Bolted Flange under bending

[dav363]

Can anyone provide a referenced source for a calculation method for assessing stress induced in flange bolts when the flange is subject to a bending moment. I think I'm right in saying one simply takes a moment about a fulcrum point for each of the bolts around the PCD, the fulcrum point being the point at which the flange would pivot due to the bending moment. Would this be the PCD of the bolt circle, or the outermost contact point between faces?

I require to use this calculation but need a reference to prove the method.

Thanks
David

 

[TGS4]

You could try EN-1591-1. I have found their flange stress calculations to be vastly superior to the calculations found in ASME Section VIII, Division 1, Appendix 2.

 

[codeeng]

If this is a standard ASME/ANSI flange you can determine the equivalent pressure due to external moments plus pressure per PV Design Manual by Moss:

Pe=(16M/piG^3) + P

 

[carthago]

EN-1591-1 = superior but complicated , Very hard to have an overview of this method.
I take is as a procedure and use as it is...
I believe it needs a dedicated software..

The method can even take into account the " scatter" .
And bolt bending, gasket stiffness

----------------
Any one got more information about the other method , namely the PVRC method, which can quantify the:
- leakage emission ( depending on the type of required " tigthness" ).
- Estimate the bolt loads

 

[tothepoint]

The PVRC has conducted many research projects on the efffect of bending moments on gasket leakage and bolt load. Check out the PVRC website for a list of their research papers on this topic. There are also many papers on the developing, leakage based BFJ design rules.

http://www.forengineers.org

 

[REFINERYPROJECTS]

It is easier to use software. However, regarding your case,
1. If bending moments on your flange due to pipeline thermal expansion,this load causes the bolt stresses to be over the allowable per Div. 1 Table UCS-23, then refer to Division 2, Appendix 4 Section 4-141 and it states that we can go to 2x the allowable for a combination of preload, pressure and thermal expansion...this section does not specifically address external loading but it does indicate that this is the maximum allowable service stress in the bolts

2. Calculate the bolt loading due to the internal pressure and external loading based on division 2 calculations. In doing this, it will allow you to use the 2x allowable criteria.

3. Expansion stresses give rise to secondary stresses and these are not required to be accounted for in Div.1 (this is by the way the main and very basic difference between Div.1 and Div.2): se also below, however.

4. As your expansion stresses seem a bit high you can check them, still staying within the frame of Div.1, hence using Div.1 allowable, but going to Div.2 for the checking method, as Div.1 doesn't provide one.

5. App.3 of Div.2 is of no use here: it is in fact the same as App.2 of Div.1 and uses the same type of loads (pressure only).

6. Check also App.4 of Div.2, and with 4-141 you should be OK. However note that the service stress in bolts should be determined including the effect of preload (of course by accounting also the effect of preload stress going towards zero under flange loads) and the effect of torsion in tightening if any.

 

[REFINERYPROJECTS]

It is easier to use software. However, regarding your case,
1. If bending moments on your flange due to pipeline thermal expansion,this load causes the bolt stresses to be over the allowable per Div. 1 Table UCS-23, then refer to Division 2, Appendix 4 Section 4-141 and it states that we can go to 2x the allowable for a combination of preload, pressure and thermal expansion...this section does not specifically address external loading but it does indicate that this is the maximum allowable service stress in the bolts

2. Calculate the bolt loading due to the internal pressure and external loading based on division 2 calculations. In doing this, it will allow you to use the 2x allowable criteria.

3. Expansion stresses give rise to secondary stresses and these are not required to be accounted for in Div.1 (this is by the way the main and very basic difference between Div.1 and Div.2: se also below, however.

4. As your expansion stresses seem a bit high you can check them, still staying within the frame of Div.1, hence using Div.1 allowable, but going to Div.2 for the checking method, as Div.1 doesn't provide one.

5. App.3 of Div.2 is of no use here: it is in fact the same as App.2 of Div.1 and uses the same type of loads (pressure only).

6. Check also App.4 of Div.2, and with 4-141 you should be OK. However note that the service stress in bolts should be determined including the effect of preload (of course by accounting also the effect of preload stress going towards zero under flange loads) and the effect of torsion in tightening if any.