Magnetic drive pump working principle

2020/08/24 18:25:55

The magnetic drive pump is composed of three parts: a pump, a magnetic drive, and a motor. The key component of the magnetic drive consists of an outer magnetic rotor, an inner magnetic rotor and a non-magnetic isolation sleeve. When the motor drives the outer magnetic rotor to rotate, the magnetic field can penetrate the air gap and non-magnetic materials, drive the inner magnetic rotor connected to the impeller to rotate synchronously, realize the contactless transmission of power, and convert the dynamic seal into a static seal. Because the pump shaft and inner magnetic rotor are completely enclosed by the pump body and the isolation sleeve, the problem of "running, emitting, dripping and leakage" is completely solved, and the leakage of flammable, explosive, toxic and harmful media in the refining and chemical industry through the pump seal is eliminated. The potential safety hazards effectively ensure the physical and mental health and safe production of employees

1. Working principle of mag drive pump
N pairs of magnets (n is an even number) are assembled on the inner and outer magnetic rotors of the magnetic drive in a regular arrangement, so that the magnet parts form a complete coupled magnetic system. When the inner and outer magnetic poles are opposite to each other, that is, the displacement angle between the two magnetic poles Φ=0, the magnetic energy of the magnetic system is the lowest at this time; when the magnetic poles rotate to the same pole, the displacement angle between the two magnetic poles Φ=2π /n, the magnetic energy of the magnetic system is maximum at this time. After removing the external force, since the magnetic poles of the magnetic system repel each other, the magnetic force will restore the magnet to the lowest magnetic energy state. Then the magnet moves and drives the magnetic rotor to rotate.

2. Structural characteristics of magnetic drive pump

1. Permanent magnet

Permanent magnets made of rare earth permanent magnet materials have a wide operating temperature range (-45-400°C), high coercivity, and good anisotropy in the direction of the magnetic field. Demagnetization will not occur when the same poles are close. It is a good source of magnetic field.

2. Isolation sleeve

When the metal isolating sleeve is used, the isolating sleeve is in a sinusoidal alternating magnetic field, and eddy current is induced in the cross section perpendicular to the direction of the magnetic force and converted into heat. The expression of eddy current is:. Among them, Pe-eddy current; K-constant; n-rated speed of the pump; T-magnetic transmission torque; F-pressure in the spacer; D-inner diameter of the spacer; the resistivity of a material;-the tensile strength of the material. When the pump is designed, n and T are given by the working conditions. To reduce the vortex, only F, D,, and other aspects can be considered. The isolation sleeve is made of non-metallic materials with high resistivity and high strength, which is very effective in reducing eddy current.

3. Control of the flow of cooling lubricant

When the pump is running, a small amount of liquid must be used to wash and cool the annular gap area between the inner magnetic rotor and the isolating sleeve and the friction pair of the sliding bearing. The coolant flow rate is usually 2%-3% of the pump design flow rate. The annular gap area between the inner magnetic rotor and the isolating sleeve generates high heat due to eddy currents. When the cooling lubricant is insufficient or the flushing hole is not smooth or blocked, the temperature of the medium will be higher than the working temperature of the permanent magnet, and the inner magnetic rotor will gradually lose its magnetism and the magnetic drive will fail. When the medium is water or water-based liquid, the temperature rise in the annulus area can be maintained at 3-5°C; when the medium is hydrocarbon or oil, the temperature rise in the annulus area can be maintained at 5-8°C.

4. Sliding bearing

The materials of the sliding bearing of magnetic drive pump include impregnated graphite, filled PTFE, engineering ceramics, etc. Because engineering ceramics have good heat resistance, corrosion resistance, and friction resistance, the sliding bearings of magnetic pumps are mostly made of engineering ceramics. Because engineering ceramics are very brittle and have a small expansion coefficient, the bearing clearance must not be too small to avoid shaft hung accidents.

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

5. Protective measures

When the driven part of the magnetic drive is running under overload or the rotor is stuck, the main and driven parts of the magnetic drive will automatically slip off to protect the pump. At this time, the permanent magnet on the magnetic drive

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Magnetic drive pump working principle