A quick share, in one minute, let you understand the selection principles of Zhongkai pumps.
Release time:
2022-09-05
Source:
The parallel adjustment method for middle-opening pumps is used when a single middle-opening pump cannot meet the delivery task, allowing for the operation of middle-opening pumps in parallel or series. When two identical centrifugal pumps are operated in parallel, although the head change is minimal, the total delivery flow increases, and the overall efficiency of the parallel pumps is the same as that of a single pump. When pumps are started in series, the total head increases while the flow change is very small. The overall efficiency of series pumps is the same as that of a single pump. After two pumps are connected in parallel, both flow and head increase, but due to the limitations of the pipeline characteristic curve, pipeline resistance increases, resulting in a total delivery volume that is twice that of the original single pump. After two pumps are connected in series, both head and flow will also increase, but...
The parallel adjustment method of the middle opening pump is when a single middle opening pump cannot meet the transportation task, it can operate in parallel or series with other middle opening pumps. When two identical centrifugal pumps are connected in parallel, although the head change is not significant, the total flow rate increases, and the overall efficiency of the parallel pumps is the same as that of a single pump. When the pumps are started in series, the total head increases, and the flow rate changes very little. The total efficiency of series pumps is the same as that of a single pump. After two pumps are connected in parallel, both flow and head increase, but due to the limitations of the pipeline characteristic curve, pipeline resistance increases, and the total delivery volume after connecting two pumps in parallel is twice that of the original single pump. After connecting two pumps in series, both head and flow will also increase, but the total head after connecting two pumps in series is still less than twice that of the original single pump.
Cavitation in a middle opening pump occurs when the pressure P1 at the inlet of the middle pump is equal to or less than the saturation vapor pressure PV of the liquid at the same temperature, causing the liquid to vaporize. Under high pressure, bubbles rapidly coalesce or burst, generating extremely high pressure and frequency shocks. The pump body will experience strong vibrations and noise, and liquid flow rate, head (outlet pressure), and efficiency will significantly decrease. This phenomenon is known as cavitation in open centrifugal pumps.
The operation (energy conversion) of a middle opening pump involves filling the pump casing with liquid to be transported before starting; after starting, the impeller is driven by the shaft to rotate at high speed, and the liquid between the blades must also rotate accordingly. Under centrifugal force, liquid is thrown from the center of the impeller to its outer edge and gains energy, leaving the outer edge of the impeller at high speed and entering the volute casing. Inside the volute casing, due to the gradual expansion of the flow path, the liquid slows down and converts part of its kinetic energy into static pressure energy, finally flowing into the discharge pipeline at a higher pressure to be sent to where it is needed. As liquid flows from the center of the impeller to its outer edge, a certain vacuum forms at the center of the impeller. Since the pressure above the tank liquid level is greater than that at the pump inlet, liquid is continuously pressed into the impeller. It can be seen that as long as the impeller keeps rotating, liquid will continuously be drawn in and discharged.
What are the selection principles for middle opening pumps? Let's briefly understand together.
The middle opening pump is a widely used general mechanical device that finds applications in petroleum, chemical industry, electric metallurgy, mining, ship selection, light industry, agriculture, civilian use, and national defense, holding an important position in national economic development.
The so-called reasonable selection of middle opening pumps means comprehensively considering investment in pump units and pumping stations, operating costs, and other comprehensive technical economic indicators to meet principles of economy, safety, and applicability. Specifically, there are several aspects:
1. It is necessary to meet flow rate and lift requirements; that is to say, it requires that the working point of the pump (the intersection point between device characteristic curves and pump performance curves) always remains within a high-efficiency range so as to save electricity and avoid damaging parts easily. 2. The selected pump should be small in size, light in weight, low in cost, good in performance, and high in efficiency. 3. It should have good anti-cavitation performance, stable operation, and long service life. 4. The selected pump should have low engineering investment and low operating costs.
Centrifugal pump
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