Shafts, rotating, sealing materials

As in all medium-pressure agglomerators that use rollers for the densification and extrusion of moist and/or plastic materials, the primary cause for roller rotation is friction between the roller surface and the material to be processed. The roller is mounted on a shaft with sealed antifriction bearings and is brought to close proximity... 

Mechanical seals are an alternative and sophisticated means of sealing a mixer shaft. The rotating seal is formed between two seal elements, not the shaft and the seal as in a stuffing box. Mechanical seals allow for very tight control of the seal surfaces and materials. Such controls make possible high-pressure seals, even without external leakage. 

Fig. 2.6. The diagram shows the essential features of the PTFE taps, but it is not a representation of any one firm s model. A is2i shaft of PTFE or of some other material covered with PTFE. It is driven by rotating the plastic cap B which engages the screw-thread of the glass moulding C. The seal against the atmosphere is provided by the bulge D. The valve closure at E is the more reliable of the two seals.

The dynamic seals for reciprocating plungers and pistons, as well as rotating shafts, require all the capabilities of modem material developments high performance plastics, bronzes,... 

The sealing of a rotating shaft under low leakage conditions is extremely difficult, therefore the stirrer shaft was built completely encapsulated by austenitic material and the transmission of the torque was realised using a permanent magnetic coupling. The magnets were based on samarium-cobalt and are able to transmit a torque of 135 Nm. 

Magnetically coupled drive mechanisms have a set of inner magnets located atop the impeller shaft that extends down into the pressure vessel. This inner magnet assembly is positioned so that it can be rotated within and be encapsulated by a small pressure vessel chamber. This chamber is made of nonmagnetic material and is attached and sealed to the head of the reactor vessel. This chamber is then surrounded by another set of matching magnets located in an... 

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