Rain falls on mobile machinery, and unless you clean and garage your front-end loader like you do your hot-rod, your loader will get wet. When your loader gets wet, the opportunity for water to make its way into your hydraulic system exists. Water, especially “free” water not dissolved in the oil, can cause corrosion, modify viscosity, reduce lubrication and increase oxidation. If water is making its way into your hydraulic oil, you should address both the cause and the solution as quickly as possible.
Water can be ingested through cracked or missing seals, through breather caps or even through exposure to extended periods of excessive humidity. Removing water from the oil might be fruitless if you cannot first find its access point and repair the leak. First check the filler/breather assembly, especially the flange-mounted gasketed type. A cracked or broken gasket will allow pooled water to drip directly into the reservoir. You may want to consider adding a filler riser, which prevents pooled water from collecting around the gasket.
Another possible location of water entry is through a broken rod seal on a cylinder. If the seal and/or wiper are cracked, worn or missing, and if the cylinder is in a “cavitation” condition where the cylinder is being pulled out, a vacuum can suck in water. This effect is exacerbated on machines operating in heavy rain or even under water. It should go without saying, proper maintenance practices, such as regular inspections, will help prevent this type of ingression.
So you have water in your oil; now what? You have three options in removing water from oil. The first option is to just change the oil. Although you will miss some of the water-contaminated oil resting within the valves, motors, lines and cylinders outside the reservoir, changing the bulk of the oil will often reduce the overall water saturation once the machine has run for a while. If saturation is still high (if the oil still looks cloudy), the oil will have to be changed once again.
A second option to remove water is to use water-absorbing filter elements. Most standard return line filter assemblies are available with media to remove free water. By changing the standard element with a water-removing element, you can slowly trap the free water as the machine is running. If water content is excessive, it may take an impractical amount of time to remove free water, and a number of filter elements might also be required. It should be noted, these elements only trap free water, and do nothing to “dry” the humid oil.
Oil has humidity, just like air, and as long as saturation is less than 100%, water remains unseen and dissolved within the oil. Oil with 99% humidity is still a bad thing, as even a small drop in temperature can cause the water to “rain” out of the oil. Highly humid oil also promotes oxidation. The problem with humid oil is that it cannot be removed with filter elements such as with free water. Special machines that heat the oil while under vacuum, called vacuum dehydrators, are available at fluid power distributors and filtration companies. They can be rented, but often for the cost of changing your machine’s oil. They can also be purchased, but are very expensive and only make sense if you have a large fleet of machines being serviced regularly.
The best method to keep oil dry is through prevention. Well-maintained oil will last indefinitely, so ensure you inspect your machine often and make repairs when required.