Vortex Breaker Calculations

??? This isn't the sort of thing you can calculate !!!

Play with the shape of the inlet...maybe multiple inlets? Have the inlet further below the surface of the liquid...?

But..I'm going to stick my neck out here...calculations for this sort of problem are as much use as peeing on a Forest fire of a chocolate tea pot!.

Come on you mathematic modelers if you think you are hard enough....

(Sorry ! ...I'm getting my alter egos muddled...must be the copious amount of red wine I had with my Lamb chop! Baaad Kitty)

hahaa,

yeah I know what you mean,

I just wanted to prove atleast that this will make a difference.

or have an idea of the effect the size of the plate will have.

Constraint is that this is an existing pipe suction, with strainers cage. So adding a plate hopefully will help with the vortex created. I'm not sure how good you guys are with your fluid, and I definitely don't want to use CFD for this, we don't have a software for it. I need a "trial" version of fluent.

Any ideas would be much appreciated!

This occurs in most mixing tanks with a conical bottom and a big discharge pipe going to the centrifugal pump. I don't know of any formula that can apply to design the vortex breaker. We did it by careful observation and did several actual trials. Try installing a cross plate right at the tank bottom discharge entry instead of a single plate or baffle.

Describe your setup please. (fluid, sump size and shape, depth, flow, inlet arrangements, strainer size and any useful info)

The inlet flow could be off-centre and cause the fluid to circle around assisting fast vortex formation.

I quick temporary fix I used to suppress vortex formation (pumping water) was to drop a few planks on the surface of the water.

A plate placed horizontal above the strainer will increase the suction area and may help.

I would rather first increase the area of the strainer first. That is use a length of pipe with the holes spread evenly. a cross piece with arms to even increase the area more may be the next step.

I did some calculations about 40 years ago to create a inlet manifold for an application where a diesel driven 4 pump station only had a shallow water depth available. The result was a big suction grid.

Simply add a flat plate with dia. not less than 1.5 of nozzle dia., taking into consideration that the plate rise up above nozzle inlet not less than 0.5 of nozzle dia.

Cavitation in a pump usually occurs on the discharge side of the impeller, but can also occur on vanes in the casing, etc so disassembling the pump after a short operating time may reveal where the cavitation is so the correct fix can be applied. The pump may also be incorrect for the application.

Normally there is ten pipe diameters of straight pipe ahead of a pump suction, if you have a strainer ahead of the 10 pipe diameters it should break any vortex.

It sounds like the pump inlet is too close to the tank discharge.

If the pipe between the tank and the pump is too small you can create cavitation in the pump as the pump is starved for flow.

If the liquid has too high a viscosity and doesn't flow you can have cavitation.

I do not have all the informations right now, interms of head, flow , pump size etc.

Basically it's a centrifugal pump, removing water from the rain water pond, at the suction of the pipe, there exist rectangular strainer. Since the sump was not designed properly, we had problems with vortex being created around the strainers.

To reduce this we propose to add, baffle plate. But need to determine/optimize the plate size. I can't seem to find any literature regarding the determination of the plate size.

But someone replied to this thread suggesting some dimensions, where did you get this particular numbers?

Thanks,

There is a factor referred to as NPSH or Net Positive Suction Head which is basically, how much head pressure you have on the suction side of the pump.

In the system you describe, is the pump self priming and pulling up from the pond or is it below the pond surface having a pipe coming out of the "wall" of the pond?

Check the pump curve and it should refer to the NPSH requirement and that should stop cavitation.

The reply that referred to the plate being 1/2 of the pipe diameter is accurate.

Yes, pump is centrifugal pump, pulling water from the pond.

Suction pipe is on the bottom of the pond.

Where did you get or find the dimension of 1.5 x Dpipe?

For this application/system, NPSHa > NPSHr

So I guess, the answer is no, it is not self priming, unless it is below the pond level, which in this case is not.

Life isn't about knowing. Life is about trying. Go on. Have a go and share the knowledge if it works!

You can use a baffle and/or modify the suction line placing the fluid end side tube (suction point) downface (this will add losses due one elbow that you can determine).

SaC.

Update:

-using dimensions as suggested on this forum

-still waiting for them to implement

blah!!! I don't like to wait!! no news is good news right??

try this thread, for more info

http://cr4.globalspec.com/thread/18720/Vortex-Breaker

The physical Level of the liquid on suction side between the suction point entry and top surface of the liquid in the suction pipe plays a vital role.

If the suction pit is conical and the liquid entry is tangential, a whirl is created, due to tangential entry of liquid, this will also cause air suction.

Pl. check up these aspects.

DHAYANANDHAN.S

<...whirl is created, due to tangential entry of liquid...>

The Coriolis Effect also comes into play.