Page 100 - Improving Machinery Reliability

72 Improving Machinery Reliability

reduces seal drag. (Note that rotating components are identified with even, and sta-
tionary components with odd numbers.)
Except for using several springs, the seal design shown in the bottom half of Fig-
ure 2-10 appears to be quite similar to the design shown in the top half. Both seals
incorporate the desirable features of many similar stationary seal designs:
Self-squaring faces. This feature may result in appreciably better seal life for
pumps with excessive shaft deflection or pumps operating with nominal shaft
deflection at high speeds.
Non-flexing springs. Spring life extension and long-term, uniform pressure can be
expected.
Pre-assembled cartridge construction. These seals can be shipped with the gland
plate in place. No field measurements or settings will be required.

However, a closer look will show functional differences in the arrangement of the
O-ring (3). It could be argued that progressive wear of the seal faces shown in the
upper half of Figure 2-10 will cause the O-ring to make sliding contact with a clean
portion of part (9), whereas advancing the stationary seal face in the lower half of
Figure 2-10 will cause the O-ring (3) to slide over a wetted and potentially contami-
nated portion of the gland plate (15).

Figure 2-10. Two different stationary seals with non-rotating springs located away from
pumped liquid.