Views: 88 Author: Site Editor Publish Time: 2020-05-07 Origin: Site
In the production of the chemical and petroleum sectors, raw materials, semi-finished products and finished products are mostly liquids. Making raw materials into semi-finished products and finished products requires a complicated process. In these processes, the pump plays the role of conveying liquid and providing pressure and flow of chemical reaction. In addition, in many devices, the pump is also used to adjust the temperature.
In agricultural production, pumps are the main irrigation and drainage machinery.
In the mining and metallurgical industries, pumps are also the most used equipment. Mine needs to use pumps to drain water. In the process of beneficiation, smelting and rolling, pumps are needed to supply water.
In the power sector, nuclear power plants require nuclear main pumps, secondary pumps, tertiary pumps, and thermal power plants require a large number of boiler feed pumps, condensate pumps, oil and gas mixed pumps, circulating water pumps, and ash pumps.
In national defense construction, pumps are needed for the adjustment of aircraft flaps, rudder and landing gear, the rotation of warships and tank turrets, and the submarine's ups and downs. High-pressure and radioactive liquids, some require pumps without any leakage, etc.
In short, whether it is an aircraft, rocket, tank, submarine, or drilling, mining, train, ship, or daily life, pumps are needed everywhere, and pumps are running everywhere. This is exactly why the pump is classified as a general-purpose machine, which is a major product in the machinery industry.
Electric pump is a pump that is driven by electricity. The electric pump is composed of a pump body, a water pipe, a pump base, a submersible motor (including cable) and a starting protection device. The pump body is the working part of the submersible pump. It consists of water inlet pipe, diversion shell, check valve, pump shaft and impeller. There are two ways to fix the impeller on the shaft.
According to the working principle, the pump is divided into positive displacement pump, impeller pump and jet pump.
The pump can also be divided into vertical pump and horizontal pump according to the position of the pump shaft.
According to the number of suction ports, the pump is divided into: single suction pump and double suction pump.
According to the prime mover of the driving pump, the pump is divided into: motor pump, steam turbine pump, diesel pump and diaphragm pump.
The impeller is installed in the pump casing and fastened on the pump shaft, which is driven directly by the motor. There is a liquid suction pipe in the center of the pump casing. Liquid enters the pump through the bottom valve and suction pipe. The liquid discharge port on the pump casing is connected with the discharge pipe.
Before the pump starts, the pump casing is filled with the liquid being conveyed; after starting, the impeller is driven by the shaft to rotate at high speed, and the liquid between the blades must also rotate. Under the action of centrifugal force, the liquid is thrown from the center of the impeller to the outer edge and obtains energy, leaving the outer edge of the impeller at a high speed and entering the volute pump casing. In the volute, the liquid decelerates due to the gradual expansion of the flow channel, and then converts part of the kinetic energy into static pressure energy, and finally flows into the discharge pipe at a higher pressure and sends it to the required place. When the liquid flows from the center of the impeller to the outer edge, a certain vacuum is formed in the center of the impeller. Because the pressure above the liquid level of the storage tank is greater than the pressure at the inlet of the pump, the liquid is continuously pressed into the impeller. It can be seen that as long as the impeller continuously rotates, the liquid will be continuously sucked in and discharged.
There are mainly flow and head, in addition to shaft power, speed and necessary cavitation allowance. There is a certain interdependence relationship between the various performance parameters of the pump. The parameters can be measured and calculated by testing the pump and drawn into curves. These curves are called pump characteristic curves. Each pump has a specific characteristic curve, provided by the pump manufacturer. The recommended performance range is usually marked on the characteristic curve given by the factory, which is called the working range of the pump. The actual operating point of the pump is determined by the intersection of the curve of the pump and the characteristic curve of the pump device. Select and use the pump so that the working point of the pump falls within the working range to ensure economical and safe operation.
In addition, when the same pump delivers liquids with different viscosities, its characteristic curve will also change. Generally, the characteristic curve given by the pump manufacturer mostly refers to the characteristic curve when delivering clean cold water. For power pumps, as the viscosity of the liquid increases, the head and efficiency decrease, and the shaft power increases, so the industry sometimes heats the liquid with high viscosity to make the viscosity smaller, so as to improve the delivery efficiency.
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