Flow rate of lubrication system for gears 2

[APmmore]

Can any one help me, how LPM of lubricating pump is selected for a gearbox. Have seen many gearboxes having 20 % as its pump LPM with respect to the sump size. But for some smaller sized separator gearboxes the LPM is twice than that of oil qty.

Is there any calculation for LPM selection based on various factors please share.

 

[racookpe1978]

Depends on the wear expected from gear-to-gear: Tooth pressure over the contact area compared to heat that must be removed created by the (1) friction between the teeth and (2) the wear (machining) energy if the two teeth actually rub against each other.

Thus, a very lightly loaded tooth with a larger contact area can be adequately lubricated by a lightweight oil or grease at low pressures at low flow rates, right?

Two very heavily loaded teeth touching each other at small areas at high speeds with tight clearances requires a very high pressure oil forced between the teeth. The same situation (heavily-loaded teeth) with very slow speeds requires a heavy grease at high pressure forced in at lower flow rates to prevent the lubricant from being squeezed out.

 

[FennLane]

The real issue with a splash lubricated gearbox will be the duration it has to run for and the power losses due to the mesh and windage.

Yu need to think that the gears not only need lubrication but also cooling as will the bearings.

I would try to budget for a minimum of 1% of the transmitted power being rejected into the oil.

If you use an oil such as Tellus 37 or Mobil DTE24 then you maximum running temperature needs to be about 80degC with a Warning at 90 and a trip ay 100.

You will need enough oil volume the maintain this temperature depending on the dissipation of the gearbox casing.

If you can't accommodate this you will need a cooler and hence a pump .