Emerson FISHER CS200 Series Instruction Manual page 5

SECONDARY
SEAT DETAIL
ERAA03487
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
PRIMARY ORIFICE
PRIMARY DISK
SEATING SURFACE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
NORMAL OPERATION
SECONDARY SEATING
SURFACE
M1131
Type CS206 Secondary Seat Protection
with Bleed
The Type CS206 provides small bleed to the downstream
system as an indication that the Secondary Seat is
providing lockup. In the event that the primary orifice
and disk cannot provide lockup, the secondary seating
surface will move into contact with a metal disk. This
metal to metal interface will allow a small amount of gas
to bleed downstream thereby increasing outlet pressure
until the Internal relief valve begins to discharge gas
to the atmosphere. The odor of this discharged gas
provides an indication that the regulator is relying on
the Secondary Seat for overpressure protection. See
Table 5 for the Downstream Pressure Build-up of the
RELIEF V LVE STEM
VALVE STEM
RELIEF VALVE STEM
VALVE STEM
SECONDARY SEAT™ DETAILED VIEW
NORMAL LOCKUP
Figure 3. CS200 Series with Secondary Seat Protection
CP200 Series with Secondary Seat
ELASTOMERIC SECONDARY
SEATING SURFACE
SECONDARY SEAT
DEBRIS OBSTRUCTING
LOCKUP
Internal relief acting in conjunction with the Type CS206
Secondary Seat Assembly.
Types CS205 and CS206 Secondary Seat
Protection Limitations
Overpressure conditions can occur
in the downstream piping when the
Secondary Seat Protection is
installed. The Secondary Seat Protection
serves only as a backup to the primary
seat for lockup. Refer to the sections on
Overpressure Protection and Maintenance.
CONTROL SPRING
CS200 Series
PRESSURE RETAINING
PLUG (DO NOT REMOVE)
METALLIC SECONDARY
ORIFICE SEATING SURFACE
TYPE CS206
LOCKUP SECONDARY SEAT WITH
METAL TO METAL BLEED
Protection
TM
CAUTION
CONTROL SPRING
RELIEF VALVE
SPRING
RELIEF SEAT
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