What is a Submersible Pump

A submersible pump is contained in an air tight, sealed motor. For using it, the entire assembly is submerged into the fluid which is to be pumped. It does not rely on the external pressure of air to lift the fluid. Rather, mechanical seals are used to ensure that the fluid does not enter the body of the motor and cause a short circuit.

Thus, it can provide a significant amount of lifting force. It is often connected to a flexible hose pipe or it is lowered down guard rails or wires. The pipe is then rested on a coupling (called a 'duck's foot coupling') and is connected to the pipe network for delivery.

Submersible pumps have found their uses and applications in places where any fluid needs to be drained out. Examples are:

• Slurry pumping
• Aquarium filters
• Extracting water from bore wells
• Extracting oil from oil wells

The last example from the list given earlier is perhaps the most important and well-known application of submersible well pumps. The specialized type used for it, are known as Electric Submersible Pumps.

In this type, there are several parts, which rotate a series of centrifugal pumps ,which in turn increase the pressure of the oil in the well, and cause it to be pushed to the surface. They use a high voltage AC power source, which varies from 3 to 5 kilo volts.

This drives a motor capable of running at high temperatures (up to 300 degrees Celsius or 150 degrees Fahrenheit), at high pressures. This motor can extract liquids from deep wells (as much as 12000 feet or 3.7 kilometers), with really high amounts of energy, which can go up to 1000 horse power.

Their rotational speed is also quite high and can go up to 4000 rotations per minute. However, these motors are not very tolerant of solids such as sand, which can often be found mixed with liquids at such depths. Electrical submersible pumps, therefore, have a low amount of efficiency. Despite these obvious flaws, they have become quite popular.

One of the uses to which they are put to is when naval vessels use them to remove contaminated water from flooded areas. They use a 440 volt AC power source, which operates a centrifugal pump, which uses its suction power to suck in the liquids.

Normally, the pumped liquid is then circulated around the motor in a tube, so as to cool down the motor, as it tends to get heated. However, this can often lead to the liquid leaking into the motor from the tube. That is why certain types of fluids are avoided to be used for such purposes.

The maintenance of submersible pumps is quite difficult. Usually, there are seals which prevent the fluids from getting inside the motor, which can lead to a short circuit. However, care must be taken with the kind of fluid that is being pumped. Different fluids react differently.

Hot water and flammable liquids must be handled quite carefully. The hot water can easily damage some parts of the motor due to its heat, while flammable liquids can easily catch fire, and cause a lot of damage to the internal parts.

When the liquids are both hot and flammable, the electric supply used to run the motor may often heat the fluids, and cause the motor to burn or explode. Thus, special parts are used to drain such fluids. This leads to heavy maintenance costs.

Also, the motor often lies completely submerged under the fluid that is being pumped out. So, damage can be easily caused to the motor and the outer parts. This also adds to the maintenance costs.