Industry news

The working principle and types of self-suction pump

2021-08-13
The working principle of the self-priming pump is to fill the pump casing with water before starting the pump (or there is water in the pump casing itself). After starting, the impeller rotates at high speed to make the water in the impeller channel flow to the volute. At this time, the inlet forms a vacuum, so that the water inlet check door opens, and the air in the suction pipe enters the pump and reaches the outer edge through the impeller channel.

The pump adopts axial liquid return pump body structure. The pump body is composed of a suction chamber, a liquid storage chamber, a scroll chamber, a liquid return hole, a gas-liquid separation chamber, etc. After the pump is started normally, the impeller sucks the liquid stored in the suction chamber and the air in the suction pipeline together, and puts it in the impeller. The inside can be completely mixed. Under the action of centrifugal force, the liquid entrains the gas to flow toward the outer edge of the scroll, forming a certain thickness of white foam belt and high-speed rotating liquid ring on the outer edge of the impeller. The gas-liquid mixture enters the gas-liquid separation chamber through the diffuser. At this time, due to the sudden decrease of the flow rate, the lighter gas is separated from the mixed gas-liquid, and the gas continues to rise and discharge through the pump body spout. The degassed liquid returns to the liquid storage chamber, and enters the impeller again through the return hole, and mixes with the gas sucked in from the suction pipe inside the impeller again, and flows to the outer edge of the impeller under the action of the high-speed rotating impeller.... ... As this process goes on again and again, the air in the suction pipeline is continuously reduced until the gas is exhausted and the self-priming process is completed, and the pump is put into normal operation.
A cooling chamber is also provided at the bottom of the bearing body of some pumps. When the bearing body heats up and the temperature of the bearing body rises more than 70 degrees, the cooling liquid can be injected into the cooling chamber through any one of the cooling liquid pipe joints. The sealing mechanism inside the pump to prevent the liquid from leaking from the high-pressure zone to the low-pressure zone is the front and rear seal rings. The front seal ring is installed on the pump body and the rear seal ring is installed on the bearing body. When the pump runs for a long time, the seal ring is worn to a certain extent and When it affects the efficiency and self-priming performance of the pump, it should be replaced.

Self-priming pumps are divided into the following categories according to the principle of action: 1. Gas-liquid mixing type (including internal mixing and external mixing); 2. Water ring wheel type; 3. Jet type (including liquid jet and gas jet). The working process of the gas-liquid hybrid self-priming pump: Due to the special structure of the self-priming pump body, after the pump stops, there is a certain amount of water in the pump body. After the pump is restarted, the air and water in the pipeline will be sucked due to the rotation of the impeller. It is fully mixed and discharged to the gas-water separation chamber. The gas in the upper part of the gas-water separation chamber overflows, and the water in the lower part returns to the impeller. Suck and pump normally. The water ring wheel self-priming pump combines the water ring wheel and the water pump impeller in a shell, and uses the water ring wheel to discharge the gas to realize self-priming. When the pump is working normally, the channel of the water ring wheel and the water pump impeller can be blocked by the valve, and the liquid in the water ring wheel can be discharged. The jet self-priming pump is a combination of a centrifugal pump and a jet pump (or ejector). It relies on a jet device to create a vacuum at the nozzle to achieve suction.
According to the type of the supporting power machine of the pump, it is divided into the self-priming pump supporting the electric motor and the self-priming pump supporting the diesel engine.
According to the structure and working characteristics that realize the self-priming function, it can be divided into internal sliding type, external sliding type, water ring wheel type and other types. Transmission methods include direct drive (including inner shaft) and belt drive. The inlet diameter is 25~200mm.

Self-priming pump selection
1. Strict procedures for purchasing water pumps.
When purchasing a water pump, it must be checked. Only when the three certificates are complete can the purchase of obsolete products and inferior products be avoided.
2. Choose self-priming pumps according to local conditions
3. Select water pumps that exceed the standard appropriately.
After determining the type of water pump, its economic performance should be considered, and special attention should be paid to the selection of the pump's head and flow and its supporting power. It must be noted that the head (total head) indicated on the pump label is different from the discharge head (actual head) during use. This is because there will be a certain resistance loss when the water flows through the water pipe and the vicinity of the pipeline. Therefore, the actual head is generally 10% to 20% lower than the total head, and the water output is also reduced accordingly.

Therefore, in actual use, it can only be estimated based on 80% to 90% of the head and flow stated on the label. The power selection of the pump can be selected according to the power indicated on the label. In order to make the pump start quickly and use safe, the power machine is The power can also be slightly larger than the power required by the pump, generally about 10% higher; if you have power, you can choose a matching pump according to the power of the power machine when you buy a pump.