ASME Sec. I External Pressure Calculation

[FabianoRibeiro]

Dear all,

Can anybody help me with Section I calculation?

In PFT-51.1.2, the code describes the method for evaluation of the maximum allowable external working pressure, which is just like Sec. VIII procedure. However, in the case of a cylinder with definite pattern openings, what consideration should I use to consider these openings? Should I include the ligament efficiency?

Best regards.

 

[prex]

You should determine the required thickness without accounting for the openings, then check that you have sufficient extra thickness to reinforce the openings.
Of course you won't find the rules for that in ASME I, and even ASME VIII doesn't treat, if I recall correctly, the case of openings in a definite pattern under external pressure.
The point is that ASME VIII requires for external pressure 50% of the reinforcement for internal pressure, but I wonder whether this can be straightforwardly applied to patterned holes. However, if you can provide 100% of the reinforcement as for internal pressure (the required thickness being still determined for the external pressure) you'll be OK.

prex

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[FabianoRibeiro]

I'm thinking of using the ligament efficiency, which is the factor that accounts for the reinforcement of the openings. However I'm not sure if that is reasonable.

 

[prex]

The ligament efficiency is for use with UG-27, so for internal pressure, I can't see how you plan to use it in UG-28.
What I suppose I would do:
1)Calculate the required thickness per UG-28
2)Consider each hole in the pattern as an isolated opening by setting the limit of reinforcement equal to half the minimum distance between holes
3)Calculate the required reinforcement per UG-37 (50% of the value required for internal pressure)
4)Check that the extra thickness in the wall is sufficient for compensation.

prex

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads