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1. A concrete pump is a construction device that transports concrete through pipes under pressure; its hydraulic system is typically a high-pressure, high-flow system. Surveys on the use of concrete pumps have shown that for many types of such pumps, the temperature of the hydraulic system can reach up to 60°C after about 40 minutes of operation; after approximately 2 hours of use, this temperature can go above 70°C. The normal thermal equilibrium temperature for the hydraulic system of a concrete pump should be around 50°C. As a result, the problem of excessive oil temperature in the hydraulic system of concrete pumps, that is, overheating, occurred. 2 Hazards of overheating in the hydraulic system of concrete pumps. Overheating in the hydraulic system of concrete pumps directly affects the proper operation of these pumps. The main hazards caused by overheating are as follows: (1) When the temperature of the working fluid rises, its viscosity decreases, leading to increased leakage in the pump and a reduction in the actual flow rate of the pump ； (2) The seals of hydraulic systems and components deteriorate at high temperatures, their ability to undergo elastic deformation decreases, which reduces their sealing performance and may even lead to seal failure, resulting in increased leakage ； (3) When the materials of the spool and valve body in the hydraulic valve differ, resulting in different coefficients of thermal expansion, thermal expansion can cause the spool to get stuck relative to the valve body, thereby preventing the concrete pump from operating ； (4) When the viscosity of the working fluid decreases, its lubricating properties are reduced, which accelerates the wear of hydraulic components, speeds up their wear-induced failure, and shortens their service life. To minimize the occurrence of the above issues, some concrete pumps have to be stopped after being in use for a certain period of time to allow the system to cool down, which reduces the frequency of starting these pumps and affects the construction progress. Therefore, corresponding measures should be taken based on the causes of heat generation in the system to control the temperature of the hydraulic system and ensure the proper operation of the concrete pump. 3 Main Causes of Heat Generation in the Hydraulic System of Concrete Pumps and Methods to Eliminate It. The heat generation in hydraulic systems can be divided into two categories based on the causes: one category is heat generation resulting from design issues ； One type is heating caused by faults in hydraulic components or improper use. Obviously, the methods for ruling out fever vary depending on its cause. 3.1 Improper design leads to heating in the hydraulic system and difficulties in eliminating this issue. (1) The inappropriate selection of hydraulic oil can cause heating in the hydraulic system. When the oil temperature is low, the system operates normally; however, after it has been running for some time, the oil temperature rises, the viscosity of the hydraulic oil decreases, which results in increased internal leaks within the system. These leaks further contribute to an increase in oil temperature, creating a vicious cycle. The solution is to select hydraulic oil with the appropriate viscosity based on the system’s load and required normal operating temperature. (2) The unreasonable design of the fuel tank reduces the heat dissipation efficiency of the hydraulic system, leading to increased heating. The main function of the fuel tank is to store hydraulic oil, but it also serves to dissipate heat, settle impurities, and separate water. The improper design of the fuel tank is evident in two aspects: first, the volume of the fuel tank is too small. Since concrete pumps are mobile hydraulic devices, the volume of their fuel tanks is generally about twice that of the hydraulic pump’s flow rate; as a result, both the cooling area of the fuel tank and its capacity to store fuel are limited ； Secondly, some fuel tanks are poorly designed structurally; the fuel intake port and the return port are located close to each other without any partition in between. This shortens the path that the fuel follows within the tank for cooling and for the settlement of impurities. As a result, most of the returned fuel ends up going directly into the fuel intake port, which reduces the tank’s cooling efficiency and causes the oil temperature to rise. The solution is to appropriately increase the volume of the fuel tank, so that its volume is between (1125~115)Q, and to maximize the distance between the oil intake port and the oil return port. A partition should be installed between the intake and return pipes to ensure the proper heat dissipation capacity of the fuel tank. (3) The heat dissipation rate is low, and the improper installation location of the cooler reduces the system’s heat dissipation capacity. There are two cooling methods for concrete pumps: air cooling and water cooling; users can choose based on actual conditions, but air cooling is more commonly used. Some concrete pumps, in order to meet the pressure requirements of the coolers, place these coolers on the return oil circuit of the mixing system, using them solely to cool the oil in that system. Due to the low flow rate in the mixing system, the cooling effect throughout the entire system is poor, which leads to overheating of the system. Solution: One approach is to use an independent cooling circuit to improve the cooling effect. Secondly, the cooler is installed on the main return oil line of the system in order to increase the heat dissipation rate and improve the cooling effect. However, two issues need to be taken into account here. The first issue is the speed of the cooling fan; its speed must not be too low, as this would reduce the cooling efficiency. The fan can be driven by an electric motor, or a low-pressure drive motor can be installed on the main return oil line so that the motor’s speed matches the heat dissipation rate. This approach also helps to mitigate the impact of pressure fluctuations in the main circuit on the cooling unit’s capacity to withstand pressure ； The second issue is the impact of pressure surges in the main system on the pressure resistance capacity of the cooler when an electric motor is used to drive the fan; in such cases, a low-pressure relief valve or check valve can be installed in the oil return line alongside the cooler to provide protection against excessive pressures. (4) Improper selection of hydraulic components leads to system overheating. Concrete pump hydraulic systems are generally high-pressure, high-flow systems; if the specifications of the hydraulic components in such systems – namely directional control valves, relief valves, and sequence valves – are not chosen appropriately, they will not be able to handle the high flow rates required. As a result, the flow velocity at the valve openings becomes too high, causing significant pressure losses and thereby increasing the oil temperature. Therefore, when designing hydraulic systems, it is essential to select components based on the highest operating pressures they must withstand, the maximum flow rates they need to handle, as well as the desired range of pressures and flow rates. This approach helps to minimize pressure losses at the valve openings, thus reducing system overheating caused by inappropriate component specifications. (5) Improper design and installation of pipelines result in high pressure losses, 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 determined strictly based on its operating pressure and flow rate, to avoid situations where the pipe diameter is too small, leading to high flow speeds, excessive pressure losses along the pipeline, and subsequent heating. At the same time, attention should also be paid to the installation of the pipelines: it is necessary to ensure an orderly appearance, while avoiding clusters of pipelines and sharp bends, as these can interfere with the natural cooling of the pipelines or cause excessive local pressure losses that lead to overheating. 3.2 Overheating of the hydraulic system due to improper use or component failures, and its resolution (1) If the level of hydraulic fluid in the tank is below the minimum level, this reduces the tank’s ability to dissipate heat. During operation of the concrete pump, it is necessary to constantly monitor the level of hydraulic fluid in the tank and ensure that it remains within the normal range, thereby maintaining effective heat dissipation. When the fluid level drops below the minimum level, it is essential to top up the tank with fluid promptly. (2) A reduced cooling efficiency of the cooler leads to an increase in the temperature of the oil, causing the system to overheat. This reduction in cooling efficiency can be caused by the following factors: a1 Blockages inside the cooler or excessive dirt on its surface, which causes the cooler’s safety devices to activate; this reduces the flow rate through the cooler, thereby decreasing the heat dissipation capacity. Poor ventilation in the cooler also lowers its cooling coefficient, further reducing its cooling efficiency. Therefore, it is essential to regularly inspect the concrete pump, clear any blockages in the cooler, and remove dirt from its surface on a regular basis, in order to ensure that the cooler functions properly and maintains its cooling efficiency. The opening pressure of the safety valve or check valve in the B1 cooler is lower than the standard value; as a result, the cooling system’s safety protection device activates even when the cooler is not clogged, causing overflow and a reduction in the cooling flow rate. Therefore, it is essential to properly adjust the opening pressure of the safety protection device before using the cooler, and to regularly check and correct this value during use. (3) Improper adjustment of the hydraulic system pressure leads to overheating in the system. In the hydraulic system of concrete pumps, safety valves, relief valves, and sequence valves are often installed due to performance requirements. If the pressure setting of the safety valve is set too low, it will open frequently, resulting in overflow losses and causing the system to overheat ； If the pressure adjustment is set too high, it will increase leaks within the system and cause the system to overheat. Therefore, the safety valves and pressure values must be calculated and adjusted properly according to the load requirements of the hydraulic system, so as to ensure that the system operates within the specified pressure range. When the main circuit of the concrete pump’s pumping system is a closed system, a heat exchange circuit must be installed in the pumping system. Attention should be paid to the set pressure of the relief valve in this heat exchange circuit; if the set pressure is too low, it will increase the directional shock in the pumping hydraulic cylinder, while if it is too high, it will result in excessive leakage losses and an elevated temperature in the system. Therefore, the setting pressure value of the relief valve in the heat exchange circuit should be determined appropriately; generally, this relief valve is set at (1~115) MPa, while the operating pressure in the oil replenishment circuit of the pumping system is 215 MPa. When a sequence valve is installed in the hydraulic system of a concrete pump, it is essential to understand the operating characteristics of the sequence valve and to adjust its operating pressure correctly. If the setting pressure of the internally controlled sequence valve is too high, when the operating pressure of the working hydraulic cylinder is lower than this setting pressure, there is a pressure loss at the valve ports of the sequence valve, which leads to an increase in temperature and subsequent heating of the system. By determining the setting pressure of the internally controlled sequence valve appropriately, it is possible to ensure that the operating pressure of the working cylinder is higher than the opening pressure of the sequence valve; in this case, the valve ports will be fully open with virtually no pressure loss, thereby avoiding system overheating caused by an inappropriate setting pressure for the sequence valve. (4) Increased internal leakage can raise the oil temperature and cause the system to heat up. The internal leakage in a concrete pump’s hydraulic system includes leakage from hydraulic pumps, cylinders, motors, and valves; as pressure oil leaks, its pressure drops while its temperature rises. If the internal leakage in the system increases, it will cause the oil temperature to rise and the system to overheat. In severe cases, this can lead to a drop in system pressure, reduced pumping capacity, lower pumping volume, weakened mixing action, and a decrease in the mixing speed. Therefore, it is necessary to regularly inspect these components, replace the corresponding sealing elements on a periodic basis, and promptly replace or repair any damaged or strained parts; in some cases, even the relevant hydraulic components need to be replaced, in order to avoid system overheating caused by component leaks. The heating problem in the hydraulic system of concrete pumps has become one of the issues that cannot be ignored; heat generated by the hydraulic system can lead to numerous faults in concrete pumps. For concrete pump manufacturers, it is essential to start with the design phase in order to minimize heat generation in their hydraulic systems. This not only increases the operational rate of the customers’ concrete pumps and extends their service life, but also helps save energy and reduce maintenance costs ； For concrete pump users, it is essential to start with proper use and maintenance, and to follow the manufacturer’s instructions carefully when operating, adjusting, inspecting, and maintaining the concrete pump, in order to reduce the incidence of failures and minimize system overheating caused by improper use. In summary, by taking appropriate measures to address the various causes of heating, it is possible to control or reduce heat generation in the hydraulic system, thereby increasing the operational rate of concrete pumps and extending their service life.