On the selection of pumps for sewage pumping stations

1、 Preface
Shanghai is a bustling modern city with the goal of becoming an international economic, financial, and trade center. This requires the city to have abundant water resources and a superior water environment that is suitable for its position.
However, due to various limitations, the city cannot achieve a complete separation system for domestic sewage, industrial wastewater, and rainwater. The polluted water bodies cannot be fully purified, and the pollution sources cannot be fully controlled. However, sewage pumping stations can be used to transport and intercept domestic and industrial wastewater. The sewage pumping station in this city plays a crucial role in controlling and improving water pollution in the city. In the sewage pumping stations in this city (such as Wuchuan pumping station), the commonly used MF (MN) pump has increasingly obvious shortcomings, such as low maintenance and installation accuracy, high noise, heavy daily management and maintenance workload, and even producing toxic and harmful gases, which endanger personal safety; At the same time, due to pump failure, the transportation and interception of sewage within the jurisdiction may not meet production targets, which will directly affect the economic and social benefits of the unit.
With the rapid advancement of science and technology in the pump industry, a large submersible sewage pump made of new materials, structures, and 5 axis turn mill machining brass parts can completely replace the original MF (MN) pump, and its development trend is rapid. The commonly used FLYGT-C (Feili) pump is a large submersible sewage pump with certain technological means and stable quality, which is widely welcomed by engineering technicians and pump station management personnel.
2、 The basic condition for FLYGT-C pump to replace MF (MN) pump is the commonality between the two pumps
The flow and head performance curves, flow and power performance curves, and flow and efficiency performance curves of the two pumps mentioned above are basically similar.
2. The temperature, caliber, flow rate, head, voltage, power, ground control board, etc. of the pumping medium (water) for the two pumps mentioned above have similarities.
3、 The advantage of FLYGT-C pump replacing MF (MN) pump is its unique high-tech content
1. FLYGT-C pump is more scientific and reasonable in structural design and manufacturing compared to MF (MN) pump. MF (MN) pump consists of multiple transmission units such as motor shaft, bearing box, water pump shaft, coupling, etc. Its shaft is made of stainless steel sleeve. The motor mainly relies on fan blades for cooling during operation, but long-term operation results in poor cooling effect. During operation, the motor itself has no protection and needs to be implemented through a control cabinet on the ground. If the motor stops running for a long time, it is easy to be affected by moisture and insulation. During operation, pumps usually use mechanical seals and packing seals, and mechanical seals require water diversion, otherwise a slight mistake will damage the water pump; The packing seal is prone to heating and softening due to continuous operation throughout the day, and requires frequent replacement. The anti-corrosion technology of the pump body and impeller is outdated, with poor corrosion resistance and very rough surface. The motor shaft and water pump shaft of the FLYGT-C pump share one, and the pump shaft is an extension of the motor shaft, made of stainless steel material. Two bearings are inside the entire submersible pump. The pump operates submerged in water and relies on the surrounding environment and the pumped medium to obtain sufficient cooling without the need for an external cooling system. The stator coil of the pump is immersed in F-grade insulation paint three times and baked three times. A thermal switch is installed in the stator coil, which is connected to the ground control cabinet through sensors for motor overload protection and oil leakage protection. The sealing performance of the motor cable inlet is particularly strong. It is composed of a cylindrical high elastic sleeve and an outer washer, which can be squeezed by the cable inlet chamber and eliminate tension and certain torque. This inlet device ensures that damaged cables can be easily replaced without using epoxy, silicone or other secondary seals. The sealing performance of a pump has its unique features, consisting of a mechanical seal that is connected in series with a double independent upper and lower seal: the lower seal (the first seal) is located between the pump casing and the oil chamber, consisting of a static ring and a forward rotating corrosion-resistant tungsten carbide dynamic ring; The upper seal (second seal) is located between the oil chamber and the motor, consisting of a ceramic stationary ring and a forward rotating carbon dynamic ring. The interface between the two seals is connected by its own spring system, and the mechanical seal can rotate clockwise and counterclockwise without damaging the sealing components and without maintenance and adjustment. The exterior of the pump and the metal surface of the pumped medium are sprayed with anti-corrosion paint. A wear-resistant ring is installed between the volute and the impeller inlet, made of steel or brass coated with clear rubber, to ensure effective sealing between the volute and the impeller inlet.
2. The installation of FLYGT-C pump is simpler and faster than that of MF (MN) pump. During the construction of MF (MN) pump, a large water pump room needs to be built, including escalators, lighting facilities, ventilation facilities, submerged pumps, wells, and other auxiliary equipment and facilities. During installation, the foundation of the pump must be solid, and it is never allowed to use the pump itself as a support point for the pipeline to bear the weight of the pipeline. It is worth mentioning that the pump is accurately aligned with the transmission cnc turning stainless steel flat square shaft. If packing is used for sealing, the radial and axial deviation of the two couplings should not exceed 0.1mm. Due to long-term operation, the foundation (triangular iron frame) gradually loosens and corrodes, making it difficult to install the pump after maintenance.
In the construction and renovation of FLYGT-C pump, there is no auxiliary equipment and facilities in the pump room required for MF (MN) pump, which greatly reduces the cost and time of civil engineering, and reduces the cost and installation time of auxiliary facilities. This is one of the biggest advantages of large submersible sewage pumps such as FLYET-C pump being able to replace MF (MN) pump. The installation of FLYGT-C pump is simple. The submersible pump slides freely from the top of the pump pit to the drainage connection seat under the guidance of no less than two parallel guide rods, and can automatically connect to the drainage connection seat without the need for installation workers to go down the well for installation and maintenance. The sealing between the pump and the drainage connection seat is completely metal to metal contact, and there is no need for drainage sealing in the form of membranes, O-rings, or gaskets. The full weight of the pump is borne by the drainage bend of the pump and the dedicated lifting chain of the pump. The load borne by the lifting chain is twice the total weight, ensuring stability.
3. FLYGT-C pump is safer and easier to operate than MF (MN) pump in management. MF (MN) pump has strict operating procedures before operation, such as opening the inlet gate valve, opening the vent valve, draining the air inside the pump, turning the coupling, and checking the clearance of the coupling. When the pump is running, it is necessary to use “frequent observation, sniffing, touching, and listening” to distinguish the operation of the pump. It is necessary to frequently walk on the steep escalators between the water and sewage pumps, especially if a female comrade is on duty, the potential fear may affect the quality of safety work and daily management. When the pump is running, there is high noise and vibration, which seriously hinders the inspection and rest of the pump station management personnel. The oil tank of the pump must be filled with lubricating grease once a week, and its bearings must not operate without lubricating grease. Otherwise, noise will be generated, the bearings will heat up, and in severe cases, the bearings will be damaged, forcing the pump to stop running. Due to continuous operation 24 hours a day, the packing at the pump’s packing area is prone to heating and becoming soft, resulting in a large amount of sewage overflow. Therefore, it is generally necessary to replace the packing once every 2-3 weeks. But it must be pointed out that when replacing the packing, the inlet gate valve must be closed first. Some inlet gate valves are manually operated, which is very cumbersome and labor-intensive for management personnel. High labor intensity refers to this aspect of work. Moreover, if some manual gate valves cannot be closed tightly, they cannot replace the pump’s packing in a timely and normal manner, resulting in the illusion that the pump cannot work properly. At the same time, a large amount of sewage overflowed and affected the working environment of the water pump room, causing a foul odor that had to stop the pump from running. The most potentially dangerous job is for the pump station management personnel to open the working hole of the pump and check if there is any garbage entanglement on the impeller inside the pump. They must strictly follow a complex set of safety operation procedures, such as filling out a work permit, using a measuring instrument to monitor, and wearing a gas mask to work. Imagine wearing a gas mask, which is both stuffy and hot, and requires a lot of effort to remove garbage from the impeller within a certain period of time, which is indeed very inconvenient. If these safety measures are not taken, a certain concentration of gas may accumulate inside the water pump, which may escape at any time, leading to a gas poisoning accident that endangers personal safety. Due to long-term contact with sewage, many pump station managers experience varying degrees of irritation, itching, and other reactions on their hands and skin, making them even more uncomfortable in the cold winter months.
If large submersible sewage pumps such as FLYGT-C pumps are used, the pump station management personnel only monitor and record them in a timely and accurate manner through the instruments and meters in the control cabinet on the ground. Due to the entire pump being submerged in water, the medium (water) conveyed by the pump plays a sound insulation role, greatly reducing noise and improving the operating environment of the pump station. Due to the fact that all lubricating oil (grease) has been filled before the pump is put into operation, it is not necessary to add lubricating oil (grease) during normal operation. Not only that, the pump does not require the necessary operation, maintenance, and inspection requirements for MF (MN) pumps in operation management. This is a major innovation in the daily management of MF (MN) pumps.
4、 Conclusion
From the selection of pumps in sewage pumping stations, the author deeply understands the insightful assertion that “science and technology are the primary productive forces”. In today’s rapidly changing modern science and technology, if sewage pumping stations want to stand firm in the fierce market competition, they must vigorously promote the use of large submersible sewage pumps such as FLYGT-C pumps. Although the price is a bit expensive, in the long run, they can indeed reduce the labor intensity of pump station management personnel, improve the operation rate of pumps, ensure the completion of sewage transportation and interception tasks, and achieve a double harvest of economic and social benefits. Therefore, large submersible sewage pumps such as FLYGT-C pumps are the best choice for sewage pumping stations.