Separation of stored grease 1

[cynwrig]

A collegue has flagged a potential problem. We have a grease packed gearbox which will have a shelf live of over five years - if it is not req'd as a spare! Does anyone know of an instance where the components of the grease have separated into oil plus the rest?

 

[plasgears]

Oil separation is common with petroleum greases. We have gone to PAO greases (synthetic), which do not separate like the petroleum types.
Some customers will scream if you are dripping out of the gearbox. We had a gearmotor that went into a printer, and we were obliged to make changes in the lube system. The grease was PAO NLGI 2, and the bearing was changed to a polymer type.

 

[cynwrig]

Plasgears, Many thanks for prompt reply - but it may have set the cat amongst the pigeons!! Guess most of us dont worry about separation because routine mtce, losses, etc hide the problem.
Cynwrig

 

[bosha]

I would think it would have to do more with thickener type(reversability considerations) or the amount of thickener,I think that would have a lot to do with bleed resistance.The whole trouble is it's supposed to separate under shear to lubricate the bearing

 

[romke]

separation of oil and grease is to a certain extend quite normal. this "bleeding" can also be observed in containers with grease. due to the influence of gravity the oil is forced out of the grease structure and therefore grease dispensers on a barrel usually have a followerplate to flatten the surface of the grease to prevent this from happening. in most cases there is no need to worry though, because when the gearbox starts operating the oil is most likely "sucked back" into the grease structure. whatever has leaked out of the container however is not retracted and this can cause both technical and cosmetic problems.

the amount of leakage is partly depending on the thickener agent of the grease but the viscosity of the fluid incorporated is of much larger importance. the thinner the fluid used, the more leakprone a grease will be.