High Temperature Gear Lube

[Philrock]

I need to find a gear lubricant that will work properly at 450 degrees F. I have found several lubricants with flash points and scuffing temperatures well above this temperature, but have also been told by an engineer at a ball bearing manufacturing company that there are no lubricants that work well at this temperature. Pitch line velocity is 1400 fpm. Contact pressures are as allowed by AGMA standards with 1.5 service factor. The gearbox is small, so unit cost is not a problem. The oil will also lubricate ball bearings in the gearbox. Any suggestions?

 

[diamondjim]

Can you recirculate the oil thru a
cooler of some type? Where is the
heat coming from? Can it be shielded
better to prevent the heat build up?

 

[Philrock]

The gearbox is submerged in drilling mud in an oil well. Pressure is 25,000 psi both inside and outside the box. Recirculation/cooling/shielding is not possible.

 

[diamondjim]

Philrock,
Can you use grease instead of oil? Of course
at that temperature grease will become almost oil.
I have seen hi-temp greases but am ignorant
about oils.

Si-123 EP Synthetic
Hi Temp Multi-Purpose Grease
supposedly good to 605 degrees.

Just search on hi temp grease on google and you
will find others.

 

[plasgears]

Consider one of the poly-alpha-olefins. They have wide temp usability limits. Make sure the grease is all synthetic.