A pump is a mechanical device that conveys or pressurizes a fluid. It transfers the original mechanical energy or other external energy to the liquid to increase the liquid energy, thereby completing the liquid transportation. The pump is mainly used to transport liquids such as water, oil, acid-base liquid, emulsion, suspension emulsion and liquid metal, as well as liquid-gas mixture and liquid containing suspended solids. The pump can only transport the flow with the fluid as the medium, but cannot transport the solid.
Application of the Pump
In the chemical and petroleum industries, raw materials, semi-finished products and finished products are mostly liquids. Making raw materials into semi-finished products and finished products requires complex technological processes, and pumps play a role in conveying and providing pressure in these processes. In addition, pumps can also be used in many installations to regulate temperature.
In agricultural production, pumps are the main irrigation machinery. Agricultural production requires a large number of pumps. Generally speaking, agricultural pumps account for more than half of the total pump output.
Pumps are also the most used equipment in the mining and metallurgical industries. The mine needs to be drained by pumps, and in the process of beneficiation, smelting and rolling, pumps are needed to supply water.
In the power sector, nuclear power plants require multi-stage pumps such as secondary pumps and tertiary pumps. Thermal power plants need a large number of boiler feed pumps, condensate pumps, oil and gas mixing pumps, circulating pumps and ash pumps.
In the defense industry, the adjustment of aircraft flaps, tail rudders and landing gear, the rotation of warships and tank turrets, and the ups and downs of submarines all require pumps. For pumps that deliver high pressure and radioactive liquids, it must be free of any leakage.
In short, whether it is in the fields of national defense such as aircraft, rockets, tanks, and submarines, or in industrial fields such as drilling, mining, trains, and ships, or in daily production and life, pumps are needed everywhere, and pumps are running everywhere. It is in this way that the pump belongs to the general machinery and is a kind of main product in the machinery industry.
According to different classification standards, pumps can be divided into many categories. Pumps can usually be divided into three categories: positive displacement pumps, dynamic pumps and other types of pumps according to their working principles. According to the driving method, it can be divided into electric pump and hydraulic pump; according to the structure, it can be divided into single-stage pump and multi-stage pump; according to the purpose, it can be divided into boiler feed pump and metering pump; Water pump, condensate pump, ash pump, circulating water pump, etc. This article focuses on centrifugal impeller pumps.
Centrifugal pump refers to a pump that transports liquid by the centrifugal force generated by the rotation of the impeller. Centrifugal pumps work by rotating the impeller to cause centrifugal motion of water. Before starting the pump, the pump casing and suction pipe must be filled with fluid, and then the motor is started, so that the pump shaft drives the impeller and the fluid to rotate at a high speed into the pipeline of the pump.
The impeller pump relies on the impeller to drive the liquid to rotate at a high speed and transfer the mechanical energy to the conveyed liquid. Different impeller types can be divided into:
1) Centrifugal pump
2) Axial pump
3) Mixed-flow pump
4) Peripheral pump
The impeller is installed in the pump casing and fastened to the pump shaft, which is directly driven by the motor. There is a liquid suction pipe in the center of the pump casing. The 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 to be conveyed; after starting, the impeller is driven by the shaft to rotate at a high speed, and the liquid between the blades must also rotate with it. 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 is decelerated due to the gradual expansion of the flow channel, and part of the kinetic energy is converted into static pressure energy, and finally flows into the discharge pipeline at a higher pressure and sent 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. Since 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 rotates continuously, the liquid will be continuously sucked and discharged.
The basic structure of centrifugal impeller pump is composed of eight parts, namely: impeller, pump body, pump cover, water retaining ring, pump shaft, bearing, sealing ring, stuffing box, and axial force balance device.
1. The impeller is the core part of the centrifugal pump. The rotational speed of the impeller is very high, and the output force is also very large.
2. The pump body is also called the pump casing, which is the main body of the pump. It plays the role of supporting and fixing, and is connected with the bracket on which the bearing is installed.
3. The function of the pump shaft is to connect the motor with the coupling and transmit the torque of the motor to the impeller, so it is the main component for transmitting mechanical energy.
4. The sealing ring is also called the leakage reducing ring.
5. Axial force balance device. During the operation of the centrifugal pump, since the liquid enters the impeller under low pressure and flows out under high pressure, the pressures on both sides of the impeller are unequal, and an axial thrust toward the inlet direction is generated, which will cause the rotor to move axially. , causing wear and vibration. The function of the axial thrust bearing is to balance the axial force.
There are many kinds of raw materials for pumps, the common ones are stainless steel, duplex stainless steel, nickel-based alloy, brass, ductile iron, gray iron, etc. Among them, CF8M stainless steel or AISI 316L stainless steel have excellent performance in corrosion resistance and high temperature resistance, which makes them widely used in petroleum, pharmaceutical, chemical and other fields.
RMC Casting Foundry can produce pump and valve parts such as pump casings, pump covers, bearing housings, impellers, etc. of the above-mentioned materials according to the needs of customers. We use precision casting (lost wax silica sol casting), shell casting and sand casting to make blanks, and then heat treatment, CNC machining, etc. to make customized pump and valve accessories. At the same time, we can also perform dynamic balance and static balance on the impeller, and the grade can reach DIN 1940 G2.5. For some pump casings, valve bodies, pump covers and other accessories, we can also do sealing tests.
Post time: Jun-25-2022