gasket seating stress

[Charan5]

Dear all,

I have a weld neck flange reduced bolt circle with dia 9.5" OD with bolts 3/4" dia and mating flange is flat face 6" flange. I am just wondering the seating stress of the gasket and the seal. Can anybody suggest what type of gasket to be used and the thickness. My design pressure of the vessel is 150 psig air service. The material of the flange is SA 516 Gr.70. Also, I am concerned about tear out from bolt OD to edge of the flange.

 

[DSB123]

If I get you right it seems like you intend to bold a raised face Weld neck flange to a flat face flange ??

Be careful. You need to check that the thickness of the flat face flange is suffiient to accommodate the bending moment caused during bolting-up of the joint. Normally a flat faced flage is mated to another flat faced flange so that you do not get the bending moment caused by the bolts.

 

[Charan5]

Thank you,

Also, I would like to know where the thickness of gasket is used calculating the minimum load to seal the gasket in Wm1 and Wm2.

 

[SnTMan]

Charan5, the gasket thickness appears, if at all, in published data for the gasket m & y values. For your service any of a number of composition gasket materials should serve. Pick one and contact the manufacturer. 1/16" or 1/8" thickness should be OK.

I'm not sure what you mean by "reduced bolt circle", but with standard dimensions tear out is not a problem.

Regards,

Mike

 

[Charan5]

Thank you,

By bolt circle is 9.5" dia and the bore diameter is 8.063" and we are using studs (instead of bolts) with 3/4" dia studs. I am using studs because I do not have room to use nuts.

 

[SnTMan]

Charan5, from what I gather, you have about a 0.34" margin between the stud OD and flange ID, and want to determine if it is adequate. I suppose you could calculate the hoop stress at 0.34" thk. as if it were a cylinder, or a similar approach.

It would appear that your 6" mating piping (if any exists) would be no larger than about 6.36" ID, it is possible to reduce the flange ID?

Since it seems you are studding into your flange, will you be able to break this joint with the studs in place?

Regards,

Mike

 

[arto]

Look in the old Taylor Forge Bolt Data Chart - it gives edge didtances & other dims by bolt size. for 3/4 bolts, they have 13/16" cL-edge. If you're really tight on space, check out Graylocs:

http://www.grayloc.com/grayloc/