Blind gasket load for operating condition

[ElCidCampeador]

Hi,

I've found a calculation of a pressure vessel designed acc. to ASME VIII Div.1. This vessel has shell+head and body flange WN std+Special blind (gasket=spiral wound).
Material: carbon steel.
Body flange and special blind are checked acc. to App.2.

In the calculation HG (gasket load for operating condition) is:

For body flange WN: HG=Wm1-H
For special blind: HG=Wm1

Why? Why are they not the same? Why for blind H=0?

Thank you

 

[Geoff13]

Not sure I understand. Appendix 2 does not provide rules for blind flanges.

Flat heads are covered in UG-34, and equation (2) is the applicable one for a bolted blind. Equation (2) does use W from Appendix 2, which is equal to W_m1 for the operating condition, but there isn't an H_G in equation (2).

Geoff

 

[david339933]

Are you sure it isn't HG = W for gasket seating condition? As P would = 0 making the hydrostatic end force (H)= 0?

 

[SnTMan]

Geoff13 has it right. The expression "For special blind: HG=Wm1" doesn't appear to be correct as the quantity HG should not appear in the blind calculations. Gasket seating condition, equation 2-5(e)(5) must be considered as well.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand