Grundfos DMH 28 Series Installation And Operating Instructions Manual page 18

• For non-degassing media with a viscosity similar to water, the
pump can be mounted on the tank (observe the maximum
suction lift).
• Flooded suction preferred.
• For media with a tendency to sedimentation, install the suction
line with filter (13i) so that the suction valve remains a few
millimetres above the possible level of sedimentation.
6i
13i
Fig. 11 Tank installation
• Note for suction-side installation: Depending on the dosing
flow and the line length, it may be necessary to install a
properly sized pulsation damper (4i) immediately before the
pump suction valve.
Observe section 6.4 Approximate values when using
pulsation dampers
Note
system-specific calculation from our calculation
program.
4i
Fig. 12 Installation with suction-side pulsation damper
• Note for discharge-side installation: Depending on the dosing
flow and the line length, it may be necessary to install a
properly sized pulsation damper (4i) on the discharge side.
To protect the system, use pulsation dampers (8i) for
rigid piping longer than 2 metres and tubing longer
Note
than 3 metres, depending on pump type and size.
Fig. 13 Installation with discharge-side pulsation damper
18
p
10i
and, if necessary, request a
8i
Risk of damage to the system!
It is always recommended to use pulsation dampers
for large high-speed pumps!
Caution
Since the pulsation is influenced by many factors, a
system-specific calculation is essential. Request a
calculation from our calculation program.
• For degassing and viscous media: flooded suction.
• Install a filter in the suction line to prevent the valves from
becoming choked.
• To protect the dosing pump and the discharge line against
excessive pressure build-up, install a relief valve (6i) in the
discharge line.
6i
Fig. 14 Installation with relief valve
With open outflow of the dosing medium or a
counter-pressure below 2 bar
• Install a pressure-loading valve (7i) immediately before the
outlet or the injection unit.
A positive pressure difference of at least 2 bar must be ensured
between the counter-pressure at the injection point and the
pressure of the dosing medium at the pump suction valve.
• If this cannot be ensured, install a pressure-loading valve (7i)
in the discharge line.
p  1 bar
p  2 bar
7i
Fig. 15 Installation with pressure-loading valve
• To avoid the siphon effect, install a pressure-loading valve (7i)
in the discharge line and, if necessary, a solenoid valve (14i) in
the suction line.
14i
Fig. 16 Installation to avoid the siphon effect
p
10i
 1 bar
p -p
p
p - p >
1 bar
2 1 _
1
2 1
p
2