Principle Of Operation - Emerson FISHER CS200 Series Instruction Manual

CS200 Series
ERAA03487
Figure 2. Type CS200IR Pressure Reducing Regulator with Internal Relief Operational Schematic
INLET PRESSURE

Principle of Operation

OUTLET PRESSURE
ATMOSPHERIC PRESSURE
Type CS200 Base Regulator Operation
Refer to Figure 2. When downstream demand decreases,
the pressure under the diaphragm increases. This pressure
overcomes the regulator setting (which is set by the control
spring). Through the action of the pusher post assembly,
lever, and valve stem, the valve disk moves closer to the
orifice and reduces gas flow. If demand downstream
increases, pressure under the diaphragm decreases.
Spring force pushes the pusher post assembly downward
and the valve disk moves away from the orifice.
CS200 Series with Internal Relief
Refer to Figure 2. The option for Internal Relief is offered
on the Types CS200 and CS205 and is standard on the
Type CS206. Internal relief is used to help minimize
overpressure. Any outlet pressure above the start-to-
discharge point of the non-adjustable relief spring moves the
diaphragm off of the relief seat, allowing excess pressure
to discharge through the vent. Typical start-to-discharge
values are 7 inches w.c. to 1.5 psi / 17 to 103 mbar above
the outlet pressure setting, depending on control spring and
if the Secondary Seat™ option is present. Refer to Table 5
for Type CS205 lockup values and Type CS206 downstream
build-up values. Refer to the CS200 Series Bulletin for
additional information regarding Internal Relief start-to-
4
RELIEF VALVE STEM
DISK
VALVE STEM
LEVER
ORIFICE
discharge both with and without Secondary Seat Protection.
If emergency conditions should exist that prevent normal
operation of the regulator or internal relief valve, the relief
valve stem acts as a secondary travel stop contacting the
underside of the closing cap and stopping the upward travel
of the relief seat. When the diaphragm continues to rise as
downstream pressure builds, the diaphragm lifts off of the
relief seat to provide relief operation.
Type CS205 with Secondary
Seat Protection
Refer to Figure 3. The Type CS205 provides
Secondary Seat Protection. As downstream demand
decreases and downstream pressure rises to the regulator
pressure lockup value, the regulator will lock up. If,
however, damage has occurred to the primary disk, to the
primary orifice's seating surface, or debris has become
lodged between the primary disk and primary orifice,
the outlet pressure will continue to rise. This additional
pressure causes the primary disk to apply additional force
to the orifice seating surface, which causes the Secondary
seating surface to move toward the Secondary disk or
sealing surface. If downstream demand decreases to
zero, then the secondary seating surface will contact
the sealing surface to provide lockup. Refer to
Table 5 for approximate lockup values provided by the
Secondary Seat.
WIRE SEAL (OPTIONAL)
CONTROL SPRING
RELIEF VALVE SPRING
DIAPHRAGM
RELIEF SEAT
PRESSURE RETAINING PLUG
(DO NOT REMOVE)
PUSHER POST