1、 Overview of Vertical Axial Flow Pump

ZLBType pump is a single-stage vertical axial flow pump, suitable for pumping clean water, sewage, rainwater, and slightly corrosive liquids. The temperature of the conveyed liquid is not higher than50℃. This type of pump is a high flow, low head pump that can be used for agricultural irrigation, water conservancy engineering, urban water supply, drainage, and sewage treatment. It can also be used for transporting circulating water in power plants, salt factories, and breeding farms, and for raising and lowering water levels in shipyards. It can also be used in industries such as metallurgy and chemical engineering, and is widely used.

IIZLBMeaning of Axial Flow Pump Model

For example:28 Z L B—70

28--The diameter of the pump outlet is28Inches;

Z--Axial flow pump;L--Vertical structure;B--Semi adjustable blades;70--Specific speed is10Except for the transformed integer obtained

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3、 Working principle and structure of vertical axial flow pump

1Working principle of vertical axial flow pump

Vertical axial flow pump is based on the lift theory of wings in aerodynamics. When the fluid bypasses the airfoil, it separates into two streams at the beginning and end of the airfoil, passing through the upper and lower surfaces of the airfoil respectively, and then converging at the tail end of the airfoil. Due to the longer distance along the lower surface of the airfoil compared to the upper surface, the flow velocity of the fluid along the lower surface of the airfoil is higher than that along the upper surface of the airfoil. Correspondingly, the pressure on the lower surface of the airfoil will be lower than that on the upper surface, and the fluid will have a downward force on the airfoil. Similarly, the airfoil will also produce a reaction force on the fluid, which is equal to this force and opposite in direction, acting on the fluid. Under this force, water is pressurized to a certain height.

2Construction of Vertical Axial Flow Pump

The structure of a vertical axial flow pump mainly includes: horn tube, impeller, guide vane body, outlet bend tube, pump shaft, bearings, packing box, transmission shaft, etc. The description is as follows:

1)Horn tube: The horn tube is a suction chamber for small and medium-sized vertical axial flow pumps, cast with cast iron. Its function is to evenly guide water towards the impeller with minimal loss.

2)Impeller: The impeller is the main working component of an axial flow pump, consisting of blades, hub, guide cone, etc.

3)Guide vane body: The guide vane body is located above the impeller, and its main function is to eliminate the rotational motion of water flow and reduce head loss. At the same time, some of the kinetic energy of the water flow can be converted into pressure energy.

4)Pump shaft and bearings: The pump shaft is made of high-quality carbon steel and is mainly used to transmit torque to the impeller.

5)Drive shaft: The connecting shaft between the vertical motor and the water pump is the drive shaft, which mainly transmits the power of the motor to the water pump.

6)Packing box: A packing sealing device is installed at the outlet bend of the pump shaft.

4Performance characteristics of vertical axial flow pump

Compared with centrifugal pumps, vertical axial flow pumps have the following advantages:

1)The head increases sharply with the decrease of flow rate,Q-HThe main reason for the increase in the curve is that when the flow rate is low, backflow occurs at the inlet and outlet of the impeller blades, and the water flow repeatedly obtains energy, similar to a multi-stage pressurization state. Therefore, the head increases sharply, resulting in an increase in shaft power.

2) Q-NThe curve is a decreasing curve, therefore, when starting the axial flow pump, the motor should be started with the gate valve fully open.

3) Q-The η curve shows a camel hump shape. The range of high-efficiency work is very small, and the efficiency quickly decreases not far from the design operating point when the flow deviates. According to the characteristics of axial flow pumps, using gate valves to regulate flow is disadvantageous, and generally only the method of changing the blade device angle can be used to change its performance curve.

4)In water pump samples, the cavitation allowance of axial flow pumps is generally required to be relatively large. Therefore, the maximum allowable suction vacuum height is relatively small. It is necessary to consider the inlet conditions of the axial flow pump, the deviation degree between the actual operating point and the design operating point of the pump during operation, and so on.

5Maintenance process of vertical axial flow pump

Vertical axial flow pumps may encounter various problems during operation. If not resolved in a timely manner, it may cause damage to parts and affect normal pumping. To troubleshoot a water pump, the first step is to correctly identify the cause of the problem and then determine the corresponding troubleshooting method.

The common causes and troubleshooting methods of vertical axial flow pumps are as follows:

1. The reasons and treatment methods for no or low water output after startup are as follows:

1)The submergence depth of the impeller is insufficient. The solution is to adjust the submergence depth of the impeller.

2)The impeller is not turning correctly. The solution is to adjust the motor direction.

3)Damaged blades or broken blade locating pins. The solution is to replace the blades or locating pins.

4)The pump inlet or impeller is blocked by debris. The solution is to remove debris.

5)The pump shaft has come loose. The solution is to reassemble or replace the pump shaft.

2The reasons and solutions for high vibration or noise are as follows:

1)The corner bolt is loose. The solution is to tighten the corner bolts and firmly pad the base.

2)The pump shaft is bent or the coupling is not concentric. The treatment method is to correct or adjust the concentricity.

3)The pump shaft and water guide bearing are worn. The solution is to replace the water guide bearing or pump shaft

4)Leaves are missing or tangled with debris. The solution is to replace the blades and remove debris from the blades.

5)Generate cavitation. The treatment method is to improve the water absorption conditions and prevent cavitation.

6)The coupling is broken or detached. The solution is to replace the coupling.

7)The bearings inside the bearing box are damaged. The solution is to replace the bearings.

3. The reasons and solutions for sudden increase or decrease in current are as follows

1)Blades with corners or tangled debris. The solution is to replace the blades and remove debris.

2)Corrosion of the water guide bearing leads to shaft sticking. The solution is to replace the water guide bearing.

3)The pump shaft or coupling is detached or broken. The solution is to replace the pump shaft or coupling.

4)The impeller casing has detached. The solution is to replace the impeller casing.

5)The opening degree of the water outlet door is too small. The solution is to check the door pin shaft and add lubricating grease.

6)The impeller has detached. The solution is to replace the impeller.

4The temperature of the bearing box is too high

1)The lubricating oil is severely insufficient. The solution is to add lubricating oil.

2)Severe wear and tear has occurred. The solution is to identify the cause and replace the components

VIZLBInstallation and use of axial flow pump

(one)Installation:

1Preparation before installation:

(1)Check the water pump body, transmission device, and motor for any damage. If the pump shaft and transmission shaft are bent, they must be straightened.

(2)Tools and lifting machinery should be complete.

(3)Refer to the installation dimension diagram and check the pump foundation and inlet pipeline to ensure they meet the installation requirements.

(4)Due to the significant impact of the structure of the inlet pool and the arrangement of several pumps in the same inlet pool on the performance of the pumps, the following points must be noted:

① The impeller should have sufficient submergence depth.

② Maintain the required distance between the pump horn and the bottom of the pool.

③ The water flow enters the pump uniformly without any vortex.

④ Several pumps operating in the same pool should not cause disturbance.

⑤ A trash rack must be installed before entering the water tank, and the flow velocity passing through the trash rack should not exceed0．3Meter per second is appropriate.

2. Installation

(1)Adjust the blade installation angle on the impeller components according to the usage situation, so that the installation angles of each blade are consistent and there should be no looseness.

(2)Use a spirit level to calibrate the levelness of the pump base, pour cement slurry, and check the levelness after the cement solidifies.

(3)The pump shaft and transmission shaft must be installed on the same vertical line, with a tolerance of less than0．04Millimeters per meter. Make the gap between the outer circle of the blade and the outer shell of the impeller chamber uniform along the circumference.

(4)After installation, check whether the nuts of each coupling and foundation screw are tightened.

3Connection between pump and motor:

(1)The elevation center position of the motor and transmission device should be determined according to the elevation center position of the installed pump.

(2)The rotation direction of the motor should be consistent with the rotation direction of the pump.

(3)After the flange surface of the rigid coupling is closed, the bolts should be tightened evenly to prevent uneven tightening from causing tilting. The flange joint surface should be checked using a transparent method or a feeler gauge, and there should be no gaps.

4Installation of water outlet pipe

(1)The outlet pipeline should be equipped with additional brackets and should not be supported by the pump body.

(2)A diffusion pipe should be installed between the pump outlet bend and the outlet valve. Its length shall not be less than five times the difference in diameter between the size and mouth of the diffusion tube.

(3)The outlet valve should be equipped with a counterweight to balance the weight of the valve.

(two)Start and Stop

(1)Before starting the pump, clean water should be injected into the upper connecting pipe of the packing box as required.

(2)After the trial operation of the pump, check that all connection parts are not loose.

(3)If abnormal sounds and vibrations occur during operation, the machine should be stopped immediately for inspection and elimination.

(4)After shutting down during the freezing season, the impeller should not be immersed in water to avoid freezing and damaging the parts.

(three)work:

(1)During operation, it is advisable to ensure that there are water droplets falling out of the packing during compression.

(2)Note that rubber bearings must not come into contact with oil.

(3)Pay attention to the temperature rise of the bearings in the transmission device and regularly replace the lubricating oil or grease in the bearings.

7ZLBAxial flow pump parameters