Emerson Fisher 67C Series - Overpressure Protection

Type XXXX
MXXXX
Month Year
Type XXXX
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INTERMEDIATE PRESSURE
PILOT SUPPLY PRESSURE
LOADING PRESSURE
TYPE 67C OR 67CS
TYPE 67CR OR 67CSR
TYPE 67CFR OR 67CFSR
SMART BLEED™ OPTION
TYPES 67CFR AND 67CFSR
W7433
TYPE 67CF OR 67CFS
Figure 2. 67C Series Operational Schematics
W8442_10/2008
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INTERMEDIATE PRESSURE
PILOT SUPPLY PRESSURE
VACUUM PRESSURE
TANK PRESSURE
VAPOR PRESSURE
LOADING PRESSURE
Internal Relief (Types 67CR, 67CSR,
67CFR and 67CFSR)
If for some reason, outside of normal operating
conditions, the downstream pressure exceeds the
setpoint of the regulator, the force created by the
downstream pressure will lift the diaphragm until the
diaphragm is lifted off the relief seat. This allows flow
through the token relief. The relief valve on the
Type 67CR, 67CSR, 67CFR or 67CFSR is an
elastomer plug that prevents leakage of air from the
downstream to atmosphere during normal operation,
thereby conserving plant air.
Smart Bleed Airset
In some cases, it is desired to exhaust downstream
pressure if inlet pressure is lost or drops below the
setpoint of the regulator. For example, if the regulator
is installed on equipment that at times has no flow
demand but is expected to backflow on loss of inlet
pressure. The Types 67CFR and 67CFSR can be
orderedwiththeSmartBleedoptionwhichincludes
an internal check valve for this application. During
operation, if inlet pressure is lost or decreases below
the setpoint of the regulator, the downstream pressure
will back flow upstream through the regulator and
check valve. This option eliminates the need for a fixed
bleed downstream of the regulator, thereby conserving
plant air.
Note
During normal operation the check valve’s
metal to metal seat allows limited flow
through the regulator from the inlet to
outlet, even when there is no downstream
demand. To prevent downstream pressure
buildup, the Smart Bleed option is only
available with the internal relief version of
the 67C Series.
Overpressure Protection
The 67C Series regulators have maximum outlet
pressure ratings that are lower than their maximum
inlet pressure ratings. A pressure relieving or pressure
limiting device is needed if inlet pressure can exceed
the maximum outlet pressure rating.
Types 67CR, 67CSR, 67CFR and 67CFSR have
a low capacity internal relief valve for minor seat
leakage only. Other overpressure protection must be
provided if the maximum inlet pressure can exceed
the maximum pressure rating of the downstream
equipment or exceeds the maximum outlet pressure
rating of the regulator.
3
67C Series