Slotted Holes Flanges

[juancito]

Dear all,

Does anyone know a reference where is stated that ASME flanges calculation is irrespective of the shape of bolt holes?.
Thanks in advance

 

[JohnBreen]

It IS NOT so stated as you are describing a nonstandard component. Slots remove additional metal from the component (compared to round holes) so the flange design rules (based upon the standard geometry) are invalid.

When you want to use a nonstandard pressure component you must qualify it per the requirements of the Code you are mandated to use. The ASME Codes give you a way to do that and FEA may be the easiest of the prescribed methods available to you.

Regards, John

 

[juancito]

Thank you very much John
Regards

 

[jte]

John-

I don't get into Div. 1 App. 2 as often as I used to... Is there any limitation or consideration of the quantity and size of bolt holes anywhere in the calc's? I'm not aware of any. If not, then could I not hypothetically cut large holes near the edge and the hole just happens to go past the edge to form a type of slot?

Or, a similar but different situation that I'm aware of where a flange for a replacement component was made with holes ON the centerlines while the existing mating flange had the holes straddling centerlines. One proposed solution was to simply re-drill the new flange so that it would have twice as many bolt holes as planned. Is there anything which would prohibit this? What if the existing flange had another set of holes drilled so that each hole had a bolt in it? Eventually you could wind up with a very short ligament between bolt holes. I'm not aware of any restriction on this in App. 2.

jt

 

[gr2vessels]

I agree, the flange calculation appx.2 is lacking specific information, like every bolt requires a hole and don't drill more holes than needed for the number of bolts used in calculations. It is indeed confusing. Is not prohibiting either the drilling of holes radially, in the edge of the flange. In fact, is allowing the drilling and tapping of holes for lifting eyes for large flanges. It does, however, specify in the clause 2-3 (definitions), that A is the OD of flange or the diameter corresponding to the bottom of the slots extending to the edge of the flange. That means the material extending along the slot to the edge of the flange does not count for strenght. It is similar to the sizing of the clamped flanges, you can make slots until you run out of material.
However, the length of the ligament between bolt holes is related to the thickness of the flange, that's the reason one cannot keep drilling holes in a flange calculated for a number and size of bolts/bolt holes.
cheers,
gr2vessels