Special bearing isolator for coal mine motor

Customer: Shenhua Group

Application: coal mine motor

Original seal: skeleton seal

Working condition: high speed, heavy dust and water vapor pollution.

Transformation scheme: double dust-proof, no drain hole design bearing isolator.

Reconstruction time: 2015

Transformation effect: no leakage, no pollution in oil tank, stable operation.

Before the introduction of bearing isolators, high-power motors and other large rotating equipment such as compressors and pumps driven by them all faced a common problem, namely lubricant leakage and contaminant intrusion. After replacing the original labyrinth seal with a bearing isolator with a unique structural design, the oil leakage problem of the equipment has been completely solved. Compared with the traditional sealing form, the advantage of bearing isolator is that as a non-contact, wear free sealing form, its service life can reach more than 5 years. Now it is widely used in pumps, motors, gearboxes, fans, steam turbines and other rotating equipment.

Take the compressor for example, it runs 24 hours a day continuously, but the service life of ordinary skeleton oil seal is only a few months, which is far from meeting the equipment design requirements. In view of the sealing performance of bearing isolators, more and more equipment manufacturers have accepted the recommendations of end users, taking bearing isolators as a high-end configuration of their production equipment. At present, bearing isolators have become the standard configuration on IEEE-841 motors and ANSI pumps. Famous manufacturers include ABB, GE, Siemens, ITT, Flowserve, and also widely used in GIW slurry pumps, Sulzer API chemical pumps, nuclear power pumps, etc.

Whether it is a pump, motor or compressor, when the traditional oil seal starts to leak, the operator will not shut down the equipment just to replace a seal. The loss of accidental shutdown of equipment is huge, and the operator will generally choose to let the equipment bearing continue to work without sealing protection, even if the equipment fails and has to be shut down for maintenance. When the equipment is disassembled in the maintenance workshop and other damaged parts are replaced, the oil seal that has been out of service for a long time will also be replaced at the same time. However, due to the failure of the seal, the bearing will operate under the conditions of insufficient lubrication and pollution, its service life will rapidly decline, it will be scrapped in advance, and it may cause damage to the equipment itself.

The speed of sliding bearing is very high, and the traditional labyrinth seal is not enough to prevent the leakage of lubricating oil in the bearing box. At the same time, the air flow carried by the motor rotor for motor cooling will also contribute to the leakage of lubricating oil. After the air is sucked in by the rotor, it passes through the stator coil to take away the heat, and at the same time, it will generate a suction force to suck out the lubricant in the bearing chamber. The leaked lubricating oil is mixed with dust to form sludge, which covers the surface of stator coil. When the oil stain accumulates more, it will affect the heat dissipation performance of the coil and cause the motor to overheat, which will reduce the working efficiency of the motor. The specially designed bearing isolator can solve the problem of oil leakage here after replacing the traditional labyrinth seal.

During the starting phase of the sliding bearing motor, the shaft will move back and forth about a quarter of an inch, that is, large axial displacement. This factor must be taken into account in the design of bearing isolators. The bearing isolator with special structure can allow the shaft to move freely, and the dynamic and static rings will not separate, nor will it cause any damage to the bearing isolator itself.