Lubrication for Refinery Mills

Correction on my previous post....its essentially a journal bearing lubricaiton ....i believe the journals are jacked first before the bearing start rotating ...and then lubrication beings .....can someone explains it in better terms how exactly ths whole things works in mills and similart situations

At rest a journal bearing (also called plain bearing or sleeve bearing) sits on the lower half of the bearing housing as gravity pulls it down and it will squeeze out any oil between the shaft and the bearing. This makes a dry spot where there is inadequate oil film to prevent wear upon start up. For large heavy shafts there often is installed a jacking pump which forces oil at high pressure into the bearing to lift (jack) the shaft slightly and wet that portion that has had all the oil squeezed out of it. If this isn't done the shaft drags against the bearing material and a significant amount of wear occurs the wear scar grows over time as a bit more of the shaft is in contact with the bearing each time this occurs. At least 90 percent of wear in sleeve bearings occurs at start up before the oil film is established.

Once the shaft is rotated the normal oil delivery system pumps oil at relativly low pressure into the bearing housing and some oil clings to the rotating shaft and is pulled down into the bearing creating an oil wedge that lifts the shaft and eliminates any metal to metal contact this is called "hydrodynamic lubrication".

I hope this helps a bit

that was very well explained ....thanks very much for your time ..!!!

Just a quick question...does that mean the lube system should have two separate pumps ...one to jack the shaft in the bearing and the second pump to supply lube oil when the shaft is rotating ....??

And is there any thumb of rule to estimate the lube requirement on a journal bearing (flow rate, presure, temp etc) ....may be from the total power thats being transmitted throu the whole system ?

Thanks in advance

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