Hydraulic Fluid Replacement frequency

[ThirdString]

How do you determine how often to change hydraulic fluid?

We have a custom-made hydraulic test machine that is fairly low pressure (2000 psi max), and it's been 10 years since the fluid was changed. We use it almost daily, but probably 1-2 hours of operating time a day.

Will the fluid break down, or will filtering for contaminants be enough? It's a pretty well sealed system, so the seals and other contacting surfaces are about the only thing that will contaminate it.

Thanks!

 

[hydtools]

You have upwards of 5000 hours on the system. How hot does the system get? Temperature > 150F will degrade the additives. Water inhaled through the tank breather will degrade the fluid.

It is time to replace the fluid.

You could have the fluid chemistry checked. But your are time ahead to just change the fluid.

Ted

 

[JJPellin]

We make decisions such as this based on pure economics. If the volume of fluid is more than about 50 gallons, it is cheaper to have the oil sampled and tested. If the fluid is clean and has all the correct properties and additives intact, then why change it? For volumes less than 50 gallons, it costs less to just change it on a periodic basis. We have multi-million dollar compressors running on oil that has not been changed in a decade, running 24/7. But we sample the oil every 90 days to be certain it is still suitable for service. I should note that this system holds over 1000 gallons.

Johnny Pellin

 

[ThirdString]

Thanks for the responses, both give some insight.

The system doesn't get too hot, as it's usually running at a lower pressure than I mentioned (2000 psi max, 800 psi norm).

And we have right around 50 gallons, so it's probably just one of those borderline decisions. Actually, with 2 machines we'll be up to 100, so it may be worth checking the cost for testing if we can find someone close.