Sichuan Xinwei Rubber Co., Ltd , https://www.boprubber.com
Introduction to the hazards and solutions of concrete pumping and shut-off
At present, helium pumps are widely used in concrete construction. The most commonly used type is the two-cylinder driven helium pump, which often experiences a "shut-off" phenomenon during pumping cycles. This issue poses two major risks: first, it can lead to segregation of coarse aggregates, with some particles drying out and causing blockages—especially when pumping low-slump concrete. Second, the transient pressure changes during valve switching can create shock loads on the hydraulic system, damaging components and increasing energy loss. These effects are particularly noticeable when pumping vertically upwards, especially at heights exceeding 50 meters.
The pump operates as a full-liquid control system, where the main oil pump supplies oil to the main cylinders (10-1, 10-2) and the distribution valve cylinder (9) through hydraulic valves (8-1, 8-2). The main cylinder cartridge valve and the distribution valve cylinder send signals to control the hydraulic valve reversal, ensuring that the movement of the main cylinder and the distribution valve is synchronized, allowing for continuous concrete pumping. The main cylinder alternately sucks and discharges to maintain a steady flow. However, during each switching cycle, a significant flow interruption occurs—commonly referred to as the "shut-off" phenomenon.
There are three main causes of this turbulence:
1. When the main cylinder reaches the end of its stroke, it sends a signal to reverse the direction of the reversing cylinder, which then switches the oil flow direction, causing the main cylinder to move in the opposite direction. This process takes at least 0.2 seconds.
2. Concrete suction efficiency in the cylinder is typically between 85% and 95%, which means a small amount of air may be drawn in. In countries like the U.S. and Europe, where pump trucks are commonly used and concrete mix design is more controlled, this issue is less noticeable due to smaller building heights and stricter aggregate grading.
3. In contrast, domestically used trailer pumps usually have lower displacement (less than 80 m³/h), and they are often used for high-rise buildings, making the shut-off problem more apparent.
By optimizing the control mode of the main oil pump, the flow interruption during helium transport can be effectively reduced, minimizing the shock during commutation and significantly improving the overall pumping performance of the helium pump. This adjustment not only enhances operational efficiency but also extends the service life of critical components.