English (GB)
26
After start-up
Torques
8.4 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 gear oil!
For product numbers, see "Service kit catalogue" on
www.grundfos.com
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]
4
5
10
13
16
18
25
28
T
M
03
6
4
64
16
12
TM
03
64
65
45
06
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
