Grundfos DMH 251 Installation And Operating Instructions Manual page 31

13.6.4 Fitting the dosing head
• Fit the dosing head and cross-tighten the dosing head screws
(1q with 2q) using a torque wrench.
See section 11. Start-up / shutdown
Note
subsequent start-up!
13.6.5 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 %.
13.6.6 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 Replacing the diaphragm for dosing head with
for
13.7.1 Removing the dosing head
1. Close the suction and discharge lines and loosen the suction
2. Loosen the six dosing head screws (1q with 2q).
3. Remove the dosing head (2).
13.7.2 Replacing a double diaphragm
1. Clean the intermediate disk (3q), sealing rings (4q) and
2. Remove both clamping sleeves (6q) slightly using pliers.
3. Measure the outer wall thickness of both new diaphragms
Torque
[Nm]
8-10
10-12
13-15
8-10
10-12
50-54
50-54
50-54
1) The shape of the diaphragm varies depending on pump type.
Q1/Q2
3q - 5q
Caution
4. Fit both new diaphragms (Q1 and Q2) and the parts (3q - 5q)
double diaphragm
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.
and discharge valve connections.
covering rings (5q). After a diaphragm breakage, replace the
parts by new ones.
After a diaphragm breakage, replace the parts by new ones.
(Q1 and Q2): s1 < s2
(Q1) (Q2)
2q
1q
2
1)
Fig. 39 Installation of diaphragm
Pos. Components
1q Dosing head screw
2q Intermediate disk
2 Dosing head
See fig. 40
Observe correct installation of diaphragms (Q1
and Q2)! See fig. 40.
Fit the thinner diaphragm (Q1) on the dosing side
and the thicker diaphragm (Q2) on the oil side/
pump side!
in the correct order, as is shown in the diagrams (the clamping
sleeves (6q) are used for centring purposes).
.
s < s
1 2
Q1 3q - 5q Q2
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