Oil with higher viscosity

Question

Oil with higher viscosity

Abualnassr (Mechanical)

(OP)

22 Jul 09 11:22

Hi.

Guys, what might be the effects of using a higher viscosity lube oil ?

I mean, if the OEM's recommendation is to use an oil with 150 SSU @ 100F and if you have to use an oil with 210 SSU @ 100F.

What do you think might happen ?

Regards,

hydtools (Mechanical) · Answer 1 · 2009-07-22 14:52:18

What is the application?
The higher viscosity may be too thick to feed a plain bearing.
The higher viscosity may be too thick for low temperature startup.
Nothing might happen.
Depends.

Ted

hydromech (Mechanical) · Answer 2 · 2009-07-22 15:13:52

Fewer leaks...

Lower pump inlet pressure...

Higher pressure losses...

More energy consumption...

The difference in viscosity is negligible...so you'll probably notice no difference at all.

If the OEM you refer to is the pump supplier, the warranty will be void.

Valve performance would suffer, but I wouldn't imagine thicker oil would harm a valve.

Regards

Adrian

Abualnassr (Mechanical) · Answer 3 · 2009-07-22 15:30:34

It is actually lube oil for a journal bearings supported centrifugal compressor.
Actually they are using now a higher viscosity lube oil, and i suggested to go back to a lower viscosity as per OEM manual.

But, they asked me weather it might make any difference or not.

hydtools (Mechanical) · Answer 4 · 2009-07-22 23:36:30

If the current lube is working, there is probably no reason to change.
How do the other oil characteristics compare OEM v. current oil? At operating temperature there may be little difference.
Are the journals pressure fed? The higher viscosity may provide a little more load capacity margin. If the lube pump is happy and the journals are happy, no reason to change.
Why do you think the oil should be changed to the OEM spec?

Ted

Abualnassr (Mechanical) · Answer 5 · 2009-07-23 03:20:28

Thanks hydtools for replying.

Well, one of the reasons i want to change it back to its original oil is that the original oil is almost half the price. And the only difference between the current oil and the original one is viscosity.

IceStationZebra (Mechanical) · Answer 6 · 2009-07-24 18:55:08

I am skeptical that the only difference is viscosity, yet the price is 50% cheaper?

One quick test would be to measure the case temperature as close to the bearings as you can get. Then change the oil and remeasure.

ISZ

Newmanite (Mining) · Answer 7 · 2009-07-26 06:21:03

Does the compressor make "life". Does it achieve the required hours or does the unit fail before hand?
Does the unit run cooler with the more expensive oil or the same as the oem product. Is the unit pressurised before start up? Direct drive lube pumps are all that effiecent until there is head pressure pushing the oil into the pump.
Compressors are awesome heat generators. What type of history do you have on the unit?

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Oil with higher viscosity