Submersible Pump Flow, Head and Usage Skills

About the flow rate and head of submersible pump

Generally, the water pump will indicate voltage, flow rate, and head. Usually, the flow rate refers to the amount of water delivered by a water pump per unit time, in liters per hour. Head refers to the height of water lift, in meters. The power is the rated power, watts. In theory, the basic physical quantities of one-dimensional fluid flow include flow rate, density, and velocity. The flow rate is the throughput per unit time at a certain position x, i.e. the flux q (x, t). Fluid density is the number of fluids per unit length at a certain time t, p (x, t). The fluid velocity is the amount of fluid movement at a certain position x at a certain time t, u (x, t). Satisfy the basic relationship: q (x, t)=p (x, t) u (x, t). Only 2 of these are independent variables.

Let's take another example of a water pump, where the flow rate of the pump=cross-sectional area × Flow rate, water pump head=suction head+pressurized water head. It is generally believed that the actual head refers to the elevation of the water surface, and the suction pressure difference and lift pressure difference correspond to the fluid density.

At rated power, the design of the pump comprehensively considers the diameter of the inlet and outlet water pipes, blade size, blade speed, operating temperature, attenuation, and service life. Regardless of factors such as pump power loss and lifespan, the flow rate is determined by the flow rate at the same true rated power and cross-sectional area of the pipe. The larger the blade, the faster the speed and the greater the flow rate. The larger the blade, the faster the rotational speed, the higher the operating temperature, the faster the attenuation, and the shorter the service life. At a constant flow rate, the larger the flow rate, the greater the pressure difference, and the higher the required power. Therefore, general pumps have high power, flow rate, and head. For pumps of the same power, ensure the head first, and then check the flow rate. At the same time, the diameter of the inlet and outlet pipes in the fish tank and the design of the water circulation path should also be reasonable, fully considering the pressure difference, in order to ensure a reasonable flow rate.

Precautions for use of Submersible pump:

1、 Q: Are you sure the direction of rotation of the motor is correct?

A: The direction of rotation of the motor should be clear. Now many types of Submersible pump can discharge water in both forward and reverse rotation, but the water output is small and the current is large in reverse rotation, and the motor winding will be damaged if the reverse rotation time is long.

2、 Q: Have you ever started the Submersible pump when the power supply voltage is abnormal?

A: Due to the relatively long low-voltage power supply lines, it is common for the terminal voltage of the lines to be too low. When the phase voltage is lower than 198 V and the line voltage is lower than 342 V, the speed of the Submersible pump motor will drop. When the rated speed is less than 70%, the startup Centrifugal switch will close, causing the startup winding to be energized for a long time, causing heating and even burning of the windings and capacitors. On the contrary, high voltage causes the motor to overheat and burn out the winding. Therefore, during the operation of Submersible pump, the operator must observe the power supply voltage at any time. If it is less than 10% lower than the rated voltage and more than 10% higher than the rated voltage, the motor should be stopped to find out the cause and eliminate the fault.

3、 Q: Do you understand the insulation resistance requirements for cable installation and Submersible pump?

A: When installing Submersible pump, the cable should be overhead, and the power cable should not be too long. When the Submersible pump is launched or lifted, do not force the cable to avoid breaking the power line. When Submersible pump works, do not sink into the mud, or it will lead to poor heat dissipation of the motor and burn out the motor winding. During installation, the insulation resistance of the motor should not be less than 0.5 megaohms.

4、 Q: Do you know the importance of Residual-current device installation?

A: Residual-current device is also called life saver. Its function can be understood from the three words "life saver". Because Submersible pump works underwater, it is easy to cause electric energy loss and even electric shock accidents due to leakage. If a Residual-current device is installed, as long as the leakage value of the Submersible pump exceeds the action current value of the Residual-current device (generally not more than 30 mA), the Residual-current device will cut off the power supply of the Submersible pump to ensure safety and avoid leakage and waste of power.

Q: Have you ever switched on or off the machine frequently?

A: Do not switch on and off the Submersible pump frequently. This is because the electric pump will produce backflow when it is stopped. If it is started immediately, the motor will start with load, resulting in excessive starting current and burning of windings. Due to the high current during startup, frequent startup will also burn out the motor winding of Submersible pump.

Q: VI. Have you overloaded your Submersible pump for a long time?

A: To avoid long-term overload operation of submersible electric pumps, do not pump water with high sediment content and always observe whether the current value is within the specified value on the nameplate. If excessive current is found, it should be stopped for inspection. In addition, the dehydration operation time of the electric pump should not be too long to avoid overheating and burning of the motor.

Tips：

7、 When the water pump malfunctions, do not disassemble it yourself. Because when dismantling by oneself, one is blindly dismantling without knowing where the fault is; Secondly, the lack of specialized tools often damages the originally intact components. The best way is to go to experienced and large-scale repair points for repairs, and promptly replace "over age" parts and certain vulnerable parts. Under normal circumstances, the water pump should be repaired every six months to prevent work with "illness".

8、 Before starting the Submersible pump, make some necessary checks. Whether the rotation of the pump shaft is normal and whether it is stuck; Whether the position of the impeller is normal; Check if there are any cracks, scratches, or breaks in the cables and cable plugs. During operation, attention should be paid to observing the changes in voltage, generally controlled within the range of ± 5% of the rated voltage. In addition, the position of the water pump in the water is very important, and it should be selected as much as possible in a place with sufficient water volume, no sludge, and good water quality. It should be vertically suspended in the water and not allowed to be horizontally placed to avoid getting stuck in the mud or being blocked by suspended solids at the pump inlet, which can lead to a sharp decrease in water output or even inability to pump water.

9、 For self priming pumps, they should be placed in a well ventilated area as much as possible to facilitate rapid heat dissipation and reduce motor temperature. Otherwise, prolonged operation can easily burn out the motor. If a farmer uses a self priming pump and fails to remove the plastic film covering the motor, the motor overheats and burns out the coil. In addition, before starting, it is necessary to check the water storage in the pump body, otherwise it not only affects the self suction performance, but also easily burns out the shaft seal components. Under normal circumstances, the water pump should be discharged within 3-5 minutes after starting, otherwise it should be stopped immediately for inspection.

10、 If stored during the non use period, the water pump should be promptly lifted away from the water source and the accumulated water inside the pump should be drained, especially in cold winter. Then place it in a dry place. Users with conditions can also apply butter to the key parts of the water pump and add lubricating oil to the bearings to prevent rusting of the components. In addition, the non service life of the water pump is not as long as possible. If left unused for a long time, it is not only prone to rusting of components, but also reduces the service life of the water pump.

Pay attention to the daily maintenance of submersible sewage pump: always check the motor. If cracks are found on the lower cover, rubber sealing ring is damaged or invalid, it should be replaced or repaired in time to avoid water infiltration into the Submersible pump. Pay attention to the use of Submersible pump protector and pay attention to some daily protection, which can better extend the service life of Submersible pump.