Selection principle of ultra-low temperature hydraulic oil viscosity
September 30, 2022
When construction machinery performs field operations in cold winter, due to the low outdoor temperature and large temperature difference between day and night, the kinematic viscosity of conventional anti-wear hydraulic oil becomes very large at low temperature, which will cause the hydraulic pump to fail to start.
If a low-viscosity grade hydraulic oil is selected, the viscosity of the hydraulic oil at high temperature is very low, which will cause problems such as leakage in the hydraulic system, wear of pump components and low hydraulic efficiency. Therefore, it is very important to select the ultra-low temperature hydraulic oil with the appropriate viscosity grade for the construction machinery working in the field in winter. How to determine the best viscosity grade of ultra-low temperature hydraulic oil depends on the hydraulic pump’s requirements for hydraulic oil viscosity, ambient temperature, the viscosity limit of the hydraulic system, the operating temperature of the hydraulic oil, viscosity-temperature characteristics and viscosity stability and other factors. Even hydraulic pumps of different brands of the same type of hydraulic pump have their own minimum viscosity, maximum viscosity and optimum viscosity range for normal operation. The maximum viscosity of a typical hydraulic pump at cold start is usually 1000 ~ 1600 mm'/s, the optimum viscosity range is 10 ~ 39 mm2/s, and the minimum viscosity is usually 5 ~ 10mm2/s. According to GB 11118.1-2011 HS viscosity grade, kinematic viscosity, viscosity index limit, combined with the Newtonian fluid characteristics of hydrocarbon liquids, it can be calculated that HS10, HS15, HS22, HS32 and HS46 at 100T, 90 degrees, 80 degrees, 70 degrees, 60 degrees , 50 degrees, 40 degrees, 30 degrees, 20 degrees, 10 degrees kinematic viscosity data, see table as below.
It can be seen from the above picture that the best temperature range for HS10 is -39°C to 40°C, the best temperature range for HS15 is -36°C to 50°C, the best temperature range for HS22 is -30°C to 60°C, and the best temperature range for HS32 The best operating temperature range of HS46 is -24 degrees - 80 degrees, and the best operating temperature range of HS46 is -18 degrees ~ 90 degrees. Among the technical specifications of hydraulic oil at home and abroad, only the Chinese national standard GB 1111& 1-2011 contains the technical specifications of ultra-low temperature hydraulic oil. Low temperature startability and high temperature operation efficiency give technical requirements. On the basis of GB 11118.1-2011 HS, to further increase the viscosity index and reduce the temperature at 1500 mm7s kinematic viscosity can effectively improve the working temperature range of ultra-low temperature hydraulic oil, and ensure that construction machinery and equipment maintain high start-up and performance in a wider temperature range. operation efficiency.
