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Join Date: Apr 2020
Posts: 15

Successive Bearing Failure in Cooling Water Motors in a Combined Cycle Plant

06/07/2022 12:51 AM

Members,

I will appreciate if you can share some insights for the following case. We experienced this on our combined cycle plant.

Successive Bearing Failure in Cooling Water Motors in a Combined Cycle Plant

We have been facing repeated bearing failures of Main Cooling Water System Motors, installed at our CCPP Plant. This is a vertical arrangement of pump and three phase induction motor designed to supply sea water to steam turbine condenser. There are 4 such arrangements for the said purpose, and non-drive end (NDE) Axial Spherical Roller Bearing 29480-E1-XL-MB (FAG) of all motors have failed, by now, within a very short span of time. These motors have just completed their commissioning phase and don’t have significant running hours. It is worth noting that during operation, all parameters including Pressure, Flow and Motor current were within range as specified in performance curve of CWP-Motor.

Motor Specifications are as below:

Direction of rotation

Clockwise, viewed from the motor top

Speed

370 rpm

Voltage

6600 V

Frequency

50 Hz

Power

3100 KW

Weight

33400 Kg

Motor Drive End Bearing

NU1052-M1 (FAG) - Grease lubricated

Motor Non-Drive End Bearing

29480-E1-XL-MB (FAG) - Oil lubricated (L-TSA68 turbine oil)

Make (OEM)

Xiangtan Electric Manufacturing Works

Maximum Transient Downward Thrust Force

530 KN

Normal Downward Thrust Force

382 KN

Variable Frequency Drive

Not installed

Cable Specifications

Cu-core, XLPE insulated, Stainless steel-tape armored, PVC sheathed, Flame-retardant grade A Power cable Single Core, ZA-YJV63-8.7/15

1×400 (3 Phase)

Shaft Grounding Brushes/ Insulation Paint on Shaft

Not installed / No

Maximum bearing life achieved until date is 2 months, and we have recently conducted inspection of one of the motor’s non-drive end bearing, which became un-operational due to abnormal noise.

Pictorial Representation (Motor NDE Bearing: 29480-E1-XL-MB (FAG) - Oil lubricated (L-TSA68 Turbine Oil)