Magnetic coupling at elevated temperatures

Magnetic couplings are utilized in many functions inside pump, chemical, pharmaceutical, course of and safety industries. They are typically used with the purpose of decreasing wear, sealing of liquids from the environment, cleanliness wants or as a safety issue to brake over if torque abruptly rises.
The commonest magnetic couplings are made with an outer and inner drive, each build up with Neodymium magnets so as to get the highest torque density as possible. By optimizing the diameter, air gap, magnet size, variety of poles and selection of magnet grade, it’s possible to design a magnetic coupling that fits any software in the vary from few millinewton meter as a lot as a quantity of hundred newton meters.
When solely optimizing for prime torque, the designers typically are inclined to forget contemplating the affect of temperature. If the designer refers again to the Curie level of the person magnets, he’ll declare that a Neodymium magnet would fulfill the necessities up to greater than 300°C. Concurrently, it is essential to include the temperature dependencies on the remanence, which is seen as a reversible loss – typically around 0,11% per diploma Celsius the temperature rises.
Furthermore, a neodymium magnet is under pressure during operation of the magnetic coupling. This implies that irreversible demagnetization will occur lengthy earlier than the Curie point has been reached, which generally limits the use of Neodymium-based magnetic coupling to temperatures beneath 150°C.
If higher temperatures are required, magnetic couplings manufactured from Samarium Cobalt magnets (SmCo) are usually used. SmCo is not as strong as Neodymium magnets however can work up to 350°C. Furthermore, the temperature coefficient of SmCo is just 0,04% per degree Celsius which signifies that it can be used in functions the place efficiency stability is needed over a larger temperature interval.
New generation In collaboration with Copenhagen Atomics, Alfa Laval, Aalborg CSP and the Technical University of Denmark a model new technology of magnetic couplings has been developed by Sintex with assist from the Danish Innovation Foundation.
The function of the challenge was to develop a magnetic coupling that would increase the working temperature area to achieve temperatures of molten salts round 600°C. By exchanging the inside drive with a magnetic material containing a higher Curie level and boosting the magnetic subject of the outer drive with special magnetic designs; it was possible to develop a magnetic coupling that began at a lower torque stage at room temperature, but solely had a minor reduction in torque stage as a function of temperature. This resulted in superior performance above 160°C, no matter if the benchmark was against a Neodymium- or Samarium Cobalt-based system. xp2i could be seen in Figure 1, where it’s shown that the torque stage of the High Hot drives has been examined as a lot as 590°C on the internal drive and nonetheless carried out with an nearly linear discount in torque.
The graph additionally reveals that the temperature coefficient of the High Hot coupling is even decrease than for the SmCo-system, which opens a decrease temperature market the place efficiency stability is essential over a larger temperature interval.
Conclusion At Sintex, the R&D division continues to be creating on the know-how, however they need to be challenged on torque level at either different temperature, dimensions of the magnetic coupling or new functions that have not previously been potential with normal magnetic couplings, so as to harvest the total potential of the High Hot expertise.
The High Hot coupling is not seen as a standardized shelf product, however as an alternative as custom-built by which is optimized for specific applications. Therefore, further improvement might be made in shut collaboration with new companions.
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