For a hydraulic system, the fluid is the most important factor to consider. But, not all hydraulic oil is compatible with every system. Also, it is difficult to find the ideal fluid that matches any system requirements. This is where hydraulic oil additives are mostly used. Adding a specific quantity of additives to base oil will help the oil to achieve the desired properties. Additives can be added to the base oil for enhancing the existing oil properties, suppressing the undesired oil properties, and imparting new properties to base oils. But, adding a large volume of additives is not preferred. More details on oil additives are mentioned in this article.
What are the additives in hydraulic fluid? Additives are chemical components or blends that are used in a specific quantity ranging between <1% to 35% to achieve the desired oil properties. The system can utilize additives or additive packages, additive mixtures, or add packs by considering the desired property for oil. The additives are multi-functional and are soluble in mineral oil and water. The different functions that an additive can offer to the fluid are emulsification, boosting reserve alkalinity, extreme pressure, antimicrobial pesticide, boundary lubricity, antimisting, viscosity-temperature stability, improved filtration, extended anti-rust performance and more.
Hydraulic oil additives are categorized into surface-active additives and active additives based on their functions. Wear inhibitors, rust inhibitors, friction modifiers, etc… are examples of surface-active additives. Examples of the active additives include viscosity index improvers, pour-point improvers, anti-oxidation additives, etc… The hydraulic oil additives can also be classified based on the system of additives used. This categorization includes additives that contain zinc & ash and additives that are zinc- and ash-free.
Different additives and their features are mentioned below in points.
- Boundary Lubricity Additives (eg: lard and canola oil): This additive will limit the metal-to-metal contact and enhance the fluid lubricity by adsorbing on the metal surface.
- Corrosion Inhibitors (eg: Alkanolamides, overbased sulfonates, Aminocarboxylates, etc.): This additive will protect the metal surface from corrosion.
- Chelating Agents (eg: ethylenediaminetetracetic acid): This additive also called water softeners or conditioners will reduce the destabilizing effect of hard water.
- Anti-oxidants: Anti-oxidants will protect the system from oxidation. Which is an attack on components due to the presence of oxygen in oil.
- Viscosity Index Improvers: These are very large polymer additives that protect the oil from thinning out due to high temperatures.
- Dispersants: Dispersants are mostly used in the engine oil with detergents to keep particles of diesel engine soot finely dispersed or suspended in the oil.
- Detergents: Detergents are used as an additive for removing dirt from hot metal surfaces and neutralizing acid content in oil.
- Anti-foaming Agents: These agents will prevent the formation of oil bubbles by weakening the oil bubble wall. Oil-insoluble silicone materials are mostly used as anti-foaming agents.
- Dyes: Dyes are colouring agents that provide desired colour to the hydraulic oil used.
- Anti-wear (AW) Agents: This additive will get attached to frictional metal surfaces to protect machine parts from wear and loss of metal.