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The Practical Pumping Handbook .................

While the balanced seal may appear to be the answer to all sealing
problems, certain services may be better served with the unbalanced
seal. For example, some applications may be more interested in security
than longevity, and this may translate into a greater desire for a high
closing force in the seal selected. Also, when sealing a cold liquid, the
increase in operating temperature may be of little concern.
Regardless of any other consideration, a balanced seal is usually
recommended when the stuffing box pressure exceeds 50 p.s.i.

6.3.6 Outside seals
The more popular arrangement positions the seal inside the stuffing
box. While this requires disassembly of the pump wet end to carry out
any maintenance on the seal, there are some significant advantages.
Temperature control of the seal area can be achieved by means of
o
a jacketed stuffing box.
An aggressive product can be kept out of the stuffing box entirely,
o
by injecting a more acceptable liquid through the flush
connections.
The seal faces can be kept cleaner by various design elements in
.
the stuffing box that will draw solid particles away from the seal
faces.
An Outside Seal reverses the orientation of the stationary face and
locates the rotating unit on the shaft outside the stuffing box gland.
The advantages of this arrangement are as follows:
1. Ease of installation.

Usually inexpensive.
.
STUFFING
BOX GLAND

..'.
ROTARY
UNIT
STATIONARY
! ! FACI =

Figure 6.8. Inside seal

96