Most excavators have filters on the suction and drain sides of the hydraulic fluid.I know its a lot cheaper changing fluid than hydraulic pumps.But if its clean and no contaminates does it wear out after heavy use or hours? Is there a test for the fluid other than color? Looks dark change it or looks kinda milky must have water in it. Thanks
Do you perform oil analysis..? If so ask your oil analysis people to give you an ISO Cleanliness Code for the oil and post the results here. Hydraulic oil can be used for hgh numbers of hours provided it's kept clean. Unless you are doing at least basic oil analysis trying to determine the end of the useful life of your oil is like trying to go 15 rounds in a boxing ring with with a World Champion with both hands tied behind your back IMHO.
Hydraulic oil contains additives such as anti-foaming additives, anti-corrosion additives, anti-wear additives, viscosity stabilisers. There's up to 7 important additives in most oils. Constant high temperatures and constant pumping through pumps and cylinders has a destructive effect on these additives, making them lose their effectiveness. Water in the form of condensation also breaks down the additives. Regular oil changes in hydraulic systems ensures maximum hydraulic performance and protection against wear and corrosion. Stick with your machine manufacturers recommendations for hyd oil change periods and you won't go far wrong.