Forced feed lubrication for HPRT and its Pump 1

[SENGUTTUVAN]

For the Refinery plant , two Lean Amine pumps are proposed - One pump of configuration HPRT-PUMP-Motor and the other installed standby with Pump-Motor . Rated power of the motor is 1203 KW and the Installed motor power is 1400 KW. The Pump speed is 2965 RPM. The motor manufacturer requires forced feed lubrication for their motor where as the pump manufacturer goes by API 610 ( energy density for hydrodynamic lube if it is 4.0 x 10power6).For our case it works out to 3.56 x 10 power6). Is it advisable to design a LOS exclusively for motor alone or it is better to include the pump also with forced feed lubrication since the main oil pump will be driven by the pump shaft itself if we include the pump itself. both pump and motor are of Sleeve type bearings only. Thanks to clarify.

 

[JJPellin]

We have three high pressure amine trains that are configured the way you describe. One of them uses a forced lube oil system for pump, motor and recovery turbine. The other two use forced lube for the pump and recovery turbine, but not the motor. In my experience, it is more common to put circulating lube oil to the pump and let the motor run with oil rings and constant level oilers. For a pump as large as yours, I would absolutely recommend using circulating, pressure-fed lube oil for the pump bearings (and the HPRT). You state that the pump uses sleeve bearings. I am surprised that the pump does not use tilt-pad thrust bearings which would require circulating lube oil.

I would not recommend driving the main oil pump from the pump shaft. We have a dozen or so large charge pumps that are configured this way. That shaft driven pump will eventually give you trouble. And, it is impossible to properly test the auxiliary oil pump auto-start feature since there is no way to "turn off" the main oil pump. Until the main oil pump (or main oil pump drive coupling) fails, you won't know for sure if the aux pump will come up fast enough to avoid a trip. I would spend the extra money to put in two oil pumps on the lube skid.


Johnny Pellin

 

[SENGUTTUVAN]

Thank U JJ. Is there any specific reason for recommending oil rings lub for the motor? As you have rightly pointed out i have noted now that the thrust bearing is of tilting pad type for the Pump ( radial brg - sleeve). For the HPRT , the radial bearings are of tilting pad and the thrust is antifriction bearing. Is it a must to have force feed lube for tilting pad bearings? Thanks to clarify.

 

[JJPellin]

I did not recommend oil ring lubrication for motors. But, that is the way that most of our motors are configured. We have an electrical group that sets the motor requirements. In my experience, putting circulating lube oil on a motor that was not designed for circulating lube oil often results in leaks.

I seem to recall reading about a tilt pad thrust bearing that did not require pressure fed circulating lube oil. But, I have never seen one. All of the machines I have ever seen with a tilt pat type of thrust bearing were lubricated with a circulating lube oil system. Even if it was possible to lubricate this style of bearing without circulating lube oil, I would not recommend it.


Johnny Pellin