Integral Relief Valve; Function; Permissible Media; Connections - Grundfos DMX 226 Notice D'installation Et De Fonctionnement

10. Integral relief valve

10.1 Function

If the pump is the only pump in the system, the integral relief
valve (optional) protects the complete discharge side of the
discharge line system from an excessive pressure build-up.
The valve opens if the pressure rises above its set opening
pressure, and the dosing medium can return to the dosing tank.
In contrast to relief valves connected in series, the integral valve
also provides pump protection if the discharge valve is dirty or
blocked.

10.2 Permissible media

Warning
Dosing heads with integral relief valve must not be
used for abrasive or crystallising media.

10.3 Connections

1. Connect the suction line to the suction valve (A).
2. Connect the discharge line to the discharge valve (B).
3. Connect the overflow line to the relief valve (C) and allow the
medium to flow by gravity into the tank or to an appropriate
overflow.
C
Fig. 25 Connections
Warning
Never start the pump if the overflow line is not
correctly connected to the relief valve.

10.4 Setting of opening pressure

10.4.1 General
The opening pressure can only be set if a pressure gauge is
installed in the system between the pump and the next isolating
valve or pressure-loading valve.
Warning
Settings on the relief valve must only be carried out
by authorised and qualified personnel!
The opening pressure of the relief valve is factory-set to the
maximum pump counterpressure specified in the technical data.
The opening pressure during operation depends on various
factors, e.g. the flow, the stroke frequency of the pump, or the
counterpressure. If an exact setting is required, the relief valve
must be adapted to the local conditions.
Warning
Never set the opening pressure to values higher than
the maximum permissible operating pressure of the
dosing system and dosing pump.
Warning
When dosing dangerous media, observe the
corresponding safety precautions!
Wear protective clothing (gloves and goggles) when
working on the dosing head, connections or lines!
26
B
A
10.4.2 Setting the valve opening pressure
To change the factory-set opening pressure, proceed as follows:
The pump must be running.
1. Remove the cap from the top part of the relief valve.
2. Close the isolating valve after the pressure gauge.
3. When overflowing of the dosing medium is heard, read the
current opening pressure on the pressure gauge.
Fig. 26 Setting of opening pressure
4. Change the pressure as follows:
– To increase the pressure, turn the knob clockwise using
pointed pliers until the desired opening pressure is reached.
– To reduce the pressure, turn the knob counter-clockwise
using pointed pliers until the desired opening pressure is
reached.
5. Open the isolating valve after the pressure gauge.
6. Refit the cap.

10.5 Venting

The relief valve can also be opened manually, thus serving as a
venting valve at the same time. If manual venting is required
(e.g. nduring start-up or when the tank has been replaced),
proceed as follows:
• Turn the knob so that the smaller cut-out rests on the nub of
the dosing head (the rotary knob is then further away from the
dosing head). The valve spring is unloaded (position B).
• Once the pump has been completely vented, turn the knob
back into position A "Operating".
Fig. 27 Knob position

10.6 Fault finding chart

Fault Cause
Discharge line
blocked.
Permanent
output from
Relief valve incorrectly
the relief
set (too low).
valve.
Diaphragm faulty.
Relief valve dirty.
A Operating
Venting
B
Remedy
Check and possibly
correct the
discharge-side dosing
system.
Set the relief valve to a
higher opening pressure.
Replace the diaphragm.
Clean the relief valve.