Eight Reasons for Excessive Oil Temperature in the Hydraulic System of Truck-Mounted Cranes and Preventive Measures

Previously, we explored the hazards posed by excessive oil temperature in the hydraulic system of truck-mounted cranes. Now, the editor will elaborate on the causes of this issue and present some preventive measures.

The choice of hydraulic oil is of paramount significance. If the quality and viscosity grade of the oil product fail to meet the specified requirements, or if different brands of hydraulic oil are blended, it can result in either overly high or overly low viscosity of the hydraulic oil. When the oil viscosity is excessively high, power loss escalates, leading to a rise in oil temperature. Conversely, if the viscosity is too low, leakage increases, also causing the oil temperature to climb.

Let’s take a closer look at this aspect. The viscosity of the hydraulic oil needs to be precisely matched to the operating conditions and requirements of the hydraulic system. If the viscosity is too high, the fluid resists flowing smoothly through the system, causing increased friction and energy dissipation. This generates heat and raises the temperature. On the other hand, if the viscosity is too low, it may not provide adequate sealing between components, allowing for more leakage and again contributing to higher temperatures.

Preventive measure: Select high-performance anti-wear hydraulic oil. It is essential to choose an oil that is specifically formulated to withstand the demands of the truck-mounted crane‘s hydraulic system, providing optimal lubrication and protection.

The construction site environment where the truck-mounted crane operates is often harsh. As the operating time accumulates, impurities and dirt can readily mix into the oil. The contaminated hydraulic oil enters the mating clearances of pumps, motors, and valves, which can scratch and damage the precision and roughness of the mating surfaces. This leads to increased leakage and subsequently raises the oil temperature.

For example, fine particles of dirt or debris can embed themselves in the mating surfaces, causing microscopic damage that over time can significantly affect the performance and sealing of the components.

Preventive measure: Generally, change the oil after cumulative working for more than 1000 hours. When changing the oil, ensure that the old oil is completely drained. When refilling the oil, employ a filter screen with a mesh size of at least 120 and add the oil to the specified level. Regular and thorough oil changes help remove accumulated contaminants and maintain the cleanliness and performance of the hydraulic system.

When abrasive particles, impurities, and dust pass through the oil filter, they tend to be adsorbed on the filter element of the oil filter. This leads to an increase in oil suction resistance and energy consumption, ultimately causing the oil temperature to rise.

A clogged oil filter restricts the flow of oil, creating a backpressure that forces the pump to work harder, generating more heat.

Preventive measure: Regularly clean and replace the oil filter. For oil filters equipped with clogging indicators, clean or replace the filter element as indicated. The performance, structure, and validity period of the filter element must comply with its usage requirements to ensure efficient filtration and unobstructed oil flow.

Air that gets mixed in the hydraulic oil can escape from the oil and form bubbles in the low-pressure areas. As these bubbles move to the high-pressure areas, they are crushed by the high-pressure oil. This rapid compression and release process generates a significant amount of heat, causing the oil temperature to rise.

The presence of air in the system disrupts the smooth operation and pressure transmission, leading to inefficient power conversion and heat generation.

Preventive measure: Regularly inspect the sealing of the oil inlet pipe interface and other sealing points to prevent air from entering. Simultaneously, after each oil change, it is crucial to bleed the air from the system to eliminate any trapped air pockets.

If there is too little oil in the hydraulic tank, the hydraulic system will lack sufficient flow to carry away the heat generated during operation, resulting in a rise in oil temperature.

Insufficient oil volume limits the system’s ability to dissipate heat effectively, as the reduced amount of fluid cannot absorb and transfer the heat as efficiently as it should.

Preventive measure: During the actual operation and maintenance process, strictly adhere to the regulations regarding the oil level of the hydraulic oil specified in the operating procedures. Maintaining the correct oil level is essential for optimal system performance and temperature control.

In cases where the ambient temperature is overly high and the equipment is utilized under a high load for an extended period, the oil temperature can become excessively high.

The external heat environment adds to the heat generated within the hydraulic system, making it more challenging to keep the oil temperature within the acceptable range.

Preventive measure: Avoid prolonged continuous heavy-load operation. If the oil temperature becomes too high, allow the equipment to idle for approximately 10 minutes to allow for some cooling before resuming operation. This helps to prevent overheating and potential damage to the system.

Typically, either water-cooled or air-cooled oil coolers are employed to forcibly lower the oil temperature of the hydraulic system. For water-cooled coolers, the heat dissipation coefficient can decrease due to dirty heat sinks or poor water circulation. In the case of air-cooled coolers, the heat sink gap of the cooler can become blocked by excessive oil dirt, and the fan may have difficulties in dissipating heat, both of which result in a rise in oil temperature.

A malfunctioning cooling system fails to remove the heat generated effectively, causing the temperature to rise and potentially affecting the performance and lifespan of the components.

Preventive measure: Regularly inspect and maintain the hydraulic oil cooling circulation system. Immediately shut down the equipment and troubleshoot as soon as a fault is detected to ensure the cooling system operates efficiently.

The gears of gear pumps and the pump body and side plates, the cylinder block and distribution plate of piston pumps and motors, the cylinder block hole and piston, and the valve stem and valve body of the reversing valve are all sealed by clearances. The wear of these components leads to an increase in internal leakage, which in turn causes a rise in oil temperature.

As components wear over time, their ability to maintain pressure and seal properly diminishes, allowing for more fluid leakage and heat generation.

Preventive measure: Timely repair and replacement of severely worn parts is essential. Regular inspections and maintenance can identify worn components before they cause significant problems and ensure the hydraulic system operates at peak efficiency.

The above information is provided for the reference and study of friends who own truck-mounted cranes.

By understanding and addressing these causes and implementing the appropriate preventive measures, truck-mounted crane owners can effectively manage and control the oil temperature in the hydraulic system, ensuring reliable and efficient operation of the equipment, extending the lifespan of components, and minimizing the risk of breakdowns and costly repairs.