Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/359954
42 July - August 2014 | www.machinerylubrication.com BeArINg lUBrICAtIoN balance sleeve, journal bearings and balance stage pieces) was recently replaced to provide increased feed water flow to the boilers following the maintenance period. This change also modified the pump recirculation system and seal water injec- tion system. As noted previously, the pump requires a lube oil system. Its purpose is to provide lubrication and cooling to the pump thrust bearing, two radial journal bearings and the motor bearings. The lube oil system is self-contained and includes a shaft-driven oil pump, heat exchanger, strainer, pressure-relief valves, thermom- eters, pressure gauges, oil drain sight flow glasses for each bearing bracket, a reservoir, and an auxiliary motor-driven lube oil pump. The primary lube oil pump is mounted on the end of the main pump shaft. The auxiliary lube oil pump is mounted adjacent to the lube oil reservoir and is used as a backup to the main lube oil pump during startup. The lube oil cooler is utilized to cool the lube oil and receives cooling water from a separate cooling water system. Signs of Bearing Problem In 2012, the modified feed pump was started to perform a pre-operational test. During the first portion of the run, vibra- tions (casing mounted) were noted as abnormal but acceptable. Audible noises resembling air expulsion and water spewing out from the pump seals were also noted. Following the test run, the pump oil sample showed an abnormal black color and particle content. An additional oil sample was obtained and sent for independent lab analysis. The elemental spectroscopy showed abnormal levels of iron and tin. Because lead was not seen in the sample, it initially was reported that no bearing damage had occurred. Based on these results and in-depth discussions, a visual inspection of the main oil pump suction filter was performed. This showed visible debris/shavings consistent with shaft and bearing materials. In order to determine where the debris was generated, the covers of the outboard and inboard bearing housings were opened. When the outboard bearing cover was lifted, mainte- nance personnel discovered strings of metal that appeared to be shavings of bearing metal (Babbitt). The outboard radial Pump shaft damage During analysis, debris consistent with machine (metal) cut- tings was revealed.