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# What is an axial flow pump

## What is an axial flow pump?

Axial flow pumps rely on the force generated by the blades of the rotating impeller on the liquid to transport the liquid along the axis. There are vertical, horizontal, inclined and tubular pumps.

## Working principle of axial flow pump

The wing is suspended in the fluid. When the fluid flows through at a certain speed, the negative pressure occurs on the wing surface and the positive pressure occurs on the wing back. The magnitude of the positive and negative pressure is related to the wing shape, angle of attack (inclination between the wing back and the liquid flow direction) and the fluid velocity.
If the fluid does not move and the wing moves in the fluid at the same speed, the wing back and wing surface are subject to the same positive pressure and negative pressure as before, that is, the wing surface (above the wing) is negative pressure and the wing back is positive pressure. Under this pressure, the wing will gain lift.
If the wing shaped blades are fixed on the rotating shaft to form a propeller and make it unable to move along the axial direction, when the rotating shaft rotates at high speed, the wing surface (lower side of the propeller) has the effect of suction due to negative pressure, and the wing back has the effect of discharge due to positive pressure. Such suction and discharge cause the flow of liquid (or gas). This is the working principle of axial flow pump.

## Characteristics of axial flow pump

The impeller of axial flow pump is equipped with 2 ~ 7 blades, which rotate in the circular tubular pump shell. A fixed guide vane is installed on the pump shell at the upper part of the impeller to eliminate the rotating motion of the liquid, turn it into axial motion, and convert the kinetic energy of the rotating motion into pressure energy. Axial flow pumps are usually single-stage, and a few are made into two-stage. The flow range is large, 1.8 ~ 3.6 million m3/h; The lift is generally below 20m. Axial flow pumps are generally vertical, the impeller is submerged under the water, and there are also horizontal or inclined axial flow pumps. When the installation position of the impeller of the small axial flow pump is higher than the water surface, it is necessary to start with the exhaust and water diversion of the vacuum pump. The blades of axial flow pump are divided into fixed and adjustable structures. The operating conditions (mainly flow) of large axial flow pump often need to change greatly in operation. Adjusting the installation angle of blade can keep the pump running in high efficiency area under different working conditions. The blade installation angle of small pumps is generally fixed. Axial flow pump is one of the highest specific revolutions among power pumps, with a specific revolution of 500 ~ 1600. The flow head and flow shaft power characteristic curves of the pump are steep in the small flow area, so it should be avoided to operate in this unstable small flow area. The axial flow pump has the maximum axial power at zero flow, so the valve on the discharge pipeline must be opened before starting the pump to reduce the starting power. Axial flow pump is mainly suitable for occasions with low head and large flow, such as irrigation, waterlogging drainage, dock drainage, water level regulation of canal ship lock, or as a large circulating water pump in power plant. The axial flow pump with high lift (made into two stages if necessary) can be used for water jet propulsion of shallow water ships.

• 1. It can transport clean water and mild sewage. The medium temperature can reach 40 ℃ and the pH value is 4-10;
• 2. Excellent water conservancy model, well made to ensure the performance requirements of users;
• 3. Double mechanical seal can reliably prevent water leakage. Due to large axial force, large pump adopts special thrust bearing, with reasonable structural design, sufficient lubrication, good heat dissipation and long service life of bearing;
• 4. The motor adopts class F insulation, high temperature resistance, and is equipped with temperature protection, monitoring, leakage and other alarm devices;
• 5. It can be equipped with an electric control cabinet in the control mode of one control two to one control four, which can realize the automatic shutdown of the pump and the automatic start of the standby pump in case of failure; Retain fault signal (self diagnosis) and other functions to ensure high reliability of operation;
• 6. The pump is submerged into the water, with good cooling conditions, good operation balance, stability, low vibration and low noise;
• 7. Users can design underground pump stations according to their needs to improve the environmental style;
• 8. The scale of the pump station is small, the civil engineering and building structure are simple, and the investment is greatly reduced, which can save 30% – 40% of the project cost of the pump station;
• 9. Machine pump integration saves time, labor and cost in installation and maintenance;
• 10. The products are in series, the high-efficiency area of the water pump is wide, in line with the user’s working conditions, efficient and energy-saving, and the operation cost is low;
• 11. Convenient management and low operation cost;
• 12. It is easy to realize remote control and unattended.

## Performance advantages of axial flow pump

Among them, the vertical axial flow pump mainly leads the fluid to the outlet by the lift of the blade. It is axial in and axial out, and has the advantages of large flow.

• 1. Submersible axial flow pump: the motor driving the water pump is a dry fully enclosed submersible three-phase asynchronous motor, which can be immersed in water for a long time. It has a series of incomparable advantages of traditional units.
• 2. Since the motor and water pump are integrated, there is no need to carry out labor-consuming and time-consuming assembly process of motor, transmission mechanism and water pump axis alignment on the installation site, and the on-site installation is convenient and fast.
• 3. Due to submerged operation, it can greatly simplify the civil engineering and building structure engineering of the pump station, reduce the installation area and save 30 ~ 40% of the project cost.
• 4. With low noise and no high temperature in the pump station, the operating environment can be improved. The whole underground pump station can be built as required to maintain the environmental style of the ground.
• 5. The submersible motor adopts double or triple mechanical seal, class F (temperature resistance 155 ℃) insulation, and the protection grade is IP68 (IEC). In terms of hydraulic model, we have absorbed the advantages of similar products at home and abroad, adopted the most advanced variable circulation and variable shaft surface velocity lift method in the world, and independently designed a new hydraulic power generation model with high efficiency, energy saving and good cavitation resistance. It has high reliability and interchangeability with traditional water pumps, which is convenient for users to select and use.
• 6. Easy to operate, easy to realize remote control and automatic control.

The use of this type of submersible electric pump is the most thorough way to solve the problem of flood control by building pump stations along rivers and lakes where the water level fluctuates greatly, and the long shaft and intermediate bearing between machines and pumps are omitted, so that the operation of the unit is more reliable.

## Precautions for axial flow pump

• 1. During trial operation, check the connecting parts to ensure that there is no looseness at each connecting part.
• 2. Electrical appliances and instruments work normally; The pipelines of oil, gas and water systems shall be free of leakage; The pressure and hydraulic pressure are normal.
• 3. Frequently check whether there are floating objects near the water inlet to prevent blockage of the water inlet.
• 4. The temperature of rolling bearing of axial flow pump shall not be greater than 75 ℃.
• 5. Pay attention to the sound and vibration of the water pump at any time, and shut down for inspection immediately in case of any abnormality.
• 6. The oil temperature in the gearbox shall be normal.

Source: Network Arrangement –  – Yaang Pipe Industry (www.epowermetals.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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