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Emergency Vent with Manhole with long Bolts

Emergency Vent with Manhole with long Bolts

Emergency Vent with Manhole with long Bolts

(OP)
I was recently given the calculation for emergency venting as per NFPA 30 using a "manhole with long bolts" 22.7.3.2.1 (2) as per the below.

CFH = 1,667*Cf*A*√(Pt-Pa)

Where;
Cf = Flow coefficient of valve (set at 0.5)
A = Area of open manhole or area of manhole lift
Pt = Absolute pressure inside the tank (inH2O)
Pa = Absolute pressure outside of the tank (inH2O)

My questions is as per below;

1) Is this calculation correct and where can I verify it?

2) How do you determine the pressure when the manhole cover is in the fully open position as required by NFPA 30 22.7.3.10 (2). I can easily calculate the opening pressure however do not know how to calculate the pressure when fully open assuming I had a predetermined length of bolt.

I look forward to replies.


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