TP80-240/2 Shaft Seals Manual
Table Of Contents
39
Types of shaft seals
Shaft seals
Seal arrangements
Grundfos offers the following types of double seals:
• Double seal mounted back-to-back, Grundfos
type O
• Double seal mounted in tandem, Grundfos type P
• Cartex-DE seal, Grundfos type Q.
Double seal (back-to-back)
Grundfos type O seal is defined as two seals mounted
in a back-to-back arrangement.
Description
This type of double seal consists of two shaft seals
mounted back-to-back in a separate seal chamber.
Fig. 56
Back-to-back seal arrangement in a CR pump
The pressure in the seal chamber must be higher than
the pump pressure. The pressure in the seal chamber
can be generated by
• a pressure intensifier when the operating pressure
is above 16 bar
• a separate pump, for instance a dosing pump, when
the operating pressure is less or equal to 16 bar or
• an existing, separate pressure source. Many appli-
cations incorporate pressurized systems.
The back-to-back arrangement with pressurized seal
chamber prevents the pumped liquid from leaking
through the shaft seal to the environment.
Applications
Double seals mounted back-to-back are recommended
for use with toxic, aggressive or explosive liquids. The
back-to-back arrangement protects the surrounding
environment and the people working in the vicinity of
the pump.
This type of shaft seal is the optimum solution for han-
dling abrasive or sticky liquids which would either wear
out, damage or block a mechanical shaft seal.
The double seal mounted back-to-back is used in
• paint industries
• distilling industries
• petrochemical industries.
Double seal (tandem)
Grundfos type P seal is defined as two seals mounted
in a tandem arrangement.
Description
This type of double seal consists of two shaft seals
mounted in tandem in a separate seal chamber. Only
Grundfos cartridge shaft seals can be used.
Fig. 57
Tandem seal arrangement in a CR pump
If the primary seal is leaking in a CR pump, the pumped
liquid will be flushed away by the flushing liquid.
The flushing liquid pressure must always be lower than
the pumped liquid pressure.
Fig. 58
Tandem seal arrangement in an AP pump
Grundfos AP sewage pumps have either
• a combination of a mechanical bellows seal and a
lip seal between the motor and the pump or
• two mechanical bellows seals mounted on either
side of the oil chamber.
The tandem arrangement prevents sewage from enter-
ing and destroying the motor.
TM02 5000 2002
•
Shaft seals
TM01 6204 1699TM00 7211 0696
•
••
G 3/8"
Inlet 3/8"
Outlet 3/8"
Oil
chamber
Bellows
shaft seals