Operation - Emerson Fisher EZR series Instruction Manual

Type EZR
INLET PRESSURE
MODULATED PRESSURE
OUTLET PRESSURE

Operation

Regulator
The Type EZR is a pilot-driven, diaphragm/plug regulator.
Tight shutoff is achieved by the diaphragm/plug pushing
against the slotted cage, the force of the closing spring and
the inlet pressure.
• Opening
As the flow increases, the outlet pressure Pd
decreases on the outlet side of the regulator and on
the pilot diaphragm.
Due to the force of the spring, the pilot opens.
The pilot flow increases, the pressure loss through the
pilot restrictor increases.
The modulated pressure Pm decreases.
The force of the closing spring and that of the Pm
becomes inferior to that provoked by the Pu, the
regulator OPENS.
• Closing
As the flow decreases, the Pd increases outlet side of
the regulator.
The force of the pilot diaphragm is overcome by the force
of the spring, the pilot closes.
6
B18
Figure 8. Type EZR Operational Schematic
The pressure loss through the pilot restrictor decreases.
The force of the closing spring and that of the Pm
becomes superior to that provoked by the Pu, the
regulator CLOSES.
Slam Shut
The pressure of the zone to be protected (generally the pipeline
on the outlet side of the regulator and after the slam shut) is
sensed by the safety manometric box (BMS).
If the pressure exceeds the set tripping pressure, the release
relay frees the valve plug.
Due to the force of the closing spring and the fluid (trying to
close), the valve plug closes on the orifice.
The gas flow is obstructed until the fault has been corrected
and the mechanism box manually rearmed.
To reopen the valve plug an equal pressure balance on inlet
and outlet sides of the regulator is required.
The mechanism box is rearmed after opening the
internal bypass.
Rearming and balancing are achieved at the same time.