PIETRO FIORENTINI NORVAL, Installation, Commisioning And Maintenance Instructions

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TECHNICAL MANUAL MT044
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1.0 INTRODUCTION
The scope of this manual is to provide the essential information for the installation, commissioning, disassembly,
re-assembly and maintenance of NORVAL regulators.
It is also appropriate to provide a brief illustration of the main features of the regulator and of its accessories.
1.1 MAIN FEATURES
The NORVAL pressure regulator is a pressure regulator for previously cleaned gaseous fluids and is suitable for
medium and low pressures.
The NORVAL is a normally open regulator and consequently opens in the event of:
- breakage of the main diaphragm
- no regulated pressure signal
The main specifications of this regulator are:
• Design pressure: up to 16 bar;
• Operating temperature range: -20 °C to 60 °C;
• Ambient temperature: -20 °C to 60 °C;
• Inlet pressure range bpe:
0.1 to 16 bar for DN 1" to 3"
0.1 to 8 bar for DN 4" to 8"
• Regulating range possible Wh:
0.0075 to 4.4 bar for DN 1" to 4"
0.012 to 1.8 bar for DN 6" to 8"
• Precision class AC: up to 5;
• Closing pressure class SG: up to 10.
1.2 OPERATION
NORVAL series regulators (Fig.1) are spring actuated devices with control of the downstream pressure by means
of an external sensing line 1.
The downstream pressure is controlled by means of the equilibrium between the action of the spring 2 and the
action exerted by the downstream pressure on the diaphragm 3.
The movement is transmitted by the shaft 4 to the obturator 5 which moves perpendicularly to the gas flow
direction. Hermetic tightness is ensured by a rubber gasket fixed to the obturator.
Regulation is therefore obtained from the confrontation between the load of the setting spring 2 and the thrust on
the diaphragm 3 deriving from the downstream pressure.
If during operation, for example, there is a drop in the downstream pressure Pa below the set-point (as a result of
an increase in the requested flow rate or a drop in the upstream pressure) an imbalance is created which causes
the obturat or 5 to open and therefore an increase in the flow until the downstream pressure
reaches the set-point again. Vice versa, when the downstream pressure rises above the set-point (as a result of
a drop in the requested flow rate or an increase in the upstream pressure) the obturator 5 closes and the flow
rate drops until the downstream pressure reaches the set-point again.