Operating Conditions; Flushing Fluid; Installation; Flushing Fluid Connection - Grundfos NKG Montage- Und Betriebsanleitung

5. Operating conditions

The operating conditions stated in the installation and operating
instructions for NK, NKG pumps also apply for tandem shaft seal
pumps.

5.1 Flushing fluid

The flushing fluid must be clean.
The flushing fluid should be selected according
Caution
to the application and must not chemically attack
the materials of the pump and the shaft seal.
The flushing fluid must have a high boiling point, good lubricating
and heat transmission properties.
The flushing-fluid flow should also be matched to the application
(recommended flow rate 25-200 l/h).
Warning
Never connect the flushing-fluid supply directly
to the public water supply system. Local
regulations must be observed.
It is possible to connect the seal chamber/cartridge seal to a
separate flushing-fluid tank. In such cases, the manufacturer's
installation and operating instructions must be observed.
5.1.1 Maximum flushing-fluid pressure and temperature
The pressure of the flushing fluid must always be lower than the
pressure of the pumped liquid.
The maximum permissible temperature of the flushing fluid
depends on the rubber material of the secondary shaft seal.
Max. permissible temperature of
Shaft seal
EPDM
FFKM
FKM
FXM
HNBR
These values apply to water as flushing fluid. If other flushing
fluids are used, contact Grundfos for the max. permissible
temperature of the flushing fluid.
5.1.2 Flushing fluid evaporation point
The tandem shaft seal arrangement can handle a pumped liquid
temperature up to 140 °C. In order to ensure proper liquid
lubrication in the the seal gap, it is very important that the
evaporation point of the flushing fluid is at least 10-15 °C higher
than the temperature of the pumped liquid.
the flushing fluid
[°C]
+120
+140
+90
+140
+90

6. Installation

6.1 Flushing fluid connection

6.1.1 Tandem seal arrangement with two separate shaft seals
in a seal chamber
1
2
3
Fig. 2 Tandem seal arrangement with two separate shaft
seals in a seal chamber
Pos. Description
A Vent screw for pumped liquid
1 Primary shaft seal pipe connection -3/8"
Secondary shaft seal pipe connection with vent screw
2
for venting of seal chamber -3/8"
3 Secondary shaft seal pipe connection -3/8"
In this tandem shaft seal arrangement, the seal chamber has
three connections. See fig. 2 and fig. 3. Pos. 1 leads to the
pumped liquid side of the shaft seal, and pos. 2 and 3 lead to the
seal chamber. All connections are close to the seal faces of the
shaft seals.
Connections
2
3
1
Fig. 3 Flow direction of flushing liquid
Dead-end solutions (see 6.2 Flushing system)
Use only connection 3 as inlet and 2 for venting.
Connection 1 must be plugged.
Circulating solutions (see 6.2 Flushing system)
Use connection 3 as inlet and 2 as outlet. The flushing fluid
lubricates and cools the secondary shaft seal.
Connection 1 must be plugged.
A
5