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# Anti vortex device at tank outlet

## Anti vortex device at tank outlet

(OP)
with reference to the above thread. I want to dicuss some things about vortex breaker device installed at the outlet. I want to add this device on outlet of a tank which is 200mm. I wanted to know that is there a thumb rule for device height; while device vanes are usually mentioned as 2/3 of the outlet diameter, how much should be the height of the vanes (or baffles)? The mass flow rate through this drain is 130 kg/s and the density is 780 kg/m3. Based on the formula (S = D +2.3 D Fr), this gives the submereged depth of 1.9 m. The tank height is 5 m. Isnt it too much height for a vortex device compared to tank height?

Shamoon

### RE: Anti vortex device at tank outlet

"Disc type. The disc type (Figure 4) acts as a baffle plate that impedes axial flow without interfering with â€‹radial flow. It is typically designed to be three times the diameter of the outlet nozzle and mounted approximately 1 in. (25 mm) above the nozzle."

### RE: Anti vortex device at tank outlet

Also your exit nozzle is very small. I've calculated this at about 5m/sec. That's very high for an exit nozzle.

It's too fast really.

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### RE: Anti vortex device at tank outlet

(OP)
what should be the height of the blades (vanes)?

### RE: Anti vortex device at tank outlet

(OP)
@bimr : where is Figure 4?

### RE: Anti vortex device at tank outlet

Look on the bottom area of the linked page for the second page.

### RE: Anti vortex device at tank outlet

(OP)
@bimr, my sincere apologies. I couldn't still find it.

### RE: Anti vortex device at tank outlet

Figure 4 is the very first figure on the linked page and is mentioned in the first sentence on the first paragraph of the linked page.

### RE: Anti vortex device at tank outlet

Vortex breakers can be the vane type, the disc type, slotted pipe collector type. The ExxonMobil Basic Design practices provide detailed guidance on the configuration and design of these, but sadly, these docs are proprietory to EM. When you are in a tough spot, use the slotted type; from memory, it has the lowest submergence depth requirement.

### RE: Anti vortex device at tank outlet

There are two pages, click the page button:

### RE: Anti vortex device at tank outlet

(OP)
does anyone have done CFD of vortex baffles?

### RE: Anti vortex device at tank outlet

I usually work on the open area under the cap being at least 1.5 and preferably 2 x the area of the outlet pipe.

I think the hydraulic institute have some good guidance.

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

### RE: Anti vortex device at tank outlet

(OP)
@LittleInch Do you have any idea, if anyone has done CFD on it? which hydraulic institute are you talking about?

### RE: Anti vortex device at tank outlet

1) No idea - but I would have thought so
2) I meant this one https://www.pumps.org/
3) Also search "vortex breaker" on this site and many many posts appear. SOme will have links to designs. https://www.eng-tips.com/search.cfm?q=vortex+break...

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

### RE: Anti vortex device at tank outlet

Looks like you need a DN400 exit nozzle, not DN200, to keep exit velocity at 1m/sec approx. Install a DN400 internal slotted pipe collector, made out of corrosion resistant material, going through the vertical axis of the tank, with collector length to cover say 70% of tank dia. Cut half slots (with each slot say 50mm or 80mm wide) at equal distances along the internal collector, with total open area of slots > cross sectional area of a DN400 pipe (ie 0.13m2). Slots to face the sidewalls of the tank. My calcs say 6 such slots will do. Cap off the far end of the collector. With this, I'd say a submergence depth of 150-200mm above the top of the collector pipe will more than suffice.

### RE: Anti vortex device at tank outlet

(OP)
Ok, with regard to the size of the tank, if I have to increase the size of the tank by twice, is there any rule or law to scale the vortex breaker too. Smaller one has exit dia 110 mm while larger one has exit dia of 200mm.

### RE: Anti vortex device at tank outlet

Vortex breaker size is mainly dependent on pipe size, not tank size.

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Also: If you get a response it's polite to respond to it.

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