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Stuffing Box Sealing

Figure 6.15: Tandem type double sea (Reproduced with permission of A. W. Chesterton Inc.)

Many pumps are equipped with a stuffing box cooling jacket that can
be used to cool a high temperature liquid or raise the temperature of an
excessively cold product.

.4.1 Seal flush
Even with a cooling jacket (or when one is not available) an excessively
hot liquid may cook the elastomers and distort other parts of the seal,
causing premature failure. Similarly, any abrasives in the pumpage can
cause rapid wear of the seal faces and also result in premature failure.

In these, and other difficult applications, the product may have to be
either diluted or replaced in the stuffing box by an appropriate seal
flush, and this can be achieved in a number of ways.

In one method, the flush is brought from a very reliable, external
source at a pressure higher than that in the stuffing box. This is
frequently used when pumping a dirty product and, in such cases, the
flush becomes the main source of lubricant for the seal faces. It will also
dilute the liquid and carry any abrasive particles from the seal faces into
the pump casing behind the impeller.
In some services the flush would be considered to have contaminated
the main process and render this an inappropriate and unacceptable
solution.
Other systems use the high pressure process fluid at the discharge
nozzle of the pump and recirculate it into the stuffing box.

101 m