Grundfos DMH 251 Installation And Operating Instructions Manual page 28

12.2 Setting the dosing capacity
Fig. 31 Setting the dosing capacity
Pos. Components
L Stroke-length adjustment knob
1l Cover
2l Locking screw
3l Screw
4l Scale ring
12.2.1 Setting the dosing flow and locking the stroke-length
adjustment knob
1. Remove the cover (1l) from the stroke-length adjustment knob
(L).
2. Use a screwdriver to loosen the locking screw (2l) by
approximately 2 turns.
3. Increase or reduce the dosing flow while the pump is running.
– Slowly turn the stroke-length adjustment knob to the left or
right to set the desired dosing volume.
4. Depending on the application, tighten the locking screw (2l) so
that the stroke-length adjustment knob can still be turned/
cannot be turned any more.
5. Replace the cover (1l).
The pump cannot be operated if the stroke-length
adjustment knob is fully open! Depending on the
pump adjustment, this value may already be
lower than 100 % on the scale for system
Caution
pressures higher than 100 bar.
Open the stroke-length adjustment knob
completely and then close by approx. 10 % in
order to set the dosing flow to 100 %.
12.3 Using the AR control unit (optional)
When using the AR control unit, observe the installation and
operating instructions for the "AR control unit" in addition to the
instructions in this manual.
12.4 Electric servomotor (optional)
To operate the servomotor, see the installation and operating
instructions for the servomotor.
12.5 Electronic preselection counter (optional)
To operate the preselection counter, see the installation and
operating instructions for the counter.
12.6 Electrically heated dosing head (optional)
To operate the temperature controller, see the installation and
operating instructions for the temperature controller.
28
3l 2l 1l
3l
L
4l
13. Maintenance
13.1 General notes
Warning
When dosing dangerous media, observe the
corresponding safety precautions!
Wear protective clothing (gloves and goggles)
when working on the dosing head, connections
or lines!
The pump housing must only be opened by
personnel authorised by Grundfos Alldos!
Repairs must only be carried out by authorised
and qualified personnel!
Switch off the pump and disconnect it from the
power supply before carrying out maintenance
work and repairs!
Before removing the dosing head, valves and
lines, empty any remaining medium in the dosing
head into a drip tray by carefully unscrewing the
suction valve.
Observe the flow direction of valves (indicated by
an arrow on the valve)!
Caution
Only tighten plastic valves by hand.
13.2 Diaphragm leakage control for diaphragm
leakage detection
If a diaphragm leakage (MLS) has been detected, first of all check
whether an error has been displayed, as different external factors
such as the heating of dosing or hydraulic medium can cause the
cracked medium between the diaphragms to be displaced into the
valve, thereby causing an error to occur.
Checks after a diaphragm leakage detection:
1. Briefly open the deaeration screw (2u) and then close it again.
2. Switch on the pump.
3. If, after a short period of time, a diaphragm leakage is
detected again, a diaphragm has broken.
After a diaphragm breakage, replace the
diaphragms and clean the non-return valve, see
Caution
section 13.7 Replacing the diaphragm for dosing
head with double
1u
Fig. 32 Dosing head with double diaphragm
Pos. Components
S Contact pressure gauge
T Ball non-return valve
U Connection piece
1u Filling screw
2u Deaeration screw
diaphragm.
S
U
2u
T