There are many types of self-priming pumps, of which, on the other hand, the water discharged by the impeller into the gas-water separation chamber flows back to the outer edge of the impeller through the left and right return holes. The water flowing back from the left return hole is directed into the impeller channel under the action of pressure difference and gravity, and is crushed by the impeller, mixed with the air from the suction line, then smashed to the volute, and the vacuum pump is pumped. Pump gear pump corrosion-resistant pump acid-resistant pump fire pump flows in the direction of rotation. It then merges with the water flowing from the right return hole and flows along the volute. As the liquid continuously hits the cascade in the volute and is continuously crushed by the impeller, it is stirred and mixed with the air to form a gas-water mixture, and continuously flows so that the gas and water cannot be separated. The mixture is peeled off at the outlet of the volute by a tongue and enters the separation chamber along the short tube. In the separation chamber, the air is separated and discharged by the outlet pipe, and the water still flows to the outer edge of the impeller through the left and right return holes, and is mixed with the air of the suction pipe. This cycle is repeated, gradually draining the air in the suction line, allowing water to enter the pump and completing the self-priming process. Sewage pump self-priming pump oil pump diaphragm pump screw pump gear oil pump
 The internal mixing self-priming pump has the same working principle as the external mixing self-priming pump, except that the return water does not flow to the outer edge of the impeller and flows to the impeller inlet. When the internal mixing self-priming pump is started, the return valve in front of the impeller must be opened to allow the liquid in the pump to flow back to the impeller inlet. The water is mixed with the air from the suction pipe by the high-speed rotation of the impeller, and the gas-water mixture is discharged to the separation chamber. Here the air is discharged and the water is returned from the return valve to the impeller inlet. Repeat this until the air is drained and the water is sucked up.
The self-priming height of the self-priming pump is related to factors such as the front seal gap of the impeller, the number of revolutions of the pump, and the liquid level of the separation chamber. The smaller the front seal gap of the impeller is, the larger the self-suction height is, which is generally 0.3~0.5 mm. When the gap is increased, the lift and efficiency of the pump are reduced except for the self-suction height. The self-priming height of the pump increases with the increase of the circumferential speed u2 of the impeller, but when the maximum self-suction height is increased, the number of revolutions increases and the self-suction height does not increase any more. At this time, only the self-priming time is shortened; When falling, the self-priming height decreases. Under other conditions, the self-priming height also increases with the increase of the storage height (but it cannot exceed the optimal storage height of the separation chamber). In order to better mix the gas and water in the self-priming pump, the blades of the impeller should be less, so that the pitch of the cascade is increased; and the semi-open impeller (or the wider impeller of the impeller channel) should be used, so that Convenient for the return water to penetrate into the impeller cascade.
Most of the self-priming pumps are matched with the internal combustion engine and are mounted on a movable trolley, which is suitable for field work.
What is the working principle of the self-priming pump? Ordinary centrifugal pump, if the suction liquid level is under the impeller, it should be pre-filled when starting, which is very inconvenient. In order to store water in the pump, the inlet of the suction pipe requires a bottom valve. When the pump is working, the bottom valve causes a large hydraulic loss. The so-called self-priming pump does not need to be filled before starting (the first time after installation, it still needs watering). After a short time of operation, the pump itself can suck up the water and put it into normal work.