Which is better, a shielded pump or a magnetic pump?

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With the development of the chemical industry and increasing awareness of the environment, the requirements for pumps used in the chemical sector are also rising. In applications involving the transport of flammable, explosive, or volatile cryogenic fluids, there are requirements for pumps to be leak-free, and such requirements have contributed to the development of shielded pumps and magnetic drive pumps. Both types of pumps are widely used in facilities across the chemical, new energy, pharmaceutical, nuclear, aerospace, and other industries. How exactly should one make the choice? Reichert suggests that one should take into account the differences between the two types of pumps, as well as the actual requirements of production, and make a decision based on a comprehensive assessment of costs. 1. Principles and structure of canned pumps and magnetic drive pumps: A canned pump is a type of sealless pump; the pump shaft and the motor shaft share the same axis, with the impeller mounted on this common shaft. The motor and the pump are integrated together and both are enclosed within a pressure vessel filled with the medium to be pumped. This pressure vessel has only static seals, while a set of wires generates a rotating magnetic field to drive the rotor. Its structure mainly consists of a pump body, impeller, stator, rotor, front and rear guide bearings, shaft sleeves, and a drive disc. An impeller is mounted at the end of the rotor shaft; it is supported by front and rear guide bearings and immersed in the medium being transported, thereby creating a sealless structure that achieves leak-free transportation. As shown in the figure: The magnetic pump consists of three parts – the pump itself, the magnetic drive unit, and the electric motor. The motor is a conventional one; there are two shafts, namely the motor shaft and the pump shaft, which are connected through a conventional coupling. The key component, the magnetic drive unit, is made up of an outer magnet, an inner magnet, and an isolation sleeve. It is mainly composed of a pump body, rotor, shaft, inner magnet, outer magnet, isolation sleeve, bearings, etc. A cylindrical external magnetic rotor is mounted on the pump shaft; the inner surface of this external magnetic rotor is evenly equipped with permanent magnets arranged in an NS-pole alternating pattern. Comparison of the characteristics of shielded pumps and magnetic drive pumps: 1. Shielded pumps utilize the principle of electric motors directly, whereas in magnetic drive pumps, the energy consumed by the motor must be transmitted to the impeller through the inner and outer magnets (with some of this energy being converted into heat in the magnets); therefore, theoretically, shielded pumps have higher efficiency than magnetic drive pumps. 2. Structurally, the biggest drawback of shielded pumps is that they cannot be repaired (it is extremely difficult); whether there are problems with the pump body or the motor during operation, users are basically unable to carry out repairs on their own. And repairing magnetic pump is not much different from repairing ordinary pumps. 3. The thickness of the isolation sleeve in magnetic pump is more than 3 times that of a shielded pump, thus ensuring better sealing performance and reliability. 4. The motor bearings of the shielded pump are lubricated by the medium; the motor does not have a fan, and its heat dissipation is achieved through the internal circulation of the medium to carry away heat. This results in a higher failure rate for such shielded motors. The motor of a magnetic pump is a standard motor that relies on a fan for cooling, offering reliability and maturity. But this also means that the noise level of this magnetic pump is higher than that of a shielded pump. 5. The structure of the shielded pump is more compact, allowing it to be smaller in size than magnetic pumps and thus saving space. 6. Shielded pumps do not have couplings, while magnetic pumps are connected to the motor via a coupling, which requires alignment. 7. Due to the issues related to magnetic materials, magnetic pumps can achieve a lower maximum power output compared to shielded pumps; this limits their use in applications that require high flow rates and high pressures and thus involve heavy loads. 8. Magnetic pumps are more suitable for highly corrosive media than shielded pumps, due to their thicker isolation sleeves. 9. In terms of cost, magnetic pump prices are lower than those of shielded pumps. As for which one to choose, it depends on what is of primary importance; factors such as price, after-sales maintenance, and performance can all be taken into consideration.