Understanding Hydraulic Fluid

Do you know what your fluid is made of? Using the right hydraulic fluid is essential to performance and hose life. 


Most hydraulic fluids are petroleum products. Some are water or a mixture of water and glycol. Synthetic fluids are now common such as phosphate esters. 


Hydraulic leaks can cause serious contamination to soil and water. We recommend proper handling and disposal of all hydraulic fluids. 


New environmentally fluids or “green” fluids have come on the market. They often are vegetable oil based because they cost less than synthetic ones and are biodegradable. They also have high lubricity and high viscosity ratings. It should be noted that they have a limited temperature range and rapid oxidation at high operating temperatures. 


Biodegradable fluids are very hard on hydraulic hoses. They permeate through standard hoses and cause the cover to degrade and moisture accumulation on the outside. This can cause premature hose failure. 


When your equipment uses green hydraulic fluids most of the time your hoses will high-grade nitrile because they are tough enough to handle biodegradable fluids like synthetic esters, polyglycols, and vegetable oils at operating temperatures of up to 250 degrees Fahrenheit. Unlike neoprene, Nitrile materials allow less permeation or fluid loss through the tube and hose. 


Remember that permeation can expose an entire hose assembly to fluid. It is important to understand and confirm the fluid’s compatibility with the tube, reinforcements, cover, fittings and seals. The same is true for any hose assembly that handles special oils or chemical agents. 


Chemical resistance is very important for your hose and coupling material. Always confirm what fluids will run through the hose. What gases or fluids might permeate the tube? This could weaken the reinforcement layers. What material will touch the hose cover in normal service or when you are cleaning equipment?


Coupling bores, ferrules and termination points need to be resistant to any corrosive chemicals they may come in contact with during operation or service. You should also ensure that internal system fluids are compatible with all seals. 


EPDMs (type P) are excellent for weather and ozone but have a poor rating for petroleum based oils. Butadienes (type C) are rated poor for weather and ozone but are excellent for petroleum oils. 


If you are unsure about the chemical compatibility for a proprietary or trade-name fluid you can always checks the MSDS. You should see a list of individual chemical components of brand-name products and the percentages they contain. The MSDS also provides information on handling, storage, and safety. 

We can assist you with any specialized applications that may require unique chemical resistance. Our manufacturers have detailed information and specialists and engineers that work out even the most challenging problems. 



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