Grundfos DMH 251 Installation And Operating Instructions Manual page 33

13.7.5 Filling with gear oil
Risk of leaking oil and damage caused by oil
loss!
Caution
For each oil change, a new flat gasket (1b) must
be fitted!
1. Check that the locking screw (B) is tightened.
2. Slacken and remove the oil-filling screw (F).
3. Set the stroke-length adjustment knob (L) to "0".
4. Slowly add the hydraulic oil through the oil-filling opening (F)
until the oil reaches the mark on the oil dipstick.
5. Wait 30 minutes.
6. Let the pump run for approx. 5 minutes with a stroke-length
setting of 0 %.
7. Let the pump run for approx. 10 minutes with a stroke-length
setting of 40 %.
13.7.6 Checking the oil level
1. Switch off the pump, check the oil level and add oil,
if necessary.
2. Refit the oil-filling screw (F).
After initial start-up and after each time the
diaphragm is changed, tighten the dosing head
screws.
Caution
After approximately 6-10 operating hours or
two days, 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
13.7.7 Cleaning the ball non-return valve
Only clean the ball non-return valve after
Note
a diaphragm breakage!
S
5s
4u
U
5u
T
Fig. 42 Contact pressure gauge
Torque
[Nm]
8-10
10-12
13-15
8-10
10-12
50-54
50-54
50-54
6s
3u
2)
2u
3u
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)
Removing the ball non-return valve and contact pressure
gauge
1. For pumps and pressure gauges in explosion-proof version,
unscrew the earth cable (4u).
2. Hold the connection piece (U) with a screwdriver and unscrew
the union nut (5u).
3. Unscrew the ball non-return valve (T) from the dosing head.
Cleaning the ball non-return valve
t7
t6
t5
t4
t3
t1
t2
t1
Fig. 43 Ball non-return valve
Pos. Components
t1 O-ring
t2 Ball non-return valve body
t3 Ball
t4 Spring sheath
t5 Pressure spring
t6 Screw part
t7 O-ring
1. Unscrew the screw part (t6) using round pliers.
2. Clean all parts. Replace faulty parts by new ones.
3. Re-assemble the ball non-return valve.
4. Refit the ball non-return valve (T).
5. Screw the contact pressure gauge (S) and connection piece
(U) back on.
6. For pumps and pressure gauges in explosion-proof version,
screw the earth cable (4u) back on.
Tighten the ball non-return valve and connection
Caution
piece by hand only.
33