Zero Point Adjustments; Operating The Pump; Shutdown - Grundfos DMH 251 Installation And Operating Instructions Manual

11.5 Zero point adjustments

11.5.1 Adjusting the zero point for system pressures up to
100 bar
The zero point of the dosing pump is factory-set to a slightly lower
counter-pressure than the rated pressure of the pump. If the
operating counter-pressure deviates considerably from this value,
an adjustment of the zero point will ensure more precise values.
Counter-pressure at the factory-set zero point of the pump
Rated pressure of the pump
[bar]
10
16
25
11.5.2 Adjusting the zero point
Fig. 30 Adjusting the zero point
Pos. Components
L Stroke-length adjustment knob
1l Cover
2l Locking screw
3l Screw
4l Scale ring
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!
Always adjust the value with the discharge line
connected and with operating counter-pressure.
1. Fit a measuring device on the suction side, for instance place
the suction line in a graduated measuring beaker.
2. Set the dosing flow to 15 %.
3. Remove the cover (1l) from the stroke-length adjustment knob
(L).
4. Use a screwdriver to loosen the locking screw (2l) by
approximately 2 turns.
5. Switch on the pump.
6. Slowly turn the stroke-length adjustment knob towards the
zero point until the dosing (the liquid level falls) stops in the
measuring device.
7. Switch off the pump.
8. Set the scale ring (4l) to zero.
– Loosen the screw (3l) in the scale ring (4l) slightly using an
hexagon key, M3.
– Turn the scale ring (4l) until both "0" are the same on the
scale and scale ring.
– Tighten the screw (3l).
Counter-pressure at the
factory-set zero point
[bar]
3
3
10
3l 2l 1l
3l
L
4l
9. 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.
10.Replace the cover (1l).

11.6 Operating the pump

When operating the pump, see sections
12. Operation and
Note
if necessary, section

11.7 Shutdown

Warning
Wear protective clothing (gloves and goggles)
when working on the dosing head, connections
or lines!
Do not allow any chemicals to leak from the
pump. Collect and dispose of all chemicals
correctly!
If possible, rinse the dosing head before shutting
Note
down the pump, e.g. by supplying it with water.
11.7.1 Switching off / uninstalling
1. Switch off the pump and disconnect it from the power supply.
2. Depressurise the system.
3. Take suitable steps to ensure that the returning dosing
medium is safely collected.
4. Carefully remove all lines.
5. Uninstall the pump.
11.7.2 Cleaning
1. Rinse all parts that have come into contact with the medium
very carefully:
– lines
– valves
– dosing head
– diaphragm.
2. Remove any trace of chemicals from the pump housing.
11.7.3 Storage
Storage of the pump:
1. After cleaning (see section
parts and reinstall the dosing head and valves, or
2. change the valves and diaphragm.
See section
13. Maintenance
11.7.4 Disposal
Disposal of the pump:
• After cleaning (see section
pump in accordance with the relevant regulations.
12. Operation
12.1 Switching on/off
Before switching on the pump, check that it is
installed correctly. See sections
Caution
and 11. Start-up /
• To start the pump, switch on the power supply.
• To stop the pump, switch off the power supply.
13. Maintenance and,
14. Fault finding chart.
), carefully dry all
11.7.2 Cleaning
.
), dispose of the
11.7.2 Cleaning
9. Installation
shutdown.
27