Emerson CP400 Instruction Manual download pdf (Page 7)

CP400 Series

Figure 3. Type CP403IT Pressure Loaded Regulator with True-Monitor™ and Internal Pressure Registration Operational Schematic

TYPE 67CPR PRESSURE

LOADING REGULATOR

WIDE-OPEN INTEGRAL MONITOR REGULATOR

PRIMARY REGULATOR

ADJUSTING

SCREW

CONTROL

SPRING

MONITOR

LEVER

GUIDED

STEM

MONITOR

DISK

VALVE

STEM

M1067

EXTERNAL CONTROL LINE PLUG

(DO NOT REMOVE IF UNIT IS

PRESSURIZED)

OPENING

SPRING

EXTERNAL CONTROL LINE

PLUG (DO NOT REMOVE IF

UNIT IS PRESSURIZED)

of gas in the downstream line. Token relief also

provides a token or signal, in the form of odor, that an

overpressure situation is occurring.

Type CP403 Integral Monitor Operation

Type CP403 combines the operation of a conventional

two-regulator wide-open monitor set into one body, see

Figure 3. The Integral True-Monitor is installed on the

inlet side of the body and serves to throttle ow and

maintain an acceptable downstream pressure in the case

where the Primary regulator fails to regulate downstream

pressure. During normal operation, the Integral Monitor

is in a wide-open state as its setpoint is set higher than

the primary regulator. See Tables 7 and 8 for guidance

regarding the setpoints of the regulator and associated

Integral Monitor sets. If the downstream pressure should

rise to the setpoint of the internal monitor due to loss of

pressure control by the primary regulator, the Integral

Monitor will assume control and regulate the ow to the

downstream system. See the Type TM600 Instruction

Manual for additional details of operation.

If a Token relief is present, the token relief will relieve

a small amount of gas to the atmosphere as an

indication that the Integral monitor is controlling the

downstream pressure.

Type CP404 Slam-shut Operation

The Type VSX4 slam-shut module on the Type CP404

regulator is a fast acting shut-off 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 9

and 10 for guidance regarding the typical setpoints

of the regulator and associated OPSO and UPSO

settings. 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 shut-off disk is normally in the open

(reset) position, see Figure 4. 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.

INLET PRESSURE

OUTLET PRESSURE

LOADING PRESSURE

ATMOSPHERIC PRESSURE

1 2 3 4 5 6 7 8 9 10 11 12 ... 19 20

CP400 Series 1

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Emerson CP400 Instruction Manual Page 7

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