The hazards and preventive measures of idling water pump
专栏:SERVICE SUPPORT
发布日期:2020-08-29
阅读量:46
作者:ESPA
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In the operation of the centrifugal pump, the idling of the water pump is not allowed.

In the operation of the centrifugal pump, the idling of the water pump is not allowed. The majority of users are "disguised" about the idling of the centrifugal pump. The reason for this is that they do not understand the cause of the idling phenomenon and do not know how to solve it. In fact, the centrifugal pump will not cause damage in a short time of idling (within 1 minute).


 The reasons for the idling of the centrifugal pump are: the inlet medium of the water pump is insufficient or the inlet pressure is not enough, or the water inlet pipe of the water pump is blocked, or the air in the water pump cavity is not exhausted.


 When the centrifugal pump is idling, the impeller does not touch or seldom touches the medium, it cannot work effectively, and the liquid cannot be sent out normally. These are all useless work. Because there is no effective work, the load on the motor is very small, and the current generated is also very small. There will be no impact on the motor. The idling of the water pump is indeed fatal to the pump. Idling water pumps are prone to cavitation, causing damage to the pump body and flow parts; idling water pumps with mechanical seals or packing seals will not be lubricated by liquid, resulting in dry grinding and rapid damage; idling water pump rotors The components and pump body will heat up, and there will be no liquid cooling. The narrow gaps (such as seal rings) are easily seized by the effect of heat expansion and contraction; the idling multi-stage centrifugal pump balance plate will not be lubricated by anyone, and the balance plate will quickly Burned to death, damaged.


    

For early warning and maintenance of the centrifugal pump idling, it is recommended to improve the design of the centrifugal pump to a higher level:

1. Treat each gap position of the centrifugal pump and expand it under allowable conditions to prevent seizure;

2. The shaft of the centrifugal pump is subjected to special process treatment, quenching and tempering, heat treatment, etc., to increase the hardness, and use low-flexibility materials to prevent large swings and seizures during idling;

3. Use mechanical seals and packing cavities that do not need to rely on liquid medium lubrication;

4. Use enclosed self-lubricating bearings without oiling.

    


Compared with other centrifugal pumps, the pump cavity of the horizontal self-priming centrifugal pump has an increased volume and has a place where water can be stored. Before the self-priming centrifugal pump works normally, the cavity must be filled with liquid. There is a period of self-priming before operation. During this period of time, air is continuously discharged to the outside of the pump. This period of time is partly idling.


Set up idling induction system. The water pump is monitored in real time through modern equipment. When the centrifugal pump is idling, it immediately alarms and automatically shuts down to protect the safety of the unit.




Precautions for use


1. Installation instructions


1. The weight of the pipeline should not be added to the water pump during installation, and there should be their own supporting body, so as not to cause deformation to affect the operating performance and life.


2. The pump and motor are of integral structure, no need to be aligned during installation, so installation is very convenient.


3. The anchor bolts must be tightened during installation to avoid the impact of vibration on pump performance during starting.


4. Before installing the pump, check carefully whether there are hard objects (such as rocks, iron particles, etc.) in the pump flow path that affect the operation of the pump, so as to avoid damage to the impeller and pump body during the operation of the pump.


5. For the convenience of maintenance and safe use, install a regulating valve on the inlet and outlet pipes of the pump and a pressure gauge near the outlet of the pump to ensure operation within the rated head and flow range to ensure the normal operation and growth of the pump. The service life of the pump.


6. When the pump is used for suction, it should be equipped with a bottom valve, and the inlet pipeline should not have too many bends, and there should be no water or air leakage.


7. The discharge pipeline such as a check valve should be installed outside the gate valve.


8. Turn the pump shaft after installation, the impeller should not have friction or jamming, otherwise the pump should be disassembled to check the cause.


9. Pump installation methods are divided into rigid connection and flexible connection installation.




2. Installation sequence


1. When the unit is transported to the site, the person with the base has already calibrated the pump and motor. When leveling the base, it is not necessary to remove the pump and motor, so the installation is very convenient;


2. Put the base on the foundation, and put a wedge-shaped iron near the anchor bolts, and pad the base by 20~40 mm high for filling with grout after leveling;


3. Check the levelness of the base with a spirit level, fill the base with cement slurry after leveling, and check the level again after the cement dries up;


4. When the power of the unit is high, the pump, motor and base may be packaged separately in order to facilitate transportation. At this time, the user needs to install and calibrate the pump unit by itself. The method is as follows: a. Clean the dirt on the plane of the motor feet, and place the pump and motor on the base; b. Adjust the pump shaft level, and fix the pump on the base with bolts after leveling to prevent it from moving; c. Lift the motor to make the pump The coupling and the motor coupling are matched, and the motor is put down to the corresponding position on the base; d. Adjust the gap between the two couplings to about 5mm, and correct whether the axis line of the motor shaft and the pump shaft coincide. The method is to flatten the ruler. Put on the coupling, the outer circle of the two couplings should be level with the flat ruler. If they do not coincide, the relative position of the motor or pump should be adjusted, or the pad should be adjusted with a thin iron sheet; e. In order to check the installation accuracy, Measure the gap between the two coupling planes with a feeler gauge at several different positions on the circumference of the coupling. The gap between the two coupling planes should not exceed 0.3mm, and the difference between the center lines of the two ends should not exceed 0.3mm. More than 0.1mm.


5. When the unit does not have a base, it needs to be installed directly on the foundation. The method is similar to that of 4., but more attention should be paid to calibration.




3. Start and stop


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(1) Preparation before starting


1. Rotate the fan blades of the motor by hand, the impeller should be free from scratching and rotate flexibly.


2. Open the inlet valve, open the exhaust valve to fill the entire pump cavity with liquid, and then close the exhaust valve.


3. Rotate the pump by hand to allow the lubricating fluid to enter the end face of the mechanical seal.


4. Jog the motor to determine whether the direction of rotation is correct.



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(2) Starting and running


1. Fully open the inlet valve and close the spit line valve.


2. Turn on the power supply, when the pump reaches the normal speed, gradually open the valve on the spit line and adjust to the required working condition.


3. Pay attention to the reading of the meter and check the leakage of the shaft seal. When the mechanical seal is normal, the leakage of the mechanical seal is less than 3 drops/min. Check that the temperature rise at the motor and bearing is ≤=70°C. If abnormal conditions are found, they should be dealt with in time.



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(Iii) stop


1. Gradually close the valve of the spitting line and cut off the power supply.


2. Close the inlet valve.


3. If the ambient temperature is lower than 0°C, the liquid in the pump should be drained to avoid freezing and cracking.


4. If the pump is not used for a long time, the pump should be disassembled and cleaned, packaged and stored.




4. Maintenance and maintenance of water pump


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(1) Maintenance and maintenance during operation


1. The water pipe must be highly sealed.


2. Prohibit long-term operation of the pump under cavitation conditions.


3. It is forbidden for the pump to run for a long time with excessive current when the pump is running.


4. When checking the pump operation regularly, the motor runs for a long time with overcurrent.


5. The pump should be supervised by a dedicated person during operation to avoid accidents.


6. The bearings should be refueled every 500 hours of pump operation. Motor power greater than 11KW is equipped with a refueling device, which can be directly injected with a high-pressure oil gun to ensure excellent bearing lubrication.


7. After the pump has been running for a long time, if the noise and vibration of the unit increase due to mechanical wear, the unit should be stopped for inspection. If necessary, the vulnerable parts and bearings can be replaced. The overhaul period of the unit is generally one year.



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(2) Mechanical seal maintenance and maintenance


1. The mechanical seal lubrication should be clean and free of solid particles.


2. The mechanical seal is strictly prohibited to work under dry grinding conditions.


3. Rotate the pump (motor) a few times before starting, so as not to break the seal ring due to sudden start.

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