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

378 Centrifugal Pumps: Design and Application
Figure 17-18. Stationary seal head rotating mating ring assembly (courtesy of
John Crane).
The selection of a single spring or multiple seal head construction is
determined by the space limits available and the liquid sealed. Single
spring construction is most often used with elastomeric bellows seals to
load the seal faces (Figure 17-19). The advantage of this type of construction
is that the openness of the design makes the spring a non-clogging
component of the seal assembly. The coils are made of a large diameter
spring wire and, as a result, can withstand a great degree of
corrosion.
Multiple spring seals require a shorter axial space. Face loading is accomplished
by a combination of springs placed about the circumference
of the shaft (Figure 17-12). Most multiple spring designs are used with
assemblies having O-rings or wedges as secondary seals.
Pusher-type seals are defined as seal assemblies in which the secondary
seal is moved along the shaft by the mechanical load of the seal and
the hydraulic pressure in the stuffing box. This designation applies to