Page 422 - Centrifugal Pumps 2E

386 Centrifugal Pumps: Design and Application

Flgyre 17-23. Seal face design for upstream pumping (courtesy of John Crane),

also sized to fit the diameter of the shaft. Small packing rings may also be
used for a seal quench as shown in Figure 17-22E.
Shaft sleeves should be used on all applications where the shaft must be
protected from the environment of the pumpage. Sleeves should be made
of corrosion and wear resistant materials. Sleeves must be positively se-
cured to the shaft and seal at one end. The sleeve should extend through
the gland plate.

Upstream Pumping
The concept of upstream pumping is new to the sealing industry and is
a further refinement of spiral groove technology developed for dry run-
ning gas compressor seals. Upstream pumping is defined as moving a
small quantity of liquid from the low pressure side of a seal to the high
pressure side. This is accomplished by a change in seal face geometry
and by incorporating spiral grooves, Figure 17-23.
A conventional flat seal design is only capable of preventing leakage
from a higher pressure stuffing box to atmosphere. A seal designed with
the upstream pumping feature can seal high pressure and move clean liq-
uid across the seal faces to a high pressure stuffing box. This type of
design creates a full liquid film at the faces and reduces horsepower loss.
This is also a new way to flush a seal face with just a few cc/minute