Introduction to Working Temperature of Shield Hydraulic System

The working temperature of the hydraulic system of shield tunneling machines is often between 30-55 ℃. At this point, the viscosity, lubrication, and wear resistance of the oil are at their optimal state, and the efficiency of the hydraulic system is the highest.

When the system temperature exceeds 65 ℃, the viscosity of the oil decreases significantly, which can lead to an increase in system leakage and damage to the sliding oil film of components such as directional valves, exacerbating component wear and leading to a faster rise in system temperature.

When the oil temperature reaches 80 ℃ or above, the operating state of the components will undergo abnormal changes, and even "jamming" may occur, affecting the normal operation of the system.

Reasons for High Temperature in Shield Hydraulic System

(1) Poor heat dissipation

The temperature of the external circulating water is too high, which leads to the poor performance of the heat exchanger. The temperature generated by the hydraulic system cannot be effectively discharged outside the tunnel, resulting in high oil temperature;

The low liquid level in the hydraulic oil tank can lead to insufficient circulation of oil in the system, which can also cause the system oil temperature to be too high to a certain extent.

Shield tunneling hydraulic system vs human anatomy

(2) Improper selection of hydraulic oil grade

Improper selection of hydraulic oil grades, especially oil viscosity indicators, will directly threaten the normal operation of hydraulic systems.

Due to the stable working environment temperature of the hydraulic system of the shield tunneling machine, the equipment user should strictly follow the instructions in the user manual to add the corresponding type of hydraulic oil.

(3) Improper pressure adjustment

When the pressure adjustment of some systems is too high, the overflow valve cannot overflow and reduce pressure normally, which will increase internal leakage and cause the system oil temperature to rise; When the return oil filter element is clogged, it can also cause high back pressure, increase oil pressure loss, and cause high oil temperature.

(4) Hydraulic pump suction

When the pump is empty, the oil will mix with air, causing cavitation and hydraulic shock under high pressure. Strong vibration and noise will cause the system oil temperature to rise rapidly.

(5) Internal leakage

If the components wear out, it will cause serious internal leakage, increase the system's volume loss, convert the lost energy into heat energy, increase the oil temperature, and then cause an increase in internal leakage, resulting in further increase in oil temperature and forming a vicious cycle; If the gap between the components is too small, friction between the relative moving parts can also cause the oil temperature to rise.

Cooling measures for shield tunneling hydraulic system

(1) Ensure heat dissipation effect

Provide water in accordance with the equipment's requirements for external water supply, strictly ensuring the temperature and quantity of water; The radiator should be regularly cleaned, inspected, and cleaned of dirt and coverings to maintain good heat dissipation performance.

Hydraulic pump station radiator

(2) Reasonable selection of hydraulic oil

Select anti-wear hydraulic oil according to the recommended brand in the excavator manual.

(3) Adjust the system pressure according to the standard

In a quantitative pump system, the oil supply pressure is regulated through an overflow valve; In variable displacement pump systems, safety valves are used to prevent system overload. Strictly adjust the valve pressure according to the standard to reduce energy loss.

(4) Prevent pipeline blockage and oil leakage

The filter element and pipeline should be regularly inspected and replaced, and the pipeline should be tightened in a timely manner.

(5) Timely repair worn hydraulic components

Regularly inspect pumps and motors, and promptly repair severely worn hydraulic components.

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