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. Max operating conditions are 350 psig and 1200 fahrenheit.

Have a missed something in ASME?

Any help would be greatly appreciated,

Chris

Dear Mr. Chris
If your Code of construction is ASME SEC VIII Div-1, then pl. refer UG-39 Reinforcement Requirment for Opening in flat Heads.
Blind Flange to be considered as Flat Head & Reinforcement to be provided for Drilled finish hole. If Requirment is not adequate then Blind flange THK to be increased or additional Reinforcement to be provided.