I. What is a centrifugal pump
A centrifugal pump is generally driven by an electric motor. Before starting the pump, the pump body and the suction line are filled with liquid. When the impeller rotates at high speed, the impeller drives the liquid between the blades to rotate together. Due to the centrifugal force, the liquid is thrown from the center of the impeller to the outer edge of the impeller (the flow rate can be increased to 15-25m/s), and the kinetic energy also increases. When the liquid enters the pump casing, due to the gradual expansion of the flow channel in the volute-shaped pump casing, the liquid flow rate gradually decreases, and a part of the kinetic energy is converted into static pressure energy, so the liquid flows out along the discharge port at a higher pressure. At the same time, a certain vacuum is formed at the center of the impeller because the liquid is thrown out, and the pressure Pa at the liquid level is higher than that at the center of the impeller, so the liquid sucked into the pipeline enters the pump under the action of the pressure difference. The impeller rotates continuously, and the liquid is continuously sucked in and pressed out. Because the centrifugal pump can transport liquid mainly by the action of centrifugal force, it is called centrifugal pump.
Second, what is a self-priming pump
All self-priming pumps use a pump body structure with axial liquid return. The pump body of the self-priming pump 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 self-priming pump is normally started, the impeller will suck the liquid stored in the suction chamber and the air in the suction pipe together. , and be completely mixed in the impeller. Under the action of centrifugal force, the liquid entrains the gas to flow to the outer edge of the scroll chamber, forming a white foam belt of a certain thickness and a high-speed rotating liquid ring on the outer edge of the impeller. The gas-liquid mixture enters the gas separation chamber through the diffusion tube. At this time, due to the sudden decrease of the flow rate, the lighter gas is separated from the mixed liquid, and the gas continues to rise and discharge through the discharge port of the pump body. The degassed liquid returns to the liquid storage chamber, and enters the impeller through the return hole again, where it is mixed with the gas sucked in from the suction pipe inside the impeller, and flows to the outer edge of the impeller under the action of the high-speed rotating impeller. As this process goes on over and over again, the air in the suction pipe continues to decrease until the air is exhausted, the self-priming pump completes the self-priming process, and the self-priming pump is put into normal operation. Because the self-priming pump has this unique exhaust capability, the self-priming pump can transport liquids containing gas without installing a bottom valve, and has a good cleaning function when used on cruise ships.
Three, the difference between centrifugal pump and self-priming pump
1. The composition is different
Centrifugal pump The pump is composed of 6 parts including impeller, pump body, sealing ring and stuffing box. The self-priming pump is divided into a suction chamber, an oil storage chamber, a vortex chamber, a liquid return hole, and a gas-liquid separation chamber.
2. Different starting methods
To start the centrifugal pump, you need to fill the water inlet pipe and the pump body with water, or use auxiliary equipment to face the water inlet pipe Pump up. When the self-priming pump is turned on, an appropriate amount of circulating water should be added to the pump body.
3. Different installations
The bottom valve must be installed under the water inlet pipe of the centrifugal pump or the air extraction equipment must be installed at the outlet. The self-priming pump needs to be equipped with a filter screen under the water inlet pipe, without the need for a bottom valve.
4. Different uses
Centrifugal pumps are mainly used for liquid transportation, cooling, industrial cleaning, aquaculture, fertilization, computing and testing, industrial equipment, and also It can be used in the transportation of electric power, metallurgy, coal and building materials industries and the manufacture of granular slurry.
The self-priming pump can turn water into fine raindrops for spraying, and is widely used in farmland, nursery, orchard and other places, clean water, seawater, acid-base chemical solution or paste slurry Can be used and can be used with most types of filter presses.
5. Different advantages
The centrifugal pump has a compact structure, with a large flow and field control range, and can be used for flow on mildly corrosive liquids Balanced, smooth operation, little vibration, and minimal installation and maintenance costs.
The structure of the self-priming pump is also very compact, it is very convenient to operate, it operates smoothly, it is easy to maintain, and it has high efficiency and long use time.
Fourth, centrifugal pump and self-priming pump which is better
In fact, self-priming pump is also a kind of centrifugal pump, but self-priming pump It has a high body height and is much larger than a centrifugal pump. It has a certain water storage capacity. It does not need to install a bottom valve in the suction pipe. After the first irrigation, it can absorb water for life. The self-priming pump can be called a centrifugal pump, and it can also be called a self-priming centrifugal pump according to its function.
The centrifugal pump plays a role in boosting. The liquid level must be higher than the pump and can be left in the pump body to start. If the liquid level is lower than the centrifugal pump, it can only be installed at the suction port of the inlet pipe. The bottom valve fills the pump and pipeline with liquid to achieve the function of self-priming, or install a water diversion cylinder at the inlet, such as a centrifugal pump whose pump does not work for a long time, the water in the inlet pipeline and the pump body is basically at the second start. There is no more, and it has to be refilled to divert water again, which is more troublesome in operation, because the sealing of the bottom valve of the inlet of the centrifugal pump that has not been used for a long time cannot achieve the effect of complete sealing. Self-priming pumps work better than centrifugal pumps. However, if it is in the form of reverse irrigation, or if there is a siphon barrel and a self-priming barrel, it is economical and practical to use a centrifugal pump. Therefore, centrifugal pumps and self-priming pumps are neither good nor bad, but only the needs of fixed working conditions, and pumps that can meet their own working conditions are reliable products.
