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People in agriculture, construction, automotive and even marine industries are often unsure about their pick when choosing between emulsifying and demulsifying lubricants because this choice highly depends on the application, operating environment and OEM’s (Original Equipment Manufacturer) recommendations for the hydraulic system in question. In this article, we will attempt to give you some insight into the distinction between Emulsification and Demulsification oils for hydraulic systems; and tell you which one is better for your machinery.


The defining property which differentiates the two kinds of oils is the way they treat the presence of water molecules in the oil. Emulsifying oil creates a stable arrangement between the oil and water molecules. It has various additives that deal with the incompatibility between the two substances. When you use them, ensure to check the hydrophilic-lipophilic balance (HLB) of the emulsifier or the combination of emulsifiers to get an ideal emulsion. Note that most emulsifiers use alcohol as water dispersant and they are not good for diesel-based fuel injection systems. Demulsifying oil, on the other hand, works better for diesel-based fuel injection systems as they are alcohol-free and they promote the separation of oil and water. The use of demulsifying oil typically separates oil and water into two layers as water is denser.


Water enters the hydraulic system due to temperature differentials and condensation. Improper sealing material also allows the condensed water to enter the machinery. The machinery that runs fairly hot during the day becomes cold in the night when it’s turned off. This is the time when it breathes in the moisture, in the presence of cold air. When the machine reheats, the moisture doesn’t vaporize; it just condenses inside the machinery and finds its way into the oil reservoir.


Emulsifying oils can give you certain advantages over Demulsification. It prevents bacteria growth that happens due to water pooling at the base of the reservoir. This water can freeze and interfere with filters. Emulsifying oils also provides rust and oxidation protection at a certain level as it reduces the contact between metallic parts and water molecules. On the other hand, emulsification makes the oil sluggish and prone to overheating thus deteriorating the performance of the oil. Water content also acts as a catalyst for oxidation which may decline the oil’s quality.


If you have large industrial equipment with big oil reservoirs that contains a system for draining water, then you should prefer demulsifying lubricants. Smaller machines like a Tractor's engine have hydraulic fluids that generally include certain dispersant agents that carry contaminants to the system's filters for removal. In such machines, emulsifying lubricants would serve you better.


Water is not much of an issue if you are operating in a dry environment. Humid environments, however, always bring the risk of water contamination. If your equipment is exposed to humidity, ensure to keep the level of water below 0.05 %. Beyond 600 ppm, water can cause harm to your machinery. Seal material should be selected with care as this can also be a source of contamination into the hydraulic systems and lead to premature degradation of the oil.


There are numerous methods of removing water from hydraulic systems. A petcock drain valve is commonly used in most large reservoirs when using a demulsifying lubricant. Coalescers, centrifuges, vacuum dehydrators and absorbent filters are a few other water removal methods.


If you cannot remove the water from your machine, you can emulsify it. You should always check OEM recommendations for the specifications of your unit so that you can take an informed decision.



Disclaimer -
This information is provided for guidance and informational purposes only. This website and information are not intended to provide investment, laboratory or manufacturing process advice.
The information contained herein has been compiled from sources deemed reliable and it is accurate to the best of our knowledge and belief. However, Castrol cannot guarantee its accuracy, completeness, and validity and cannot be held liable for any errors or omissions, as the results change depending on the working condition/environment. Changes are periodically made to this information and may be made at any time.
All information contained herein should be independently verified and confirmed.