NFPA 30 Week Roof-to-Shell Seam
NFPA 30 Week Roof-to-Shell Seam
(OP)
Table 22.4.1 (a) refers to a week roof-to-shell seam. To have a week roof to shell seam do you have to comply to the frangible roof joint as per API 650 or can you just have a week roof to shell joint by grinding portions out?
My second question.... Are you allowed to fabricate an emergency vent with a manhole with long untigtened bolts? If so how would you calculate the venting capacity of the actual manhole to suit the requirements set out in API2000?
Thanks
My second question.... Are you allowed to fabricate an emergency vent with a manhole with long untigtened bolts? If so how would you calculate the venting capacity of the actual manhole to suit the requirements set out in API2000?
Thanks





RE: NFPA 30 Week Roof-to-Shell Seam
Regarding question 2, NFPA 30 requirements for emergency vents require it to be evaluated by an independant third party. If you choose to use a long-bolt emergency vent (which is allowed), it will require evaluation to be compliant with NFPA 30. As to the calculation method, the equations are clearly defined in API 2000.
RE: NFPA 30 Week Roof-to-Shell Seam
I think I remember using the guide of the bottom should be 1.6 or 1.8 times the design pressure of the top. Which I think that parameter was from 650 frangible design.
Use an example of a 12-ft diameter vessel, no way to meet 650, but many of the principles could be applied.
RE: NFPA 30 Week Roof-to-Shell Seam
In the attached calculation we have proved the pressure at which the manhole cover will begin to lift but cannot prove that it will be able to vent the total amount and at what pressure it will vent the total calculated amount.
Any assistance would be appreciated.
RE: NFPA 30 Week Roof-to-Shell Seam
RE: NFPA 30 Week Roof-to-Shell Seam
RE: NFPA 30 Week Roof-to-Shell Seam
RE: NFPA 30 Week Roof-to-Shell Seam
I just have a couple of queries regarding your calculations.
1) Are the units constant throughout ie. is the manhole area to be in in2 or ft2?
2) Absolute pressure inside tank... Is this the maximum design pressure taken from API 650 Appendix F or the pressure at which the manhole will begin to lift?
Look forward to your response.
RE: NFPA 30 Week Roof-to-Shell Seam
CFH = 1,667*Cf*A*√(Pt-Pa)
Where;
Cf = Flow coefficient of valve
A = Area of manhole or area of manhole lift
Pt = Absolute pressure inside the tank
Pa = Absolute pressure outside the tank
I would like to know:
1) Are the units constant throughout ie. is the manhole area (A) to be in in2 or ft2?
2) Absolute pressure inside tank... Is this the maximum design pressure taken from API 650 Appendix F or the pressure at which the manhole will begin to lift?
Any advice would be greatly appreciated.