Type FL
4
the main spring, in addition to pilot loading pressure, provide
loading pressure to keep the main valve diaphragm and plug
assembly tightly shut off.
When the inlet pressure rises above the set pressure,
the pressure on the pilot diaphragm overcomes the pilot
control spring and opens the pilot valve plug. The pilot
then exhausts the loading pressure from the main valve
diaphragm chamber. The pilot continuously exhausts gas
when the inlet pressure is above the set pressure. The inlet
pressure unbalance overcomes the main spring force and
opens the diaphragm and plug assembly.
As the inlet pressure drops below the set pressure, the pilot
control spring closes the pilot valve plug and the exhaust to
atmosphere stops. Force from the main spring, along with pilot
loading pressure, pushes the diaphragm and plug assembly
onto the knife-edged seat, producing tight shutoff.
Backpressure Regulator
As long as inlet pressure remains below setpoint, the pilot
control spring keeps the pilot valve plug closed. Inlet pressure
passes through the upper port around the upper portion of the
valve plug and then through the hollow passage in that valve
plug. Force from the main spring, in addition to pilot loading
pressure, provide downward loading pressure to keep the main
valve diaphragm and plug assembly tightly shut off. When inlet
pressure rises above the set pressure, pressure on the pilot
diaphragm overcomes the control spring to close the upper
port and stroke the valve plug to open the lower port. The pilot
exhausts loading pressure from the main valve diaphragm
chamber. Inlet pressure unbalance overcomes the main spring
force to open the diaphragm and plug assembly.
While the main valve is throttling, the upper port of the pilot
stays closed. The pilot exhausts only when it repositions the
main valve. As inlet pressure drops below setpoint, the pilot
control spring overcomes the diaphragm force to stroke the
valve plug down to close the lower port and open the upper
port. Force from the main spring, along with pilot loading
pressure, pushes the diaphragm and plug assembly onto the
knife-edged seat, producing tight shutoff.
Installation
!
WARNING
Personal injury or equipment damage, due
to bursting of pressure-containing parts may
result if this relief valve or backpressure
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.
Additionally, physical damage to the relief
valve or backpressure regulator could break
the pilot off the main valve, causing personal
injury and property damage due to bursting
of pressure-containing parts. To avoid such
injury and damage, install the regulator in a
safe location.
1.
Only personnel qualified through training and
experience should install, operate, and maintain a relief
valve or backpressure regulator. Before installation,
make sure that there is no damage to, or debris in
the main valve body or pilot. Also, make sure that all
tubing and piping are clean and unobstructed.
CAUTION
After assembly, check for shutoff and
leakage to atmosphere.
2. A Type FL relief valve or backpressure regulator may
be installed in any orientation, as long as flow through
matches the direction of the arrow on the main
valve body.
3. Apply a good grade of pipe compound to the external
pipeline threads for a screwed body, or use suitable
line gaskets for a flanged body. Use approved piping
procedures when installing the valve.
!
WARNING
When used in relief valve service, the Type FL
main valve and pilot both exhaust gas. In
hazardous or flammable gas service, personal
injury, death, or property damage may occur
due to fire or explosion of vented gas that
has accumulated. To prevent such injury or
damage, provide piping or tubing to vent the
gas to a safe location. The exhaust piping
must be designed and installed to guard
against excessive flow restriction. This piping
must be protected against condensation or
debris that could clog it.
For safety during shutdown, vent valves
are required immediately upstream
and downstream of the main valve on a
backpressure or bypass installation.
4. If system operation during maintenance is required,
install isolating and vent valves as needed.
