Pumps centrifugal Packing, shaft

The motion of the piston rod is reciprocating through this packing as contrasted to the rotating motion of the centrifugal compressor or pump shaft. In many applications, it is important to prevent any part of the shaft that has heen inside the cylinder and exposed to the gas from being... 

Shaft seal requirements and two common types of seals, packed stuffing boxes and simple mechanical seals, are described and discussed in this section. A packed box typically is used on slow- to moderate-speed machinery where a slight amount of leakage is permissible. A mechanical seal is used on centrifugal pumps or other type of fluid handling equipment where shaft sealing is critical. 

It is not always possible to use a standard stuffing box to seal the shaft of a centrifugal pump. The pump suction may be under a vacuum so that outward leakage is impossible, or the fluid may be too hot to provide adequate cooling of the packing. These conditions require a modification to the standard stuffing box. 

There have been tremendous advances in the design of centrifugal pump mechanical seals, yet many new pumps employ ancient rope-type packing to prevent product leakage around the shaft. 

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