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Sizing Vent for High Pressure Steam Feed

Sizing Vent for High Pressure Steam Feed

Sizing Vent for High Pressure Steam Feed

(OP)
Hi
We're trying to size a vent for a tank that may potentially experience 70 psig steam @ 150 lb/h. Typical feed will be a grain slurry with some vapour. Before the tank there is a back pressure regulator supposed to decrease the P down to atmosphere.

The inlet to tank is 2" size, and we're thinking a 4" outlet vent would be sufficient. We want to size the vent so that the vessel is not considered a pressure vessel (so that the pressure in the tank never exceeds 103kPa or 14psi) even if the HP steam enters if the BP regulator fails.

Unfortunately we don't really have any good fluids books for resources or the API info either. Would you use the Bernoulli equation with losses

P1/rho + V1^2/2g + Z1 = P2/rho + V2^2/2g + Z2 +fLV^2/2Dg

where 1=in vessel; 2=at end of vent (14psi); setting the P1-P2=14psi and iterating to find the line size until this condition is met? Do you assume V1=V2 thus P1-P2=losses from entrance, constriction and vent length?

Also do you assume constant density (and is it the density of the steam entering)?

Thanks.

RE: Sizing Vent for High Pressure Steam Feed

You really should get your hands on the proper references. In this case you probably should refer to API 2000.

RE: Sizing Vent for High Pressure Steam Feed

You also need to worry about vacuum relief after that tank has been steamed for a while and someone shuts the steam off.  Many tanks have been sucked in over the years because this was not taken into consideration.  Do a search in this forum and the PSV forum and you'll find some very good discussion on it.

Good luck,
Latexman

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