1. Introduction A concrete pump is a construction device that transports concrete by pressure through pipelines. The hydraulic system of a concrete pump is generally a high-pressure, high-flow-rate system. Surveys of concrete pump usage have revealed that in many types of concrete pumps, the hydraulic system temperature can reach as high as 60°C after approximately 40 minutes of use, and the thermal equilibrium temperature can exceed 70°C after approximately 2 hours of use, while the normal thermal equilibrium temperature of a concrete pump hydraulic system should be around 50°C. Therefore, the problem of excessively high oil temperature, or overheating, has arisen in the concrete pump hydraulic system. The hazards of overheating in the hydraulic system of a concrete pump: Overheating in the hydraulic system of a concrete pump directly affects the normal operation of the pump. The hazards caused by overheating are mainly as follows: (1) After the temperature of the working fluid rises, the viscosity of the working fluid decreases, the leakage of the pump increases, and the actual flow rate of the pump decreases; (2) The seals of the hydraulic system and components deteriorate at high temperatures, the elastic deformation ability decreases, the sealing performance decreases, or even the seal fails, and the leakage increases; (3) When the valve core and valve body materials of the hydraulic valve components are different and the coefficients of thermal expansion are different, the valve core and valve body may jam due to thermal expansion, causing the concrete pump to be unable to work; (4) When the viscosity of the working fluid decreases, the lubrication performance of the working fluid decreases, the wear of hydraulic components accelerates, the wear failure of components is accelerated, and the service life of components is shortened. In order to avoid the above phenomena as much as possible, some concrete pumps have to be stopped after a certain period of use to allow the system to cool down, thereby reducing the start-up rate of the concrete pump and affecting the construction progress. Therefore, corresponding measures should be taken to control the temperature of the hydraulic system and ensure the normal use of the concrete pump. The main causes and troubleshooting methods of heating up the hydraulic system of concrete pump. The heating up of the hydraulic system can be divided into two categories according to the cause of heating up: one is the heating up caused by design reasons; the other is the heating up caused by hydraulic component failure or improper use. Obviously, the troubleshooting methods are different depending on the cause of heating up. Unreasonable design causes heating up of the hydraulic system and its troubleshooting (1) Improper selection of hydraulic oil grade may cause heating up of the hydraulic system. When the selected hydraulic oil is at a low oil temperature, the system works normally, but after the system works for a period of time, the oil temperature rises and the viscosity of the hydraulic oil decreases, resulting in increased internal leakage of the system. The increase in leakage further promotes the rise in oil temperature, forming a vicious cycle of oil temperature. The solution is to select hydraulic oil with appropriate viscosity according to the system load and normal working temperature requirements. (2) Unreasonable design of oil tank reduces the heat dissipation effect of hydraulic system. The main function of the oil tank is to store hydraulic oil, but it also has the functions of heat dissipation, sedimentation of impurities and separation of water. The oil tank design is unreasonable, mainly in two aspects: First, the oil tank volume is too small. Since the concrete pump is a mobile hydraulic equipment, the oil tank volume is generally about one time the hydraulic pump flow rate. Therefore, the heat dissipation area and oil storage capacity of the oil tank are small. Second, some oil tanks are not designed in a reasonable way. The suction pipe and the return pipe are close together and there is no partition in the middle, which shortens the cooling circulation of the oil in the oil tank and the path of sedimentation impurities. It even causes most of the return oil to directly enter the suction pipe, which reduces the heat dissipation effect of the oil tank and raises the oil temperature. The solution is to appropriately increase the oil tank volume to (1125~115)Q, and increase the distance between the suction pipe and the return pipe as much as possible. A partition should be set between the suction and return pipes to ensure the heat dissipation power of the oil tank. (3) The heat dissipation flow rate is small and the cooler installation position is unreasonable, which reduces the heat dissipation capacity of the system. There are two cooling methods for concrete pumps: air cooling and water cooling. Users can choose according to the actual situation, but air cooling is generally more common. Some concrete pumps, considering the pressure requirements of the cooler, place the cooler on the return oil line of the mixing system, only cooling the oil in the mixing system. Because the flow rate of the mixing system is relatively small, the overall cooling effect is poor, causing the system to overheat. Solutions include: 1) Using an independent cooling circuit to improve cooling efficiency. 2) Placing the cooler on the main return oil line of the system to increase the heat dissipation flow and improve cooling efficiency. However, two issues should be considered: First, the cooling fan speed should not be too low, otherwise the cooling effect will be reduced. An electric motor can be used to drive the fan, or a low-pressure drive motor can be installed on the main return oil line to match the motor speed with the heat dissipation flow. This also solves the problem of the main circuit pressure surge affecting the cooler's pressure-bearing capacity. Second, if an electric motor is used to drive the fan, the pressure surge of the main system can affect the cooler's pressure-bearing capacity. In this case, a low-pressure overflow protection valve or check valve can be installed in parallel with the cooler on the return oil line to provide maximum pressure protection for the cooler. (4) Improper selection of hydraulic components causes system overheating. Concrete pump hydraulic systems are generally high-pressure, high-flow systems. If the hydraulic components in the system, mainly the directional valves, relief valves and sequence valves, are not selected reasonably and cannot meet the high flow requirements, the flow velocity at the valve port will be too high during use, resulting in a large pressure loss and an increase in oil temperature. Therefore, when designing hydraulic components in the hydraulic system, it is necessary to select components according to the maximum working pressure, the maximum flow rate, and the required pressure and flow adjustment range of the hydraulic components, and minimize valve port pressure loss, thereby reducing system overheating caused by improper selection of hydraulic component specifications. (5) Improper pipeline design and installation cause large pressure loss, causing pressure energy to be converted into heat energy. In the design of hydraulic systems, the design and installation of pipelines cannot be ignored. The diameter of each pipeline should be strictly designed according to its working pressure and flow rate to avoid the pipeline diameter being too small, resulting in excessive flow velocity, excessive pressure loss along the pipeline, and overheating. At the same time, attention should be paid to the installation of pipelines. The appearance should be neat, and pipelines should be kept away from accumulation and sharp bends, which may affect the natural heat dissipation of the pipelines or cause excessive local pressure loss and heat generation. Due to improper use of the hydraulic system or component failure, the hydraulic system may overheat and the following troubleshooting steps may be taken: (1) The hydraulic oil level in the tank is lower than the minimum level, which reduces the heat dissipation power of the tank. During the use of the concrete pump, the hydraulic oil level in the tank should be observed at any time and kept within the normal oil level range to ensure the heat dissipation effect of the tank. When the hydraulic oil level in the tank is lower than the minimum level, oil should be added to the tank in time. (2) The cooling effect of the cooler is reduced, causing the oil temperature to rise and the system to heat up. The cooling effect of the cooler is reduced, which may be caused by the following reasons: a1. The cooler is blocked or has a lot of dirt on its surface, causing the cooler safety device to open, reducing the cooler flow rate and reducing the heat dissipation flow rate. Or the cooler is poorly ventilated, which reduces the cooling heat transfer coefficient of the cooler and reduces the cooling effect. Therefore, the concrete pump must be checked and the cooler must be cleared regularly during use. The dirt on the surface of the cooler must be cleaned regularly to ensure that the internal flow of the cooler is unobstructed and the external flow is clean, so as to ensure the cooling effect of the cooler. b1. The opening pressure of the cooler safety valve or check valve is lower than the standard value, causing the cooler safety protection device to open when the cooler is not blocked, resulting in overflow and diversion, which reduces the heat dissipation flow rate of the cooler. Therefore, the opening pressure of the safety protection device must be correctly adjusted before the cooler is used, and the opening pressure value of the safety protection device must be checked and corrected regularly during use. (3) Improper adjustment of hydraulic system pressure causes the system to heat up. In the hydraulic system of concrete pump, due to performance requirements, the system is often equipped with safety valves, overflow valves and sequence valves. If the safety valve pressure is set too low, it will open frequently, causing overflow losses and system overheating. If the pressure is set too high, it will increase internal leakage and cause system overheating. Therefore, the safety valve and pressure value should be correctly calculated and adjusted according to the load requirements of the hydraulic system to ensure that the system operates within the specified pressure range. When the main circuit of the concrete pumping system is a closed system, a heat exchange circuit must be installed in the pumping system. The set pressure of the relief valve in the heat exchange circuit should be carefully considered. If the set pressure is too low, it will increase the reversing impact of the pumping hydraulic cylinder; if the set pressure is too high, it will cause excessive overflow losses and excessive system temperature rise. Therefore, the adjustment pressure value of the relief valve in the heat exchange circuit should be reasonably determined. Generally, the adjustment value of this relief valve is (1~115) MPa, and the working pressure of the pumping system's oil replenishment circuit is 215 MPa. When a sequence valve is installed in the concrete pump hydraulic system, it is essential to understand the working characteristics of the sequence valve and correctly adjust its working pressure. If the adjustment pressure of the internal control sequence valve is too high, when the working pressure of the working hydraulic cylinder is lower than its adjustment pressure, there will be pressure loss at the valve port of the sequence valve, which will cause a temperature rise and cause the system to heat up. Reasonably determining the setting pressure of the internal control sequence valve can make the working pressure of the working cylinder higher than the opening pressure of the sequence valve. When the sequence valve is working, the valve port will be fully open and there will be basically no pressure loss at the valve port, thereby avoiding system heating caused by improper setting pressure of the sequence valve. (4) Increased internal leakage can cause the oil temperature to rise and the system to heat up. Internal leakage of the hydraulic system of concrete pump includes internal leakage of hydraulic pump, hydraulic cylinder, hydraulic motor and hydraulic valve. During the leakage process, the pressure of the pressure oil drops and the temperature rises. If the internal leakage of the system increases, it will cause the oil temperature to rise and the system to overheat. In severe cases, it will cause the system pressure to drop, the pumping to be weak, the pumping displacement to decrease, the stirring to be weak, and the stirring speed to decrease. Therefore, these components should be checked regularly, the corresponding sealing components should be replaced regularly, and the damaged or scored parts should be replaced or repaired in time, or even the corresponding hydraulic components should be replaced, so as to avoid system heating caused by component leakage. Overheating in the hydraulic system of concrete pumps has become a significant issue, leading to numerous pump malfunctions. Concrete pump manufacturers should strive to minimize hydraulic system overheating through design improvements. This not only increases pump uptime and extends pump lifespan but also saves energy and reduces maintenance costs. Concrete pump users should adhere to strict usage and maintenance guidelines, strictly following the manufacturer's instructions for proper use, commissioning, inspection, and maintenance to reduce failure rates and minimize overheating caused by improper operation. In short, addressing the various causes of overheating and implementing appropriate measures can control or mitigate hydraulic system overheating, thereby improving pump uptime and extending pump lifespan.