Basic types and characteristics of drainage pumping stations: The type of drainage pumping station depends on the depth of the inlet pipe, the incoming water flow, the type and number of pumping units, hydrogeological conditions and construction methods. The type of drainage pump station should be selected from the aspects of cost, layout, construction and operating conditions. The following are some typical drainage pumping stations to illustrate their advantages and disadvantages and applicable conditions. Figure 1 shows a combined circular drainage pump station with a horizontal pump and self-priming. Suitable for medium and small displacement, no more than four pumps. The circular structure is under good stress conditions, and it is easy to adopt the sinking method to reduce the construction cost. The pump is easy to start and easy to operate according to the water level in the water absorption well. The disadvantage is that the arrangement of the unit and the auxiliary equipment in the machine is difficult. When the pump room is deep, the workers are inconvenient and the motor is easily damp. As the motor goes deep underground, ventilation should be considered to reduce the temperature between the machines.
Figure 1 Combined circular drainage pumping station
1-Drainage Canal 2-Pool 3-machine room 4-pressure pipe 5-horizontal sewage pump 6-grid
If the horizontal pump in this type of pumping station is changed to a vertical centrifugal pump (or an axial flow pump can also be used), the above disadvantages can be avoided. However, the vertical centrifugal pump installation technology requirements are relatively high, especially when the pump house is deep, and the transmission shaft is very long, the intermediate bearing and the fixed bracket must be provided to avoid the oscillation of the transmission shaft when the pump is running. Because this type can reduce pump room area, reduce engineering cost, and improve the operating conditions of electrical equipment and workers' operating conditions, it is still widely used in China. Figure 2 shows a joint-type rectangular drainage pump station with installed pumps and self-priming. Large pump stations are suitable for this type. When the number of pumps is four or more, the rectangular machine room is adopted, which is convenient in the arrangement of the unit, the pipeline and the auxiliary equipment, and the startup operation is simple and easy to realize automation. The electrical equipment is placed on the upper layer, it is not easy to get wet, and the workers operate in good condition. The disadvantage is that the construction cost is high. When the soil quality is poor and the groundwater level is high, it is not suitable for construction due to unfavorable construction.
Figure 2 Combined rectangular drainage pumping station
1-Drainage Canal 2-Pool 3-machine room 4-pressure pipe 5-vertical sewage pipe 6-vertical motor 7-grid
When the soil quality is poor and the groundwater level is high, it is reasonable to separate the collection basin from the machine in order to reduce construction difficulties and reduce project cost. It is relatively easy to construct a separate depth pond. In order to reduce the depth of the underground part of the machine, the pump's water absorption capacity should be used as much as possible to improve the machine room elevation. However, it should be noted that the allowable vacuum height of the pump should not be used to the limit, so as to avoid difficulty in water absorption after the pumping station is put into operation. Because in the design, various design and non-conformities that may occur during construction and pipe fouling after pumping, pump wear, and reduced power frequency cannot be accurately estimated in advance, it is necessary to leave room for proper.
Figure 3 Split-type circular drainage pumping station
1-Drainage Canal 2-Pool 3-machine room 4-pressure pipe 5-pump unit 7-grid
The main advantage of the split-type pumping station is that the structural treatment is simpler than the joint construction, the construction is convenient, and there is no danger of sewage infiltration and flooding by the sewage between the machines. Its biggest disadvantage is that it needs to be vacuumed to start. In order to meet the uneven water in the drainage pumping station, the pump is started more frequently, which brings difficulties to the operation. Co-construction drainage pumping station When the pump axis elevation in the machine is higher than the water level in the sump (ie, the machine room and the sump's bottom plate are not at the same elevation), the pump should also be started with vacuum. This type is suitable for the condition that the soil is hard and the construction is difficult, and the machine room has to be raised in order to reduce the amount of excavation. In terms of operation, its shortcomings are the same as the sub-construction. Less is used in actual projects. Figure 4 shows the screw pump station arrangement. The sewage water pipe enters the water tank of the screw pump, and the motor and related electrical equipment of the screw pump are arranged in the machine room 3. The sewage is lifted by the screw pump and then enters the water outlet 5, and the grille 4 is arranged at the beginning of the channel.
Figure 4 Screw pump station
1-Inlet pipe 2-spiral pump 3-machine room 4-grid 5-outlet
The pump can be pumped without a collecting tank, and no underground or semi-underground pump room can be built to save civil construction investment. The pumping of the screw pump does not require a closed pipe, so the head loss is small and the power consumption is relatively low. Because the spiral part of the screw pump is open, it is convenient for maintenance and overhaul. It does not need to be inspected during operation. It is easy to implement remote control and use in unattended pumping stations. It can also be installed directly in the sewer to raise sewage. The screw pump lifts any solids that can enter the pump blade, such as rags, cans, stones, weeds, plastic bags, and waste bottles. Therefore, it is not necessary to provide a grille in front of the pump. The grille is located behind the pump and above the ground for easy installation, overhaul and removal. When using a screw pump, accessories and equipment such as the suction horn, bottom valve, inlet water and outlet valve normally used in other types of sewage pumps can be completely eliminated.
Screw pumps also have special features not found in other pumps: for example, when lifting activated sludge and oily sewage, the sludge particles and silk flowers are not broken due to their slow rotation speed. It is used for sludge removal in the sedimentation tank, which can make the sedimentation sludge have a certain concentration effect. However, the screw pump also has its own shortcomings: due to mechanical processing conditions, the pump shaft can not be too thick and too long, so the lift is low, generally 3 to 6 m, and foreign introduction can reach 12 m. Therefore, it is not suitable for high lifts, where the water level changes greatly or when the water is a pressure pipe. Where large heads are required, two or more stages of pumping are often used. Unlike other pumps, it is slanted, due to its large size, large footprint, and more steel consumption. In addition, in the case of an open arrangement of the screw pump, when the pump is running, odor escapes due to the agitation of the sewage. With the continuous improvement of the quality of various domestic submersible pumps, more and more new or rebuilt drainage pump stations have adopted various forms of submersible pumps, including submersible axial flow pumps for drainage, submersible mixed flow pumps, submersible centrifugal pumps, etc. The biggest advantage is that it does not require a special machine room, and the submersible pump is directly placed in the collecting well, but the quality requirements of the submersible pump, especially the submersible motor are high. Figure 5 shows the submersible pumping station layout, which integrates the collecting well with the machine. Using the submersible pump, the submersible pump unit 1 is placed directly in the collecting well 2, and even an open pumping station can be used, without the superstructure and The crane is fixed, the unit is compact, the pump directly absorbs water, and the effluent is discharged from the original water pipe through the pump outlet.
Figure 5 Submersible pump drainage pump station
In engineering practice, the types of drainage pumping stations are varied. For example: a combined pumping station, the collecting basin is semi-circular, the machine room is rectangular; the elliptical pumping station is built; the collecting pool is open or covered; the underground part of the pumping station is a circular reinforced concrete structure, and the ground part is made of rectangular brick. Masonry and so on. The type of adoption should be determined according to the specific circumstances and after the technical and economic comparison of multiple programs. According to China's design and operation experience, where there are no more than four pumping stations and three or less rainwater pumping stations, the underground part of the structure is the most economical, and the form of the above-ground structures must be The surrounding buildings are adapted. When the number of pumps exceeds the above number, the underground and above-ground parts may adopt a rectangle or a combination of rectangles; the underground part is sometimes used to make the circular structure more economical and easy to sink well, and it is also possible to adopt the collecting pool and the machine. Separated into two structures, or the pump is divided into two underground circular structures, the upper part can be treated as a rectangle or a waist. This arrangement is suitable for rainwater pumping stations or confluence pumping stations with large flow rates. For pumping stations that generate flammable, explosive and toxic gases, they must be designed as separate buildings and appropriate protective measures should be applied.
