Diaphragm Controller (Optional); Connecting The Power Supply Cable; Start-Up / Shutdown; Initial Start-Up / Subsequent Start-Up - Grundfos DMH 251 Installation And Operating Instructions Manual

10.4 Diaphragm controller (optional)

Warning
Explosion-proof pumps with diaphragm leakage
detection are fitted with a contact pressure gauge
in explosion-proof version.
The pressure gauge must be earthed.
Connecting the earth cable (4u), see fig. 25.
S
5s
4u
U
5u
T
Fig. 25 Diaphragm controller
Pos. Components
S Contact pressure gauge
5s Union nut
6s Contact output
T Ball non-return valve
U Connection piece
2u Deaeration screw
3u O-rings
4u Connection for earth cable
5u Union nut
* 2) or locking unit (instead of contact pressure gauge
and its connection)

10.5 Connecting the power supply cable

Warning
Disconnect the power supply before connecting
the power supply cable!
Before connecting the power supply cable, check
that the rated voltage stated on the pump
nameplate corresponds to the local conditions!
Do not make any changes to the power supply
cable or plug!
The assignment between the plug-and-socket
Caution connection and the pump must be labelled
clearly (e.g. by labelling the socket outlet).
The pump can be automatically started by
Caution
connecting the power supply!
• Do not switch on the power supply until you are ready to start
the pump.
10.5.1 Versions with mains plug
• Insert the mains plug in the mains socket.
10.5.2 Versions without mains plug
Warning
The pump must be connected to an external
clearly labelled mains switch with a minimum
contact gap of 3 mm in all poles.
• Connect the motor to the power supply in accordance with
local electrical installation regulations and the connection
chart on the terminal box cover.
24
6s
3u
2)
2u
3u
Warning
The specified enclosure class can only be
ensured if the power supply cable is connected
with the same degree of protection.
Observe the direction of rotation!
To protect the motor, install a motor protecting
Caution
switch or motor contactor, and set the bimetal
relay to the rated motor current for the available
voltage and frequency.

11. Start-up / shutdown

11.1 Initial start-up / subsequent start-up

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!
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.
The pump housing must only be opened by
personnel authorised by Grundfos Alldos!
Repairs must only be carried out by authorised
and qualified personnel!
Observe the flow direction of valves (indicated by
an arrow on the valve)!
Caution
Only tighten plastic valves by hand.
11.1.1 Checks before start-up
• Check that the rated voltage stated on the pump nameplate
corresponds to the local conditions!
• Check that all connections are secure and tighten,
if necessary.
• Check that the dosing head screws are tightened with the
specified torque and tighten, if necessary.
• Check that all electrical connections are correct.
• Cross-tighten the dosing head screws using a torque wrench.
Torques
Pump type
DMH 251, 10 bar
DMH 251, 16 bar
DMH 251, 25 bar
DMH 252
DMH 253
DMH 254
DMH 255
DMH 257
11.1.2 Oil filling
The pump is factory-checked, and the oil is
drained for shipping purposes. Before start-up,
add the special oil supplied with the pump.
Note
The piston flange is filled with oil for easy start-
up. The stroke-length adjustment knob must only
be adjusted if the gear oil has been added,
otherwise the oil will leak from the piston flange.
1. Slacken and remove the oil-filling screw (F).
2. Slowly add the hydraulic oil supplied with the pump through
the oil-filling opening (F) until the oil reaches the mark on the
oil dipstick.
3. Set the stroke-length adjustment knob (L) to "0".
Torque
[Nm]
8-10
10-12
13-15
8-10
10-12
50-54
50-54
50-54