Grundfos DMH 251 Installation And Operating Instructions Manual page 30

Suction side
1)
Fig. 36 DN 32 valve, suction side and discharge side
The O-rings must be correctly placed in the
specified groove.
Caution Observe the flow direction (indicated by an arrow
on the valve)!
Only tighten plastic valves by hand.
13.6 Replacing the diaphragm and gear oil for dosing
head with single diaphragm (no diaphragm
leakage detection)
Warning
Wear protective clothing (gloves and goggles)
when working on the dosing head, connections
or lines!
The dosing diaphragm should be replaced with
each gear oil change.
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.
Only use original Grundfos Alldos gear oil!
Note
For product number, see service instructions.
Pump type
DMH 251 Single/double
DMH 252, 10 bar Single/double
DMH 252, 16 bar Single/double
DMH 253 Single/double
DMH 254
DMH 254
DMH 255
DMH 255
DMH 257
DMH 257
Collect the gear oil in a container and dispose of
Note
it correctly.
30
Discharge side
2)
Version Description
1.3 l white oil
(Paraffin 55 DAB7)
1.3 l white oil
(Paraffin 55 DAB7)
1.3 l DHG 68
1.3 l DHG 68
Single 3.5 l DHG 68
Double 4.5 l DHG 68
Single 3.5 l DHG 68
Double 4.5 l DHG 68
Single 5.5 l DHG 68
Double 7.5 l DHG 68
13.6.1 Drain gear oil
Fig. 37 Drain gear oil
Pos. Components
B Locking screw
1b Gasket
F Oil-filling screw with dipstick
L Stroke-length adjustment knob
1. Unscrew the locking screw (B) and collect the gear oil in a
container.
2. Screw the locking screw (B) and the new gasket (1b) back in
and tighten securely.
Risk of leaking oil and damage caused by oil
loss!
Caution
For each oil change, a new flat gasket (1b) must
be fitted!
13.6.2 Removing the dosing head
1. Close the suction and discharge lines and loosen the suction
and discharge valve connections.
2. Loosen the six dosing head screws (1q with 2q).
3. Remove the dosing head (2).
13.6.3 Replacing a single diaphragm (no diaphragm leakage
detection)
• Remove the diaphragm and fit a new diaphragm (Q) on the
suction side. See fig. 38.
2q
1q
2
Fig. 38 Replacing a single diaphragm
Pos. Components
1q Dosing head screw
2q Intermediate disk
2 Dosing head
Q Diaphragm
F
L
1b
B
Q