Data Sheet

Bulletin 71.1:CP400
8
Figure 6. Type CP404IN Pressure Loaded Regulator with Slam-Shut Module and Internal Pressure Registration Operational Schematic
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
LOADING PRESSURE
M1068
TYPE VSX4 SLAM-SHUT MODULE
MAIN REGULATOR
TYPE 67CP LOADING REGULATOR
EXTERNAL CONTROL LINE PLUG
(DO NOT REMOVE IF UNIT IS
PRESSURIZED)
Type CP404 Slam-Shut Operation
The Type VSX4 slam-shut module on the Type CP404
regulator is a fast acting shutoff device that provides
overpressure (OPSO) or over and underpressure
(OPSO/UPSO) protection by completely shutting
off the ow of gas to the downstream system. See
Tables 8 and 9 for guidance regarding the typical
setpoints of the regulator and associated OPSO
and UPSO sets. The Type VSX4’s actions are
independent of the Type CP404 regulator and of
variations to the inlet pressure. The Type VSX4
provides the option of internal or external downstream
pressure registration. External registration requires a
downstream sensing line.
The Type VSX4 shutoff disk is normally in the open
(reset) position, see Figure 6. If the downstream
pressure below the slam-shut diaphragm increases (or
decreases) until it reaches the slam-shut setpoint, this
diaphragm moves upward (or downward) to release
the trip mechanism which allows the spring force on
the stem to push the disk against the seat, shutting
off all gas ow. Refer to the Type VSX4 Instruction
Manual to reset the slam-shut device.
In order for the Underpressure Shutoff (UPSO) of
any slam-shut to be triggered, the downstream pipe
pressure must drop below the UPSO setpoint. In the
case of a downstream line break, numerous factors
can prevent the downstream pipe pressure from
decreasing below the slam-shut UPSO setpoint.
These factors include the distance of pipe to the break,
the diameter of the pipe, size of the break and the
number of restrictions, such as valves, elbows and
bends, downstream of the regulator and/or slam-shut
device. Due to these factors additional protections
should be installed to stop ow in the event of a
line break.
Installation
The CP400 Series regulators may be installed in
any position. However, the spring case vent of the
67CP Series loading regulator, Type CP403 Monitor
Regulator and Type CP404 Slam-Shut device should
be pointed downward. Dimensions are shown in
Figure 8.
If gas escaping through the CP400 Series,
Type 67CPR token relief valve could constitute a
hazard, the pilot spring case vent must be piped to a
location where escaping gas will not be hazardous.
If the vented gas will be piped to another location,
use obstruction-free tubing or piping at least equal in