Emerson EZH and EZHSO Series Pressure Reducing Regulators Arkusz Danych Pobierz pdf (Strona 5)

Bulletin 71.2:EZH and EZHSO

5

Pilot Descriptions

The EZH and EZHSO Series pressure reducing

regulators include a PRX Series pilot mounted on the

EZH and EZHSO Series main valves for pressure-

reducing or monitoring applications. PRX Series

pressure reducing pilots have the ability to handle a

wide range of setpoints from 14.5 to 1160 psig /

1.00 to 80.0 bar.

Type PRX/120: Outlet pressure range of 14.5 to

435 psig / 1.00 to 30.0 bar. The Type PRX/120 can be

used as the pilot on single stage pressure reducing

regulators, as the monitor pilot or as the working pilot

in wide-open monitor systems or as the working pilot

for monitoring and working regulators in the working

monitoring systems.

Type PRX/120-AP: Outlet pressure range of 435 to

1160 psig / 30.0 to 80.0 bar. The Type PRX/120-AP can

be used as the pilot on single stage pressure reducing

regulators, as the monitor pilot or as the working pilot

in wide-open monitor systems or as the working pilot

for monitoring and working regulators in the working

monitoring systems.

Type PRX/125: Identical to the Type PRX/120 except

the restriction screw is removed. The Type PRX/125

can only be used as the monitor override pilot on

working monitor applications.

Type PRX/125-AP: Identical to the Type PRX/120-AP

except the restriction screw is removed. The

Type PRX/125-AP can only be used as the monitor

override pilot on working monitor applications.

Pilot Supply Filter Regulator

The Type SA/2 pilot supply lter regulator provides a

constant supply pressure to the PRX Series pilot that

is approximately 45 psig / 3.1 bar over set pressure.

The Type SA/2 has an integral 5-micron lter.

Principle of Operation

Type EZH - Spring-To-Close Version

Type EZH Single-Pilot Regulator

The pilot-operated Type EZH (Spring-to-Close

Version) will fail in close position in the case of main

valve diaphragm failure or lack of supply pressure to

the pilot (see Table 4 for Failure Mode Analyses).

The pilot-operated Type EZH (Spring-to-Close Version)

(Figure 2) uses inlet pressure as the operating

medium, which is reduced through pilot operation

to load the regulator actuator diaphragm (lower

chamber). Outlet or downstream pressure opposes

loading pressure in the actuator and also opposes the

pilot control spring.

Pilot is supplied with pressure coming from pre-

regulator Type SA/2, which reduces inlet pressure to

the constant value of outlet pressure plus approximately

45 psi / 3.1 bar.

When outlet pressure drops below the setting of the

pilot control spring, pilot control spring force on the pilot

lower diaphragm opens the pilot valve disk, providing

additional loading pressure to the lower chamber of the

regulator actuator diaphragm. This diaphragm loading

pressure opens the main valve disk, supplying the

required ow to the downstream system. Any excess

loading pressure in the lower chamber of the actuator

diaphragm and on Type PRX escapes downstream

through the bleed restriction in the pilot.

When the gas demand in the downstream system

has been satised, the outlet pressure increases.

The increased pressure is transmitted through the

downstream control line and acts under the lower pilot

diaphragm. This pressure exceeds the pilot spring

setting and moves the Type PRX lower diaphragm,

closing the orice and interrupting the loading pressure

supply to the lower chamber of the regulator actuator

diaphragm. The excess loading pressure acting under

the regulator actuator diaphragm and on the Type PRX

lower pilot bleeds to the downstream system through a

bleed restriction in the pilot.

A check valve, set at 75 psi / 5.2 bar is installed

between outlet pressure and loading pressure impulse

lines; this valve will protect the main valve diaphragm

assembly from excessive differential pressure during

startup if incorrect start up procedures are used.

Do not exceed 75 psi / 5.2 bar differential pressure

between the outlet pressure and loading pressure

impulse lines.

Type EZHSO - Spring-To-Open Version

Type EZHSO Single-Pilot Regulator

The pilot-operated Type EZHSO (Spring-to-Open

version) will fail in open position in the case of main

valve diaphragm failure or lack of supply pressure to

the pilot (see Table 4 for Failure Mode Analyses).

Emerson EZH and EZHSO Series Pressure Reducing Regulators Arkusz Danych Strona 5

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Emerson EZH and EZHSO Series Pressure Reducing Regulators Arkusz Danych Strona 5

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