Richter MNK-B Series - Manual (Page 7)

Series MNK-B, close-coupled design Page 7
9230-055-en Revision 09
TM 7345 Edition 10/2008
2.6.2 Special operating conditions
In the standard design the can chamber and
the plain bearings are cooled and lubricated
by a flushing flow.
Owing to properties of the medium (e.g. sticking due
to inadmissible solids entrainment, clogging, gas
entrainment etc.) the cooling flow can be interrupted
and, as a result, an inadmissible temperature rise may
occur. Provide appropriate monitoring facilities.
See Section 5.6.
For safe pump operation, we recommend a flow rate
of 0.3 to 1.1 Q
opt
. If the pump is operated outside this
range, it must be ensured that the max. admissible
flow rate according to the pump characteristic curve is
not exceeded and that the max. admissible operating
temperature according to Section 2.6.7 is observed.
If the flow rate is too high, the differential pressure
upstream and downstream of the plain bearings could
fall so much that a lack of lubrication or dry-running
may occur.
If the flow rate is too low, the medium may heat up so
much owing to the fluid friction that the max.
admissible surface temperature of the relevant
temperature class is exceeded.
Overloading, overheating, non-observance of the
design data or the incorrect selection of the magnetic
drive can lead to the decoupling of the inner and outer
magnet assemblies. As a result, eddy currents may be
induced on the inner and outer magnet assemblies
and an inadmissible temperature rise may occur.
The situation is to be remedied by providing
appropriate monitoring facilities. See Section 5.6.
The plant NPSH value (NPSHA) should be minimum
0.5 m higher than the NPSH value of the pump
(NPSHR) to prevent a lack of lubrication or dry-
running of the plain bearings.
2.6.3 Chargeable liquids
For operation with chargeable liquids with a
conductivity <10
-8 S/m inert gas must be used for
flushing during evacuation if the lining of the pump is
non-conductive. See Section 6.3.
2.6.4 Identification
The identification on the pump relates to the pump
section. A separate declaration of conformity must be
provided for the motor and for other attachments as
well as corresponding identification.
Example of the identification of the pump section:
CE Ex II 2 G/D T1-T4.
This designation means that the pump may be used in
atmospheres which may ignite above the temperature
class T4, i.e. >135 °C.
The temperature class with the highest ignition
temperature is always decisive for the entire unit, e.g.
pump, coupling, motor.
Example 1: Pump T3, coupling T4, motor T4
Example 2: Pump T4, coupling T4, motor T3
In both cases the unit may only be used in
atmospheres which may ignite above the temperature
class T3, i.e. > 200 °C.
The general rule is that the admissible limit value of
the medium temperature in accordance with Section
2.6.7 must be taken into account..
2.6.5 Check of the direction of rotation
If there is also a risk of explosion during the
installation phase, the check of the direction of
rotation must under no circumstances be conducted
by briefly switching on the unfilled pump in order to
prevent an inadmissible rise in temperature at the
plain bearings.
We recommend you to only perform a check
of the direction of rotation with filled pump and
with a rotating field instrument. See also
Section 6.1.2.
2.6.6 Mode of operation of the pump
The pump may only be started with the suction side
shut-off element fully opened and the discharge side
shut-off element slightly opened. Start-up against a
closed check valve is also possible. The discharge
side shut-off element is to be regulated to the
operating design point directly after run-up.
See also Section 5.4.1.
Operation with closed shut-off elements in the
suction and/or discharge lines is not permitted!
There is a risk that even after a short time
high surface temperatures on the pump
housing may occur owing to rapid heating of
the liquid in the pump interior.
A rapid rise in the pressure inside the pump
involves the risk of overloading to the point of
bursting.
The pump must not be in operation in the
unfilled or partially filled state (dry
running). This results in serious damage to
the pump and additional risks to the environment
can arise.
Dry-running cannot only occur with an
insufficiently filled interior but also in the event
of high gas contents in the liquid medium.
Operation of the pump outside the admissible
operating range may also lead to dry-running (e.g.
due to evaporation in the interior).