How To Improve The Life Of A Submersible Pump

In order to improve the life of the submersible sewage pump, most manufacturers at home and abroad are now trying to find a way to protect the pump, that is, when the pump leaks, overload, overtemperature and other faults, it can automatically alarm, and automatically stop for repair. However, we believe that 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.
But that's not the crux of the matter, the protection system is just a remedy in the event of a pump failure, a more reactive approach. The key to the problem should be to start from the root and completely solve the problems of the pump in terms of sealing and overload, which is a more active approach. To this end, we apply the auxiliary impeller hydrodynamic seal technology and the non-overload design technology of the pump to the submersible sewage pump, which greatly improves the reliability and bearing capacity of the pump seal and prolongs the service life of the pump.
1. Application of hydrodynamic sealing technology for auxiliary impeller
The so-called auxiliary impeller hydrodynamic seal refers to the installation of an open impeller in the opposite direction of the coaxial direction near the back of the impeller back cover of the pump. When the pump is working, the auxiliary impeller rotates with the pump spindle, and the liquid in the auxiliary impeller will also rotate together, and the rotating liquid will produce an outward centrifugal force, which on the one hand resists the liquid flowing to the mechanical seal and reduces the pressure at the mechanical seal. On the other hand, it prevents the solid particles in the medium from entering the friction pair of the mechanical seal, reduces the wear of the mechanical seal grinding block, and prolongs its service life.
In addition to the sealing effect, the auxiliary impeller can also play a role in reducing the axial force, the axial force in the submersible sewage pump is mainly composed of the differential pressure force acting on the impeller and the gravity of the whole rotating part, the direction of action of these two forces is the same, and the resultant force is formed by adding two forces. It can be seen that under the condition that the performance parameters are exactly the same, the axial force of the submersible sewage pump is greater than that of the general horizontal pump, and the balancing difficulty is more difficult than that of the vertical pump. Therefore, in the submersible sewage pump, the reason why the bearing is easy to damage is also related to the large axial force.
If the auxiliary impeller is installed, the direction of the differential pressure force acting on the auxiliary impeller is opposite to the resultant force of the above two forces, which can cancel out part of the axial force, and also plays a role in prolonging the life of the bearing. However, there is also a disadvantage of using the auxiliary impeller sealing system, that is, a part of the energy is consumed on the auxiliary impeller, generally about 3%, but as long as the design is reasonable, this part of the loss can be reduced to a minimum.
Second, the application of the non-overload design technology of the pump
In the general centrifugal pump, the power always increases with the increase of the flow rate, that is to say, the power curve is a curve that rises with the increase of the flow rate, which will bring a problem to the use of the pump: when the pump is running at the design working point, generally speaking, the power of the pump is less than the rated power of the motor, and the use of this pump is safe; But when the pump head decreases, the flow rate increases (as can be seen from the pump's performance curve) and the power increases.
When the flow rate exceeds the design point flow rate and reaches a certain value, the input power of the pump may exceed the rated power of the motor, causing the motor to overload and burn out. When the motor is overloaded, it either protects the system action and stops the pump from rotating; Either the protection system fails and the motor burns out.
The head of the pump is lower than the design working point head, which is often encountered in practice, one situation is that when the pump is selected, the head of the pump is selected too high, and the pump is used to reduce the head when it is actually used; On the other hand, the working point of the pump is not easy to determine in use, in other words, the flow rate of the pump needs to be adjusted frequently; There is also the case where the pump needs to be used in a frequent change of location. These three situations may overload the pump and affect the reliability of the pump. It can be said that for pumps that do not have full head characteristics (including submersible sewage pumps), their range of use will be greatly limited.