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Application
To obtain an accurate top pressure system for remote control
in tanks during filling, storage and emptying conditions. The
constant pressure system is applicable for control of one or
more tanks working with the same top pressure.
Construction
The Constant pressure system is a modulating system that
comprises a Pressure Supply (PS) valve and a Pressure
Exhaust (PE) valve, which can be connected to a tank top
system by means of a T-piece, a mixproof T-valve or directly
installed in the gas line.
The system is available in two standard sizes:
11⁄2 and 2, with the following recommended capacities:
Working pressures: 0,5 - 4 bar.
Gas supply: 1-2 bar above working pressure
max. 6 bar (86 psi).
Please see PD leaflets on the individual PE, PS and mixproof
T-valve for further detailed information.
Operation
The PS and PE valves are controlled by means of the same
set point pressure, which is identical to the required working
pressure. The set point pressure is applied to the top of each
valve and together with the reference pressure (actual tank
pressure connected to the lower side of the PS valve) the two
valves will maintain the preset tank pressure automatically.
Gas supply takes place through the PS valve, which will open
when working pressure falls below set point pressure, i.e.
when tank is emptied.
When working pressure exceeds the set point pressure, i.e.
during tank filling, the PS valve will close and the PE valve will
open and blow off for collection or atmospheric discharge.
A dead band built into the PS valve ensures that the two
valves are never open simultaneously and thus avoiding gas
losses.
Dimension Filling/Emptying
Speed
11⁄2 Max. 500 hl/h
2 Max. 1000 hl/h |
 Benefits
Automatic control of working pressure
Reduced loss of CO2
Low investments and fast pay back in terms of
reduced CO2 usage
Fully CIPable of all parts in contact with product
Easy variation of set point pressure
Applicable to manual or computerized control
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When the PS and PE valves are
mounted together with a
mixproof T-valve, CIP of gas mains and valves can take place
independently of vessel cleaning and with product in the tank.
Cleaning
When including the Constant pressure system in the CIP of
gas mains, the connection to the tank top must be closed
with a mixproof T-valve.
Furthermore, a 6 mm change-over valve can be included in
the pressure transmission pipe of the PS valve to secure
cleaning of the above pipe and to avoid CIP liquid going into
the housing.
With CIP flow in the same direction as gas flow and set point
pressure still on, the PE valve should further have a control
signal for force opening to establish correct cleaning conditions.
In special applications cleaning of the PE valve should take
place from the CIP nozzle in the valve housing. In such cases
the valve should also be force opened (see PD leaflet on PE
valve).
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Mounting
Vertical mounting of the PE and PS valves is recommended.
Under special circumstances other positions of the PE valve
are acceptable. Please note that connection of the PS valve
always requires a conical pipe connection on tank side for
free operation of valve disc (see PD leaflet on the PS valve).
Maintenance
It is important that the valves are inspected regularly. The PE
valve and the PS valve are equipped with small holes in the
side of the housing. These holes will indicate a possible leakage.
Routine checks for leakages of gas or liquid from these
holes should be made regularly. Gaskets and O-rings to be
replaced approx. every 2-3 years.
Extra Equipment
6 mm CIP valves for (PS) pressure transmission pipe
& PE valve
Connecting mixproof T-valve
Connecting butterfly valve and T-piece
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