In hydraulic systems, water often enters the oil through condensation, leaks, or improper handling. Moisture not only causes oil emulsification and a decline in its lubricating performance, but also increases the risk of system wear and failure.
Here are several practical methods you can use to remove water from hydraulic oil, thus you can keep your equipment running smoothly and reliably.
7 Ways to Help You Remove Water from Hydraulic Oil
Gravity Separation
Generally, water is heavier than hydraulic oil. By taking advantage of this feature, water can be separated. If you place the oil in a stable state for several hours, the water will settle at the bottom. You can then drain it through a discharge valve. Although this method is simple and inexpensive, it only removes free water. Finally, emulsified water remains, so it’s not a complete solution.
Centrifugal Separation
With centrifugal separation, the hydraulic oil spins at high speed, forcing water out by density difference and then flows out from the automatic drainage device. This method is particularly efficient for free water and can remove a large amount of water in a short time. Therefore, it is commonly used for hydraulic oils with high water content. However, it removes only part of the emulsified water and is most effective when the viscosity of hydraulic oil is less than 30cSt.
Heating
By utilizing the property that water evaporates at high temperatures, the hydraulic oil is heated until it reaches above the boiling point of water and turns into water vapor to escape.The method is also relatively simple to operate, but you need to carefully monitor the temperature to prevent overheating and damage to the hydraulic oil. More Suitable for small and medium-sized systems.
Vacuum Distillation
Vacuum distillation works by lowering the surrounding pressure so the boiling point of water drops. This allows the moisture in hydraulic oil to evaporate at a much lower temperature. Unlike simple heating, this process does not require raising the oil temperature too high, so you avoid oxidation or degradation. As a result, the oil keeps its stability and lubricating performance.
One key advantage is the precision. Vacuum dehydration can bring water levels down to the ppm range, making it ideal for industries like aerospace, precision manufacturing, and power generation where oil purity is critical. It removes almost all forms of water, including dissolved and emulsified moisture, and can also eliminate contaminants such as fuel or refrigerants. That means you solve issues like cloudy fluid effectively.
On the downside, this method requires specialized equipment and professional handling. The cost is higher, so you need to plan for the right budget if you want to use this option.
Absorbent Polymer Filter
This filter is usually filled with super-absorbent polymers. When it comes into contact with water, it will rapidly expand and form a gel, firmly locking free water and some emulsified water to prevent them from entering the oil again. Compared with mechanical filters, it can not only catch solid particles, but also solve the problem of water contamination at the same time.
The filters are easy to install and won’t interrupt operation, making them ideal for routine maintenance. Due to the limited water absorption rate of polymers, it is necessary to regularly inspect and replace the filter element. They must be checked and replaced every 3–6 months. When you use it in situations where there is too much liquid, its effect will not be obvious.
Coalescence Filter
The special fiber material inside the coalescing filter element can gradually bring small water droplets together and form larger ones in hydraulic oil. When the water droplets grow to a certain extent, they will settle to the bottom due to the gravity and thus separate from the oil.
This method is widely used for low-viscosity hydraulic oils and removes free water effectively. However, just like the absorbent polymer filter, you need regular maintenance and timely change your hydraulic filters to maintain good performance.
Demulsifier
Demulsifiers such as polysiloxane and polyethylene glycol are chemical additives designed to deal with emulsified water in hydraulic oil. Once water enters the system, it often mixes with the oil and forms an emulsion. The fluid then turns cloudy and loses its proper lubricating ability.
By adding a demulsifier, you can break the bond between oil and water. The water molecules then cluster into larger droplets, settle at the bottom of the tank, and can be drained out easily.
That said, the performance of a demulsifier depends on the oil formulation, operating temperature, and other factors. Using too much may even hurt the fluid’s properties. In practice, you should rely on test results to decide the right dosage and make sure the additive works without side effects.
If none of the above methods work, the only option for you is to flush the hydraulic system and refill it with fresh hydraulic oil. You had better circulate the hydraulic oil in the system at least five times to ensure that there is no residual moisture in the hydraulic system.
Methods of Prevent Water Entering Hydraulic Fluid
Headspace Dehumidification
Headspace Dehumidification is an effective method to prevent hydraulic oil from absorbing moisture. A dehumidifier is installed between the oil surface and the tank cover, which lowers the humidity in the air and keeps damp air from entering the oil.
Therefore, this method is not designed to remove water that is already inside the fluid. Instead, it focuses on prevention and delivers longer-lasting protection. You’ll find it especially useful in high-humidity settings such as port machinery, wind power units, and paper production lines.
Hydrophobic Agent
Hydrophobic agents, such as organosilicon compounds and fluoropolymers, work by creating a water-repellent layer on the surface of hydraulic oil. This barrier can reduce the opportunity for water molecules to combine with oil molecules, thereby reducing the risk of free water and dissolved water entering the system.
After you add it, the hydraulic oil will exhibit stronger water resistance. Even in a humid environment or under working conditions with condensate water, it can maintain relatively stable performance.
The main advantage of hydrophobic additives is that they extend the service life of your hydraulic oil, cut maintenance costs, and protect key components like pumps, valves, and seals from water damage. Besides, they also help reduce filter clogging and replacement frequency caused by water contamination. It is often used in industries with high humidity such as steel, paper, and port machinery.
Other Precautions
Proper Environment: Store your hydraulic system and oil in a dry, temperature-controlled space. When adding oil, you should use dedicated tools and avoid exposing it to rain or ambient moisture.
Regular Inspection: Use high-quality hydraulic seals and routinely check for wear or aging. This will help you prevent humidity or condensation from entering the tank through small gaps.
Temperature Control: Frequent cold starts or rapid temperature fluctuations will lead to the formation of condensation water. Keeping your system temperature stable reduces water buildup.
Prevention is usually more effective and cost-efficient than dealing with problems afterward. By establishing a complete hydraulic oil water-management routine, you can extend your equipment’s life and lower operational risks.
Conclusion
If this problem is not solved in time, moisture will seriously affect the performance of the hydraulic system, leading to increased wear and higher risk of failure.
If you want to further optimize your hydraulic equipment or need expert advice, contact our technical team. TARGET will provide the best solutions for your hydraulic system, ensuring your machinery runs efficiently and reliably for a long term.
