Page 403 - Centrifugal Pumps 2E

368 Centrifugal Pumps: Design and Application

Figure 17-8. Heat soak from the process fluid (courtesy of John Crane).

Pressures in the stuffing box should be kept above the pressure at the
inboard seal. As a rule of thumb, the stuffing box is normally 10% or a
minimum of 25 psig above the product pressure against the inboard seal.
For low pressure installations, a pressurized loop and axial flow pump-
ing ring shown in Figure 17-11 can be considered. Here, as the shaft ro-
tates, the pumping ring moves liquid to a reservoir tank where heat is
removed from the system. Liquid returns to the bottom of the stuffing
box and continues to remove heat from the seal area.