vacuum priming for submersible turbine pump 1

[zinman]

My client wants to replace a pair of vertical turbine pumps with submersible turbine pumps to reduce noise complaints from nearby residents. The vertical turbines are installed in cans connected to the nearby lake, which varies in level. With a submersible, the intake will be higher than the vertical turbine intake by the length of the submersible motor.

My question: Is vacuum priming the pump can a viable solution to lift the lake water to the submersible pump intake during low lake level conditions?

 

[dickon17]

A foot valve/strainer at the bottom of the can might work. Be careful to calculate sufficient flow to cool the submersible motor. This would be dependant on the clearance between the motor and the can.

 

[Artisi]

it is feasible to place a submersible in a "chamber" and make it into a self-priming unit, although in your situation it doesn't sound easy - therfore a sketch of what you propose would be helpful.

 

[zinman]

I am new to this forum. How do I submit a sketch? Re cooling the motors, I will specify a pipe sleeve attached to the pump body above the motor, open at the bottom, which will force the flow past the motor. I have used these in the past in booster pump applications with good results.

 

[Artisi]

You can try the following link to post a sketch

http://www.freeimagehosting.net/

 

[thewellguy]

I'm not sure I understand what your attempting to do. However, I will am that a submersible turbine that you discribing is never allowed to run "dry."

 

[Mark1669]

Submersible pumps can be mounted horizontally. I regularly design pump stations with this orientation. This would probably eliminate your problem with the pump suction being higher that the water level.

In either case you have to make sure you seal the motor leads as they exit the pump can. In the case of the pumps mounted vertically with a vacuum reprime, it simply won't work if you're drawing air across the motor lead. In the case of the pumps mounted horizontally, you want to keep the water from leaking out of the can across the leads.

There are several methods for sealing the motor leads. You can run the leads through a stub-out piece of pipe and fill this with resin (make sure the outer cable insulation is removed leaving the individual insulated wires, water will leak between the outer insulation and the inner).OZ Gedney offers a conduit sealing busing which I believe is rated to about 100 psi (good for most flooded applications)ref:

http://www.o-zgedney.com/PDF/R1thru24.pdf

page RA17. For applications where suction pressure exceeds 100 psi we've used a marine connector which screws into an NPT connection in the pump can (sorry I can't remember the manufacturer). The motor cable is spliced inside of the can.

Dickon17 is correct about motor cooling. Submersible motors run hot. They are required to have a minimum velocity of water flowing over them. The manufacturer's IO&M will specify this value. A link to Franklin's follows for reference:

http://www.franklin-electric.com/Manual/contents.html

I would not recommend using the vacuum reprime / vertical orientation design. It adds a level of complexity that makes the design very unreliable.

 

[Artisi]

It is possible mount a submersible pump in a vacuum primed vessel - many "moons" ago I took out a patent on this very arrrangement sighting noise attentuation as the patent - these units were used for wellpoint dewatering in residential areas where normal electric driven pumpsets were a problem. Selecting the right pump in terms of cable sealing, mechanical seal arrangement is important. Similar units are built by a Dutch company " Hudig " (not sure of the spelling now)- worth a check on the internet or ask me further questions as necessary.