Monitoring Systems; Installation - Emerson Tartarini FL Series Instruction Manual

Type FL

Monitoring Systems

Monitoring regulation is overpressure protection by
containment, therefore, there is no relief valve to vent
to the atmosphere. When the working regulator fails
to control the pressure, a monitor regulator installed
in series, sensing the downstream pressure, goes
into operation to maintain the downstream pressure
at a slightly higher than normal pressure. During an
overpressure situation, monitoring keeps the customer
on line. Also, testing is relatively easy and safe. To
perform a periodic test on a monitoring regulator,
increase the outlet set pressure of the working
regulator and watch the outlet pressure to determine if
the monitoring regulator takes over at the appropriate
outlet pressure.
Wide-Open Monitoring Systems (Figure 3)
There are two types of wide-open monitoring
systems: upstream and downstream. The difference
between upstream and downstream monitoring is
that the functions of the regulators are reversed.
Systems can be changed from upstream to
downstream monitoring and vice-versa, by simply
reversing the setpoints of the two regulators. The
decision to use either an upstream or downstream
monitoring system is largely a matter of personal
preference or company policy.
In normal operation of a wide-open configuration,
the working regulator controls the system's outlet
pressure. With a higher outlet pressure setting, the
monitor regulator senses a pressure lower than its
setpoint and tries to increase outlet pressure by
going wide open. If the working regulator fails, the
monitoring regulator assumes control and holds the
outlet pressure at its outlet pressure setting.
Figure 3 shows a Type FL Wide-Open Monitor
configuration with a Type PRX/131 pilot included. The
Type PRX/131 pilot is referred to as a quick dump
or booster pilot as it helps to boost the pressure
release. The Type PRX/131 is fitted to the monitor
regulator and allows the regulator to operate faster.
When the Type PRX/131 detects an increase in
downstream pressure, it allows the Type FL monitor
regulator to release pressure off the downstream
side of the diaphragm so it closes faster. The
Type PRX/131 pilot is always attached to the monitor
regulator in a Wide Open Monitor or Working Monitor
configuration. The Type PRX/131 should have a
setpoint about 5 to 10 psig / 0.34 to 0.69 bar above
the monitor pilot setpoint.
6
Working Monitoring Regulators (Figure 3)
In a working monitoring system, the upstream
regulator requires two pilots and it is always the
monitoring regulator. The additional pilot permits
the monitoring regulator to act as a series regulator
to control an intermediate pressure during normal
operation. In this way, both units are always operating
and can be easily checked for proper operation.
In normal operation, the working regulator controls
the outlet pressure of the system. The monitoring
regulator's working pilot controls the intermediate
pressure and the monitoring pilot senses the system's
outlet pressure. If the working regulator fails, the
monitoring pilot will sense the increase in outlet
pressure and take control.
note
The working regulator must be rated
for the maximum allowable operating
pressure of the system because this will
be its inlet pressure if the monitoring
regulator fails. also, the outlet pressure
rating of the monitoring pilot and any
other components that are exposed to
the intermediate pressure must be rated
for full inlet pressure.
Working monitor installations require a Type FL main
valve with a Type PRX/120 or PRX/120-AP working
pilot and a Type PRX/125 or PRX/125-AP monitoring
pilot for the upstream regulator and a Type FL with the
appropriate Type PRX/120 or PRX/120-AP pilot for the
downstream regulator.

installation

WaRning
!
Personal injury or equipment damage,
due to bursting of pressure-containing
parts may result if this regulator is
overpressured or is installed where
service conditions could exceed the
limits given in the Specification section
and on the appropriate nameplate or
where conditions exceed any rating of the
adjacent piping or piping connections.
To avoid such injury or damage, provide
pressure-relieving or pressure-limiting
devices to prevent service conditions
from exceeding those limits. also, be
sure the installation is in compliance with
all applicable codes and regulations.