26
1. Connect the electrical power supply.
2. Depending on the installation, start the pump, where possible,
without counter-pressure.
See installation example for easy deaeration of the dosing head
in section
9. Installation.
3. Set the stroke-length adjustment knob (L) to 0 %.
4. Let the pump run for approx. 5 minutes.
5. Check the oil level.
– Set the stroke-length adjustment knob (L) to 40 %.
– Let the pump run for approx. 10 minutes with a stroke-length
setting of 40 %.
– Switch off the pump, check the oil level and add oil,
if necessary.
– Refit the oil-filling screw (F).
The pump is now ready for operation.
After start-up
Torques
11.4 Setting the pressure relief valve
The pressure relief valve is set to the pressure given by the
customer, or to the rated pressure (maximum counter-pressure).
The opening pressure can be set to a lower value by the
customer.
Opening pressure of the pressure relief valve
Setting the opening pressure
• To set the operating pressure, a pressure gauge must be
installed in the discharge line and an isolating valve must be
installed after the pressure gauge.
• To set the pressure relief valve, use a screwdriver.
Fig. 28 Setting the opening pressure
Set the pressure relief valve as follows:
1. Close the isolating valve after the pressure gauge.
2. Remove the cover (1m) from the pressure relief valve.
3. Start the pump.
4. Using a screwdriver, slowly turn the adjusting screw (2m) of
the pressure relief valve counter-clockwise until the desired
opening pressure is obtained.
Fig. 29 Setting the pressure relief valve
5. Replace the cover of the pressure relief valve.
6. Open the isolating valve after the pressure gauge.
Warning
Risk of injury caused by squirting oil!
Oil may squirt from the oil deaeration when the
pump is running. Do not completely unscrew the
oil deaeration screw.
Wear protective clothing (gloves and goggles)
when working on the dosing head, connections
or lines!
Note
Rod length of oil dipstick: 35 mm.
Immersion depth to marking: approx. 5 mm.
Note
Check the oil level at least every two weeks and
add oil, if necessary.
Only use original Grundfos Alldos gear oil!
For product number, see service instructions.
Pump type Version Description
DMH 254 Single 3.5 l DHG 68
DMH 254 Double 4.5 l DHG 68
DMH 255 Single 3.5 l DHG 68
DMH 255 Double 4.5 l DHG 68
DMH 257 Single 5.5 l DHG 68
DMH 257 Double 7.5 l DHG 68
Caution
After initial start-up and after each time the
diaphragm is changed, tighten the dosing head
screws.
After approximately 6-10 operating hours or
two days, cross-tighten the dosing head screws
using a torque wrench.
Pump type
Torque
[Nm]
DMH 254 50-54
DMH 255 50-54
DMH 257 50-54
Rated pressure of the pump
[bar]
Opening pressure of the
pressure relief valve
[bar]
45
10 13
16 18
25 28
TM03 6464 4506TM03 6465 4506
Caution
Risk of damage to the pump or system!
When blocked, the pressure relief valve does not
work properly and can produce pressures of
several hundred bar in the pump or system.
Do not block the pressure relief valve during
adjustments!
2m
1m
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