Troubleshooting and prevention of Pipe blockage faults in concrete pumping equipment

With the rapid development of highway construction, some domestic and imported concrete pumping equipment has been widely used by construction units. However, during the concrete pouring operation, due to improper use, equipment pipe blockage faults occur from time to time, which not only affects the project progress but also directly impacts the project quality.

1. Causes of pipe blockage

Under normal circumstances, concrete forms a columnar fluid at the center of the pumping pipeline and flows in a suspended state. The surface of the fluid is coated with a layer of cement slurry. The cement slurry layer, acting as a lubricant, comes into contact with the pipe wall, and there is basically no relative movement between the aggregates. When the movement of some aggregates in the coarse aggregate is blocked, the movement speed of the subsequent aggregates gradually slows down due to the impact, causing the coarse aggregates in the pipeline to aggregate. The mortar supporting the coarse aggregates is squeezed away, and the remaining gaps are filled by small aggregates. In this way, the density of aggregates increases, causing the aggregates in this section of the pipeline to expand radially along the pipeline. The cement slurry lubrication layer is damaged, the movement resistance increases, the speed slows down, and eventually the movement stops, resulting in blockage.

The determination and elimination methods of the location of the blocked pipe

Blockage at the feed inlet

Phenomenon: The pumping action and hydraulic system are both normal, with no abnormal sounds or vibrations. There are large aggregates or lumps in the hopper, which get stuck or bulge at the feed port and cause blockage.

Troubleshooting method: Rotate the pump in reverse to break up the lumps, return the concrete to the hopper for re-mixing, and then pump it forward. If it doesn't work, manual cleaning is required to eliminate it.

The blockage at the discharge port of the distribution valve

Phenomenon: The pumping system suddenly stops operating, accompanied by abnormal sounds. The equipment vibrates strongly, but there is no corresponding vibration inside the pipeline.

Troubleshooting method: Pour 15 to 30 liters of cement slurry into the hopper, and repeatedly start the pump in both forward and reverse directions to force the passage to open. If this method is ineffective, it can only be eliminated manually. Remove the connecting pipe and clear the debris inside the valve.

The S pipe valve is clogged

Phenomenon: The blockage at the S pipe valve gradually formed. The main reason is that after the concrete was pumped, it was not promptly flushed with high-pressure water, causing the concrete to remain in the S pipe. Over time, it gradually thickened, accumulated and consolidated, resulting in a blockage.

Troubleshooting method: After the concrete pumping is completed, the pump body and S-pipe must be thoroughly rinsed with high-pressure water. When rinsing is ineffective, a chiseling can be used to remove the residue until it is completely clean.

The concrete conveying pipeline is clogged

Phenomenon: When the conveying pressure gradually increases, but the material level in the hopper does not drop, no material is discharged from the pipeline outlet, the pump vibrates, and the pipeline is accompanied by strong vibration and displacement, it can be determined that the pipeline is blocked.

Judgment of blockage locations: Blockages typically occur in elbow pipes, conical pipes, and sections with vibration. At this point, you can use a small hammer to strike along the pipeline. The place where the sound is dull is the blocked area. A clear and crisp sound is normal. Listen with your ear. A rustling sound is normal, and a shrill sound indicates a blockage.

Troubleshooting method: When pipe blockage occurs, the method of repeatedly rotating the pump forward and backward should be immediately adopted to gradually suck the concrete at the pump outlet back into the hopper for re-mixing and then re-conveying. It can also be unblocked by striking with a wooden hammer in combination with the forward and reverse rotation pumps. When the above methods are ineffective, it indicates that the blockage is severe. After identifying the blocked section, remove the pipe, blow it with high-pressure air, strike it with a heavy hammer or rinse it with high-pressure water. Once it is thoroughly cleaned, reconnect the pipe and continue the concrete pumping work.

Measures to prevent clogging of pumped concrete

When installing and designing pipelines, it is advisable to avoid 90° and S-shaped bends as much as possible to reduce the resistance of pumping concrete and prevent blockage.

(2) To ensure the continuity of concrete pumping operations and the quality of concrete pouring, the intervals between operations should not be too long to prevent blockage. If for some reason the interval is long, the pump should be started once every 5 to 10 minutes or rotated in reverse and forward several times to prevent clogging.

(3) Pumped concrete must strictly follow the designed mix proportion for pumped concrete and strictly control the slump.

(4) The particle size of the selected aggregates must meet the requirements and generally should not exceed one quarter of the diameter of the conveying pipe.

(5) Before pumping concrete, the pipes should be lubricated with clean water. Mortar should be pumped first and then concrete to prevent blockage.

(6) In hot summer, wet straw bags should be used to cover the pipes to prevent the concrete from collapsing too quickly during pumping and causing pipe blockage.