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 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 rated motor power, but it is increased when the pump head is lowered From the 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 situations can overload the pump and affect the pump's availability. 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 to overload the pump, pump with this performance, both the selection or use, will be very convenient and can be *. In addition the motor power is not too big, you can save considerable equipment costs.