Emerson EZH and EZHSO Series Pressure Reducing Regulators Ficha de datos descargar pdf (Pagina 7)

Bulletin 71.2:EZH and EZHSO

Type EZHSO (Figure 3) uses inlet pressure as the

operating medium, which is reduced through pilot

operation to load the regulator actuator diaphragm

(lower chamber). The upper chamber of

Type EZHSO actuator and the PRX Series pilot are

both 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. This pressure on the upper chamber

of the regulator actuator diaphragm opposes the main

spring force that tends to open the regulator. Outlet or

downstream pressure opposes the pilot control spring.

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 regulator actuator diaphragm and

Type PRX escapes downstream through the bleed

restriction in the pilot.

When outlet pressure increases over the setting of the

pilot spring, the pilot valve disk will be closed, reducing

loading pressure to the lower chamber of the regulator

actuator diaphragm; the pressure in the upper

chamber will force the regulator to close.

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

between inlet pressure to upper actuator casing and

loading pressure impulse lines; this valve will protect

the main valve diaphragm assembly from incorrect

start-up procedures, avoiding excess high pressure

differential between inlet and loading pressure.

Monitoring Systems

Monitoring regulation is overpressure protection by

containment, therefore, there is no relief valve to vent

to the atmosphere. When the working regulator fails

to control the pressure, a monitor regulator installed

in series, which has been sensing the downstream

and control pressure, goes into operation to maintain

the downstream pressure at a slightly higher value

than normal set pressure. During an overpressure

situation, monitoring keeps the customer on line. Also,

testing is relatively easy. To perform a periodic test on

a monitoring regulator, increase the outlet set pressure

of the working regulator and watch the outlet pressure

gauge to determine if the monitoring regulator takes

over at the appropriate outlet pressure.

Table 4. Failure Mode Analyses

PART NAME CONDITION CAUSE EFFECT REGULATOR TYPE REGULATOR REACTION MODE

Filter

Filter blocked /

Clogged

Debris or aromatics

present in the gas

Decrease of supply

pressure gives

decrease of loading

pressure

EZHSO Open - - - -

EZH - - - - Close

Pilot disk

Pilot cannot be

closed

Debris or aromatics

present, Sour gas

Increase loading

pressure

EZHSO Open - - - -

EZH Open - - - -

Pilot lower

diaphragm

Pilot cannot control

Debris or aromatics

present, Sour gas

Decrease loading

pressure

EZHSO Open - - - -

EZH - - - - Close

Pilot upper

diaphragm

Pilot cannot feed the

regulator

Debris or aromatics

present, Sour gas

Decrease loading

pressure

EZHSO Open - - - -

EZH - - - - Close

Regulator

diaphragm

Not proper

performance of

the loading

pressure chamber

Debris or aromatics

present, Sour gas

Balancing of

Pressures and

charge or discharge

of the loading

pressure chamber

EZHSO Open - - - -

EZH - - - - Close

Pilot

Frozen pilot,

Type SA/2

not working

Moisture in the gas,

high pressure drop

Type SA/2 loading

upper casing of

regulator, Pilot

not supplying

loading pressure to

lower casing

EZHSO - - - - Open

EZH - - - - Close

1 2 3 4 5 6 7 8 9 10 11 12 ... 27 28

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Emerson EZH and EZHSO Series Pressure Reducing Regulators Ficha de datos Pagina 7

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