Submersible pumps are water filled and rely on the water they are submerged into as their internal lubrication for their motors. The motors are reliable when applied with their design limits of hydraulic loading, temperature and power requirements. Typical domestic, agricultural and municipal systems are great applications for these motors. The motors are often used in applications that can exceed the design criteria of the motors. Failure can occur and the advantage of these motors can be lost very quickly. Here are some common problems that can result in the failure of the motors.

Overheating problems

This is a common issue that affects the motors. Causes for overheating include overloading the motors, pumping hot water, loss of cooling flow of the water past the motor, scale or ochre build-up and frequent starts and stops of the motor.

Submersible motors should cool themselves in one way or another. This is typically accomplished universally by transferring the internally generated heat of the motor to the water that is flowing past it and into the pump. A lot of standard water well motors are usually designed to do this but add more safety margin.

The thrust bearing supports the thrusting weight of the pump of the column of water being lifted by the pump. Standard water well motors are designed in a way that the thrust bearing is lubricated by water. A small film of water between the thrust-bearing elements provides lubrication between the surfaces.

If your submersible pumps for hire overheat for some reason, this water film can boil. If it boils, the lubricating water film will be lost and at this point, the bearing surfaces will come into contact with each other and cause it to overheat. Failure of the thrust bearing can occur.

The failure of the stator is another issue that happens when motors overheat. Typical wet wounds and submersibles that are filled with water use PVC insulation that is used to insulate the copper windings whilst immersed in the water.

The wire has a maximum usable temperature of 70 degrees Celsius for standard motors and 100 degrees Celsius for higher-temperature pumps. If these temperatures are exceeded, the insulation is damaged and a winding phase to phase, winding turn to turn or winding phase to ground hitch can easily happen. When these faults arise, failure of the pump is unavoidable.

Motor seals

The motor seals keep the well water from getting into the motor of the pump. Both oil-filled and water-filled motors should do this to keep abrasives out of the internal bearings of the motor. In aggressive water, the acids can cause internal corrosion if they are allowed into the motor.

Standard well submersible pumps use a single mechanical seal. The seal can be of ceramic, carbon or carbide. Silicon carbide is a premium seal and is harder than carbon ceramic and it is very useful in sandy well applications. This means that if you want a high-quality seal, you should consider silicon carbide but it is more expensive.