1. Permanent magnet
The permanent magnet made of rare earth permanent magnet material has a wide working temperature range (-45-4℃), high coercivity, good anisotropy in magnetic field direction, and no demagnetization when the same pole is close, so it is a good magnetic field source.
2. isolation sleeve
when metal isolation sleeve is used, the isolation sleeve is in a sinusoidal alternating magnetic field, which induces eddy current on the cross section perpendicular to the direction of magnetic field lines and converts it into heat. The expression of eddy current is: where PE-eddy current; K-constant; N refers to the rated speed of the pump; T-magnetic transmission torque; F-pressure in the spacer; D-inner diameter of spacer;
the resistivity of a material;
-tensile strength of the material. When the pump is designed, N and T are given working conditions, and the vortex can only be reduced from F and D aspects. Using nonmetallic materials with high resistivity and high strength to make isolation sleeve has obvious effect in reducing eddy current.
4. Sliding bearing
Materials of sliding bearing of magnetic 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 brittle and have a small expansion coefficient, the bearing clearance should not be too small to avoid shaft locking accidents.
because the sliding bearing of the magnetic pump is lubricated by the conveyed medium, different materials should be selected to make the bearing according to different media and working conditions.
3. control of cooling and lubricating fluid flow
when the stainless steel magnetic pump is running, a small amount of liquid must be used to wash and cool the annular gap between the inner magnetic rotor and the isolation sleeve and the friction pair of the sliding bearing. The flow rate of coolant is usually 2%-3% of the design flow rate of the pump, and the annular gap between the inner magnetic rotor and the isolation sleeve generates high heat due to eddy current. When the cooling lubricant is insufficient or the flushing hole is blocked, the temperature of the medium will be higher than the working temperature of the permanent magnet, so that the inner magnetic rotor will gradually lose its magnetism and the magnetic actuator will fail. When the medium is water or water-based liquid, the temperature rise in the annular region can be maintained at 3-5℃; When the medium is hydrocarbon or oil, the temperature rise in the annular region can be maintained at 5-8℃.
5. protective measures
when the driven parts of the magnetic drive run under overload or the rotor is stuck, the driving and driven parts of the magnetic drive will automatically slip off to protect the stainless steel magnetic pump. At this time, the permanent magnet on the magnetic actuator will produce vortex loss and magnetic loss under the action of the alternating magnetic field of the active rotor, which will cause the temperature of the permanent magnet to rise and the magnetic actuator to slip and fail.