The pace of construction of modern cities in China is getting faster and faster, and the scale of cities is expanding. The scale of the infrastructure needs to adapt to it is also expanding, the city's water consumption is increasing, and the drainage volume is also increasing, so the management, maintenance, repair and dredging of sewerage pipes is also increasing. Among them, the desilting of sewerage pipes is very important and has become a task that cannot be ignored by the relevant departments. As there are often problems with sewage and other debris dumped by residents and cement mortar from infrastructure sites in the sewerage pipes, these debris precipitate and silt up. Too much siltation will cause blockage of the pipes, and if they cannot be cleared and unblocked in time, they will cause sewage overflow, pollute the environment, cause economic losses and bring trouble to the residents' lives.

According to the above situation, the relevant departments have adopted many methods to solve the desilting in the sewerage pipe, but they are not very satisfactory, as follows.

    1、Mechanical dredging method

Mechanical dredging method is the more commonly used method in China. The specific method is: first of all, put the TT piece through the pipe section that needs to be cleared, tie one end of the TT piece to the wire rope, tie one end of the rope to the clearing tool, and set up a winch on each of the two inspection wells in the clearing pipe section. When the TT piece passes through the pipe section, the wire rope is tied to one winch, and the other end of the clearance tool is tied to the other winch through the wire rope, then the winch is used to winch the wire rope back and forth, driving the clearance tool to hang the silt into the downstream inspection well, so that the pipe can be cleared. The power of the winch can be manual or motorized, which needs to be decided according to the actual situation.

Mechanical dredging method is applicable to various diameters of sewerage pipes, mainly for the situation when the pipe is more seriously blocked, the silt is densely bonded, and the effect of hydraulic cleaning is not good. However, this method will also have shortcomings, for example, workers are labor-intensive and need to manually go down the well to finish sending TT pieces from one wellhead to another. Due to the harsh working environment in the well, it is very easy to cause safety accidents.

    2、Hydro-desilting method

The hydraulic desilting method is to make a desilting device that can hold back water and put it into the pipeline by the inspection well. Due to the small size of the wellhead, the whole device cannot be put down, so the method of transporting the parts of the device first and then assembling them in the pipeline is generally adopted. After the dredging device is assembled, it is placed in a certain position of the pipe to block the sewage in the pipe in the upstream of the device, and when the water level reaches a certain height, the water is released so that the upstream water forms a current to remove the sediment in the pipe. When the sediment is washed away, the dredging device moves downstream and then carries out water collection and dredging. Although this method can remove the silt, a considerable amount of work needs to be done inside the pipe. Also, the sludge content is very high, and the effluent in the pipe itself must have a certain flow rate, the sludge should not be too much, the upstream effluent must not flow away from other branches, and it must also be ensured that no water from the upstream flows back to nearby buildings. Otherwise, although in a certain place in the pipe with the air plug, but because of the pipeline system pulse, a blocked, upstream sewage can also flow to other sections of the pipe, which can’t be in the pipe water accumulation, the air plug will not be able to swim down. The consequence is that only the use of hydraulic flushing trucks or water flushing from other places, both labor and water.

In response to the above problem, the relevant departments proposed the use of high-pressure cleaning machine on the city sewer dredging program, after the test proved that the effect is very significant.