Machinery Lubrication

Machinery Lubrication Jan-Feb 2018

Machinery Lubrication magazine published by Noria Corporation

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moving out of the centrifuge through the clean oil output port. As the solid particles move to the bowl wall, some of the solid matter sticks to the sides of the bowl, but much of it is concentrated as a slurry of solid particles in the oil. If you were to slowly feed the oil for a long period of time so all the particles moved to the wall, you could remove all the particles as solid matter stuck to the sides of the bowl. However, such a slow feed rate and the amount of time spent scraping solid matter from the centrifuge bowl would be too imprac- tical and labor- intensive for actual production. Much of the solid matter can be removed before the bowl fills up. Draining the slurry from the centrifuge before the bowl fills permits a higher feed rate without sludge spilling over into the cleaned oil. is greatly extends the runtime between bowl cleanings and also reduces or eliminates sludge spilling into the cleaned oil. e amount of sludge concentrated in the centrifuge bowl will depend on the G-force and the feed rate. A higher G-force will equal a higher concentra- tion of sludge. e feed rate must be low enough for the centrifuge to do its job and settle the sludge to the outer wall. At some point, the bowl will fill with sludge and spill over into the cleaned oil. When this occurs, the centrifuge will be removing very little, if any, contaminants, as they spill over into the cleaned oil as fast as they are removed. To remedy this situation, either slow the feed rate so all particles move to the outer wall and only cleaned oil is discharged, or stop the centrifuge and drain the sludge before it spills over. How often should the centrifuge be stopped and the bowl drained? An approximate starting point is deter- mined by the bowl size. Operating any centrifuge longer than the bowl capacity is like trying to put 10 gallons of sludge in a 5-gallon bucket. e runtime between drains will vary by the G-force, the oil's viscosity and the percent of contamination. e volume between drains will remain about the same. Programmable centrifuge control- lers can remove the burden of manually draining the sludge from the centrifuge, allowing automatic, one-pass cleaning. Applications While results will depend on how each centrifuge is used, some reports have shown 99.6 percent of particulate being removed from used engine oil. Fleet services have been able to clean their engine oil and blend it back with a percentage of new oil, reducing the cost of replacement oil by 70 percent. Hydraulic shops have also cleaned and reused oil that was contaminated during repairs. One manufacturer of extruded aluminum parts in the auto industry had 5,000 gallons of oil which had become contaminated with graphite in the pressing process and needed to be replaced at $15 per gallon, plus the cost of disposal. Centrifuging the oil brought it back into service for a savings of $75,000. e manufacturer now maintains its oil with a pair of bowl centrifuges. Another company has saved more than $250,000 annually by switching to centrifuging and reusing the synthetic oil in its natural gas compressors after previously discarding the oil at the change interval. As you can see, a centrifuge can offer many advantages and provide an effective method of oil reclamation. Be sure to consider this option the next time you need to discard or replace your used oil. ML 24 | January - February 2018 | www . OIL RECLAMATION

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