A magnetic pump drive comprises a double-walled isolating shell having an inner shell and an outer shell. Chemical pumps The inner shell and the outer shell are in contact at least along a cylindrical section of both shells. In the contact area, a channel system is incorporated between the shells by means of which channels the intactness of both shells may be checked. Channels of the channel system have the shape of a screw-channel. The magnetic pump drive so constructed closely approximates the characteristics of one constructed with a unitary thick-walled isolation shell. Magnetic pumpsA magnetic pump comprising a driver driven by a motor, a rotor encircled by the driver and connected with an impeller of the pump, the driver and rotor having an identical number m of permanent magnets on opposite cylindrical faces, of which two opposing magnets form a pulling pair, a stationary isolation shell having a cylindrical section and encircling the rotor, the stationary isolation shell being in contact with the medium to be pumped on its inside and sealed against the housing of the pump, and through which shell the force of the permanent magnets passes for effecting the drive from the driver to the rotor, the isolation shell particularly comprising an outer and an inner shell, the outer shell and the inner shell making contact against each other at least in the cylindrical section and comprising a channel system in the area of contact between the outer and inner shells, the channel system being in the outer shell and comprising regularly distributed, interconnected grooves. Magnetic pump drives have been known in the art for many years. The known drives have proven to be reliable in the chemical industry and in nuclear power stations. Because there is no shaft duct and thus no leakage along a shaft out of a sealing, these pumps have only gaskets which are more easily handled and which are much less prone to a leak than a seal against a rotating shaft. The channel system allows a check of the intactness of the outer shell and the inner shell by humidity sensors or pressure gauges. At the same time, the basic shape of a one-piece, thick-walled isolation shell is retained as much as possible. The basically robust design of a thick-walled isolation shell is especially appreciated in the cylindrical section of the double-walled isolation shell since a small gap between the permanent magnets of each magnet pair is still kept for obtaining a good efficiency. In other words the danger of damage is rather high in the cylindrical section. Since not only the outer shell but also the inner shell may be damaged, both shells should be designed so that each shell copes with the pressure of the system of which the pump is one part. Even if one shell bursts, the other shell is capable of withstanding the pressure prevailing within the pump. An exception to this rule is described later.

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2012-01-17

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