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RumA pumps are important equipment for lifting water from deep wells. During operation, the entire unit is submerged in water to extract groundwater to the surface. They are used for domestic water supply, mine emergency rescue, industrial cooling, farmland irrigation, seawater lifting, ship ballast adjustment, and fountain landscapes. Hot water submersible pumps are used for hot spring bathing and are also suitable for extracting groundwater from deep wells, as well as for water lifting projects in rivers, reservoirs, and canals. They are mainly used for farmland irrigation and water supply for humans and livestock in high mountain areas, and can also be used for central air conditioning cooling, heat pump units, chiller pump units, and drainage in cities, factories, railways, mines, and construction sites. The general flow rate can reach 5~650m³/h, and the head can reach 10-550 meters.

RumA pump working principle

There are several types of submersible pumps; the windings in the motor can be oil-immersed, water-immersed, or dry-type. You must read the manual before use to avoid errors. If the pump has not been used for a long time, the impeller must be rotated manually before operation; otherwise, it may seize due to prolonged inactivity and burn out the windings. Before starting the pump, the suction pipe and the pump interior must be filled with liquid. After starting, the impeller rotates at high speed, causing the liquid inside to rotate with the blades. Under the action of centrifugal force, the liquid flies away from the impeller and is ejected outward. The velocity of the ejected liquid gradually decreases in the diffusion chamber of the pump casing, while the pressure gradually increases, and then it flows out from the pump outlet and discharge pipe. At this time, a vacuum low-pressure zone without air or liquid is formed at the center of the blades because the liquid is thrown to the periphery. Under the action of atmospheric pressure on the liquid surface, the liquid in the sump flows into the pump through the suction pipe. In this way, the liquid is continuously sucked up from the sump and continuously flows out from the discharge pipe.

RumA pump mechanical structure

The submersible electric pump unit consists of four main parts: the water pump, the submersible motor (including the cable), the water delivery pipe, and the control switch. The submersible pump is a single-suction, multi-stage vertical centrifugal pump. The submersible motor is a sealed, water-filled, wet-type, vertical three-phase squirrel-cage asynchronous motor. The motor and the water pump are directly connected via a claw-type or single-key sleeve coupling. It is equipped with three-core cables of different specifications. The starting equipment includes air switches and autotransformer reduced-voltage starters of different capacity ratings. The water delivery pipes are made of steel pipes with different diameters, connected using flanges, and gate valves are used for control in high-head electric pumps. A labyrinth-type sand guard and two reverse-assembled skeleton oil seals are installed on the upper part of the submersible motor shaft to prevent flowing sand from entering the motor. The submersible motor uses water-lubricated bearings. The lower part is equipped with a rubber pressure-regulating membrane and a pressure-regulating spring, forming a pressure-regulating chamber to adjust pressure changes caused by temperature. The motor windings use polyethylene insulation and nylon-sheathed water-resistant magnet wire. The cable connection follows cable joint procedures: remove the joint insulation, scrape off the varnish layer, connect the wires separately, weld them firmly, wrap with a layer of raw rubber, then wrap with 2-3 layers of waterproof adhesive tape, and finally cover with 2-3 layers of waterproof rubber tape or bond a layer of rubber (bicycle inner tube) with water-resistant adhesive to prevent water ingress. Each guide shell stage of the submersible pump is equipped with a rubber bearing. The impeller is fixed to the pump shaft with a tapered sleeve. The guide shells are connected into a single unit using threads or bolts. A check valve is installed at the upper part of high-head submersible pumps to prevent damage to the unit caused by water hammer during shutdown. The motor is sealed using precision spigot bolts, and the cable outlet is sealed with a rubber gasket. There is a water filling hole and an air vent hole at the upper end of the motor, and a drain hole at the lower part. Upper and lower thrust bearings are installed at the lower part of the motor. The thrust bearings have grooves for cooling and mate with a stainless steel thrust disk to withstand the axial forces of the water pump.

RumA pump precautions for use

1) Install a residual current device (RCD): An RCD, also known as a life-saving device, serves the purpose implied by its name. Since submersible pumps operate underwater, they are prone to leakage currents that can cause energy loss or even electric shock accidents. If an RCD is installed, it will cut off the power supply to the submersible pump whenever the leakage current exceeds the RCD's trip current value (generally not exceeding 30 mA), thereby preventing energy waste due to leakage and ensuring safety. 2) Do not start the pump if the supply voltage is abnormal: On long low-voltage supply lines, excessively low voltage at the line end is common. When the phase voltage drops below 198 V and the line voltage drops below 342 V, the submersible pump motor speed decreases. If the speed fails to reach 70% of the rated speed, the starting centrifugal switch remains closed, causing prolonged energization of the starting winding, which may overheat and even burn out the winding and capacitor. Conversely, excessive voltage causes motor overheating and winding burnout. Therefore, during operation, the operator must continuously monitor the supply voltage. If the voltage falls more than 10% below the rated voltage or rises more than 10% above the rated voltage, the motor should be stopped to identify and rectify the fault. 3) Avoid frequent switching: Do not frequently switch the submersible pump on and off. When the pump stops, backflow occurs; immediate restart subjects the motor to a loaded start, resulting in excessive starting current that can burn out the windings. Since the starting current is very high, frequent starts can also damage the submersible pump motor windings. 4) Do not allow the submersible pump to operate under overload for extended periods: To prevent prolonged overload operation, do not pump water with high sand content, and continuously monitor whether the current value remains within the rating specified on the nameplate. If excessive current is detected, stop the pump for inspection. Additionally, avoid prolonged dry running of the electric pump to prevent motor overheating and burnout. 5) Ensure correct motor rotation direction: Verify the motor's rotation direction. While many types of submersible pumps can discharge water in both forward and reverse rotation, reverse rotation yields lower flow rates and higher current. Prolonged reverse rotation will damage the motor windings. 6) Cable installation and insulation resistance requirements for submersible pumps: When installing the submersible pump, suspend the cable and avoid excessive power cord length. Do not subject the cable to mechanical stress when lowering or lifting the pump to prevent power cord breakage. During operation, do not allow the pump to sink into mud, as this impairs motor heat dissipation and can burn out the motor windings. During installation, the motor's insulation resistance must not be less than 0.5 MΩ. 7) Perform regular inspections and promptly address any issues: Regularly inspect the motor. If cracks are found in the bottom cover, or if the rubber sealing ring is damaged or has failed, replace or repair it immediately to prevent water ingress into the submersible pump.

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