Using of higher grade lube oil for reciprocating compressor

[enguest]

Hello,

Happy new year to all!!!
we are going to replace the existing lube oil in our compressor with a higher grade (150 vs. 100). The lube oil circulates between crankcase and lube oil cooler (air h-xchanger). Basically, we want the lube oil that leaves the crankcase to have higher temperature. The control system is set up to give permission to load the compressor only when the lube reaches 65 degC at the exit from the crankcase.

It's difficult to contact vendor now as long time elapsed since purchase. The compressor manual allows using both grades.

Can you please advise if we use higher grade (more viscous) lube it will have higher temperature at the exit from the crankcase? (assume circulation flowrate is the same)

thanks in advance

 

[JJPellin]

Why do you want hotter oil leaving the crankcase? If we were to want hotter oil leaving the crankcase of a reciprocating compressor, we would normally accomplish this by increasing the temperature of the oil delivered to the crankcase. This is usually done by use of one or more bypasses at the lube oil cooler. Some systems bypass part of the cooling water to reduce the cooling. Others bypass some of the oil flow around the cooler. Since you use an air cooler, the second option would be relevant to your application. You could also slow down the fan on the air cooler or block a portion of the cooling area of the cooler.

With all this said, if the original manufacturer's documentation allows for the higher viscosity oil, then it is a suitable substitute and can be used. If you do not change anything with the cooler, but only change to the heavier oil, I would expect your oil temperature to increase slightly. Without more information, I cannot even speculate how much increase you might see.

Johnny Pellin