What would be a reasonable in-service target cleanliness level for Morgoil Bearing lubrication?
Lubricant is BP Spemo HB 460.
Cold Rolling Mill Back-Up Roll Bearing lubrication.

I like to use a green-yellow-red coding system for characterizing oil condition.

In Morgoil applications it seems that water is more of a problem than dirt. I have tested many samples from these systems. Water less than 600 ppm is green. 600 to 800 ppm is yellow and greater than 800 ppm is red. Of course Karl Fisher is a not the most reliable test method so to some extent water limits depend upon the reliability of the lab you are using.
As far as contamination level with particulates <19/17/14 is green and >*/21/18 is red.

Petri
Morgan recommends 80 micron(200 mesh)for the main filter and 100 micron (150 mesh) for the secondary filters.
Frank