Series MNKA bearing pedestal assembly 4
Page 7
9250-003-en
Revision 01
TM 10458
Published 06/2022
2.6.2 Special operating states
In the standard version, the plain
bearing is lubricated and cooled by the
internal flushing circuit.
Due to properties of the liquid (e.g. sticking due to
inadmissible solids ingress, clogging, gas
ingress), the flushing / cooling flow can be
interrupted, resulting in an inadmissible tempera-
ture rise. Ensure suitable monitoring measures.
See
section 5.6
.
For safe pumping operation, we recommend a
flow rate of 0.3 to 1.1 Q
Opt
. When operating
outside this range, it must be ensured that the
maximum permissible flow rate according to the
pump characteristic curve is not exceeded and
that
the
maximum
permissible
operating
temperature according to
section 2.6.7
is
maintained.
If the flow rate is too high, the differential pressure
upstream and downstream of the plain bearing
may be reduced to such an extent that there is a
risk of insufficient lubrication or dry running.
If the flow rate is too low, the medium may heat up
so much due to the fluid friction that the maximum
permissible
surface
temperature
of
the
corresponding temperature class is exceeded.
Overloading, overheating or failure to observe the
design data or incorrect selection of the magnetic
coupling can lead to decoupling of the inner and
outer rotors. As a result, eddy currents are in-
duced at the inner or outer rotor and an impermis-
sible temperature rise may occur. Ensure suitable
monitoring measures. See
section 5.6
.
The machine NPSH value (NPSHA) should be a
minimum 0.5 m higher than the NPSH pump value
(NPSHR) to prevent a lack of lubrication or dry
running of the plain bearing.
2.6.3 Rechargeable liquids
When operating with chargeable
liquids (conductivity <10
-8
S/m), purge
with inert gas when draining if the
pump lining is non-conductive. See
section 6.3
.
2.6.4 Marking
The Ex marking on the pump refers to
the pump part. A separate declaration
of conformity must be available for the
shaft coupling and motor or for other
attachments, and a corresponding
marking must be present.
Example of the marking on the pump part:
When
mounting
the
pump
with
non-Ex
components (e.g. motor, shaft coupling), it is
recommended to remove or obscure the Ex
marking on the pump part and, if applicable, other
attachments.
In this case, the declaration of conformity without
ATEX marking applies.
For surface temperatures that mainly depend on
the operating conditions of the pump, DIN EN
ISO 80079-36 Chapter 11.2 f) and g) state that
no temperature class or temperature may be
specified. In this case, the marking must include
temperature range identification (e.g. T4 to T3 for
gas or for dust T135 °C to T200 °C).
The temperature class is to be determined by the
operator according to
section 2.6.7
Temperature
limits.
2.6.5 Direction of rotation check
If there is also a risk of explosion during the
installation phase, the direction of rotation check
must never be carried out by briefly switching on
the unfilled pump. This prevents an impermissible
increase in temperature at the plain bearing.
We recommend checking the direction of rotation
only when the coupling is disengaged or with a
rotating field meter! See also
section 6.1.2
.
2.6.6 Pump operating mode
The pump may only be started with the suction
side shut-off device fully open and the pressure
side shut-off device slightly open. It is also
possible to start the pump against a closed non-
return valve. Immediately after start-up, the
pressure-side shut-off device must be adjusted to
the operating point.
See also
section 5.4.1
.
Operation with closed shut-off devices in the
suction and/or discharge line is not permitted!
There is a risk of high surface tem-
peratures on the pump housing after
only a short time due to rapid heating
of the liquid inside the pump.
A rapid increase in pressure inside
the pump poses the risk of over-
stressing to the point of bursting.
The pump must not be operated in
an unfilled or partially filled condi-
tion (dry running). This will result
in severe damage to the pump and
may pose additional hazards to the
environment.
Dry running can occur not only if the
interior is not sufficiently filled, but
also if the gas content in the pumped
liquid is too high.
