Shaft seals positive drive seal

Most screw compressors are of the oil-lubricated type. There are two types—the semihermetic and the open-drive type. In the former, the motor is located in the same housing as the compressor, while in the latter the motor is located outside of the compressor housing and thus requires a shaft seal. The only moving parts in screw compressors are two intermeshing helical rotors. The rotors consist of one male lobe, which functions as a rolling piston, and a female flute, which acts as a cylinder. Since rotary screw compression is a continuous positive-displacement process, no surges are created in the system. 

There are two methods of converting a simple seal to positive drive. Both methods, which use collars secured to the drive shaft by setscrews, are shown in Figure 19.5. In this figure, the end tabs of the spring are bent at... 

Proper mechanical design principles determine the option of cantilevered or centerhung rotor, the shaft diameter, the type and position of bearings, and seal design. The drive train, whether belt driven or direct coupled, is determined by the power requirements and the shaft orientation. The housing must be sufficient to contain the temperature and pressure of the operation and to provide adequate inlet and outlet nozzles for the process fluids. 

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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