ASME flange calculations design bolt load Vs. applied bolt load
ASME flange calculations design bolt load Vs. applied bolt load
(OP)
Hi,
I am trying to understand the main differences between ASME & another code which derives from it regarding flange calculations.
If I take a look at the ASME flange design calculations, I see that everything is focused on the design bolt load, which is the greater of Wm1 & Wm2 (operating & seating conditions).
Moment MG due to the reaction of the gasket is then calculated, for the operating condition, as MG = HG*hg, with HG = Wm1
If I take the code I am working on, what I read is the following:
The moment due to the reaction of the gasket is MG = HG*hg, where HG is the difference of the applied bolt load and the sum of other loads acting on the flange:
HG = W - HD - HT
Then, calculations go on with stresses SR, SH & ST... Exactly in the same way as for the ASME.
What I do not understand is:
- Where exactly is it said in the ASME that the design bolt load (max(Wm1,Wm2)) is NOT TO BE EXCEEDED?
- Is the assumption HG = W - HD - HT correct, knowing that W is the actually applied bolt-up load?
Thanks a lot for your support on this topic, I am definetly stuck...
I am trying to understand the main differences between ASME & another code which derives from it regarding flange calculations.
If I take a look at the ASME flange design calculations, I see that everything is focused on the design bolt load, which is the greater of Wm1 & Wm2 (operating & seating conditions).
Moment MG due to the reaction of the gasket is then calculated, for the operating condition, as MG = HG*hg, with HG = Wm1
If I take the code I am working on, what I read is the following:
The moment due to the reaction of the gasket is MG = HG*hg, where HG is the difference of the applied bolt load and the sum of other loads acting on the flange:
HG = W - HD - HT
Then, calculations go on with stresses SR, SH & ST... Exactly in the same way as for the ASME.
What I do not understand is:
- Where exactly is it said in the ASME that the design bolt load (max(Wm1,Wm2)) is NOT TO BE EXCEEDED?
- Is the assumption HG = W - HD - HT correct, knowing that W is the actually applied bolt-up load?
Thanks a lot for your support on this topic, I am definetly stuck...





RE: ASME flange calculations design bolt load Vs. applied bolt load
W = H + Hp
Hg = W - H = H + Hp - H
Hg = Hp
Your Code:
Assuming W = H + Hp, and Ht = H - Hd, as per Apx 2,
Hg = W - Hd - Ht = W - Hd - (H - Hd)
Hg = W - H
then Hg = Hp, same as Apx 2. Why the different formulation, I don't know.
The above applies to operating case, W = Wm1
Calculations in Apx 2 are to be used for design only, and it is known and expected that actual service bolt loads will exceed design loads. See Apx S for a fuller discussion.
Regards,
Mike
RE: ASME flange calculations design bolt load Vs. applied bolt load
RE: ASME flange calculations design bolt load Vs. applied bolt load
Thanks a lot for your answers.
As I am not familiar with ASME, can you please describe the terms H & Hp ?
Because in my code W = n*T*(...thread parameters), where T is the torque in lbs.ft applied to each bolt and n the number of bolts.
Actually what I do not understand in ASME is that the bolt load used for design seems different from the true bolt load (as the one I describe just above).
Thanks a lot for your clarifications.
RE: ASME flange calculations design bolt load Vs. applied bolt load
Hp is contact load on the gasket, Hp = 2 * b * pi * G * m * P, b is effective gasket width, m is a gasket factor dependent on the type of gasket.
BTW, I hope your (...thread parameters) has the unit of feet.
Regards,
Mike
RE: ASME flange calculations design bolt load Vs. applied bolt load
Actually I am trying to show that the code I am using is far too conservative compared to the ASME. My customer claims the formulas are the same, but on this particular topic it seems I disagree...
Appendix 2 is the Taylor Forge method, correct?
Yes my formulas are always converted in metric units, including the applied torque (N.m).
Thanks a lot for your feedback, I appreciate.
RE: ASME flange calculations design bolt load Vs. applied bolt load
The closest you could say it gets is the optional provision that W = Ab * Sa (W = actual bolt area * allowable bolt stress), but again it is based on Sec II. Part D allowables, not applied stress.
Regards and good luck,
Mike
RE: ASME flange calculations design bolt load Vs. applied bolt load