Submersible sewage pump has been more and more people's attention, the use of a more and more wide range, from the original purely for the transport of fresh water to the present can transport a variety of domestic sewage, industrial wastewater, construction sites drainage, liquid feed, etc. Wait. In municipal engineering, industry, hospitals, buildings, restaurants, water conservancy construction plays a very important role in all walks of life. But everything is divided into two, the most critical issue for the submersible sewage pump is the reliability issue, because the submersible sewage pump is used under the liquid occasion; the medium is mixed with a mixture of solids containing liquid; Pump and motor close; pump is vertical layout, the weight of rotating parts and impeller pressure in the same direction. These problems make the submersible sewage pump in sealing, motor carrying capacity, bearing arrangement and selection requirements than the average sewage pump is higher. In order to improve the life of submersible sewage pump, most domestic and foreign manufacturers are now on the pump protection system think of a way that the pump leaks, overload, over-temperature and other failures can automatically alarm and automatically shut down for repair. However, in our opinion, it is necessary to set up a protection system in the submersible sewage pump, which can effectively protect the safe operation of the electric pump. However, this is not the crux of the problem. The protection system is only a remedy after a pump failure. It is a relatively passive approach. The crux of the problem should be from the very beginning, to completely solve the pump in the sealing, overload and other issues, this is a more proactive approach. To this end, we apply the sub-impeller hydrodynamic sealing technology and pump no-overload design technology to the submersible sewage pump, greatly improving the pump seal reliability and carrying capacity and prolonging the service life of the pump. First, the application of the impeller hydrodynamic sealing technology The so-called vice impeller hydrodynamic seal is installed on the back of the pump impeller rear cover near the coaxial reverse direction to install an open impeller. When the pump is working, the auxiliary impeller rotates with the pump main shaft, and the liquid in the auxiliary impeller will also rotate together. The rotating liquid will generate an outward centrifugal force that on the one hand withstands the liquid flowing to the mechanical seal and lowers the mechanical Sealing pressure. On the other hand prevent the solid particles in the medium from entering the friction pair of the mechanical seal, reduce the abrasion of the mechanical seal and prolong the service life of the mechanical seal. Vice impeller in addition to play a sealing role, but also can play a role in reducing the axial force in the submersible sewage pump axial force is mainly caused by the liquid pressure on the impeller pressure force and the entire rotating part of the composition of gravity, which The direction of action of the two forces is the same, the resultant force is formed by the sum of two forces. It can be seen that under the same performance parameters, the axial force of the submersible sewage pump is larger than that of the horizontal pump, and the balance is more difficult than the vertical pump. Therefore, in the submersible sewage pump, the bearing is easily damaged because of the large axial force and has a great relationship. And if the installation of the deputy impeller, the liquid pressure on the Deputy impeller in the direction of the force is the opposite of the combined force of these two forces, so that you can offset part of the axial force, also played an extended bearing The role of life. However, there is also a disadvantage of using an aero-impeller seal system that consumes about 3% of the energy on the aero-impeller, but as long as the design is reasonable, this loss can be reduced to a minimum. Second, the application of pump without overload design technology In a general centrifugal pump, the power is always increased with the flow rate increases, that is, the power curve is a curve with an increase in flow rate, which pump The problem with using this pump is that when the pump is running at a design point, the pump's power is generally safer than the motor's rated power, but when the pump head is lowered, the flow increases Pump performance curve can be seen, the power also increases. When the flow rate exceeds the design point flow and reaches a certain value, the pump input power may exceed the motor rated power and cause the motor overload and burn. Motor overload operation either protects the system from stopping the pump; otherwise, the motor is burnt out due to a failure of the protection system. Pump head is lower than the design conditions of the use of head lift, in practice are often encountered, a situation is the pump selection, the pump lift election too high, but the actual use of the pump is to reduce head Use; the other case, in the use of the pump is not good to determine the operating point, in other words, the pump flow need to be adjusted frequently; there is a case where the pump needs to be changed frequently used. These three conditions can overload the pump and affect the reliability of the pump. It can be said that, for the pump without full lift feature, including submersible sewage pump, its use range will be greatly limited. The so-called full lift characteristic, also known as no overload characteristic, means that the power curve increases very slowly with the increase of the flow rate. Even more desirably, when the flow rate increases to a certain value, the power not only will not rise but will decrease, In other words, the power curve is a hump curve, if so, we simply select the motor rated power slightly more than the hump point power value, then the flow of 0 to the maximum flow of the entire range, regardless of your operating conditions Point of operation, the pump power will not exceed the motor power.
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