FFS-EU
Petroleum
- Sep 11, 2020
- 2
When assembling flanged joints, a typical target bolt stress is 40-70% of its SMYS, see e.g. ASME PCC-1 Appendix O. If you look at the allowable stresses for bolt materials (e.g. SA-193-B7) in ASME II Part D, you will find that these are much lower. That is, when assembling a regular flange connection, we stress the bolt (way!) beyond its allowable stress.
This makes me wonder:
1. Do you agree with the above: i.e. we do not consider the allowable bolt stress values when calculating/applying the target bolt assembly stress?
2. What is the significance of the allowable bolt stress values specified in ASME II Part D, for which calculation should we use them?
3. When designing a flange, the bolt stress is one of the loads that matter: It leads to circumferential bending of the flange. Which bolt load would you enter in the flange design calculation? Equivalent to:
(a) bolt allowable stress (which is less than actual),
(b) target bolt stress from torqueing,
(c) same as (b) but increased with a conservative safety factor?
Any other thoughts on the subject - please feel invited to share.
This makes me wonder:
1. Do you agree with the above: i.e. we do not consider the allowable bolt stress values when calculating/applying the target bolt assembly stress?
2. What is the significance of the allowable bolt stress values specified in ASME II Part D, for which calculation should we use them?
3. When designing a flange, the bolt stress is one of the loads that matter: It leads to circumferential bending of the flange. Which bolt load would you enter in the flange design calculation? Equivalent to:
(a) bolt allowable stress (which is less than actual),
(b) target bolt stress from torqueing,
(c) same as (b) but increased with a conservative safety factor?
Any other thoughts on the subject - please feel invited to share.