sumergence allowance with vortex breaker 1

[pumpmann]

hi
what is the guidance on the submergence to be allowed when you are using a vortex breaker on your suction pipe?
you can reduce the submergence when a vortex breaker is installed, am I correct?

 

[Artisi]

A so-called "vortex breaker" is really an anti-rotation device usually fitted to cancell any rotational effect of the pump impeller which can extend beyond the pump inlet. Having a vortex-breaker installed will not change good engineeering / hydraulic practice regarding submergence. Even with a "vortex breaker" installed surface or sub-surface voticies can still be encountered coming from the sump floor, or walls, or protrusions in the sump -such as trash-racks, compartment dividers etc.

 

[stanier]

Refer to HI/ANSI 9.8 Pump ntake Design. Also Pumping Station Design by Sanks or the US Army website.

 

[pumpmann]

if you calculate the submergence with HI formula, should you use the are of the bellmouth or the pipe to calculate the velocity and submergence?

another question
what the guidelines on submersible pumps regarding submergence?

 

[ccfowler]

Rather than concentrating on a formula or other somewhat arbitrary guidelines, it is most important to pay close attention to the configuration of the specific system to minimize vortex formation. Depending on the specific situation, the use of a vortex breaker may actually magnify the problem that it is intended to resolve.

It is most important to provide the most gentle possible introduction of the flow to the pump suction bell with the least practical rates of acceleration of the flow. Every reasonable effort must be made to avoid the introduction of turbulence and to avoid rapid fluctuation of the flow rate through the pump. Once formed, a vortex can persist for a very long time (hours), and a vortex created well upstream of the the pump suction can augment any vortex creation problem in the vicinity of the pump.

Codes and standards are very helpful and should always be respected, but it is almost always unwise to apply them as a simple form of "cookbook recipe." Look to these for the valuable guidance that they can and do provide, but pay more attention to all of the characteristics of the specific situation to optimize the result of your work.

I've experienced a number of pump suction situations where just clearing out needless flow obstructions and cleaning up a troublesome flow situation well upstream of the pump greatly reduced the perceived problem at much less cost than had been anticipated. Pumps are always an integral part of a much greater system, and solutions to problems almost always involve careful study of the entire system.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[Artisi]

Hi ccfowler,

Some of the best practical advice I've seen for quite a while - especially the last paragrah, deserves a star.