What Fluids Can Be Used for Hydraulic Cylinders?

Hydraulic cylinders depend on certain fluids to function properly and safely. The fluid to be used is determined by the application, operating environment, and manufacturer's suggestions. The primary types of fluids utilized in hydraulic systems are:

1. Mineral-Based Hydraulic Oils

The most widely used hydraulic fluid.
Made from refined petroleum and sometimes supplemented with additives.
Offers excellent lubrication, corrosion protection, and thermal stability.
Utilized in most industrial, agricultural, and construction machinery.

2. Synthetic Hydraulic Fluids

Constructed from chemically formulated materials for improved performance.
Provide increased resistance to very high and low temperatures and oxidation.
Frequently utilized in aviation, high-performance equipment, and harsh environments.

3. Water-Based Fluids

Water-glycol and water-oil emulsions.
Have fire resistance and are therefore often used in such applications as steel mills and mines.
Less lubricative than the oil-based fluid, and attention must be exercised in system design.

4. Biodegradable Hydraulic Fluids

Constructed of vegetable oils or synthetic esters.
Environmentally friendly substitute for petroleum-based fluid.
Applied in ecologically sensitive operations such as forest use and ocean use.

5. Automatic Transmission Fluid (ATF)

• Sometimes employed in lighter-duty hydraulic usage.
• Has friction modifiers and detergents.
• Not suitable for heavy-duty hydraulic use because of its special nature.

Every hydraulic fluid has strengths and weaknesses, and the appropriate selection depends upon factors such as temperature range, pressure, flame resistance, and effect on the environment. Always check the recommendations of the equipment maker before making a selection of hydraulic fluid.