Emerson EZH and EZHSO Series Pressure Reducing Regulators Ficha de datos descargar pdf (Pagina 8)

Bulletin 71.2:EZH and EZHSO

Wide-Open Monitoring Systems (Figure 4)

There are two types of wide-open monitoring systems:

upstream and downstream. The difference between

upstream and downstream monitoring is that the

functions of the regulators are reversed. Systems can

be changed from upstream to downstream monitoring

and vice-versa, by simply reversing the setpoints

of the two regulators. The decision to use either an

upstream or downstream monitoring system is largely

a matter of personal preference or company policy.

In normal operation of a wide-open conguration,

the working regulator controls the system’s outlet

pressure. With a higher outlet pressure setting, the

monitor regulator senses a pressure lower than its

setpoint and tries to increase outlet pressure by going

wide-open. If the working regulator fails, the monitoring

regulator assumes control and holds the outlet

pressure at its outlet pressure setting.

Figure 4 shows an upstream wide-open monitor

Type EZH (fail-to-close) and a downstream active

regulator Type EZHSO (fail-to-open). In this

installation, if the Type EZHSO regulator no longer

controls downstream pressure, it will remain open,

letting the Type EZH monitor regulator take control

of the downstream pressure. Should the Type EZH

fail, the monitor regulator will close and protect the

downstream system from overpressure condition.

Working Monitoring Regulators (Figure 5)

In a working monitoring system, the upstream

regulator requires two pilots and it is always the

monitoring regulator. The additional pilot permits

the monitoring regulator to act as a series regulator

to control an intermediate pressure during normal

operation. In this way, both units are always operating

and can be easily checked for proper operation.

In normal operation, the working regulator controls

the outlet pressure of the system. The monitoring

regulator’s working pilot controls the intermediate

pressure and the monitoring pilot senses the system’s

outlet pressure. If the working regulator fails, the

monitoring pilot will sense the increase in outlet

pressure and take control.

Working monitor installations require a Type EZH or

EZHSO main valve with a Type PRX/120 or

PRX/120-AP working pilot and a Type PRX/125

or PRX/125-AP monitoring pilot for the upstream

regulator and a Type EZH or EZHSO with the

appropriate Type PRX/120 or PRX/120-AP pilot for the

downstream regulator.

Figure 4. Wide-Open Monitoring System Operational Schematic

INLET PRESSURE

LOADING PRESSURE

PILOT SUPPLY PRESSURE

OUTLET PRESSURE

ATMOSPHERIC PRESSURE

TYPE PRX:

S - BLEED PORT

B - SUPPLY PORT

L - LOADING PORT

A - SENSING PORT

TYPE SA/2:

V - SENSING PORT

R - PILOT SUPPLY PORT

M - INLET PORT

TYPE EZH TYPE EZHSO

TYPE SA/2

CHECK VALVE

TYPE SA/2

TYPE PRX

L A

M1164

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