Emerson CS400 Datasheet download pdf (Page 7)

Bulletin 71.1:CS400

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

Refer to Figures 4 and 5. When downstream demand

decreases, the pressure under the diaphragm

increases. This pressure overcomes the regulator

setting (which is set by the regulator control spring).

Through the action of the pusher post assembly, lever

and valve stem, the valve disk moves closer to the

orice and reduces gas ow. If demand downstream

increases, pressure under the diaphragm decreases.

Spring force pushes the pusher post assembly

downward, the valve disk moves away from the

orice and the gas ow increases downstream as the

regulator opens in response to the decreased pressure

underneath the diaphragm.

The Type CS400IR regulator includes an internal

relief valve for overpressure protection. If the

downstream pressure exceeds the regulator setting

by 7 to 28 in. w.c. / 17 to 69 mbar (depending on the

main spring used), the relief valve opens and excess

gas is vented through the stabilizer vent in the upper

spring case.

The Types CS400IT and CS400ET provide a low

capacity/token relief. Token relief provides relief

from minor overpressure caused by nicks or dents

on the orice or by thermal expansion 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 CS403 combines the operation of a conventional

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

see Figures 6 and 7. 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 Table 6 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 regulator 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.



The Type VSX4 slam-shut module on the Type CS404

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 7

and 8 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 CS404 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 Figures 8 and 9. 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. To reset the slam-shut after

gas has been shutoff, reference the Type VSX4

Instruction Manual for additional details.

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.

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Reducing Regulators 1
Bulletin 71.1:CS400 10

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Emerson CS400 Datasheet Page 7

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