Submersible sewage pump is a pump and motor Siamese, and at the same time submerged work under the pump products , and general horizontal or vertical sewage pump, submersible sewage pump has the obvious advantages of the following aspects: Compact structure, small footprint. Submersible sewage pump submersible work, so can be installed directly in the sewage tank, without the need to build a dedicated pump room for the installation of pumps and machines, you can save a lot of land and infrastructure costs. 2 installation and maintenance easy. Small submersible sewage pump can be freely installed, large submersible sewage pumps are generally equipped with automatic coupling device can be automatically installed, installation and maintenance quite convenient. 3. Continuous operation for a long time. Submersible sewage pump due to pump and motor coaxial, short shafts, rotating parts light weight, so the bearing load (radial) is relatively small, longer life expectancy than the average pump. 4. There is no cavitation damage and irrigation water and other issues. Especially after the point to the operator has brought great convenience. 5. Vibration noise, low motor temperature, pollution-free environment.
It is because of the above advantages, 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 Site drainage, liquid feed and more. 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 impeller fluid dynamic sealing technology
The so-called Vice-impeller hydrodynamic seal is the installation of an open impeller coaxial opposite to the back of the pump impeller rear cover. 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, which 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. In addition to sealing the secondary impeller play a 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 in the case of identical performance parameters, the axial force of the submersible sewage pump is larger than that of the horizontal ones, and the balance is more difficult than the vertical ones. Therefore, in the submersible sewage pump, the bearing is easy to damage the reason is also a great relationship with the axial force. If the deputy impeller is installed, the direction of the liquid pressure exerted on the impeller is opposite to the resultant force of the above two forces, so that a part of the axial force can be canceled and the bearing life extended. 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 pump without overload design technology applications
In a typical centrifugal pump, the power is always increased with the increase of the flow rate, that is to say, the power curve is a curve that increases with the increase of the flow, which brings a problem to the use of the pump: At design duty point operation, the pump's power is generally safe to use, as it generally is less than the rated motor power, but increases as the pump head decreases (as can be seen from the pump's performance curve) 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 pumps without full lift characteristics (including submersible sewage pumps), the range of use is greatly limited. The so-called full head characteristic (also known as no overload characteristics) refers to the power curve increases with the flow rate increases very slowly, more desirably when the flow rate increases to a certain value, the power will not only rise again, but will have Drop, that is, 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, whether you are in that one Operating conditions point, the pump power will not exceed the motor power and the pump overload, with this performance of the pump, either selection or use, will be very convenient and reliable. In addition the motor power is not too big, you can save considerable equipment costs.
