Fisher 2625 Pneumatic Volume Booster

Product Description

Fisher 2625 is a SIL3‑certified pneumatic volume booster manufactured by Emerson Fisher, designed to work with valve positioners for throttling control valves. It amplifies air flow volume to accelerate actuator stroking speed for large‑volume pneumatic actuators. Variants include standard aluminum 2625, stainless‑steel 2625SST for corrosive service, and radiation‑resistant 2625NS for nuclear‑grade application. Built‑in integral bypass restriction and soft‑seat structure avoid positioner saturation while preserving steady‑state positioning accuracy. Maximum working supply pressure reaches 150 psig, supports instrument air or natural gas as working media.

Product Features

• High‑flow pneumatic volume amplification, drastically improve stroke speed of large‑size control valve actuators
• Integral adjustable bypass restriction: fast response for large signal step change, smooth tracking for small slow signal variation
• Soft‑seat tight shut‑off design, reduces continuous air consumption and prevents positioner relay saturation
• SIL3 functional safety certification by exida, suitable for SIS safety‑related valve loops
• Fixed deadband mechanical structure, stable performance with little drift during long‑term operation
• Multiple material options: standard aluminum body, 2625SST stainless‑steel for corrosive environment, 2625NS nuclear‑radiation resistant version
• Direct actuator‑mount installation, simple pneumatic piping connection with positioner output port
• Compatible with Fisher DVC series digital valve positioners and traditional pneumatic / electro‑pneumatic positioners
• Wide operating temperature range, suitable for outdoor and heavy‑duty process plant environment
• Supports both modulating throttling control and on‑off emergency trip valve application by adjusting bypass setting

Application Scenarios

• Petrochemical and refinery large‑size control valves requiring fast actuator stroke speed
• SIS emergency shutdown valves (ESD) for quick valve trip action within required safety response time
• Power plant boiler and turbine auxiliary control valve with large‑volume pneumatic actuators
• Oil‑gas on‑shore and offshore platform modulating and emergency trip valve assemblies
• Chemical plant critical process loop where fast valve movement cannot be achieved by positioner alone
• Nuclear power unit safety‑related pneumatic actuator using 2625NS radiation‑resistant variant

Common Problems & Troubleshooting

• Valve actuator still strokes slowly after installing booster: Check supply air pressure meets requirement; inspect piping blockage or undersized tubing; readjust integral bypass restriction setting; verify booster inlet‑outlet piping direction is correct.
• Valve hunting, unstable oscillation during modulating control: Adjust bypass restriction screw for proper damping; check air supply contains moisture or oil contamination; inspect actuator spring‑pack mechanical friction; avoid over‑amplified volume gain.
• Excessive continuous air consumption: Inspect soft‑seat internal seal damage caused by dirt particles; check for loose piping thread leakage; perform tightness test for booster body and diaphragm assembly.
• No amplification effect, booster almost no output flow: Confirm instrument air is clean dry oil‑free supply; inspect internal orifice blocked by dust or rust particles; check diaphragm rupture inside volume booster.
• Good for large step signal but poor response for small signal change: Tune integral bypass restriction to open appropriate degree; do not fully close bypass for modulating throttling service (fully‑closed bypass only for on‑off trip valves).
• Booster internal component premature aging: Ensure air supply free of oil and hydrocarbon; EPDM elastomer material will degrade under petroleum‑based lubricant contamination; replace worn seals and diaphragms during scheduled maintenance.
• SIS safety application mismatch risk: Use correct SIL‑certified 2625 / 2625SST model; do not apply non‑SIL variant in safety instrumented loop; follow exida safety manual for proof‑test interval.