The magnetic pump2017-11-08
The magnetic pump consists of a pump, magnetic actuators, motors of three parts. Key components of magnetic actuator by the external magnetic rotor sleeve, inner magnetic rotor and non magnetic components. When the motor drives the outer magnetic rotor, the magnetic field can penetrate the air gap and non-magnetic material, driven by the magnetic rotor and impeller connected for synchronous rotation, to achieve non-contact power transmission, the dynamic seal into static seal. As the shaft, the rotor is within a magnetic pump, isolated sets of completely closed to completely solve the problem of "run, run, drip, leak, remove the oil refining chemical industry flammable, explosive, toxic and harmful media through the pump seal leakage security risks, effectively ensure the workers health and safety of.
First, the working principle of magnetic pump
N of the magnet (n is even) arranged according to the laws in the magnetic clutch assembly inside and outside the magnetic rotor, the magnet part consisting of magnetic coupling system. When the inside and outside the two poles in different relative displacements, two poles between the angle phi = 0, the lowest energy magnetic system; when rotates to the relative displacement of two poles, pole angle between phi = 2 pi /n, the maximum magnetic energy of magnetic system. Remove the external force, due to the magnetic system of magnetic poles repel each other, magnetic magnet will return to the lowest energy state. So the magnet generates motion and drives the magnetic rotor to rotate.
Two, structural characteristics
1 permanent magnets
Permanent magnet operating temperature range is made of rare earth permanent magnet wide (-45 - 400 DEG C), high coercivity, magnetic anisotropy direction is very good, also won't happen in the same demagnetization phenomenon when is close, is a good source of magnetic field.
2 isolation sleeve
In the metal isolation, isolation sets in a sinusoidal alternating magnetic field, in a cross section perpendicular to the direction of magnetic field lines induced eddy currents and transformed into heat. The expression of eddy current is:. Among them Pe eddy current; K constant; rated speed of N pump; T magnetic drive torque; pressure within F spacer sleeve; inner diameter of D spacer sleeve; resistivity of material; tensile strength of material. When the pump design is good, T, n is a given condition, to reduce the eddy current only from F, D, etc.. Selection of high resistivity, high strength of the non-metallic materials to produce isolation sets, the effect is very obvious in reducing the eddy current.
3 control of coolant flow rate
When the pump works, a small amount of liquid must be used to flush the gap between the inner magnetic rotor and the isolation sleeve and the friction pair of the sliding bearing. The flow rate of the coolant is usually 2%-3% of the pump design flow, and the annular gap between the inner magnetic rotor and the isolation sleeve produces high heat due to eddy currents. When the coolant is not enough or poor flushing holes to plug, will result in permanent magnet medium temperature is higher than the operating temperature of the inner magnetic rotor gradually loses magnetism, the magnetic actuator failure. When the medium is water or water base liquid, the temperature rise of the annular gap region can be maintained at 3-5, when the medium is a hydrocarbon or oil, the temperature rise of the annular gap region can be maintained at 5-8.
4 sliding bearing
Magnetic pump sliding bearing material impregnated graphite, filled PTFE, engineering ceramics, etc.. Because the engineering ceramics have good heat resistance, corrosion resistance and friction resistance, the sliding bearing of magnetic pump is made of engineering ceramics. Because the engineering ceramics are very crisp and the expansion coefficient is small, so the bearing clearance must not be too small, so as to avoid the occurrence of axle bearing accident.
Due to the magnetic pump sliding bearing to transport the media for lubrication, it should be based on different media and the use of working conditions, the use of different materials production of bearings.
5 Protection Measures
When the magnetic actuator driven components running in case of overload or rotor stuck, magnetic clutch master and slave unit will automatically slip to protect the pump. The magnetic drive permanent magnet on the rotor in the active role of the alternating magnetic field, will produce eddy loss, magnetic loss, resulting in permanent magnet temperature, magnetic clutch slip failure.
Three, the advantages of magnetic pump
Compared with the centrifugal pump with mechanical seal or packing seal, magnetic pump has the following advantages.
1 pump shaft from the dynamic seal into a closed static seal, completely avoid the media leakage.
2 no independent lubrication and cooling water, reduce the energy consumption.
3 by the coupling drive into a synchronous drag, there is no contact and friction. Low power consumption, high efficiency, and with damping vibration damping effect, reducing the impact of the motor vibration on the pump and pump cavitation of the impact of the motor.
4 overload, the internal and external magnetic rotor relative slip, the motor, the pump has a protective effect.
Four, running notes
1 prevent particles from entering
(1) there are ferromagnetic impurities and particles into the magnetic actuator and bearing friction is not allowed. (2) the transfer of the easy crystallization or precipitation of the media to be promptly washed (after the pump to the pump cavity filling the water, running 1min after discharge clean), in order to protect the life of the sliding bearing. (3) the delivery of media containing solid particles should be filtered at the inlet of the pump flow tube.
2 prevent demagnetization
(1) magnetic moment can not be designed too small. (2) should be in the specified temperature conditions, the medium temperature is strictly prohibited. The temperature sensor of the outer surface of the magnetic pump isolation sleeve is provided with a platinum resistance temperature sensor to detect the temperature rise of the ring gap region, so that the temperature exceeds the limit alarm or stop.
3 prevent dry friction
(1) no idling. (2) the medium is prohibited to take time off. (3) the outlet valve is closed under the condition of the pump running time should not exceed 2min, to prevent overheating and failure of magnetic driver.