UG46(j) why this 11/16" requirement 1

[FJTOM]

I was trying to find an elliptical manway (11 x 15)to put into a 12ga small shell. All seemed to have heavy walls. I happened across UG46(j) which requires 11/16" wide flat gaskets on internally energized manway. What is the reasoning or engineering behind this requirement?

 

[racookpe1978]

What do you mean by "internally energized"?

What pressure will your thin-walledd vessel see?

Gasket width must be wider than the bolt holes that penetrate the (usual) gasket.

 

[vesselfab]

racookpe

this is a cover that has yoke and pulls from outside

no bolt holes

 

[FJTOM]

Right you are vesselfab.
I've done the calculations on this manway as a nozzle and it does not require a wall anywhere near 11/16". (I did say 11/16" gasket width, but UG46(j) actually says minimum gasket bearing width, not quite the same).
Commercially available code manways seem to have at least 3/4" wall, so manufacturers must know about this.

I would still like to know the logic, if any behind this requirement. The large weight of this type of manway will kill this project. Can I use thinner wall?
Any help from the code mavens would be appreciated.

 

[vesselfab]

You will not be able to find the formed neck to fit the cover and yoke.

by the time you got partial data on a smaller neck and a code stamp for different yoke design....

you will have wasted a lot of time, effort and money

They are cheeeeeep

just call up LA Boiler and order one and don't worry about it.

 

[FJTOM]

Thanks vesselfab.
The cost of the manway was not an issue. This vessel has trunions on both ends (heads,horizontal vessel)and the eccentric weight of the manway required a much larger motor to turn the vessel, probably killing the project.

Thanks for your help.