Setting The Pressure Relief Valve - Grundfos DMH 25 Series Installation And Operating Instructions Manual

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!
Rod length of oil dipstick: 35 mm.
Note
Immersion depth to marking: approx. 5 mm.
Check the oil level at least every two weeks and add
oil, if necessary.
Only use original Grundfos gear oil!
Note
For product numbers, see "Service kit catalogue" on
www.grundfos.com
Pump type Version
DMH 254 Single
DMH 254 Double
DMH 255 Single
DMH 255 Double
DMH 257 Single
DMH 257 Double
After start-up
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 254
DMH 255
DMH 257

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
Rated pressure of the pump
[bar]
4
10
16
25
26
Description
3.5 l DHG 68
4.5 l DHG 68
3.5 l DHG 68
4.5 l DHG 68
5.5 l DHG 68
7.5 l DHG 68
Torque
[Nm]
50-54
50-54
50-54
Opening pressure of the
pressure relief valve
[bar]
5
13
18
28
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
Risk of damage to the pump or system!
When blocked, the pressure relief valve does not
work properly and can produce pressures of several
Caution
hundred bar in the pump or system.
Do not block the pressure relief valve during
adjustments!
5. Replace the cover of the pressure relief valve.
6. Open the isolating valve after the pressure gauge.
1m
2m