Analysis and Solutions for Excessively High Oil Temperature in Excavators

Excessively high oil temperature is a common fault in the hydraulic system of excavators. Its causes are complex and often difficult to handle. Regarding the phenomenon of excessively high oil temperature in the XEM220LC hydraulic excavator, the following analysis can be conducted and solutions proposed.

The heat dissipation efficiency of the radiator is low.

By replacing the finned heat sink with a plate-fin heat sink, the heat dissipation area can be increased by 8cm ², and the temperature difference between the inlet and outlet of the heat sink can be raised from 7°C to 10°C, with a very obvious effect.

(2) The check valve on the hot return oil circuit is malfunctioning.

The return oil back pressure of the existing system is 0.3MPa, and the protection pressure of the oil cooler is 0.2MPa. In theory, the back pressure of the return oil should be as low as possible while meeting the system back pressure requirements. The oil temperature of this machine is too high. It might be due to: the resistance of the radiator being greater than the protection pressure, causing the hot oil in the return oil line to return directly to the oil tank without passing through the radiator. The system cleanliness is poor. The check valve is stuck with dirt, the valve core is in the normally open position, and the radiator is not functioning. The opening pressure of the check valve cannot be guaranteed. Under the premise of meeting the system back pressure, the 0.30MPa check valve can be changed to a 0.15MPa check valve, and the protection pressure of the oil cooler can be increased to 0.35MPa.

(3) The air duct arrangement of the engine is unreasonable

The unreasonable aspects of the existing air duct are:

① The air intake of the radiator is insufficient. Some long slots can be made on the side door to increase the air intake.

There are gaps around the radiator and the engine, which have not been effectively sealed. Moreover, the front of the counterweight block is concave, causing the hot air to form vortices, resulting in poor heat dissipation. Sponge can be pasted between the radiator and the engine for sealing, and the front of the counterweight block can be changed from concave to flat.

③ The main pump of the hydraulic system lacks an insulating plate, causing the hot air from the engine to directly blow towards the rear side wall of the hydraulic oil tank, resulting in an increase in the oil temperature inside the tank. It can be improved by adding heat insulation boards.

(4) The fins of the radiator air duct in the hydraulic system fall over or the oil passage is blocked, resulting in increased air resistance and poor heat dissipation effect.

The fallen fins should be adjusted in time, and the blockages in the air ducts should be cleared. Regular flushing with water at a certain pressure is necessary to ensure the unobstructed flow of the air ducts.

(5) Improper selection of hydraulic oil grade or poor oil quality.

If the viscosity of the hydraulic oil is too low, it will increase internal leakage, reduce efficiency and generate heat. If the viscosity is too high, the pressure loss of the fluid will increase, generating a large amount of heat and causing the oil temperature to be too high. Meanwhile, poor-quality oil is prone to emulsification, which can accelerate the damage of hydraulic components.

After the above improvements, the temperature difference between the inner and outer walls of the fuel tank dropped from 8°C to 1-2°C.