Series
SCK,
Mechanical seal RG-4, stationary, double, liquid sealed
Page
4
9220-014-en
Revision 11
TM 7827
Edition 03/2019
4.2.2 Stationary, double mechanical seal
RG-4, liquid sealed
A pump fitted with a double mechanical seal must
not be filled with a product before the pressurisa-
tion system provided has been started up.
Otherwise damage could occur, e.g. opening of the
wetted sealing gap, before start-up.
To guarantee safe operation, the pressure of the bar-
rier fluid must be 1-2 bar above the pressure of the
process medium at the mechanical seal at Q=0 m
3
/h.
It must be ensured that the sealing pressure does not
exceed the admissible pressure of the mechanical
seal used.
The required sealing pressure can be determined as
follows:
2/3 of the delivery pressure at Q = 0 m
3
/h
+
supply pressure
+
1 -2 bar safety margin
The supply pressure is measured in bar at the pump
suction nozzle. If no measuring point is available, the
supply pressure can be calculated using the following
formula.
Using the same formula, the delivery pressure at
Q=0 m
3
/h can be determined with the pump character-
istic curve.
2
,
10
)
(kg/dm
x
(mFS)
H
=
(bar)
p
3
p
=
supply pressure or delivery pressure
H
=
supply height or delivery head
=
density
Are the available connections correctly
made?
SE
- barrier fluid inlet
SA
- barrier fluid outlet
See also sectional drawing in
Section 7.2
4.3 Improper operations and their
consequences (examples)
Inadmissible modes of operation, even for
brief periods, may result in serious damage
to the unit.
In connection with explosion protection, potential
sources of ignition (overheating, electrostatic and in-
duced charges, mechanical and electric sparks) may
result from these inadmissible modes of operation;
their occurrence can only be prevented by adhering to
the intended use.
For examples, see installation and operating manual
SCK,
Section 6.6
.
5
Maintenance
The regulations and recommendations of
the mechanical seal manufacturer must
always be observed.
See also the installation and operating man-
ual for the SCK series.
It is important to replenish in good time any sealing
liquid which has escaped and to monitor the sealing
liquid pressure.
It is important to replenish in good time any sealing
liquid which has escaped and to monitor the sealing
liquid pressure.
Refer also to the description of the pressurisation sys-
tem used and
Section 4.2.2
.
If the sealing liquid pressure is too high, this indicates
a defect in the mechanical seal even though the
mechanical seal on the atmosphere side is completely
tight.
The pump must then be shut down so that no serious
damage occurs.
Substantial damage generally occurs if the aggressive
process medium enters the pressurisation system as
a result of a drop in the sealing liquid pressure to be-
low the minimum pressure.
If there is a risk that pressure surges occur in the
plant, precautions must be taken to prevent damage.
To this end, for example, the barrier fluid pressure can
be increased.
5.1 Disassembly stationary,
double-acting mechanical seal
RG-4, liquid sealed
Dismantling can be checked using the sectional
drawings in
Section 7
and
Section 9
of the
installation and operating manual SCK as well as the
components available.
5.1.1 Dismantling of impeller,
back plate and RG-4
●
First of all relieve the mechanical seal by undoing
the attachment screws
901/5
.
●
Undo screws
901/6
and washers
554/6
of the
bearing pedestal / back plate. Move the back plate
almost up to the impeller with light hammer blows.
