Selection principle of viscosity of ultra-low temperature hydraulic oil

January 20, 2024

Selection principle of viscosity of ultra-low temperature hydraulic oil

When construction machinery conducts field operations in cold winter, due to the low outdoor temperature and large temperature difference between day and night, the motion viscosity of conventional anti-wear hydraulic oil becomes very large at low temperature, which will cause the hydraulic pump to fail to start.

If the low viscosity grade hydraulic oil is selected, the viscosity of the hydraulic oil is very low at high temperature, which will cause leakage in the hydraulic system, pump component wear and low hydraulic efficiency. Therefore, the selection of ultra-low temperature hydraulic oil with appropriate viscosity grade is very important for construction machinery in winter field operations. How to determine the best viscosity grade of ultra-low temperature hydraulic oil depends on the requirements of hydraulic pump for hydraulic oil viscosity, ambient temperature, viscosity limit of hydraulic system, use temperature of hydraulic oil, viscosity temperature characteristics and viscosity stability, etc. All kinds of hydraulic pumps and even different brands of hydraulic pumps of the same type have their own minimum viscosity, maximum viscosity and optimal viscosity range for normal operation.

The maximum viscosity of a typical hydraulic pump cold start is usually 1000 ~ 1600 mm'/s, the best viscosity range is 10 ~39 mm2/s, and the minimum viscosity is usually 5 ~ 10mm2/s.

According to the viscosity grade, kinematic viscosity and viscosity index limits of GB 11118.1-2011 HS and combined with the Newtonian fluid characteristics of hydrocarbon liquids, HS10, HS15, HS22, HS32 and HS46 can be estimated at 100T, 90 °, The motion viscosity data of 80 degrees, 70 degrees, 60 degrees, 50 degrees, 40 degrees, 30 degrees, 20 degrees and 10 degrees are shown in Table 10 below

It can be seen from the above figure that the best operating temperature range of HS10 is -39 degrees ~40 degrees, the best operating temperature range of HS15 is -36 degrees ~50 degrees, the best operating temperature range of HS22 is -30 degrees ~ 60 degrees, and the best operating temperature range of HS32 is -24 degrees ~ 80 degrees. The optimal operating temperature range of HS46 is -18 ° C to 90 ° C.

In the domestic and foreign hydraulic oil technical specifications only the Chinese national standard GB 1111&1-2011 contains ultra-low temperature hydraulic oil technical specifications, through the viscosity grade, viscosity index, motion viscosity 1500 mm2/s temperature and pour point and other indicators for ultra-low temperature hydraulic oil low temperature start-up and high temperature operation efficiency is given technical requirements.

On the basis of GB 11118.1-2011 HS, further increasing the viscosity index and reducing the temperature when the motion viscosity is 1500 mm7s can effectively improve the operating temperature range of ultra-low temperature hydraulic oil, and ensure that the construction machinery and equipment maintain a higher start-up and operating efficiency in a wider temperature range.

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