Oil-Cooled Submersible Pump

An oil-cooled submersible pump is a borewell pumpset variant in which the motor stator is jacketed in dielectric oil rather than being cooled by the pumped water flowing past it. The design is used in low-water-table conditions, in pumps that may run dry for short periods, and where supply voltage fluctuates widely.

Function

The pump end is identical to a conventional submersible: stacked centrifugal stages lift water through the rising main. The motor is built with its stator windings sealed in an oil bath; heat generated in the windings is conducted into the oil and then transferred to the surrounding water through the metal jacket. Because the cooling medium is not the pumped water, brief dry-run events damage the motor less rapidly.

Design and specifications

Indian manufacturer Kirloskar Brothers Limited (KBL) markets the oil-cooled motor in its KU-series submersibles and claims a 10-15% energy saving over water-cooled motors of the same rating, together with tolerance of wider voltage fluctuations. Like water-cooled pumps, oil-cooled units fall under BIS IS 8034 (Submersible Pumpsets, second revision 2002) for technical conformance, and many models carry BEE star labelling for energy efficiency.

Operation

Installation is identical to a Submersible Pump: the pumpset is lowered into the borewell suspended on the rising main, with a power cable run alongside. Periodic oil-level and oil-quality checks are part of preventive maintenance, since oil degradation eventually compromises insulation.

Subsidy and adoption

The pumpset is eligible for state energy-efficient pump replacement schemes, BEE-star programmes and certain DBT-agriculture irrigation packages. Adoption is heaviest in low-yield borewell areas of peninsular India.

References

Kirloskar Brothers Pump Range. Kirloskar Brothers Limited.
IS 8034 Submersible Pumpsets. Bureau of Indian Standards.