Hydraulic system oil heating and high temperature can cause malfunctions such as inflexible operation, discontinuous operation, weak work, and reduced working pressure. The following brief analysis and discussion will be conducted on the causes and hazards of hydraulic system heating, as well as preventive measures.

1 Reasons for oil heating

(1) The fuel tank capacity is too small, the heat dissipation area is insufficient, no oil cooling device is installed, or although there is a cooling device, its capacity is too small.

(2) The quantitative pump oil supply system that selects the oil pump capacity according to the fast forward speed will have most of the excess flow flowing back from the relief valve under high pressure and generating heat during operation.

(3) When the unloading circuit in the system malfunctions or stops working due to the absence of an unloading circuit, the oil pump cannot unload, and all the flow of the pump overflows under high pressure, resulting in overflow loss and heat generation, causing the oil to heat up.

(4) The system pipeline is too thin and long, with too many bends, resulting in significant local pressure loss and pressure loss along the way.

(5) The precision of the components is insufficient and the assembly quality is poor, resulting in significant mechanical friction losses between relative movements.

(6) The fitting clearance of the mating parts is too small, or the clearance is too large due to wear and tear, resulting in large internal and external leakage, causing significant volume loss, such as a decrease in pump volumetric efficiency and rapid heating.

(7) The working pressure of the hydraulic system is adjusted higher than actual needs. Sometimes it is necessary to increase the pressure in order to work due to tight sealing, or due to damaged seals or increased leakage.

(8) The high temperature of the climate and working environment leads to an increase in oil temperature.

(9) Improper selection of oil viscosity, high viscosity results in high viscosity resistance, while low viscosity leads to increased leakage. Both situations can cause the oil to heat up.

2 The hazards of high temperature

(1) Causing mechanical deformation, moving parts with different coefficients of thermal expansion in hydraulic components become stuck due to reduced clearance, resulting in malfunction and affecting the transmission accuracy of the hydraulic system, leading to a decrease in the working quality of the components.

(2) By reducing the viscosity of the oil and increasing leakage, the volumetric efficiency of the pump and the overall efficiency of the system will significantly decrease. Due to the decrease in oil viscosity, the oil film of moving parts such as slide valves becomes thinner and cut, resulting in increased frictional resistance and intensified wear.

(3) Deform rubber seals, accelerate aging and failure, reduce sealing performance and service life, and cause leakage.

(4) Accelerate oil oxidation and deterioration, and precipitate asphalt substances, reducing the service life of hydraulic oil. The precipitation blocks the damping small holes and gap type valve ports, causing the pressure valve to get stuck and unable to operate, the metal pipeline to elongate and bend, and even rupture.

(5) Lowering the air separation pressure of oil causes dissolved air in the oil to escape, resulting in air pockets and a decrease in the performance of the hydraulic system.

3 Preventive measures

(1) According to different load requirements, regularly check and adjust the pressure of the overflow valve to make it just right.

(2) Reasonably choose hydraulic oil, especially the viscosity of the oil. If conditions permit, try to use a lower viscosity to reduce viscosity friction loss.

(3) Improving the lubrication conditions of moving parts to reduce friction losses is beneficial for reducing workload and heat generation.

(4) Improve the assembly quality and self precision of hydraulic components and hydraulic systems, strictly control the fit clearance of mating parts, and improve lubrication conditions. Using sealing materials with low friction coefficients and improving sealing structures to minimize the starting force of hydraulic cylinders and reduce the heat generated by mechanical friction losses.

(5) Add necessary cooling devices.

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