roughly estimate mechanical seal flow requirement

[Leclerc]

I need to estimate mechanical seal flow requirements for a project's worth of centrifugal pumps, so that, with an applied margin, I can specify seal water circulation pumps, pumping tanks, line sizes, etc., etc.. I have some estimates from a previous plant plant design, but that plant is about three times the normal flowsheet flow of the present plant in question.

How can I roughly, but quickly do this estimate, and can I use the past data: how can I scale it down?

regards
Leclerc

 

[rzrbk]

With the given information, I would recommend scaling the new flush requirements from the previous plant estimates based on a ration of the total number of seals instead of the total flow.

 

[Scipio]

If you're talking about a primary external flush, like an API Plan 32, a pretty reasonable ballpark is 3-5 USGPM of flush water, per seal. Two things to watch out for I've seen overlooked before. First that's per seal - between bearing pumps with two seals will have double that flow rate. Second be careful with standby units, if they aren't fitted with solenoids to block the flush when they aren't running, even the standby units will have flush going through the seal. Some owner/operators prefer the excessive flush water rates to the possibility of a solenoid valve not opening, or someone forgetting to open a manually blocked in flush.