Europe,
Middle
East,
and
Africa
Only
Type FL
8
Figure 6.
Types BFL and FL Operational Schematic
BFL/
FL/
INLET PRESSURE, Pu
REGULATOR MOTORIZATION
PRESSURE, Pm
MONITOR MOTORIZATION
PRESSURE, Pm
DOWNSTREAM OR IN A
SAFE AREA, Pb
STABILIZED PRESSURE, Pup
PS/80
PILOT
MONITOR
REGULATOR
OUTLET PRESSURE, Pd
SLAM-SHUT
PS/79
PILOT
A
A
A
OPERaTION
The purpose of this device is to protect the system against
possible overpressure, while keeping the reduction line in service.
The monitor controls downstream pressure at the same point
as the main regulator and is set a little higher than the latter.
Under normal operation, the monitor is fully open as it
detects a pressure value lower than it’s set value. If, due
to any regulator fault, downstream pressure increases,
when it exceeds the tolerated level, the monitor comes into
operation and adjusts pressure to it’s own set value.
Slam-shut Device
The slam-shut device has a shutter and individual seat. It
functions independently of the regulator/monitor. The shutter
can only be hand-opened, by rotating the slam-shut reset
shaft counter clockwise. To keep the shutter open, the
actuator-pilot series OS/80X or OS/80X-PN is used. Both
series are designed to operate on maximum and minimum,
maximum only, or minimum only pressure.
When the system’s downstream pressure is at normal operating
value, the actuator-pilot remains set and prevents the slam-shut
reset shaft from turning by keeping the slam-shut shutter open.
When downstream pressure varies beyond it’s set limits,
the actuator-pilot releases the reset shaft and the shutter is
closed by the thrust of the spring.
Regulator
The Diaphragm Unit (permanently connected to the shutter)
divides the regulator control head into two chambers.
One of the chambers is connected to regulated
pressure (Pd), and the other to motorization pressure (Pm)
produced by the pilot according to pressure downstream.
Due to underpressure, the regulator spring acts on the
diaphragm unit and closes the shutter.
The shutter moves to an open position when the force
produced by motorization pressure (Pm) acting on the
diaphragm unit becomes greater than the force produced
by downstream regulated pressure (Pd) added to the load
of the regulator spring. The shutter stays idle when the
two forces are equal, under these conditions, downstream
pressure is equal to the system’s set value.
Any change in requested flow-rate produces a variation in
downstream regulated pressure and the regulator controlled
by the pilot opens or closes to deliver the requested flow-
rate while keeping downstream pressure stable.
monitor
The Monitor or emergency regulator is used as a safety
device in gas pressure reduction systems.
