Wet well pump noise.

[KathrynJane]

I know the manufacturers dry well factory test noise level for a pump, but I am using the wet well version. Surely submersing the pump will damp the noise produced (no pun intended ).
How do I work out the equivalent noise for the operating submersible pump??

 

[d23]

KathrynJane,

As a multi stage submergible pump manufacture I will try to offer a little, but I’m not real sure what you’re after with this so please be patience with me.

Noise is a vibration. The short answer is for you to use a device (transducer) to measure the vibration levels at the pump during operation. Being submerged in a liquid will dampen the audible noise of a pump, but the audible noise levels themselves are not the problem. The problem is; “what is the vibration that is causing the noise.” Any source of vibration will cause a shorter than expected run life from the pump.

Some sources of vibration:

There is fluid shear when operating a submergible centrifugal pump. There are methods to limit the effects of fluid shear in a centrifugal pump during the design phase of the pump, but fluid shear does exist and contributes to the overall pump vibration.

If there is air or vapor entering the pump with the liquid stream there will be additional vibration in the pump. In a perfect world you will only pump a clear, clean fluid stream. In the real world this fluid stream does not exist.

Misalignment of any type can cause vibration. This misalignment can be from many sources, but one that I see on somewhat regular bases is due to engineers not taking thermo expansion of the equipment into account. If you test equipment in a 70 degree Fahrenheit environment, then operate it in a 280 degree Fahrenheit environment the operating results will be different. Metal growth will cause close tolerance equipment to fail if it is not taken into account. As a rule the pump stages themselves are not the big problem for metal growth, but the axial load handling thrust bearing is. Typically thrust bearings have <.003 percent tolerance.

Variable speed drives operating the motor that drives the pump can cause a lot of additional vibration. If you operate a pump over a given speed range and happen to hit a critical speed it will destroy a pump in a matter of minutes. I normally use a Holtzer (not sure of spelling) formula for predicting critical speeds, then give it about 5% each side of the predicted speed.

I’m not sure if this information is what you are after, but hope it helps some!