Which of the following are the two most common types of hydraulic fluid?

The two most common types of hydraulic fluid used in hydraulic systems are mineral-based fluids and water-based fluids. Mineral-based fluids are derived from refined petroleum products and are widely utilized due to their good lubricating properties, thermal stability, and compatibility with various hydraulic system components. These fluids offer excellent protection against wear and corrosion, making them a popular choice in many industrial applications.

Water-based fluids, including water-glycol emulsions and water-oil emulsions, are also important because they provide excellent fire resistance and are often used in applications where the risk of fire is a concern. Their lower flammability compared to mineral oils makes them suitable for certain environments, especially in industries involving high temperatures or flammable materials.

Other fluid types mentioned, like synthetic-based fluids, glycerin-based fluids, silicone fluids, vegetable-based fluids, and gas-based fluids, while they may find niche applications, do not surpass mineral-based and water-based fluids in terms of common usage across most hydraulic systems. This distinction is crucial for understanding the predominant hydraulic fluids in industry today.