Page 402 - Centrifugal Pumps 2E

Mechanical Seals 367

Figure 17-7. Balanced seal heat generation (courtesy of John Crane).

tion of a heat exchanger or abrasive separator when required (Figure 17-
9). Another method of supplying additional cooling to a stuffing box is
shown in Figure 17-10. This seal is equipped with a pumping ring and
heat exchanger. The pumping ring acts like a pump, causing liquid to
flow through the stuffing box. Liquid is moved out the top of the stuffing
box and through the heat exchanger, returning directly to the faces at an
inlet at the bottom of the end plate. As liquid is circulated, heat is re-
moved at the seal and stuffing box. This is an extremely efficient method
of removing heat because the coolant circulated is only in the stuffing
box and does not reduce the temperature of the liquid in the pump. A
closed loop system such as this is commonly used on hot water pumps.
For double seal installations, the heat load for each seal must be con-
sidered, as well as the heat soak from the process. The flow of coolant
can be achieved through the use of an external circuit with a small pump.