Features
Magnetic pump is composed by pump, magnetic couplings and motor three parts. Pump shaft left side has impeller and right with internal magnetic rotor, pump shaft is supported by bearing. Bracket connection pump and motor ensure internal and external magnetic rotor position accuracy. When the motor drives outside magnetic rotor spinning, the magnetic field through air gap and isolation sleeve, drive internal magnetic rotor synchronous rotating, thus drives impeller to rotate.
1.1. pump Pump is generally selected corrosion resistance, high strength of engineering plastic, ceramic, such as stainless steel, corundum production material, it has good corrosion resistance and can be made from the media. Such as CQB magnetic-driving pumps series contact liquid parts are made by chemicals resistance fluoroplastic alloy. Fluoroplastic alloy can be thermoplastic processing ultra-high molecular weight fep and one more plastic blending, can add packing. If ultra-high molecular fep and ptfe composed of plastic alloy, former weight ratio is 0.1%一99.9%, the latter one is 99.9%一0.1%, using dry powder grind or dry grinding mill blending. Use hot or cold sintering process into various products, overcome ptfe clod flow and deformation shortage, can prolong the service life.
Magnetic pump bearing is submerged in transmission medium, and uses medium to lubricate and cool. National commonly used bearing is graphite and reinforced plastics. Graphite especially dipping graphite has good corrosion resistance, self-lubricity, low friction coefficient, application range is very wide, but graphite brittle, intensity is lower, the bending and axial local overload is very sensitive, should pay special attention to. Using steel as body, porous bronze as middle layer, plastic as surface layer three layers of composite bearing with high compressive strength, small friction coefficient, dimension stability, sound muffing, in recent years has been applied.
1.2、magnetic couplings
Magnetic coupler is the key component of achieving no contact torque transmission and completely without leakage. Generally disc shaped and cylindrical two forms. Due to the disc shaped by two face-to-face annular coupling between sets of magnet and composed, two ring magnets exists between the axial force, especially in large power and axial force, it is very difficult to overcome, and less commonly used. Cylindrical magnetic coupling including magnetic rotor and internal magnetic rotor, and sleeve three components, external magnetic rotor connects with motor, and in the atmosphere, magnetic rotor and pump shaft together, the rotor is filled in the pump housing and inclusive of isolation and submerged in transmission medium, sleeve between rotors and fixed in the pump housing, pump shell and sleeve internal form connecting, completely sealed chamber. The magnets on internal magnetic rotor outside cylndrical surface and external magnetic rotor along the circle direction arranged, forming "combined push-pull magnetic circuit".
Currently available for magnetic pump selected magnetic material is more, commonly, ferrite and AlNiCo, SmCo5(refer as 1:5), Sm(Co,Cu,Fe,Zr)7.4(refer as 2:17), Nd-Fe-B, etc. The priority is rare earth permanent magnet, the most powerful is Nd-Fe-B, its biggest energy deposition and 104T x, A/m above, intrinsic coercive force exceeds 1120kA/m, extremely popular. But its working temperature cannot exceed 120 degrees Celsius, can choose SmCo5 as permanent magnet, Sm(Co,Cu,Fe,Zr)7.4 energy deposition is about 192 x 103T•A/m, its working temperature can be as high as 300 degrees Celsius.
Cylindrical coupler in design, processing, assembling and shall pay great attention to the rotor position between magnetic rotors, otherwise, it will produce radial force. The radial force, not only influence on torque transmission and also had a direct impact to bearing life, if serious, can make the magnetic couplings can not work. The key to solve the radial force is ensuring internal and external necessary magnetic rotor coaxial tolerance. When magnetic pump assemble and disassemble, should has special tooling and tools to protect personnel and parts from break and injured.
In the work, sleeve is in an alternating magnetic field, responds to vortex. This kind of eddy, on one hand, consume shaft power and reduce the transmission efficiency. On the other hand, chaned to heat, transfer to medium, and improve the circulation medium temperature. So sleeve design must pay attention to the choice of materials and geometrical shape and size,
especially for conveying liquid vaporization easily. After giving the pump parameters and requirements, sleeve loss power P main factor is approximate to P∝d2/p•σ, d is sleeve diameter, p is material resistivity. σis material allowable tensile stress. Visible, the main ways of reducing vortex loss is selecting high resistivity, high strength material and minimize sleeve diameter
Usually the sealing materials divided into two categories: metal materials and nonmetal materials. Metallic materials have high mechanical strength, wall thickness can be controlled in thinnest, to reduce gap between internal and external magnetic rotor, increase transmission efficiency and reduce sleeve internal generated electricity eddy loss. Generally domestic adopts 1Cr18Ni9Ti and alloy. Nonmetal material has good corrosion resistance, won't produce electric vortex loss, can improve the transmission efficiency, but often gets conveyance medium pressure and temperature restrict to limit applicable scope, and domestic commonly used is ptfe.
