1. Sliding bearings
Magnetic pump sliding bearing materials are impregnated graphite, filled with PTFE, engineering ceramics and so on. Because engineering ceramics have good heat resistance, corrosion resistance and friction resistance, the sliding bearings of magnetic pump are made of engineering ceramics. Because engineering ceramics are very brittle and the expansion coefficient is small, the bearing clearance should not be too small to avoid shaft holding accidents.
Because the sliding bearing of the magnetic pump is lubricated by the medium conveyed, different materials should be selected to make bearings according to different media and working conditions.
2. Isolation sets
When the metal isolating sleeve is used, the isolating sleeve is in a sinusoidal alternating magnetic field, and the eddy current is induced and converted into heat on the section perpendicular to the direction of the magnetic field line. The expression of eddy current is: where Pe- eddy current; K -- constant; n - the rated speed of the pump; T- magnetic drive moment; F- Pressure in the sleeve; D- sleeve inner diameter; The resistivity of a material; -- Tensile strength of the material. When the pump design is good, n and T are given conditions, to reduce the eddy current can only be considered from F, D and other aspects. Using high resistivity, high strength non-metallic materials to make the isolation sleeve, in the eddy current reduction effect is very obvious. Three. Cooling lubrication fluid flow control
When the pump is running, a small amount of liquid must be used to wash and cool the ring gap area between the internal magnetic rotor and the isolation sleeve and the friction pair of the sliding bearing. The coolant flow rate is usually 2%-3% of the designed flow rate of the pump. The annular gap area between the inner magnetic rotor and the isolation sleeve generates high heat due to eddy current. When the cooling lubrication liquid is not enough or the flushing hole is not smooth or blocked, the medium temperature will be higher than the working temperature of the permanent magnet, so that the internal magnetic rotor will gradually lose magnetism, and the magnetic drive will fail. When the medium is water or water-based liquid, the temperature rise in the ring gap region can be maintained at 3-5℃. When the medium is hydrocarbon or oil, the temperature rise in the annular gap region can be maintained at 5-8℃.
3. Permanent magnet
Permanent magnets made of rare earth permanent magnet materials have a wide operating temperature range (-45-400℃), high coercivity, good anisotropy in magnetic field direction, and no demagnetization phenomenon will occur when the same pole is close to each other, so they are a good magnetic field source.
4. Protection measures
When the driven parts of the magnetic drive run under overload or the rotor is stuck, the main and driven parts of the magnetic drive will slide off automatically to protect the machine pump. At this time, under the action of the alternating magnetic field of the active rotor, the permanent magnet on the magnetic drive will generate vortex loss and magnetic loss, resulting in the temperature rise of the permanent magnet and the slippage failure of the magnetic drive.
