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How to remove water from hydraulic fluid

    Oil is contaminated by various kinds of impurities such as gases, liquids, and solids. In fact,  water has been known for centuries to be one of the most destructive things inside an internal combustion engine. Fortunately, it’s also one contaminant you don’t need to worry too much about.

    If your lubricant or hydraulic fluid gets continually or occasionally exposed to high water levels then it could cause serious harm. If you’re looking for proof of water contamination, you’ll need to dig deep into the earth. This damage looks like:

    • Corroding metal
    • Wear in hydraulic components
    • Losses due to dielectric
    • Fluid breakdown
    • Additive precipitation and oil oxidation
    • Lubricant reduction

    What sources lose water?

    There are numerous ways water can become polluted so it could get into your oil and equipment through any number of different pathways. Some common ones include:

    • Water vapor
    • Leakage from reservoirs
    • Actuators wear out after time
    • Leakage from heat exchange systems
    • New oil

    If water gets inside your fluids and equipment, then there could be some serious consequences like bearing failure, accelerated abrasive wear (wear), corrosion of metals, increase in electrical conduction, viscosity variation, loss of lubricity, and fluid additives breakdown. Controlling water contamination is crucial for keeping your systems running smoothly.


    One way to deal with an overheating issue is by changing the oil. Although you may miss out on some of the water contaminated oil sitting inside the valve, motor, line and cylinder parts outside the reservoir, changing most of the oil will usually help lower the overall level of contamination once the machine has been running for awhile. If saturation remains high after changing the oil, then the oil has to be replaced yet again.

    Not everyone is going to do a complete teardown along with a chemical and mechanical cleaning of each component and the system each time a fluid changeover is performed. So let’s examine what should be done at the bare minimum to clean a hydraulic system through flushing.

    Step 1

    When you’re done, make sure your fluids are drained! Drain them completely, pay attention to the reservoir, check the lines, cylinders, accumulator housings, and also the filters. Make sure there aren’t any leaks! Replace the filters when you’re finished.

    Step 2

    With a lint-free cloth, clean the reservoir of any sludge and deposits. Then make sure the entire reservoir is completely free of any soft or loose paint.

    Step 3

    Flushing the system with a lower-viscosity fluid that is similar to what you’re using should help reduce the amount of sedimentation. Make sure your valve is regularly closed and opened to make sure the system is properly cleaned. You may want to filter your fluid before use to make sure there aren’t any contaminants.

    Step 4

    Drain the flushing fluid as hot and as quickly as possible. Replace the filters and inspect/clean the reservoir again.

    Step 5

    Fill the system to approximately 75 percent with the fluid to be used. Bleed/vent the pump. If the pump has a pressure relief or bypass, it should be wide open. Run the pump for 15 seconds, then stop and let it sit for 45 seconds. Repeat this procedure a few times to prime the pump.

    Step 6

    Open the bypass and allow the pump to run for a minute.

    Close the bypass and wait for the pump to stop running.

    Let the pump sit for 5 minutes.

    Step 7

    When you start the pump, let the fluid flow back to the reservoir.

    If the level drops below 25%, add more fluid until it reaches 50%.

    Step 8

    Refill the reservoir to 75% and run the system every 5 minutes. When you shut down the system, bleed the air out of the system. Be careful when you hear the pump making noises as this may indicate a problem with your system.


    Hydraulic oil water removal systems remove hydraulic fluid from

    Removing water from hydraulic oil increases its lifespan considerably.

    Different ways exist for removing water from an object. There are both pros and cons to each method. You need to consider them carefully before deciding which one works best for you.


    Gravity separation

    Because water usually has a higher specific gravity then hydraulic fluid, it tends to sink to the bottom of a tank if left undisturbed for long enough.

    In simple systems, simply letting the water out by itself might suffice. By increasing the temperature of the water used for flotation, using a conical separator improves its ability to separate oil from water.

    Advantage: Simple device, low cost of water removal.


    Water absorbing elements

    Super absorbent polymers (SAPs), which convert from free water into highly viscous gels by integrating cations such as Na+ or K+, are used for hygienic products like baby diapers and sanitary napkins. They are also Osmosis works by pulling water molecules from outside the cell through its membrane into the interior where they diffuse across

    Water absorption is limited by the elasticity of the polymers used to form the gel structure. Water cannot be removed from an object by applying greater force. It doesn’t dissolve in oil/synthetic ester formulations. A layer structure of the element prevents its transfer to the hydraulic system.

    Advantages: Low cost for small quantities, easy handling, good degasification properties, simple operation, low maintenance requirements, long service life, compact design, etc.


    Cellulose filter

    A cellulose filter has limited ability to remove dissolved water from an emulsion. It works by passing the mixture through a bed of small diameter wood fibers


    As the droplet travels through the coalescing element, free water settles onto its surface. Droplets then become trapped inside the coalescing element because they cannot escape from its interior. As smaller droplets join together into bigger droplets, they become denser and heavier. Water drops larger than one millimeter cannot be separated from smaller ones using gravity alone. They must use an additional layer of material (such as paper) for them Water is collected at the base of the house (on the bottom for phosphates above) and it can be released through an open valve.

    Advantages: It has a high dewatering rate for high water content materials such as hydraulic oil and diesel fuel; it removes fine particles from one material simultaneously; and it allows high flow rates up to 2000 GPM.



    Magnify the difference in density between two liquids by using centrifuging. Gravity separators separate liquids from solids by using their weight; centrifuges use spinning force to separate fluids They also remove some dissolved solids from the solution depending upon the relative strengths of the emulsion vs the solvent. the centripetal force of the separator They are a good choice for continuous de­contaminating liquids with good water separation properties.

    Advantages: High dewatering rate for high water content (>80%).


    Positive pressure dehydrators

    Negative pressure systems use vacuum pumps to draw air from outside the system, which then passes through an evaporator coil where heat energy is extracted from the air stream. A blower introduces air into the reaction chamber. As the dry air enters the reaction chamber, it pulls the remaining liquid into itself. The operating fluid is circulated through the reaction chamber by means of two pumps.

    Advantages: It’s less expensive than vacuum


    Vacuum dehydrators

    Vacuum pumps create vacuums inside chambers using suction. Vacuum pumps suck ambient air into the vacuum chamber. A vacuum draws out surrounding air and proportionally decreases its relative humidity. Oil distributes evenly throughout the vacuum chamber over a wide surface area, which results in a thick and uniform liquid layer.

    Because of the temperature rise when coming into contact with hot oil, the air becomes drier and absorbs moisture from the oil. The moist air is sucked out by the vacuum pump. Depending on the applied pressure, heat, and vacuum level, either evaporation or boiling occurs during flash vaporization.

    Advantages: Can remove up to 99% of impurities without damaging the oil itself; requires no heating (which could damage some types of oils); removes even heavy metals like lead and mercury; can be done at home using simple household items; works well on most kinds of oils.



    Contamination by water is an ongoing problem. Solving issues involves finding the best ways to deal with them depending on their nature and the systems they involve. Instead of trying things out by yourself, we recommends seeking help from someone who knows better.

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