Deep Water Submergable Pump Repair

I think you're confused.Submersible pump - Wikipedia, the free encyclopedia

Thank you for comments. Our observation that these pumps used as deepwell sea water operation are not having control to check the salt less ( fresh )water level inside pump.But there is protection of high current of winding of motor.

Regards

Sadasivam

Submersible pumps are provided with all safety devices such as over load protection, low level protector etc. Please check with the safety devices of the pump and if any of them are defective replace/repair it.

What type of submersible pump is it,for de-watering,sewage or deep well?. Some sewage pumps are cooled by transformer oil, some deep-well pumps are cooled by freshwater. Check seals and thermal sensor(PTC) in motor winding.

I suspect that at least part of the problem here is language translation. In addition to submergable/submersible that all the others have pointed out, the word fresh has multiple meanings. In normal English (at least in the USA) fresh water means water that contains very little or no salt (sodium chloride), as the water in rivers and lakes, and most underground water. Fresh is also used to mean something akin to new, as well as cold. So fresh water entering a submerged pump could mean sea water that has just entered the pump from the surrounding ocean, rather than water having no salt, which would have to be piped from a separate supply.

I'm no pump expert! I can imagine that non-salt water would be preferred over salted water inside the motor, since salted water is a better conductor of electricity and is more corrosive.

On the other hand, salted water is more dense than non-salted water. For a deeply submerged pump that was supplied with non-salt water for cooling inside the motor, the pressure inside the motor would be due to the weight of the column of non-salt water between the pump and the surface, plus any pressure inside the supply tank. The pressure outside the motor would be due to the (greater) weight of the column of sea water between the pump and the surface. If the cooling water supply tank is not pressurized, then the greater pressure outside the pump would tend to force salt water past the seals to the inside of the pump, where the greater conductivity and corrosiveness could cause problems.

In order to cool the motor, the cooling water must have adequate circulation. There must be some form of pump at least to start this circulation. Once started and the motor up to operating temperature, convection could conceivably keep the water flowing. On the other hand, if the fact of being submerged in deep water does not in itself provide sufficient cooling, then this must be a fairly large motor...

Was this pump designed for deep sea submersion, or only for fresh (well) water use?

What we have here, is failure to communicate.

I agree that submersable pumps usually use the pumped fluid as the cooling source.

There are pumps that use oil to back up bearing seals and such.

Obviously, contacting the manufacturer has not happened.

If the OP could supply the pump model and brand, perhaps someone here would be willing to do the rest................................................ for them.

OP, what have you done so far?

Submersible motors are often cooled by the water surrounding or flowing past the motor. If there is insufficient flow across the motor, it will overheat. You should contact the pump motor manufacturer for the proper flow requirements to provide cooling. Many motors used on submersible pumps are equipped with a shroud around the motor and intake. As all the water must now pass the motor to reach the intake, cooling is increased. That is the single best strategy at very low cost to prevent overheating. I am assuming the motor has overheat protection. If not add such device to the pump controls. You will likely need to contact the manufacturer for specifications.

Sadasivan,

Your ARE correct.

When Electric submersible deep well pumps are used in seawater Offshore such as in a Seawater Lift application for a drilling or production rig. They do use Electric "Wet Wound" electric motors which have Fresh / Tap Water as the lubrication and internal cooling medium for the motor.

Check the mechanical seal in the top of the motor. If it has failed, the suction from the pump end's intake (located just above the motor seal) will create a vacuum on the head of the motor drawing the fresh water out of the motor.

Also these type of motor have pressure equalization diaphragms in them to equal the pressure of internally in the motor as the out side environment. Every time the motor /pump is pulled out of service , before they are re-installed the motors need to be topped off with fresh water again.

There are several other possible reasons the motor could over heat. Electrical power, not enough flow around the motor, motor bearings, pump-end failing.

Have a qualified service tech inspect the unit (pump and motor).

Regards

BGuillot

BGuillot

Your reply looks very useful.We have noticed diaphragms and mechanical seal are damaged, bearing bushes worn out. We do not understand why motor should run dry causing winding failure

Regards

Sadasivam