Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

Mechanical Seals 413
Figure 17-51. Heat checked mating ring surface damaged through 360°
This type of failure may also occur after a longer period of time in service
if the pump had developed excessive axial end play, causing the seal
to run solid. In this case, checks should be made to determine if the seal
had been properly set at its working height and had sufficient flow to the
seal cavity.
Partial heat checking of the sealing surface through an arc less than
180° opposite the flush inlet is the result of not properly distributing the
flow of coolant in the stuffing box. In this case, a circumferential groove
may be added to the gland plate at the outside diameter of the mating ring
or an additional inlet 180° from the existing inlet should be considered.
In this particular case, it would also be a good idea to check the squareness
of the face of the stuffing box with the shaft to be sure the alignment
is correct and that the mating ring has not been pulled to one side when
installed.
Hot localized patches of material have been previously discussed in the
theory of operation for a mechanical seal. The development of a hot spot
is illustrated in Figure 17-52. When a seal operates in an unstable condition
for a short period of time, the localized hot spot will appear to be
very small. The surface distress at the hot spot occurs because of rapid
heating in operation followed by rapid cooling due to the liquid at die seal
faces changing to a gas. When the liquid at the seal faces flashes or va-