ASME Section I PG-29 Dished Heads 1

[M1Can]

I am looking for some help interpreting the required thickness of a semielipsoidal head with a manway. In the past we sized the head thickness based on a blank unstayed head and provided reinforcement for the manway opening ( Re PG-29-4)

But we were recently reviewing a new customers calculations and they size the thickness of the head per PG-29.3 which results in a head thickness of almost double that required for a blank unstayed head ( although no reinforcement is required).

I think it comes down to what is considered "a flanged in manway" , is this an opening integral to the head ie pressed in. The frames for the manways we have experience with are bar rolled and welded into the head , which we check to ensure that they provide adequate reinforcement for the opening.

Any help on this will be greatly appreciated


M1 Engineering

http://www.m1engineering.ca

 

[prex]

To me a flanged-in opening is when a hub is extruded in the metal of the shell, normally towards the inside. This kind of construction was used in the past for oval openings, where the cover was placed inside, so that the gasket was compressed by the internal pressure (so called autoclave closures). Of course you won't see anything similar in modern vessels.
In my opinion your approach based onto PG-29.4 is the correct one.

prex

http://www.xcalcs.com

Online tools for structural design

 

[GenB]

"But we were recently reviewing a new customers calculations and they size the thickness of the head per PG-29.3 which results in a head thickness of almost double that required for a blank unstayed head ( although no reinforcement is required)."
Are going to use the flanged-in manway or the welded ring?
why are you mixing the two;
if you customer calculated with a flanged-in and the construction is with a welded ring your customer calcs are wrong.
I think that only Cleaver-Brooks fabricate flanged-in manways these days.

 

[M1Can]

Thankyou Prex and GenB for both your replies, I think I am OK now , although I believe the code could be clearer on what is considered a flanged-in manway is ( Section VIII has a sketch but they call it a flued opening).

I also agree with GenB that the calculation needs to reflect a welded ring manway.

Thanks Again

M1 Engineering

http://www.m1engineering.ca