How to Deal with Concrete Pump Truck Pipe Blockage?

I. Causes of Pipe Blockage

Under normal circumstances, commercially produced concrete forms a columnar fluid in the center of the pumping pipeline, flowing in a suspended state. The surface of the fluid is coated with a layer of cement slurry, which acts as a lubricant in contact with the pipe wall. Essentially, no relative movement occurs between the aggregates. When certain coarse aggregates encounter obstruction, the movement speed of the following aggregates is gradually affected and slows down, causing the coarse aggregates in the pipeline to accumulate. The mortar supporting the coarse aggregates is squeezed away, and the resulting gaps are filled by finer aggregates. This increases the density of the aggregates, causing the aggregated material in that section of the pipeline to expand radially. The cement slurry lubricating layer is destroyed, movement resistance increases, speed decreases, and eventually, movement stops, resulting in a blockage.

II. Identifying Blockage Locations and Solutions

1. Blockage at the Feed Inlet
Phenomenon: The pumping action and hydraulic system operate normally without unusual noises or vibrations. Larger aggregates or lumps in the hopper become stuck or arched at the feed inlet, causing a blockage.
Solution: Reverse the pump operation to break up the lumps, allowing the concrete to return to the hopper for remixing before resuming forward pumping. If this fails, manual clearing is required to resolve the issue.

2. Blockage at the Distribution Valve Outlet
Phenomenon: The pumping system suddenly stops operating, accompanied by unusual noises and significant equipment vibration, though no corresponding vibration is observed in the pipeline.
Solution: Pour 15–30 liters of cement slurry into the hopper and repeatedly switch between forward and reverse pumping to force the passage open. If this method proves ineffective, manual intervention is necessary. Disconnect the relevant pipe section and remove any debris from the valve.

3. Blockage at the S-Tube Valve
Phenomenon: Blockages at the S-tube valve develop gradually, primarily due to failure to promptly clean with high-pressure water after pumping concrete. Residual concrete remains in the S-tube, accumulating and hardening over time, leading to a blockage.
Solution: After pumping concrete, always clean the pump body and S-tube thoroughly with high-pressure water. If cleaning is ineffective, use a drill rod to break up and remove the residue until it is completely clear.

4. Blockage in the Concrete Delivery Pipeline
Phenomenon: When the delivery pressure gradually increases, the hopper level does not decrease, no concrete is discharged from the pipeline outlet, the pump vibrates, and the pipeline exhibits strong vibration and displacement, a pipeline blockage can be confirmed.
Identifying the Blockage Location: Blockages typically occur at bends, tapered pipes, and sections exposed to vibration. Gently tap along the pipeline with a hammer; a dull sound indicates a blockage, while a clear sound suggests normal flow. Alternatively, listen for a sandy sound (normal) or a harsh sound (blockage).

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When a blockage occurs, immediately attempt to clear it by repeatedly switching between forward and reverse pumping. This will gradually draw the concrete back into the hopper for remixing before resuming pumping. Alternatively, use a wooden hammer to tap the pipeline while switching between forward and reverse pumping to restore flow. If these methods prove ineffective, the blockage is severe. Once the blocked section is identified, disconnect the pipe, and use high-pressure air, a heavy hammer, or high-pressure water to clean it thoroughly. After ensuring the pipeline is completely clear, reassemble it and resume concrete pumping operations.

For more information, please contact: Ms. Stella +86 18942525262 wpt@mandiwi.com