The pump is one of the essential equipment in the sewage treatment project, its role is to lift the relatively low elevation of sewage to the subsequent relatively high elevation of the treatment unit, to provide sufficient power for the smooth progress of sewage treatment. Whether the pump selection is correct for the stability of the entire system, the economy of investment and operation, the rationality of the operating results have a significant impact.
1?Factors affecting pump selection1.1?Pump installation site environment
Usually in the sewage treatment of water pumps are divided into two kinds, one is installed outside the sewage, known as centrifugal pumps that is the dry pumps, the other is directly mounted on the sewage, known as submersible pumps. The two pumps have their advantages and disadvantages, need to be selected according to different occasions. Centrifugal pump operation, impeller blades rotate at high speed to generate centrifugal force, the medium will be transported to the high-pressure end of the outlet, and in the suction port to form a negative pressure inhalation of the medium as a cycle. Because of its installation in the sewage outside, running only the pump suction pipe and impeller submerged in the sewage, to keep the equipment dry, to avoid contamination of the pump body
, convenient for subsequent management, maintenance and repair. However, due to its structure, if the water pump without water can not transport media, and very easy to damage the impeller and the pump body resulting in equipment damage.
Submersible pump working principle is also the use of centrifugal force, but because the pump body is installed in the pool, running pumps and fittings are submerged in the water, there is no water intake pipe and pump suction range of the problem, the pool's effective volume will be larger, the disadvantage is that the equipment immersed in sewage corrosion, maintenance and management and repair is more troublesome. Sewage treatment involves a wide variety of sewage, there are people's daily life discharged sewage, industrial production of wastewater discharged in the production of wastewater, and industrial wastewater discharged by different industries have different characteristics, only the selection of appropriate pumps, sewage treatment works can be stable and effective operation.
? 1.2?Pump conveyor mediumAccording to the amount of impurities contained in the conveyor medium can be divided into clear water pumps and sewage pumps two kinds of pumps. Clear water pumps on the cleanliness of the transport medium requirements are high, generally require the medium in the volume of solids content does not exceed 0.1%, particle size is not greater than 0.2mm, otherwise it is very easy to clog the pump, the pump body, impeller damage. The structural principle of the sewage pump with the same clear water pump, but some internal structure changes, such as increasing the pump flow channel, increase the impeller clearance, cancel the impeller ring, increase the serrated piece
, so you can transport the media containing more impurities. For various types of sewage selection of pumps is based on the following principles
1) for the higher cleanliness, physico-chemical properties similar to the clean water sewage, such as cleaning wastewater, oily wastewater, etc., it is recommended to use clean water pumps for transport;
2) for sewage containing a large number of impurities (such as larger solid particles, a variety of fibers), such as domestic wastewater, textile wastewater, wastewater from the paper industry, etc., it is necessary to select the sewage pump to operate.
3) For corrosive or high-temperature sewage, special material corrosion-resistant pumps, such as plastic, stainless steel and other materials manufactured pumps must be targeted, otherwise the pump body is easily corroded, so that the operation of the entire system is affected.
1.3?Pump specific model selection
Before selecting the specific model of the pump, you first need to calculate the flow rate and head of the required pump according to the specific design parameters, and then according to the characteristics of the actual pump curve for comparison and selection.
1.3.1?Calculation of pump flow
1.3.2?Calculation of pump head
The total head of the pump is determined by the suction height of the pump, the height of the lift and the head loss of the pipeline in three ways, once the pump flow, pipe diameter and piping arrangement to determine
, the design head of the pump can be determined.
H≥h1+h2+h3+h4(m)
H-Total head of pump (m);
h1-head loss of suction pipe (m), generally including suction flare, 90 ° elbow, straight line section, valves, tapering pipe, etc.; h2-head loss of outlet pipe (m), generally including tapering pipe, check valves, valves, short pipes, 90-degree elbow (or), straight line section, etc.; h2-head loss of outlet pipe (m), generally including tapering pipe, check valve, valve, short pipe, 90-degree elbow, or Tee), straight sections, etc.;
h3-collector pool lowest working water level and the need to lift the highest water level between the height difference (m);
h4-safety head (m), the estimated head can be based on 0.5m ~ 1.0m; detailed calculations should be used with caution, so as not to shift the point of the working conditions.