Causes and prevention methods of high temperature

2022-08-26
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Reasons and prevention methods for high temperature rise of hydraulic system

1. Reasons for high temperature rise

(1) according to the person in charge of relevant technology research and development of China Zhongwang who participated in the project, the volume of the oil tank is too small, the heat dissipation area is not enough, the oil cooling device is not installed, or although there is a cooling device, its capacity is too small

(2) the quantitative pump oil supply system with oil pump capacity is selected according to the fast forward speed, During operation, most of the excess flow will overflow back from the overflow valve under high pressure and generate heat

(3) when the unloading circuit in the system fails or the unloading circuit is not set, the oil pump cannot unload when it stops working. All the flow of the pump overflows under high pressure, causing overflow loss and heating, resulting in temperature rise

(4) the system pipeline is too thin, too long, too much bending, and the local pressure loss and pressure loss along the way are large

(5) the accuracy of components is not enough and the assembly quality is poor, and the mechanical friction loss between relative movements is large

(6) the fitting clearance of fitting parts is too small, or the clearance is too large after use and wear, resulting in large internal and external leakage, resulting in large volume loss, such as reduced volumetric efficiency of the pump and fast temperature rise

(7) the working pressure of the hydraulic system is adjusted much higher than the actual need. Sometimes the pressure has to be increased to work because the seal is too tight, or because the seal is damaged and the leakage increases

(more than 47000 sets of calibrated temperature measuring instruments 8) the oil temperature rises due to the high climate and operating environment temperature

(9) choose the viscosity of the oil improperly. If the viscosity is large, the viscosity resistance is large, and if the viscosity is too small, the leakage will increase. Both cases can cause heating and temperature rise

2. Harm of too high temperature rise

(1) thermal deformation occurs to the machinery, and the moving parts with different thermal expansion coefficients in the hydraulic components get stuck due to their smaller matching clearance, causing action failure, affecting the transmission accuracy of the hydraulic system, and leading to poor working quality of the parts

(2) reduce the viscosity of the oil, increase the leakage, and significantly reduce the volumetric efficiency of the pump and the efficiency of the whole system. As the viscosity of the oil decreases, the oil film of moving parts such as slide valves becomes thinner and cut, and the friction resistance increases, resulting in increased wear

(3) deform the rubber seal, accelerate aging and failure, reduce sealing performance and service life, and cause leakage

(4) accelerate the oxidation and deterioration of the oil, and precipitate bituminous substances, reducing the service life of the hydraulic oil. The precipitates block the damping holes and slot valve ports, causing the pressure valve to be stuck and unable to act, and the metal pipeline to stretch and bend, or even break

(5) reduce the air separation pressure of the oil, and the dissolved air in the oil escapes, resulting in cavitation, which reduces the working 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 select hydraulic oil, especially the viscosity of oil. When the conditions allow, the experimental force, deformation, displacement and other rate control and maintenance can be carried out, and a lower viscosity can be used as far as possible to reduce the friction loss of viscosity

(3) improve the lubrication conditions of moving parts to reduce friction loss, which is conducive to reducing working load and heating

(4) improve the assembly quality and accuracy of hydraulic components and hydraulic systems, strictly control the fitting clearance of mating parts and improve lubrication conditions. Adopt sealing materials with small friction coefficient and improve the sealing structure to reduce the starting force of the hydraulic cylinder as much as possible, so as to reduce the heat generated by mechanical friction loss

(5) add or strengthen the cooling capacity if necessary

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