Tube / Pipe Lines; Connecting The Suction And Discharge Lines - Grundfos DMH 25X Installation And Operating Instructions Manual

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 ≥ 2bar
7i
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.
p
14i
Installation to avoid the siphon effect
Related information
6.4 Approximate values when using pulsation dampers
p - p
> 1 bar
_
1
2 1
p
2

6.7 Tube / pipe lines

6.7.1 General
Warning
To protect the dosing system against excessive pressure
build-up, install a relief valve in the discharge line.
Only use the prescribed line types!
All lines must be free from strain!
Avoid loops and buckles in the tubes!
Keep the suction line as short as possible to avoid cavita-
tion!
If necessary, use swept bends instead of elbows.
Observe the chemical manufacturer's safety instructions
when handling chemicals!
Make sure that the pump is suitable for the actual dosing
medium!
The flow must run in the opposite direction to gravity!
The resistance of the parts that come into contact with the
media depends on the media, media temperature and op-
erating pressure. Ensure that parts in contact with the me-
Caution
dia are chemically resistant to the dosing medium under
operating conditions!

6.8 Connecting the suction and discharge lines

Warning
All lines must be free from strain!
Only use the prescribed line types!
• Connect the suction line to the suction valve.
- Install the suction line in the tank so that the foot valve
remains 5 to 10 mm above the bottom of the tank or the
possible level of sedimentation.
• Connect the discharge line to the discharge valve.
Connection of hose lines
• Push the hose firmly on the connection nipple and, depending
on the connection, secure using a connection counterpart or
hose clip.
• Fit the gasket.
• Screw the hose on the valve using the union nut.
Connection of hose lines
27