Submersible pumps are a widely used water treatment tool. Unlike ordinary water pumps, submersible pumps are integrated with motors and pumps, and work underwater. Submersible pumps can be divided into well submersible pumps, working face submersible pumps, sewage pumps, sand-draining submersible pumps, mining vertical pumps, etc.
1. Working Principle and Performance Characteristics of Submersible Pumps A submersible pump is a general-purpose water-lifting machine that integrates a motor and pump, operating submerged in water. Its working principle involves the motor driving an impeller to rotate at high speed via the pump shaft. Under centrifugal force, the impeller performs work on the liquid, converting mechanical energy into liquid energy. The liquid (water) is ejected from the impeller and ejected outwards. The ejected liquid gradually slows down and its pressure gradually increases within the diffuser chamber of the pump casing before flowing out through the discharge pipe at the pump outlet. Submersible pumps are designed to prevent entanglement and clogging. Some models are also equipped with tearing mechanisms or cutting devices to tear and discharge long fibers, ribbons, and other materials in the water. The inherent weakness of submersible pumps is that they primarily pump soft media. The sand content in the water is limited to within 3%. High sand content can easily damage the seals, and if water enters the motor, the bearings and winding insulation will be damaged, leading to motor burnout.
2. Installation and Use of Deep Well Submersible Pumps: Submersible pumps generally have certain requirements regarding the upper and lower limits of power supply voltage and frequency. High-power submersible pumps must employ reduced-voltage starting or soft starting to minimize impact on the power grid, other electrical equipment, and the pump itself. The installation and use of submersible pumps should be based on the correct model selected according to the operating environment, and relevant precautions should be taken into account.
2.1 Submersible Pump Selection and Operating Environment The selection of a submersible pump should be based on the characteristics of the operating conditions. The main considerations during selection include flow rate, head, and installation method. Only when the selected head is close to the actual required head can the pump operate efficiently and energy-savingly. Improper selection will have a significant impact on pump operation.
Generally, the operating environment for deep well submersible pumps should meet the following requirements:
(1) A three-phase AC power supply with a power frequency of 50Hz and a rated voltage tolerance of ±5%;
(2) The solid content (by mass) is not greater than 0.01%;
(3) The water pump inlet must be below the water level by 1m, but the submersion depth shall not exceed 70m below the static water level, and the bottom of the pump shall be at least 1m away from the bottom of the well.
(4) The well must be vertical, the well wall must be smooth, and the well pipes must not be misaligned.
2.2 Installation of Deep Well Submersible Pumps The installation of deep well submersible pumps first requires checking whether the power supply line, grid voltage, frequency, and control switch meet the operating conditions; secondly, the pump must have good grounding measures; check whether the electrical control cabinet is installed correctly and properly grounded; and check that the lifting equipment is safe and reliable.
The water pump shall be installed in the following order:
(1) Remove the filter screen located in the middle of the water pump, unscrew the water filling plug and the water drain plug, fill the machine with clean neutral water, and then tighten the plugs. Check all connection parts of the motor for leaks, and seal any leaks.
(2) The insulation resistance of the motor shall not be less than 150 megohms when measured with a 500-volt megohmmeter, and the impeller shall rotate freely without jamming when pried with a screwdriver.
(3) First connect the short water pipe to the check valve body, install a clamp under the upper flange of the short water pipe, and then gently lift the water pump into the well so that the clamp sits on the well cover.
(4) Use another set of clamps to clamp the long water pipe and lift it to connect with the short water pipe. Then remove the clamps and lift the other long water pipe. Repeat this process until the installation is complete. Then cover the well cover and fix the clamps on the well cover. Then install the curved water pipe, valve, outlet pipe, and deep well submersible pump.
(5) During the installation process, a pipe gasket should be placed between the two flanges of the pipeline. When tightening the bolts, they should be tightened symmetrically. The cable should be tied in the groove on the water supply pipe flange. The cable should not be used as a sling, and the cable should not be damaged.
2.3 Precautions for using deep well submersible pumps The following precautions should be taken when installing and operating deep well submersible pumps:
(1) Care should be taken to protect the cable during hoisting to prevent damage. The lifting capacity of the hoisting device (such as tripod, hoist or electric hoist, etc.) should be greater than the weight of the submersible pump, and sufficient margin should be left. Before hoisting, manually rotate the impeller to check whether the rotation is flexible, whether the main contactor contacts are in good contact, whether there are any cracks or scratches on the cable and cable joints, whether the grounding of the motor casing is reliable, and use a multimeter to check the continuity of the three-phase circuit.
(2) When starting the submersible pump, it should rotate smoothly without vibration or abnormal noise. Observe whether there are obvious fluctuations in the motor operating current and line voltage before and after starting. Note that for submersible pumps that are installed for the first time or run after maintenance, they can only be started on the spot for observation. If any abnormality is found in the submersible pump, it should be stopped immediately. Check whether the rotation direction is correct and whether the installation is proper. The pump can only be run after the cause is found and the fault is eliminated.
3. Analysis of Common Failures of Deep Well Submersible Pumps The following six scenarios are common failures of deep well submersible pumps during use:
(1) Cannot pump water or seriously insufficient head: At this time, the water pump will turn on and off, and the submersible pump will make a lot of noise when it is running dry. This phenomenon is mostly due to the damage of the submersible pump bearing.
(2) Poor sealing: The shaft extension end of the water pump motor has a double-end mechanical seal component, which is made of highly wear-resistant material. After a period of use, the seal component may leak oil or water due to wear or natural aging. In addition, there are circular rubber sealing rings forming a sealing gasket on each mechanical mating surface to prevent water from seeping into the pump body. However, since the motor used in the submersible pump has a very high speed, the mechanical seal end face will inevitably suffer severe wear during long-term use.
(3) Damaged and leaking water outlet pipe: You can hear the normal rotation sound of the submersible pump wheel hanging in the deep well (the meter is also rotating normally), but no water can be pumped or only a small amount of water comes up. In most cases, the water outlet pipe is damaged.
(4) Pump jamming: The water pump does not turn, but a buzzing sound can be heard. This is mostly because the pump impeller is jammed by foreign objects. For example, due to geological reasons, the well water in our school has a high sand content, which can easily damage the filter screen.
(5) Leakage: Leakage is one of the common faults of water pumps. The fault phenomenon is that when the switch is closed, the leakage protection device in the power distribution room will automatically trip. This is because water enters the pump body of the submersible pump, causing leakage in the motor windings.
(6) Starter capacitor failure: When the power is connected, a buzzing sound can be heard, but the submersible pump motor does not turn; if the impeller is gently turned, the submersible pump can turn immediately, which indicates that the capacitor is damaged.
