Fisher EZL Instruction Manual page 3

"D" PORT
SENSE
PRESSURE
"A" PORT
INLET PRESSURE
P590 SERIES PILOT
SUPPLY FILTER
E0944
INLET PRESSURE
OUTLET PRESSURE
LOADING PRESSURE
ATMOSPHERIC PRESSURE
INLET PRESSURE
OUTLET PRESSURE
Figure 2. Type EZL with Type 6352 Pilot and Type P590 Pilot Supply Filter Operational Schematic
ATMOSPHERIC PRESSURE
LOADING PRESSURE
Principle of Operation
Single-Pilot Regulator
The pilot-operated Type EZL (Figure 2 or 3) uses inlet
pressure as the operating medium, which is reduced
through pilot operation to load the actuator diaphragm.
Outlet or downstream pressure opposes loading
pressure in the actuator and also opposes the pilot
control spring.
When outlet pressure drops below the setting of
the pilot control spring, pilot control spring force on
the pilot diaphragm thus opens the pilot valve plug,
providing additional loading pressure to the actuator
diaphragm. This diaphragm loading pressure opens
the main valve plug, supplying the required flow to the
downstream system. Any excess loading pressure on
"C" PORT
LOADING PRESSURE
TYPE 6352 PILOT
TYPE EZL MAIN VALVE
the actuator diaphragm escapes downstream through
the bleed restriction in the pilot.
When the gas demand in the downstream system
has been satisfied, the outlet pressure increases.
The increased pressure is transmitted through
the downstream control line and acts on the pilot
diaphragm. This pressure exceeds the pilot spring
setting and moves the diaphragm, closing the orifice.
The loading pressure acting on the main diaphragm
bleeds to the downstream system through a bleed
restriction in the pilot.
Adjustment
The adjustment of the regulator is performed by
means of the pilot adjusting screw, which varies the
compression of the control spring. Adjustment is
performed while the regulator is in operation with
Type EZL
3