Decrypt The Reason For High Temperature Hydraulic Oil System

Problems caused by high hydraulic oil temperature

Excessive temperature rise of hydraulic oil can cause thermal deformation of the machine. Moving parts with different coefficients of thermal expansion in hydraulic components will become stuck due to their smaller fit gaps, causing malfunctions, affecting the transmission accuracy of the hydraulic system, and changing the quality of parts. difference.

It can also reduce the viscosity of the oil, increase the leakage, and significantly reduce the volumetric efficiency of the pump and the efficiency of the entire system. As the viscosity of the oil decreases, the oil film of moving parts such as spool valves becomes thinner, and the frictional resistance increases, resulting in increased wear. High temperature will deform rubber seals, accelerate aging failure, reduce sealing performance and service life, and cause leakage.

In addition, the increase in temperature also accelerates the oxidation and deterioration of the oil, and precipitates bituminous substances, which reduces the service life of the hydraulic oil. The precipitates block the damping orifice and the slit valve port, causing the pressure valve to become stuck and unable to move, the metal pipe is stretched and bent, or even ruptured. The temperature rise also reduces the air separation pressure of the oil, and the dissolved air in the oil escapes, resulting in air pockets, which reduces the working performance of the hydraulic system.

The main reasons for the excessive temperature rise of hydraulic oil are:

• The oil tank volume is too small, and the heat dissipation area is not enough; no oil cooling device is installed, or although there is a cooling device, its capacity is too small.
• The fixed pump oil supply system with the capacity of the oil pump selected according to the fast forward speed will cause most of the excess flow to overflow from the overflow valve under high pressure and generate heat during operation.
• The unloading circuit in the system fails or because the unloading circuit is not set, the oil pump cannot unload when it stops working. The entire flow of the pump overflows under high pressure, resulting in overflow loss and heat generation, leading to heating.
• The system piping is too thin or too long, bent too much, local pressure loss and pressure loss along the way are large.
• Insufficient component accuracy and poor assembly quality, and large mechanical friction loss between relative motions.
• The fitting clearance of the matching parts is too small, or the clearance is too large after use and wear, and the internal and external leakage is large, resulting in large volume loss. If the volumetric efficiency of the pump decreases, the temperature rises quickly.
• The working pressure of the hydraulic system is adjusted much higher than the actual need. Sometimes it is because the seal is too tight, or the seal is damaged, and the leakage increases, and the pressure has to be increased to work.
• The high temperature of the climate and working environment causes the oil temperature to rise.
• The viscosity of the selected oil is improper, the viscosity is large, the viscosity resistance is large, the viscosity is too small, the leakage will increase, and both cases can cause heat and temperature rise.

Preventive Measures

1. According to different load requirements, frequently check and adjust the pressure of the overflow valve to make it just right.
2. Reasonable choice of hydraulic oil, not to mention the viscosity of the oil, when conditions permit, try to use a lower viscosity to reduce viscosity friction loss.
3. Improve the lubrication conditions of moving parts to reduce friction loss, which is conducive to reducing work load and heating.
4. Improve the assembly quality and accuracy of hydraulic components and hydraulic systems, strictly control the clearance of matching parts and improve the lubrication conditions. The use of sealing materials with a small friction coefficient and improved sealing structure to reduce the starting force of the hydraulic cylinder as much as possible to reduce the heat generated by the mechanical friction loss.
5. Add or strengthen cooling capacity when necessary.

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