Shielded electric pump is widely used in chemical, nuclear industry and other important occasions. It solves many problems that can not be solved by general pumps. But with the rapid development of science and technology, a lot of new problems have been put forward for shielding electric pumps.
The main feature of the canned motor pump is that the motor part and the pump part are one, that is, sharing a motor shaft, thus eliminating the middle connection part, thus solving the leakage problem that the dynamic seal is very difficult to solve. But here is only relative to the external environment for the leakage of the pump, actually this leakage still exists, but this part of the leakage of no leakage to the external environment, but directly "to" internal leakage of canned motor, resulting in the transport medium containing solid particles under the condition of the transport medium containing the solid particles "to shield motor internal leakage will cause what kind of consequences, will be how to solve this problem, 2 transport medium containing solid particles of shielded electric pump due to the shielding electric pump generally adopts graphite bearing and surfacing (or spray welding) hard alloy bearing sleeve is composed of attrition," leakage "is bound to flow of graphite bearing friction shield motor inside the medium containing solid particles to pay. Under normal conditions, this part of the transmission medium can play the role of lubrication bearings, while taking away the heat generated by shielding motor loss, play a cooling role. However, when the transport medium containing solid particles, the solid particles in the flow through the gap between the graphite bearing and bearing sleeve, friction with the graphite bearing and the bearing sleeve, which accelerates the wear of graphite bearing and bearing sleeve, once the attrition wear, or in the wear process, the pump will not provide normal the flow and pressure head, and even cause downtime or burning motor.
3 theoretical analysis in order to solve the above problem, we may wish to do a test, a rolling bearing is fixed on the top of the container, such as an inverted, when they were together vertically downward into the liquid, we put the air is considered as an ideal gas, according to Boyle Mariotte (Boyle - Maotte) law in: the container cavity volume and rolling bearing volume difference); V, 'the volume within the container air - liquid level rise; P0 atmospheric pressure; the air inside the container P/ level after rising pressure.
The theoretical analysis and test of liquid level rise increased, when the air pressure inside the container is increased to a certain value, the value and the pressure of the container when the liquid inside and outside pressure vessel increased in the container to achieve balance, this level is no longer.
So long as we know the liquid pressure P2 and the container to remove the net volume of rolling bearings, can use the Boyle mariottes law finally launched anti the volume of air inside the container, so that the liquid can increase the number under the pressure of P2, the level must be able to guarantee the rolling bearing used with contact surface. Considering the fluctuation of the liquid level in the container and the change of the pressure P2, the calculated values should be adequately compensated.
4, the actual application of the above test results, we developed a gas sealed bearing structure of vertical shielding electric pump. The electric pump is provided with an inverted, inner and empty upper end and a shaft to be welded into a closed cylindrical cylinder for the lower rotor shaft cap of the shielding motor. The cylindrical cylinder is welded to the rotor and rotates along with the rotor. When the cylinder is welded with the rotor, the airtight test must be carried out to ensure that the cavity of the cylinder and the rotor are not leak.
Through the careful design of the structure in the axial rolling bearings on the bearing positioning, relative bearing structure is simple, directly increase the axial length of the bearing chamber, the rotor shaft part correspondingly lengthened, is also using the above result, the bearing is installed on the upper part of the upper bearing chamber, the lower left there is a period of rising liquid distance, the bearing is not in contact with the transport medium (such as).
This "leakage" to the circulation route of transmission medium shielding inside the motor is changed, because the "leakage" to the conveying medium shielding inside the motor does not need lubrication of rolling bearings, which is mainly from the upper part of the motor shield between the stator and the rotor back to the pump, to shield motor cooling effect, which can to reduce this part of the "leak" flow, which reduced the volume loss. Because of the change of the loop path, the resistance of the "leakage" to the transmission medium inside the shielding motor becomes smaller, thus reducing the energy required for the circulation of this part of the conveying medium.
The vertical shield electric pump has no problems during the practical use, and solves the difficult problem that the conveying medium contains solid particles, and meets the requirements of users.
5 conclusion the vertical principle of gas shielded electric pump seal type bearing structure by Boyle Mariotte's law of gas pressure changes with the change in volume, the use of rolling bearing instead of graphite bearing, solve graphite bearing and welding (or spray welding) hard alloy bearing sleeve is composed of the high cost of attrition and the use of short cycle defects, most (on page ninth) that can be variable switching without loss of power and not stop the case. The starting current is smaller because the high speed is initiated in the case of S= 0.5. The same is true when the low speed pole moves toward the medium speed pole. Therefore, independent winding can reduce the electrical losses in the pole changing process.
Pole changing speed regulating motor from high speed to extreme direction
