The important indicator of hydraulic oil for hydraulic breakers is the viscosity. A lower viscosity will increase leakage and reduce volumetric efficiency; An increase in viscosity can lead to increased frictional losses and may even cause cavitation or jamming. The hydraulic oil commonly used in hydraulic systems has a movement speed of 106m/s (50 ℃).

(1) Good viscosity temperature performance: When the hydraulic system is working, the oil temperature increases with pressure loss. If the viscosity temperature performance of the hydraulic oil is poor, it will significantly decrease, causing poor lubrication, increased leakage, and affecting working accuracy; If the viscosity increases during winter start-up, it will affect the start-up. So it is required that the viscosity change range be small within the working temperature range. Generally, the temperature index of hydraulic oil is above 90.

(2) Good antioxidant performance: When the hydraulic breaker is working, as the oil temperature gradually increases, the oil is more and more prone to oxidation and deterioration. Especially under high temperature conditions, the oxidation rate is very fast, and the oil oxidation will generate sludge and sediment, polluting the system and affecting its normal operation.

(3) Good rust prevention performance: When hydraulic breakers are stored for a long time, hydraulic components are prone to rust, which requires hydraulic oil to have good rust prevention performance.

(4) Good anti foam performance: if the hydraulic oil has foam, it will make the hydraulic hammer crawl and make noise.

(5) Good anti emulsification performance: If water is mixed into hydraulic oil, substances with poor stability in the hydraulic oil will generate hydrophilic organic acids and soaps, which will emulsify under the stirring of the pump, reduce lubrication, and affect the working performance of the breaker.

(6) Good lubrication performance: The clearance between the moving parts of hydraulic components is very small, generally ranging from a few micrometers to 100 micrometers. In order to improve the service life of the components, it is required to form a high-strength oil film on the moving surface to form liquid lubrication and reduce wear.

(7) Good compatibility is required: The oil should not have or have minimal chemical reactions with various materials to prevent deterioration and failure.

(8) Freezing point: It is required that the freezing point of hydraulic oil should be 10 ℃ lower than the ambient temperature. Otherwise, due to the low temperature, the viscosity of the oil will increase, affecting the start-up of the breaker and even preventing it from working.