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Vortex Breaker Article

Vortex Breaker Article

RE: Vortex Breaker Article

I do not understand "a problem with a flash vessel that is cavitating due to vortex formation"

There is much industry experience with pump cavitation.... but not vessels

Can you show us vessel drawings, describe process conditions and further explain the problem ?

The only flash vessel I have had experience with are those associated with boiler blowdown.... these vessels are designed to encourage internal vortex flow to disengage flash steam from condensate.

Pumps drawing from boiler blowdown vessels frequently have transient NPSHa problems and cavitation problems are frequent.

Is this your problem ?

MJCronin
Sr. Process Engineer

RE: Vortex Breaker Article

It's not really cavitation but vapour drawdown / coning / gas or air entrainment.

A four cross plate will get you quite a long way, but 850 nozzle is quite big. You must be getting a large flowrate / velocity?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Vortex Breaker Article

To prevent gas from vortexing down into a liquid exit nozzle, you need a well designed vortex breaker and adequate liquid submergence depth, measured from the vortex breaker top. Vortex breaker configuration may be this cross plate type or a slotted liquid collection pipe. Used to have a copy of the ExxonMobil design method for these many years ago, but not anymore. Offhand, you'd need at least 100mm liquid submergence. Max liquid exit nozzle liquid stream velocity also should not be more than 1m/sec.

RE: Vortex Breaker Article

(OP)
I am well aware of normal vortex breaker design and design rules for outlet velocity. I am mainly interested in literature articles specifically discussing the benefit of the cover on preventing gas carry under / vortex formation vs no cover.

A number of previous threads have referred to the link I posted in the original post suggesting it specifically discusses this topic. I just want to read that article if anyone saved a copy :)

The flowrate is large hence the DN 850 nozzle and the submergence is adequate based on ANSI however CFD results indicate vapour carry under and that the plate would be beneficial to prevent this. Hence I am looking for articles that discuss this topic.

RE: Vortex Breaker Article

Perhaps you already know this - see figure 6-30 / eqn 6-137 on min submergence in drain nozzles - Perry Chem Engg Handbook 7th edn.

RE: Vortex Breaker Article

(OP)
Thanks MJCronin. I had already found that article when searching the web. I am not sure if it is the same as the original link though.

RE: Vortex Breaker Article

You say this is a flash vessel, so you've also got to have adequate degassing of the liquid phase before it enters the DN850 liquid exit nozzle. Use Stoke's Law ( or the appropriate expression ) for adequate disengagement of a 300micron gas bubble from the liquid phase. Essentially, the superficial liquid drawdown velocity ( in a vertical vessel say) should be less than the terminal rising velocity of the 300micron gas bubble. This criterion is typically used when the liquid exit stream feeds a pump. A vortex breaker is assumed to be in place with adequate min submergence.

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