(20 min.) Case Study: Installing different contact angle bearings made the equipment out of service for 6 months

Akhil Jeet Rathore, Deputy Manager, Indorama Eleme Petrochemicals & Fertilizers Ltd.


Lesson learnt – Installing different contact angle bearings made the equipment out of service for 6 months


Chiller / refrigerant compressors are used in industries to cool down a gas as required by the process. In my case, the twin screw compressor is used to cool down natural gas. It has a male & a female rotor, supported by sleeve bearings for radial loads & back to back paired angular contact ball bearings for thrust load. The equipment was having high vibrations & was pulled out to overhaul. The sleeve & the thrust bearings were damaged & were replaced with new.

The OEM recommended bearings were 7317A, of which 4 bearings were required. While the stock availability was 2 bearings of 7317A & 2 bearings of 7317B. With A & B indicating different contact angles. No options left, the compressor was assembled with the 7317A & 7317B bearings. As the equipment was put into operation there was some reduction in noise & vibration but was still on higher side & kept on increasing as the equipment was running. And after an operation of 4 weeks the equipment was stopped again due to high noise & vibration & was kept as emergency standby. It was planned to overhaul when the correct bearings are available.

The bearings were received in Dec-19 & were replaced with the old ones & equipment was put into service again. This time it was running perfectly fine with no abnormal noise & low vibration values.
The case concludes that ignoring the bearing suffixes can lead to complete stoppage of an equipment. Thrust bearings are very critical & if are to be installed in pairs on different rotors, they should have the same contact angle.


A condition monitoring Enthusiast with 11+ years of experience in the field. Worked with industries like Cement, Automobile, Refinery, Petrochemicals & fertilizers. Learning everyday