1. Sewage pump is a pump and motor Siamese, and at the same time submerged work under the pump products, compared with the general horizontal pump or vertical sewage pump, the sewage pump clearly has the following advantages: 1. Structure Compact, small footprint. The sewage pump can be directly installed in the sewage tank due to its submerged operation. There is no need to build a dedicated pump house to install the pump and machine, which can save a lot of land and infrastructure costs.
2 installation and maintenance easy. Small sewage pump can be freely installed, large 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. Due to the coaxial pump and motor shaft, the shaft is short and the weight of the rotating parts is light, so the load on the bearing (radial) is relatively small, and the service life is much longer than that of the ordinary 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, sewage pumps have 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 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 parts. The most critical issue for sewage pumps is the reliability issue, because the sewage pump is used under liquid conditions; the medium to be conveyed is a mixture of liquids containing solid materials; the pump and The motor is in close proximity; the pump is upright and the weight of the rotating part is in the same direction as the impeller is subjected to water pressure. These problems make the 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 the sewage pump, most domestic and foreign manufacturers are now on the pump protection system to find a solution, that is, the pump leaks, overload, over-temperature and other failures can automatically alarm and automatically shut down for repair. However, we think it is necessary to set up a protection system in the sewage pump, which can effectively protect the safe operation of the 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 impeller hydrodynamic sealing technology and pump no-overload design technology to the sewage pump to greatly improve the pump seal reliability and carrying capacity and prolong 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 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.
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 sewage pumps), the range of use will be 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.
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