Functional Principle - Grundfos Vaccuperm VGB-103 Montage- Und Betriebsanleitung

4.2 Functional principle

The compact dosing unit comprises a vacuum regulator and a
dosing regulator.
4.2.1 Vacuum regulator
The vacuum regulator is a pressure reducing valve, which
reduces the overpressure from the chlorine tank side to the
negative pressure on the vacuum side. The valve at the vacuum
regulator opens, when after switching on the injector a sufficient
vacuum has built up at the outlet side.
The regulator is passive.
Note
Regulation of the dosing quantity has to be made at
other components of the system.
4.2.3 Vacuum chlorine gas dosing system
J
A
Fig. 10 Principle of a vacuum chlorine gas dosing system
Pos. Description
A Chlorine cylinder
B Vacuum regulator
C Dosing regulator
D Injector
E Adsorption filter (option)
F Safety valve (option)
G Change-over device (option)
H Water apparatus (option)
I Differential pressure regulator (option)
J Chlorine gas pressure line
K Chlorine gas vacuum line
Functioning of a vacuum chlorine gas dosing system
Handling, transport and storage of chlorine for the disinfection of
drinking and pool water are a challenge for plant engineers. This
is the reason why the vacuum principle has been used in dosing
systems for a long time. The pressure of the chlorine gas is
reduced to a vacuum.
This method prevents escape of chlorine gas. In the event of a
pipe burst no chlorine gas can escape, only ambient air is drawn
in.
Vacuum chlorine gas dosing systems are composed of three
principal components.
12
F
B
G
E
The vacuum regulator includes the following safety components.
• Safety relief valve: If the gas inlet valve of the regulator is
soiled, the safety relief valve opens. The gas escapes through
the overpressure line into the adsorption filter. If the filter is
full, the gas sensor triggers an alarm.
• If the vacuum on the negative pressure side collapses, the
valve in the regulator closes, and the chlorine gas flow is
stopped.
• Liquid trap (option): A liquid trap can be installed upstream in
order to prevent liquid chlorine from penetrating the regulator.
4.2.2 Dosing regulator
The dosing regulator regulates the chlorine gas flow with a valve.
The flow is read at the top of the ball in the measuring glass.
I
C
K
K
Vacuum regulator (B)
The vacuum regulator is a pressure reducing valve, which
reduces the overpressure from the chlorine tank side to the
negative pressure on the vacuum side. The valve opens, when a
sufficient vacuum has built up on the outlet side. Vacuum
regulators with pressure gauge and liquid trap are available for
more safety.
Dosing regulator (C)
The chlorine gas flow is adjusted with the dosing regulator. This
can be effected manually or automatically via motor control.
Injector (D)
Injectors have the task to bring chlorine gas into the water flow.
They operate according to the principle of water jet pumps. The
injector body comprises a nozzle with a successional diffuser.
Between the nozzle and the diffuser there is a narrow annular
gap, where chlorine gas is sucked out of the dosing line through
the injector head. A diaphragm non-return valve at the end of the
vacuum line prevents the ingress of water into the vacuum line.
Differential pressure regulator (I)
Regulates the difference of the pressures before and after the
rate valve to a constant value. Adjusted dosing flow stays
constant even when the injector vacuum varies.
D
H