5 Function description
5.2 Pump unit structure
5.2 Pump unit structure
13
16
17
18
19
15
14
12
20
Fig. 7: Pump unit structure
12
Outer housing
17
Coupling intermediate ring
13
Cartridge pump
18
Motor-side coupling half
14
Overflow valve (optional)
19
Motor
15
Pump bracket
20
Pump bracket foot
16
Pump-side coupling half
5.3 Functional principle
Screw pumps are rotating pumps. Their displacement effect results from three rotating screws
1
and
2
and the enclosing cartridge housing
3
. The cartridge housing is installed in an outer housing
12
.
Radial support of the screws is effected through the sliding contact in the cartridge housing that de-
pends on lubrication by the pumped liquid. Screw pumps are therefore not suitable for dry running and
can only be used up to specific pressure limits and viscosity limits. Due to the narrow tolerances pump-
ing of suspended solids is not possible.
Axial support of the main screw
1
is carried out by the ball bearing
6
. Various shaft seals
7
are avail-
able for sealing the main screw at the outlet from the housing. In order to reduce the pressure at the
shaft seal, a balancing cylinder
5
is mounted at the main screw. The sealing chamber is connected with
the suction chamber via a relief line.
An assembled overflow valve
14
(optional) protects the pump against excessive pressure that could
cause housing parts to burst.
The default direction of the rotation of the main screw is clockwise viewed from the motor
19
and is
marked on the pump flange by an arrow.
The flow direction is marked on the outer housing by two arrows.
5.4 Housing variants
Outer housings are offered in two different materials.
Fig. 8: Material housing variants: GJS (figure left), steel (figure right).
12
OIC 18en-GB Edition 2020-01
Operating instructions
