What is the difference between a self-priming pump and a centrifugal pump? We call water pumps with self-priming function as self-priming pumps. Common self-priming pumps on the market are: plastic self-priming pumps (plastics include: PP, PVDF, fluoroplastics, fluorine-lined), stainless steel self-priming pumps ( sus304, sus316), self-controlled self-priming pumps (also called vertical self-priming pumps), etc. Centrifugal pumps refer to pumps that use centrifugal force to work. They can all be called centrifugal pumps, such as magnetic pumps (large and small), pipeline pumps , Sewage pumps, vertical pumps and other pumps. In the industrial field, the frequency of use of centrifugal pumps is unmatched by other pumps.

Self-priming pump:

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 a 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.

Self-priming pumps all adopt the pump body structure with axial liquid return. 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 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. ——From Baidu Encyclopedia

Centrifugal pump:

Refers to the centrifugal force generated when the impeller rotates to transport the liquid pump.

After the centrifugal pump is started, the pump shaft will drive the impeller to rotate at a high speed, forcing the pre-filled liquid to rotate between the blades. Under the action of inertial centrifugal force, the liquid moves radially from the middle of the impeller to the outer periphery.

The liquid medium gains energy during its movement through the impeller, resulting in an increase in static pressure and an increase in flow velocity. When the liquid leaves the impeller and enters the pump casing, it decelerates due to the gradual expansion of the flow passage in the casing. Part of the kinetic energy is converted into static pressure energy, and then flows into the discharge pipe tangentially.

When the liquid is thrown from the middle of the impeller to the outer periphery, a low pressure zone will be formed in the middle of the impeller. Under the action of the total potential energy difference between the liquid level of the storage tank and the middle of the impeller, the liquid will be sucked into the middle of the impeller. Relying on the continuous operation of the impeller, the liquid is continuously sucked and discharged. The mechanical energy obtained by the liquid in the centrifugal pump is manifested as an increase in static pressure energy. ——From Zhihu

classification:

Self-priming pump: Self-priming pump is also a pump that relies on centrifugal force to transport liquid, so self-priming pump is also a kind of centrifugal pump, which can be called self-priming centrifugal pump. Self-priming pumps include: plastic self-priming pumps, stainless steel self-priming pumps, vacuum self-priming pumps, cast iron self-priming pumps, self-control self-priming pumps, etc.

Centrifugal pump: The range of centrifugal pump is much larger than self-priming pump.

According to the number of impellers: single-stage pump, multi-stage pump;

According to working pressure: low pressure pump, medium pressure pump, high pressure pump;

According to the impeller suction mode: single suction pump, double suction pump;

According to the position of the pump shaft: horizontal pump, vertical pump;

According to the way of impeller access: volute pump, guide vane pump;

According to purpose: oil pump, sewage pump, sewage pump, waste gas pump, circulation pump, etc.;

How to choose in use?

In specific working conditions, such as sewage treatment plants, electroplating plants, power stations, communities, photovoltaics and other specific sites, how do we choose between self-priming pumps and centrifugal pumps? It is definitely better to choose a centrifugal pump because the liquid level is higher than that of the pump to flow into the pump, because the efficiency of the centrifugal pump is higher than the self-priming pump. However, some processes, such as sewage treatment, require the use of self-priming pumps to transport sewage from the sewage tank to other places, because self-priming pumps have a certain self-priming ability.