioning, gaskets, etc... I just wanted to make sure I don't pull a bolt so hard that I damage my flange.

Thanks again all.

Subvanpatent