Brand: Fisher

Fisher EZH/EZHSO Pilot-Operated Pressure Regulator

Name: Fisher EZH EZHSO Pressure Reducing Regulator
Brand: Fisher
SKU: EZH

Description

Fisher EZH and EZHSO pilot-operated pressure reducing regulator

The Fisher EZH is a pilot-operated, pressure-balanced, soft-seated gas pressure reducing regulator for high-pressure transmission and city gate stations, large distribution systems and power plant gas feeds. The EZHSO is the spring-to-open companion. This page follows the EMEA edition of the manufacturer datasheet.

Seven Star LLC supplies the Fisher EZH family in Oman and the GCC as an independent supplier in Muscat. The model code carries the failure action and the safety add-on, so it is decoded below before any quotation.

Decoding the EZH family

Code	Meaning	Note
EZH	Spring-to-close pilot-operated pressure reducer	Closes on diaphragm failure or loss of pilot supply (see failure table)
EZH-OS2	EZH with Type OS2 slam-shut device	Overpressure or overpressure and underpressure shutoff
EZHSO	Spring-to-open version	Fails open in the failure modes analysed by the maker
EZHSO-OS2	EZHSO with Type OS2 slam-shut	Slam-shut plus spring-to-open main valve

Fisher EZH technical specifications

Parameter	Specification
Manufacturer / part number	Fisher (Emerson) / EZH and EZHSO (EMEA datasheet)
Allowable pressure PS	Up to 100 bar
Inlet pressure	1 to 100 bar
Outlet set range	1 to 80 bar
Minimum differential, EZH	1 bar
Minimum differential, EZHSO	3.8 bar (DN 25, 50, 80); 1.8 bar (DN 100); 1 bar (DN 150, 200)
Maximum differential	99 bar (EZH); 96.2 bar (EZHSO)
Accuracy class	Up to ±1% (EZH); up to ±2.5% (EZHSO)
Lock-up pressure class	Up to +5%; lock-up zone class up to 5%
Operating temperature	-20 to 60 °C; -30 to 71 °C optional
Sizes	DN 25, 50, 80, 100, 150 and 200, inlet and outlet the same
Flange ratings	PN 16B, 25B, 40B; ANSI 150 RF, 300 RF, 600 RF
Pilot system	Types PRX and SA/2
Body, actuator, connecting parts	Steel
Plug and orifice	Stainless steel
Soft parts	Plug disc and slam-shut O-rings in nitrile (NBR) or fluorocarbon (FKM)
Slam-shut OS2	Response time under 1 s; accuracy up to ±2.5% (diaphragm and bellows) or ±5% (piston); set range 0.010 to 100 bar
Noise attenuation	Optional Whisper Trim cage, up to 8 dB

How the EZH controls outlet pressure

The EZH uses the inlet gas as its operating medium. The pilot reduces it to a loading (motorization) pressure that acts on the actuator diaphragm against the outlet pressure and the pilot control spring. When the outlet falls below the pilot setting, the pilot opens, motorization pressure rises and the main plug opens. When demand is satisfied, the outlet rises, the pilot closes and the loading gas bleeds into the downstream system. The pilot bleeds all of its gas downstream, so no gas is vented to atmosphere.

In the EZHSO the upper diaphragm chamber is filled with pressure from the SA/2 stabilizer filter, which opposes the main spring that tends to open the valve. Adjustment is done on the pilot adjusting screw with a gauge on the downstream side, and a small downstream flow must be present so the outlet can vent when lowering the setpoint.

Monitoring systems and failure behavior of the EZH

The datasheet describes two monitoring arrangements. In a wide-open monitor, an upstream regulator stays fully open while the downstream active regulator controls; if the active unit fails open, the monitor takes over, and if the monitor itself fails it closes. A common pairing is an EZH monitor upstream of an EZHSO active regulator. In a working monitor system, the upstream regulator carries two pilots (PRX/120 working and PRX/125 monitoring) and is always in service, so both units can be checked in operation. The working regulator must be rated for the maximum allowable operating pressure.

The failure mode table in the datasheet shows, for example, that a blocked filter or a torn diaphragm leaves an EZH closed and an EZHSO open, whereas a pilot disk that cannot seal opens both. This is the reason to choose EZH or EZHSO deliberately for each stage of a reduction line.

Fisher EZH selection and ordering checklist

Spring-to-close (EZH) or spring-to-open (EZHSO) action and its place in the monitor arrangement.
Slam-shut: none, or OS2 for overpressure or for overpressure and underpressure.
Size DN 25 to 200 and end connection (PN or ANSI class).
Inlet minimum and maximum, set pressure and peak flow; check minimum differential for the chosen size.
Gas composition: natural gas, air, propane, butane, LPG, city gas, nitrogen, carbon dioxide and hydrogen are listed, and FKM soft parts are available where liquid aromatics are present.
Temperature band: standard -20 to 60 °C or optional -30 to 71 °C.
Whisper Trim cage if noise must drop by up to 8 dB.
Pilot types PRX/120, PRX/125 and their AP versions as required.

Maintaining the Fisher EZH in the line

The top-entry design lets operators inspect, clean and replace trim without removing the body from the pipeline. For DN 100, 150 and 200 an easy maintenance system is supplied: remove the top plug, extract the trim assembly, remove the pad holder and change the pad. One operator can do this on DN 100, two on DN 150 and 200, and no special tools are required.

Keep gas filtered, because microparticles and sour gas are listed as failure causes for the pilot disk and diaphragms. Spare pads, pilot diaphragms and the stabilizer filter element are the usual consumables. Test the slam-shut trip and the monitor takeover on commissioning and at planned intervals.

Typical applications in Oman and the GCC

The EZH family fits pressure reduction at gas receiving and metering stations, fuel gas supply to gas turbines and power plant boilers, and the offtakes of transmission pipelines feeding industrial cities. High turn-down is useful where plants shift between low and high demand. Stations in Oman are often in hot, sandy locations, so check the optional -30 to 71 °C band against the station design, and keep the pilot lines clean of dust.

Information to send with a Fisher EZH RFQ

EZH, EZHSO or OS2 variant, and monitor or worker role.
Size, flange rating and face-to-face requirement.
Gas, inlet and outlet pressure ranges, flow and temperature.
Slam-shut set points and noise limits.
Spares required (pads, diaphragms, pilots).

Documents and quotation

The EMEA datasheet for the EZH and EZHSO is attached on this page.

Send the EZH code and your station data to Seven Star LLC in Muscat and we will respond with a quotation for the matching configuration.

Datasheets & Documents

Datasheet Fisher EZH EZHSO Datasheet (EMEA) Download

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About brand

Fisher is the control valve brand of Emerson. Its history starts in 1880 in Marshalltown, Iowa, where William Fisher, working at the town waterworks, invented a constant-pressure pump governor and founded a company to make it. Emerson bought Fisher Controls in 1992, and Marshalltown remains a main engineering and manufacturing site for Fisher valves. The brand covers control valves, actuators, FIELDVUE digital valve controllers, regulators and level controllers.

Seven Star LLC is an independent supplier listing Fisher control valves, actuators, positioners, regulators and spare parts for buyers in Oman and the GCC. Replacement valves and trim are matched from the serial number on the valve nameplate.

Fisher company profile

Origin	William Fisher's constant-pressure pump governor, Marshalltown, Iowa, USA (1880)
Ownership	Owned by Monsanto from 1969; sold to Emerson in 1992 and combined with Rosemount as Fisher-Rosemount, later Emerson Process Management. Today a brand of Emerson.
Main site	Marshalltown, Iowa, USA
Product families	Sliding-stem and rotary control valves, spring-diaphragm and piston actuators, FIELDVUE digital valve controllers, pressure regulators, displacer and digital level controllers
Typical duty	Throttling control of liquids, gas and steam, high-pressure and severe service, instrument supply and gas pressure reduction

Milestones

1880: William Fisher builds a constant-pressure pump governor in Marshalltown, Iowa.
1969: Monsanto acquires Fisher Controls.
1992: Emerson buys Fisher and combines it with Rosemount as Fisher-Rosemount, later Emerson Process Management.

Fisher valves, actuators and instruments

Series	Type	Typical use
easy-e ES, ET, EZ	Sliding-stem globe and angle valves	Cage-guided globe valves: ES with unbalanced plug, ET with balanced trim for higher pressure drop; EZ unbalanced with a seat ring retainer for viscous or dirty fluids
GX	Compact globe valve with integral actuator	Standard chemical and process duty where a compact valve package is preferred
HPT, HPAT	High-pressure globe and angle valves	Pressure classes up to ASME CL2500, compressor recycle and high-pressure letdown
V150, V200, V300, V250	Vee-Ball segmented ball and full-bore ball control valves	High-capacity control of liquids, gas and fibrous or slurry service
CV500	Eccentric rotating plug valve	Erosive, coking and dirty service
8560, 8580	High-performance butterfly valves	Large-line throttling and on-off control
657, 667, 1052, 1061, easy-Drive	Spring-diaphragm, piston and electric actuators	657 and 667 for sliding-stem valves; 1052 and 1061 for rotary valves; easy-Drive where no air is available
FIELDVUE DVC6200, DVC2000, 3610J	Digital valve controllers and positioners	HART positioning with valve diagnostics; 3610J pneumatic positioner for rotary actuators
627, 1098-EGR, 67C	Pressure regulators	Gas pressure reduction, pilot-operated regulation and instrument air supply
DLC3100, 2500	Digital and pneumatic level controllers	Displacer level and interface on separators and scrubbers

Where Fisher valves are used

Fisher control valves and regulators are standard equipment in oil and gas production, refineries, gas processing and LNG, petrochemicals, power plants and water systems. Typical loops are separator level and pressure, compressor anti-surge and recycle, fuel gas pressure reduction, feedwater and steam control, and chemical dosing. FIELDVUE controllers add diagnostics that help plan valve maintenance before a turnaround.

Ordering Fisher valves and spare parts: what we need

For spares, send the serial number from the valve nameplate together with the valve type, size, pressure class, trim and actuator type and size. Emerson keeps the build record behind the serial number, so plug, seat ring, cage, packing and diaphragm kits can be matched without guesswork. For a FIELDVUE or regulator, send the full model and type number and the mounting details. For a new valve add the process data: fluid, flow range, inlet and outlet pressure, temperature, leakage class, fail position, air supply and signal.

Facts checked against Emerson Fisher product information and published company histories, October 2026.

Browse Fisher products by category: Control Valves, Valve Actuator, Valve Positioner, Regulators, Level Transmitter.

FAQ

Questions about the Fisher EZH/EZHSO Pilot-Operated Pressure Regulator

Answers from our engineering team on installation, compatibility and integration.

01What is the difference between EZH and EZHSO?

EZH is spring-to-close, EZHSO is spring-to-open. They react differently to diaphragm or pilot failure.

02What pressure limits does the EZH have?

Inlet pressure is 1 to 100 bar, outlet set range 1 to 80 bar, with allowable pressure up to 100 bar.

03What sizes and flanges are available?

DN 25, 50, 80, 100, 150 and 200 in PN 16B, 25B, 40B and ANSI 150, 300 and 600 RF.

04Does the EZH vent gas to atmosphere?

No. The pilot bleeds all loading gas to the downstream system during operation.

05Can the EZH be fitted with a slam-shut?

Yes. The EZH-OS2 and EZHSO-OS2 add a Type OS2 slam-shut for overpressure or overpressure and underpressure protection.