TP80-80/4 Shaft Seals Manual

40
Types of shaft seals
Shaft seals
Applications
Double seals mounted in tandem are recommended for
crystallising, hardening or sticky liquids in
• pharmaceutical industries (i.e. production of dex-
tran)
• negative pressure deaeration systems (vacuum)
• industries handling potentially hardening oil prod-
ucts
• industries producing caustic soda (sodium hydrox-
ide - NaOH)
• industries producing hydrated lime (calcium hydrox-
ide - Ca(OH)
2
• Sewage.
Cartex-DE shaft seals
Grundfos type Q seal is a Cartex-DE double seal.
Description
The Cartex-DE seal is a double-pressure-balanced
shaft seal pre-assembled in one unit for use in centrifu-
gal pumps.
The Cartex-DE seal is available as a single seal and as
a double seal, depending on the application.
The Cartex-DE double seal can be mounted
• in tandem (Grundfos type P) or
• back-to-back (Grundfos type O).
For further information about tandem or back-to-back
seal arrangements, see page 39.
The Cartex-DE seal is independent of the direction of
rotation.
Fig. 59
Cartex-DE seal
Fig. 60 Cartex-DE shaft seal in tandem and back-to-
back arrangement
The figure shows that the two arrangements affect the
functionality of the shaft seal in different ways.
In the tandem arrangement the pumped liquid pressure
(PP) is higher than the flushing liquid pressure (PF).
This pressure distribution displaces the shaft axially to
the right allowing pumped liquid to be pressed into the
gap between the rotating and the stationary parts. As a
result of the displacement, the O-ring moves to the right
and seals against the flushing liquid coming from the
lower right side of the chamber.
In the back-to-back arrangement the pumped liquid
pressure (PP) is lower than the flushing liquid pressure
(PF). The pressure distribution displaces the shaft axi-
ally to the left allowing flushing liquid to be pressed into
the gap between the rotating and stationary parts. As
the shaft moves to the left, the O-ring follows and seals
against the pumped liquid coming from the upper left
side of the chamber.
During operation the coolant is pumped by the rotating
pump shaft from the tank through the shaft seal. The
circulating coolant prevents overheating of the shaft
seal.
Fig. 61
Cooling of a Cartex-DE seal
TM02 7109 2603
TM02 7449 3503TM02 7114 2703
P
P
P
F
P
F
P
P
O-ring
O-ring
Tandem arrangement
Back-to-back arrangement
Cartex-DE shaft
seal
Tank with
coolant