Drilling Holes in Pressure Vessel Flanges

[chris812]

Hello,

I have been designing a pressure vessel for the last week. I have based all my maximum allowable stresses on ASME code but can't figure out how to include drilled holes. I plan to be using a pipe welded to a cap at one end and attached to a blind flange with holes drilled in it at the other.

I am sure that the added holes will compromise the stress acting on the flange but don't know how to measure (or calculate) this. I also imagine that there would be a minimum distance between holes allowed.

If needed I am using pipe with ID of 1.1" and wall thickness of 0.11". The cap is elliptical and the flange is a nominal 1" 300 class slip on. All material is 304H stainless steel. I plan to drill a 1/2 diameter hole in the center of the blind flange.

Any help would be greatly appreciated,

Chris

 

[Mech_Engineer]

It's going to be geometry-dependent, but you'll have to take a look at the stress concentration factor for the hole and/or run an FEA model of the vicinity you're worried about.

Here is a book I have that helps with calculating stress concentration factors of features like holes in plates:

https://www.amazon.com/dp/0471538493/?tag=pfamazon01-20