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WRC 368, pressure thrust to be included in manhole calculation?

WRC 368, pressure thrust to be included in manhole calculation?

WRC 368, pressure thrust to be included in manhole calculation?

(OP)
We have a pressure vessel manufactured according to ASME Section VIII div. 1.  An inspector has rejected our design because we didn't take in consideration the pressure thrust on the manhole opening design per WRC 368.  

I've try to explain to the inspector that all stress caused by the pressure (pressure thrust included) in a nozzle are taking care by paragraphs UG-37, UG-40 & UG-41.

Weld strength path W2-2 (UG-41) measure the stress caused by the pressure thrust.

Who's right?  
 

RE: WRC 368, pressure thrust to be included in manhole calculation?

julien,
Unfortunately, the inspector might be right, because in given circumstances, the pressure thrust is in addition to the stresses you compensate with replacement area of the manway cut-out.
As far as I know, for the manways in high stress applications the WRC 368 is a standard calculation using PV Elite. I believe the same applies for Compress. However, I wouldn't bother with WRC 368 for a handhole in a standard air receiver.
cheers,
gr2vessels

RE: WRC 368, pressure thrust to be included in manhole calculation?

There are two different issues:
- when you satisfy UG-37 you insure that the cutout in the wall is replaced by sufficient material in order to take the pressure thrust that was acting on the cutout before the cut, and is now acting on the cover that transfers it to the nozzle neck. No other check is normally required to insure conformance to the code, unless loads other than pressure are also acting.
- WRC 368, like WRC 297 and WRC 107, allow for an estimation of local stresses at the periphery of the opening. If you are required to perform such calculations, you need to include the pressure thrust as if it was an external load.
See also FEM Analysis of a Large Nozzle-to-Cylinder Shell Junction

prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides
http://www.levitans.com : Air bearing pads

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