Heavy duty industrial gears sets including spur, helical and bevel designs require extreme pressure lubricant, to provide protection against shock loads. Further it should provide protection against wear and reduce sludge formation.


  1. Drain the gearbox completely (warm gear oil) and inspect internally. Where it is necessary to raise the bulk oil temperature, the heater rating should not exceed 11.5 KJ/m 2 (7.5 W/in 2).
  2. Remove sludge deposits manually. Flush the gearbox with flushing oil/ new gear oil. Note: Do not use water, steam, kerosene, or gasoline for flushing.
  3. Discard the flushing charge and ensure that the gear box lubrication system and sumps is free of contamination. If the examination is not satisfactory, repeat the procedure.
  4. Refill with the appropriate viscosity Gear Oil and check the oil level.

If a gearbox is known to be sludge-free the normal top-up procedure can be followed, in which the new oil is mixed with the original oil. Use oil of the same grade in the gear box to maintain the lubricant at filler plug level. Check the lubricant level at each lubrication job, and if required top up by adding frequent small quantities, rather than occasional large charges.

Inspect the system regularly at an interval of every 250 hours of operation, for an initial period of three months and thereafter the frequency may be extended gradually, to normal manufacturers’ recommended periods, as long as conditions are satisfactory.

As a general principle, oil that has been in use for some time should be renewed completely. Drain and refill the housings as per manufacturers’ recommended periods, or twice yearly whichever is earlier.