CP400 Series
6
Principle of Operation
Type CP400 Base Regulator Operation
The CP400 Series has spring-to-close construction.
The CP400 Series uses a 67CP Series loading
pressure regulator to supply loading pressure to the
top of the main diaphragm. Since the loading pressure
regulator controls the main regulator, adjustment
to the downstream pressure is made to the loading
pressure regulator. The load pressure supplied by the
loading regulator is constant and equal to the desired
downstream pressure plus the pressure required to
overcome the light closing spring.
Increasing Downstream Demand
As downstream demand increases, the outlet pressure
registering on the underside of the main diaphragm
decreases and the constant loading pressure above
the main diaphragm forces the diaphragm downward.
This downward diaphragm motion is transferred
through the lever causing the main disk to move away
from the orice seating surface to supply additional
ow downstream to the required demand.
Decreasing Downstream Demand
As downstream demand decreases the outlet pressure
registering on the underside of the main diaphragm
increases forcing the main diaphragm upward. This
upward motion is transferred through the lever causing
the main disk to move toward the orice seating surface
to reduce ow to meet the required demand.
Zero Downstream Demand (Lockup)
As downstream demand decreases further, the outlet
pressure registering under the main diaphragm
together with the closing spring act to close the
main disk against the orice seating surface. At this
point the loading regulator will continue to supply
a small amount of gas downstream that is equal to
the capacity of the bleed restriction in the diaphragm
assembly. As downstream demand decreases to zero
ow outlet pressure rises to meet the lock-up pressure
of the loading regulator. This causes the loading
regulator to lock up to stop all ow downstream.
Type numbers with a “T”, for example, Type CP400IT,
provide a token or low capacity relief. The Token relief
provides relief from minor overpressure caused by
nicks or dents on the orice or by thermal expansion
Figure 2. Type CP400IN with Internal Pressure Registration Operational Schematic
M1082
INLET PRESSURE
OUTLET PRESSURE
LOADING PRESSURE
ATMOSPHERIC PRESSURE
TYPE 67CP PRESSURE
LOADING REGULATOR
CLOSING SPRING
PUSHER POST
MAIN DIAPHRAGM
LEVER
VALVE STEM
VALVE DISK
ORIFICE
EXTERNAL CONTROL LINE
PLUG (DO NOT REMOVE
IF UNIT IS PRESSURIZED)
CONTROL SPRING
LOADING
REGULATOR
DIAPHRAGM
(12 pages)
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