First, the working principle of the magnetic pump

The n pairs of magnets (n is an even number) are regularly arranged on the inner and outer magnetic rotors of the magnetic actuator, so that the magnet portions form a complete magnetic system. When the inner and outer magnetic poles are in opposite poles, that is, the displacement angle Φ=0 between the two magnetic poles, the magnetic energy of the magnetic system is the lowest; when the magnetic pole rotates to the same pole, the displacement angle between the two magnetic poles is Φ=2π. /n, at this time the magnetic energy of the magnetic system is the largest. After the external force is removed, the magnetic force will restore the magnet to the state with the lowest magnetic energy because the magnetic poles of the magnetic system repel each other. The magnet then moves to drive the magnetic rotor to rotate.

Second, the structural characteristics

1. Permanent magnets

The permanent magnet made of rare earth permanent magnet material has a wide operating temperature range (-45-400 ° C), high coercive force, good anisotropy in the direction of the magnetic field, and no demagnetization when the same pole phase is close. It is a good source of magnetic field.

2. Isolation sleeve

When a metal isolating sleeve is used, the spacer is in a sinusoidal alternating magnetic field, and an eddy current is induced and converted into heat in a section perpendicular to the direction of the magnetic field line. The expression of the eddy current is: Wherein Pe- eddy current; K-constant; n-rated speed of the pump; T-magnetic drive torque; pressure in the F-sleeve; D-sleeve inner diameter; resistivity of a material; When the pump is designed, n and T are given by the working conditions. To reduce the eddy current, only F, D, and so on can be considered. The use of high-resistivity, high-strength non-metallic materials to make the isolation sleeve, the effect is very obvious in reducing the eddy current.

3. Cooling fluid flow control

When the pump is running, it is necessary to flush and cool the annular gap between the inner magnetic rotor and the spacer and the friction pair of the sliding bearing with a small amount of liquid. The flow rate of the coolant is usually 2% to 3% of the pump design flow rate, and the annulus region between the inner magnetic rotor and the isolation sleeve generates high heat due to the eddy current. When the cooling lubricating fluid is insufficient or the flushing hole is not smooth or blocked, the medium temperature is higher than the working temperature of the permanent magnet, so that the inner magnetic rotor gradually loses magnetism and the magnetic actuator fails. When the medium is water or water-based liquid, the temperature rise in the annulus region can be maintained at 3-5 ° C; when the medium is hydrocarbon or oil, the temperature rise in the annulus region can be maintained at 5-8 ° C.

4. Sliding bearing

The material of the magnetic pump sliding bearing is impregnated graphite, filled with polytetrafluoroethylene, engineering ceramics, and the like. Because engineering ceramics have good heat resistance, corrosion resistance and friction resistance, the sliding bearings of magnetic pumps are mostly made of engineering ceramics. Since the engineering ceramics are very brittle and the expansion coefficient is small, the bearing clearance must not be too small to avoid the occurrence of a shaft hazard.

Since the sliding bearing of the magnetic pump is lubricated by the medium to be conveyed, the bearing should be made of different materials according to different media and working conditions.

5. Safeguard

When the driven part of the magnetic actuator is operated under overload or the rotor is stuck, the main and driven parts of the magnetic actuator will automatically slip off and protect the pump. At this time, the permanent magnet on the magnetic actuator will generate eddy loss and magnetic loss under the action of the alternating magnetic field of the active rotor, causing the temperature of the permanent magnet to rise and the magnetic actuator to slip off.

Third, the advantages of magnetic pump

The magnetic pump has the following advantages compared to a centrifugal pump that uses a mechanical seal or a packing seal.

1. The pump shaft is sealed by a dynamic seal into a closed static seal, completely avoiding media leakage.

2. Eliminates the need for separate lubrication and cooling water, reducing energy consumption.

3. From the coupling drive to synchronous drag, there is no contact and friction. Low power consumption, high efficiency, and damping damping effect, reducing the impact of motor vibration on the pump and the impact of the cavitation vibration of the pump on the motor.

4. When overloaded, the inner and outer magnetic rotors are relatively slippery, which has a protective effect on the motor and the pump.

Fourth, the operation notes

1. Prevent particles from entering

(1) Ferromagnetic impurities and particles are not allowed to enter the magnetic actuator and the bearing friction pair. (2) After transporting the medium which is easy to crystallize or precipitate, it should be flushed in time (after pumping, pump the water into the pump chamber, drain it after 1 minute) to ensure the service life of the sliding bearing. (3) When transporting media containing solid particles, it should be filtered at the inlet of the pump flow tube.

2. Prevent demagnetization

(1) The magnetic moment cannot be designed too small. (2) It should be operated under the specified temperature conditions, and the medium temperature is strictly prohibited. A platinum resistance temperature sensor can be installed on the outer surface of the magnetic pump isolation sleeve to detect the temperature rise of the annulus region, so that the alarm or shutdown occurs when the temperature exceeds the limit.

3. Prevent dry friction

(1) It is strictly forbidden to idling. (2) The medium is strictly forbidden. (3) When the outlet valve is closed, the continuous running time of the pump shall not exceed 2 minutes to prevent the magnetic actuator from overheating and failing.

Concerned about surprises

Label: How the magnetic pump works

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