When do I need a vortex breaker 7

[olef]

Can anyone give med the formula (or reference to the formula)for when a vortex breaker is needed in a vessel. I am particularly concerned about the liquid/liquid interface in a 3 phase separator.

Regards
OleF

 

[imok2]

Olef,
Sizing one is not really a science. They are typically two pieces of metal welded together in a criss-cross and about 1.5 times the pipe diameter in height.

 

[imok2]

You will usually need one whenever you think you will pull in a vapor with the effluent. The votex will set up a low pressure opening in the vortex which will mix vapor with fluid

 

[MJCronin]

olef,

If your question is, "Under what circumstances does a vessel need a vortex breaker in a center drain opening ? In my opinion... always install a vortex breaker.

Remember, a vortex breaker is installed so that a vortex does not develop when the vessel is being pumped down. The VB is installed to protect the pump (and, of course to eliminate a possible cause of pump probelems that is difficult to verify). A pump may be within its NPSHr requirements and still have poor operation due to vortices being formed within the suction piping.

My experience has been that this is such a "low cost" item and that many clients simply require them on all pumped drains on all new vessels. There are no ASME/ANSI standard dimensions for vortex breakers.

Each process chemical company seems to have developed a "process vessel guideline" with details of VBs that they want installed in new vessels.

My thoughts only


MJC

"There comes a time in the affairs of man when he must take the bull by the tail and face the situation." W.C. Fields

 

[olef]

Thanks for good answers. I think I will have to be a little more specific.

In this particular application a vortex breaker or any restriction in the outlet is out of the question. So I will have to have a minimum interphase level that is sufficiently high. On the other hand, I don't want to waist operation volume on an unnecessary safety margin.

So what I'm asking for is a way to predict the development of the vortex in the lower of two liquids.

Regards
OleF

 

[imok2]

OLIF:
Try this web site:

http://www7.nationalacademies.org/usnctam/Fluid_Dynamics.html

 

[imok2]

Olif, I think this is a better site:

http://in3.dem.ist.utl.pt/lxlaser2002/papers/paper_1_3.pdf

 

[quark]

Minimum submergence required to prevent air vortexing into the pump is,

S = D + [(0.574Q)/D^1.5]

Where, S = Minimum submergence required in inches
D = Suction bell diameter in inches
Q = Flow rate in USGPM

This equation is given by Butleja in thread378-51850
He says the reference is ANSI/HI 9.8-1998, section 9.8.7

I personally checked this equation for a chilled water system and results are very good.

Regards,


Believe it or not : Eratosthenes, a 3rd century BC true philologist, calculated circumference of earth with the help of a stick and it's shadow. The error was just 4% to the present day calcuated value.

 

[MJCronin]

quark,

Doesn't your formula apply only to water ?

My understanding was that this HI Standard formula was developed for use in cooling tower, or similar applications.

MJC

"There comes a time in the affairs of man when he must take the bull by the tail and face the situation." W.C. Fields

 

[hacksaw]

to address an earlier response " a vortex breaker or any restriction in the outlet is out of the question"

the purpose of the vortex breaker is to reduce the restriction to flow caused by the vortex...in effect you achieve the least amount of restriction by introducing an obstacle to flow.

additionally on the basis of the interface level, the vortex can actually becomes more serious at a lower flows than with single phase fluids.

 

[olef]

Hacksaw, my customer absolutely does not want a vortex breaker in the outlet, because of such things as drill cuttings and other debris.

It is logical that it gets worse with two liquids of more or less equal densities, as gravity won't help close the vortex to the same degree as with water/air.

However, I still haven't found a good engineering source on how to analyze the system.

As always, I am looking for a neat little equation that contains all the parameters I expect and no more, but I guess life isn't always that easy.

Regards
OleF

 

[quark]

MJC!

You may be right. I never saw that document myself. But what I feel is that any fluid with rho/mu value equal to or less than that of water may fit into this equation as the main reason for vortices is turbulence. What do you think?

Good point Hacksaw.

Regards,


Believe it or not : Eratosthenes, a 3rd century BC true philologist, calculated circumference of earth with the help of a stick and it's shadow. The error was just 4% to the present day calcuated value.