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At present, concrete pump trucks are widely used in concrete construction projects. The concrete pumps used are mainly double-cylinder driven concrete pumps, and concrete flow interruption commonly occurs at the moment of pumping direction change. This flow interruption phenomenon has two major drawbacks: first, it can easily lead to concrete segregation, with some of the concrete losing water and becoming hard, which in turn causes blockages in the pipes – this is especially true when pumping concrete with a low slump ； Secondly, the release of concrete pressure in the pipelines and distribution valves at the moment of direction change exerts stress on the hydraulic system of the concrete pump, leading to damage to certain components and increased energy loss. Flow interruption has a significant impact when pumping vertically upward, especially at heights of over 50 meters. 1. Cause analysis: Figure 1 shows the hydraulic schematic diagram of a two-cylinder driven concrete pumping system in an open hydraulic system. This pump is a fully hydraulic control concrete pump; the constant-power main oil pump supplies oil to the main cylinders 10-1, 10-2 and the distribution valve cylinder 9 through the hydraulic valves 8-1, 8-2. The plug valve of the main cylinder and the cylinder of the distribution valve send out signals to control the directional change of the hydraulic valves, thereby coordinating the movement sequences of the main cylinder and the distribution valve cylinder and enabling the cycling of concrete pumping. In this process, the two cylinders of the main cylinder 10 take turns sucking in and discharging concrete to achieve continuous concrete pumping. During each reversal process, the concrete flow typically exhibits a distinct pattern of flow-stop-flow, namely what is commonly referred to as flow interruption. Figure 1 Schematic diagram of the hydraulic system for the concrete pump 1 – Motor ； 2-Tank ； 3-Primary oil pump ； 4-Return oil filter ； 5-Air filter ； 6-Overflow valve ； 7-Pressure gauge ； 8-Hydraulic valve ； 9- Distribution valve cylinder ； 10-There are three reasons for the interruption in the flow of concrete in the main cylinder: ① When the main cylinder reaches near the end of its travel distance, a signal is sent to the reversing cylinder to cause it to reverse direction, which in turn causes the oil circuit of the main system to reverse as well; the main cylinder 10 then moves in the opposite direction. This process takes at least 0.2 seconds ； ②The suction efficiency of concrete being drawn into the concrete pump is usually only 85% to 95%; inevitably, a small amount of air is drawn in as well, resulting in a short period of idle operation ； ③When reversing, the concrete drawn into the concrete cylinder experiences an increase in pressure as it is discharged outward; it has a certain degree of compressibility, which also constitutes a short distance of idle travel. Due to the reversal and the two periods of idle time, flow interruption occurs during concrete pumping. 2. Solution: The method to address the interruption in pumping is to minimize the switching time and increase the speed at which the piston of the main cylinder moves at the start of switching, so as to ensure continuous pumping of concrete before the pressure of the concrete in the pipes and distribution valves is completely released. This helps to reduce the segregation of concrete due to interruptions in pumping, as well as the backpressure resulting from the release of pressure in those pipes and valves during switching. For most pumping systems, the flow interruption problem can be resolved by using an electrically proportional control constant-power plunger pump. Since electric proportional control plus constant power control gives priority to electric control variables over constant power control, the displacement is adjusted by the control current when the power is below the hyperbolic value. During the switching process, and before the cylinder piston starts moving the concrete in the pipeline after switching, the system pressure is usually lower than the pumping pressure. It is possible to increase the displacement of the main oil pump in order to enable rapid switching of the distribution valve, thereby reducing the time from switching to the start of moving the concrete and ensuring that the flow of concrete appears continuous. Typically, two proximity switches can be installed in the water tank located between the hydraulic cylinder and the concrete cylinder. The positions of the start and end points for signal acquisition are determined based on the displacement of the main hydraulic pump, as well as the diameter and stroke of the main hydraulic cylinder. The key to such control lies in determining the start and end positions of the signal acquisition points during the electric proportional control phase; the distance between the proximity switches is usually 5% to 10% of the total stroke. Upon receiving the start signal, the proximity switch transmits it to the programmable controller or the holding relay; the controller or relay then controls the supply of the current required (usually several hundred mA) to the proportional solenoid of the main oil pump, thereby causing a sharp increase in the pump’s discharge volume. This allows for rapid direction change and the initiation of the delivery of concrete through the distribution valves and pipes. Adjust the position of the cutoff proximity switch so that electrical control is stopped once the cylinder begins to push the distribution valve and the concrete in the pipes, thereby allowing continuous constant-power control of the oil pump. In actual use, the starting and ending positions of the feed port can be adjusted accordingly based on the specific conditions of the concrete pump, in order to maximize the continuity of the concrete flow during pumping. Abroad, especially in countries in Europe and the United States, pump trucks are widely used; their capacity is high, and strict controls are applied to the aggregates and grading of concrete. Building sizes and heights are relatively small, so the problems and risks associated with flow interruption are not very significant ； In China, drag pumps are commonly used, with a discharge capacity generally below 80 m3/h; buildings are large in scale and height, resulting in relatively significant flow interruption phenomena. By selecting and setting the control method for the main oil pump, it is possible to effectively resolve the issue of interrupted concrete delivery, reduce switching shocks, and **improve the pumping performance of the concrete pump