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Water pump usage

2022-07-02

(1) Selection of water pump


According to the actual needs of drainage and irrigation, the type and number of pumps suitable for rated flow and rated head are selected to ensure that the drainage and irrigation tasks can be completed efficiently and economically. The general method of selecting drainage and irrigation pump is as follows:
Determine the design flow of the pump.
Determine the design head of the pump.
③ Determine the caliber of the water pump.
④ Determine the type of water pump.
⑤ Use the "pump performance table" and "pump performance comprehensive spectrum chart" to select the pump model.
⑥ Determine the number of pumps.
(2) The choice of power machine

Motor and diesel engines are mainly used in two categories.


The main characteristics of the motor are: at the same power, the motor is smaller than the diesel engine, light weight, stable operation, small vibration, simple structure, pump house civil investment is less, and simple operation, convenient maintenance, reliable work, low operation cost, easy to realize automatic control. However, including transmission and transformation equipment, its equipment investment is high, there must be power supply, and it is greatly affected by the grid voltage.

The main characteristics of diesel engine are: it is not limited by power supply, easy to change speed operation, more mobile, flexible. But its structure is more complex, easy to produce failure, operation, maintenance is more troublesome, higher requirements, costs and running costs are also higher than the motor.

It can be seen that the two have their own advantages and disadvantages, which kind of power machine to use, should consider the conditions and characteristics of different areas, according to local conditions to choose the right type.

(3) Check the water pump before starting


In order to ensure the safe operation of the pump, the pump should do a comprehensive and careful inspection of the unit before starting, especially the new installation or pump that has not been used for a long time. Before starting, more attention should be paid to the inspection work, so as to find problems and deal with them in time. The main check contents are as follows.

① Check whether the anchor screws and connecting bolts of the water pump and power machine are loose or fall off, if so, tighten or fill.
② Turn the coupling or pulley, check whether the impeller rotation is flexible, there is no normal sound in the pump, judge whether the steering is correct. For a newly installed pump, it is essential to check its steering at the first start.

For centrifugal pumps directly connected to the motor, check whether the steering of the pump is consistent with the steering arrow on the pump. If not, just replace any two wires of the motor. If there is no steering arrow on the pump, the pump shell is volute type, can be judged according to the shape of the pump, that is, the direction of rotation of the pump and the volute from small to large direction; For the pump is not volute type, it can only be judged from the shape of the blade, that is, the pump should rotate along the bending direction of the blade.

For the centrifugal pump driven by diesel engine, it can be judged directly according to the mutual position between the diesel engine and the pump and the way of rotation used. Because the steering of the diesel engine is fixed counterclockwise from the power output. If the steering is not correct, the transmission mode or installation position of the diesel engine must be changed.

Check whether the tightness of the packing gland is appropriate.

(4) Check the lubrication of bearings, whether the lubricating oil is sufficient and clean, and whether the amount of oil meets the requirements.
⑤ Remove debris (blockage and floating objects) at the inlet of the centrifugal pump to prevent debris from being sucked into the pump and damaging the impeller after the boot.
⑥ Check the protection and safety work, the tools and other objects on the unit should be removed before starting, so as not to be shaken down or cause unnecessary losses after starting.
⑦ Add water to the centrifugal pump, until the pump body on the vent plug emit water.
⑧ centrifugal pump before starting, should first close the gate valve on the outlet pipe. Because the flow is zero when the centrifugal pump shaft power minimum, this will make the unit load and bear resistance moment greatly reduced, easy to start smoothly. Otherwise, it may make the unit difficult to start or even cause an accident.

(4) Start of water pump

When the water pump and inlet pipe are fully filled with water, close the valve of the air vent or water filling device, and then start the power machine (motor or diesel engine). The outlet pipe of the centrifugal pump is generally equipped with a closed valve. After the unit starts up to the rated speed, the gate valve should be opened immediately for water, otherwise the water flow in the pump will continue to circulate in the pump shell and heat up, causing damage to some parts of the pump.

If the outlet of the centrifugal pump is equipped with pressure gauge, it should be closed before starting, and then connected for measurement after the water is normal at the end of starting, so as not to damage the pressure gauge because the pressure in the pump exceeds the range of the meter when the gate valve is closed.

(5) Monitoring of water pump operation
① Pay attention to the abnormal sound and vibration of the unit. Centrifugal pump in normal operation, the unit should be smooth, sound should be normal continuous. If the unit vibration is too large or there is noise, it means that the unit has a fault, then it should stop to check, eliminate hidden dangers.
② Pay attention to the inspection of bearing temperature and oil quantity. Centrifugal pump operation should often use thermometer or semiconductor point thermometer to measure the temperature of bearings, and check whether lubricating oil is enough. The maximum allowable temperature of general sliding bearings can reach 85℃, and the maximum allowable temperature of rolling bearings can reach 90℃. In actual work, if there is no thermometer or semiconductor point thermometer, you can also touch the bearing seat by hand. If you feel hot, the temperature is too high and you must stop the machine for inspection. Generally, too much or too little refueling and oil is too thick or mixed with other impurities can make bearings hot. The lubricating oil in the bearing should be moderate. For bearings lubricated with oil rings, the oil ring is generally immersed about 15mm. Ball bearings are lubricated with butter, which is added to about 1/3 of the capacity of the bearing box. The oil change time is usually 500h once, and the oil change of the new water pump is appropriate in advance. The number of refueling quantity and the time of oil change can be carried out according to the provisions of the manufacturer.

Pay attention to check the temperature of the power machine. The temperature of the power machine should be checked frequently during its operation. If the temperature is too high, stop the machine immediately.

④ Pay attention to whether the pump packing seal is normal. Packing can not be pressed too tight or too loose, there must be water dripping in succession during operation, according to experience, water dripping from packing culver to about 60 drops per minute is appropriate. In addition, we should pay attention to whether the water inlet joint is tight and whether the water pump inlet is leaky.
⑤ Pay attention to the change of instrument pointer. The instrument can reflect the operation of the pump water device, often the pump failure, the instrument has warning, so we should often pay attention to observe the situation of various instruments. General rural power drainage and irrigation system are equipped with ammeter, voltmeter and power meter, some centrifugal pump, mixed-flow pump also equipped with vacuum meter and pressure gauge. If the operation is normal, the position of the meter pointer is always stable in one position. If abnormal conditions occur in operation, the instrument will change and beat violently, and the reason should be found out immediately. For example, a rise in the vacuum gauge reading may be due to a blocked intake pipe or a drop in the water level; The pressure gauge reading rises, possibly because the outlet pipe is blocked; Pressure gauge reading drops, may be due to belt slip and pump speed reduction, or because of air leakage in the inlet pipe and inhaled air, or because the impeller is blocked. For motors, when operating at the required line voltage, an increase or decrease in ammeter readings means an increase or decrease in pump shaft power. Therefore, attention should be paid to whether the ammeter reading exceeds the rated value, generally not allowed to long-term overload motor operation.
⑥ Pay attention to the change of water level into the pool. If the water level into the pool is lower than the specified minimum water level, the pump should be stopped to avoid cavitation and damage the pump impeller. If the water pump inlet or into the pool before there is debris blocked, should be removed immediately.