Control Valves & Actuators Glossary
Control valves, actuators, positioners, trim selection, and the final control elements that move a process. 67 terms in this topic - each defined in plain English on its own page.
The final control element is where the controller's output touches the process, and the control valve is its most common form. These definitions cover valve types and trim, actuators and positioners, sizing and characterization language (Cv, rangeability), and the failure behaviors (fail-open, fail-close, cavitation, flashing) that valve specifications exist to manage. Get the valve wrong and no amount of tuning upstream will save the loop.
67 Terms
What Is a Characterized Ball Valve?
How a V-notch or segmented ball becomes a high-rangeability throttling valve for slurries and gas.
Read → GlossaryHigh-Performance Butterfly Valve
Double and triple-offset control valves, dynamic torque near 70-80 degrees, and their usable range.
Read → GlossaryWhat Is a Volume Booster?
How a booster relay fast-strokes a large actuator, plus the bypass tuning that stops it hunting.
Read → GlossaryWhat Is an Actuated Valve?
Any valve fitted with a powered actuator for remote and automatic control.
Read → GlossaryWhat Is an Actuator?
The muscle that moves valves and dampers - pneumatic, electric, hydraulic types and fail-safe action explained.
Read → GlossaryAir Filter Regulator (Air Set)
The local fitting that filters instrument air and steps header pressure down to a device's supply pressure.
Read → GlossaryAir-to-Open vs Air-to-Close Valve
How ATO and ATC map signal to travel, and the trap where control, positioner, and fail action must agree.
Read → GlossaryWhat Is Anti-Cavitation Trim?
How multi-stage, drilled-cage, and stacked-disc trims stage pressure so vapor never forms.
Read → GlossaryWhat Is a Back Pressure Regulator?
The regulator that holds upstream pressure by relieving excess flow, common on separators and wellheads.
Read → GlossaryBalanced vs Unbalanced Valve Plug
How a cage-guided balanced plug cancels force to shrink the actuator, at the cost of a shutoff leak path.
Read → GlossaryWhat Is a Ball Valve?
The quarter-turn shutoff valve that dominates oil and gas isolation.
Read → GlossaryWhat Is a Block Valve Station?
The mainline valves that section a pipeline to bound a spill.
Read → GlossaryWhat Is a Blowdown Valve (BDV)?
The fail-open device that vents trapped inventory to flare during emergency depressuring, sequenced after the shutdown valves close.
Read → GlossaryWhat Is a Butterfly Valve?
The compact quarter-turn disc valve for large utility and process lines.
Read → GlossaryWhat Is C6+ Characterization?
Why GCs lump hexanes-plus into one peak, how a fixed split assigns properties, and its effect on rich-gas energy billing.
Read → GlossaryHow do you calibrate a valve positioner?
Run the autostroke routine to learn full travel, verify stroke against the 4-20 mA input, and set zero and span manually if autocal fails.
Read → GlossaryCavitation vs Flashing in Control Valves
Both boil the liquid in the valve; whether pressure recovers decides which one you have and how to fix it.
Read → GlossaryWhat Is a Check Valve?
The self-acting one-way valve that stops backflow to pumps and compressors.
Read → GlossaryWhat is check valve slam in a pump station?
The bang and surge when a discharge check valve snaps shut on reverse flow after a pump trips, and how to stop it.
Read → GlossaryWhat Is a Conservation Vent (Breather Valve)?
The weight-loaded pressure and vacuum breather that lets atmospheric tanks breathe while cutting vapor loss.
Read → GlossaryWhat Is a Control Valve?
The final control element that throttles flow to hold setpoint - body, actuator, positioner, and loop role explained.
Read → GlossaryWhat Is Control Valve Actuator Sizing?
Matching thrust or torque to a valve from unbalanced force, seat load, friction, and dynamic torque.
Read → GlossaryControl Valve Noise & Low-Noise Trim
Aerodynamic vs hydrodynamic noise, whisper trim, path treatments, and the 85 dBA threshold.
Read → GlossaryWhat Is Control Valve Sizing?
Turning flow, pressure drop, and fluid into a required Cv, and why oversizing wrecks control.
Read → GlossaryWhat Is a Diaphragm Valve?
The flexible-diaphragm valve that seals the flow from the actuator - weir vs straight-through, for corrosive and sanitary duty.
Read → GlossaryWhat Is a Double Block and Bleed Valve?
The two-seat arrangement with a bleed between that gives verified positive isolation for safe maintenance.
Read → GlossaryWhat Is an Electric Valve Actuator?
The motor-and-gearbox drive (MOV) that opens and closes valves at remote, no-air sites with torque and limit control.
Read → GlossaryESD Valve
The fail-safe, fast-closing isolation valve that acts as the final element of an emergency shutdown, driving a process to a safe state.
Read → GlossaryFail-Open vs Fail-Closed Valve
How spring and air action set a valve's safe failure position, and why HAZOP picks it - not convenience.
Read → GlossaryWhat Is a De-Energize-to-Trip ESD Valve?
The fail-safe valve held open by a normally energized solenoid that springs shut on any loss of power or signal.
Read → GlossaryWhat is a fast-acting recycle valve for hot recycle?
Antisurge valve that strokes open in under a second on a trip using boosted actuation, delivering hot recycle before surge.
Read → GlossaryWhat Is Flow Coefficient (Cv)?
The capacity number that sizes a valve for a given flow and pressure drop, with its metric equivalent Kv.
Read → GlossaryWhat Is a Flow Diversion Valve on a Pasteurizer?
The safety-critical divert valve, its dual-stem proof-of-closure, and why its state is the most audited HTST signal.
Read → GlossaryWhat Is a Full Stroke Test on a Safety Valve?
The full-travel test that strokes a shutdown valve fully closed to prove it reaches the safe state and seals.
Read → GlossaryWhat Is a Gate Valve?
The rising-stem isolation valve used across oil and gas piping.
Read → GlossaryWhat Is a Globe Valve?
The plug-and-seat throttling valve behind most control valves.
Read → GlossaryGlobe Valve Flow Direction
Flow-to-open versus flow-to-close on a globe valve, the trade-offs, and why the body arrow must be respected.
Read → GlossaryWhat Is an HVAC Damper?
The bladed device that throttles duct airflow - parallel vs opposed blades, modulating vs isolation, and fire and smoke dampers.
Read → GlossaryWhat is a Kimray back-pressure valve?
The throttling globe valve that holds gas pressure on separators and treaters, and how it differs from a relief valve.
Read → GlossaryWhat Is a Knife Gate Valve?
The thin sharp-edged blade gate that shears through slurries and mud - and how it differs from a wedge gate valve.
Read → GlossaryWhat Is a Latching Solenoid Valve in Irrigation?
The bistable valve that holds position on a brief pulse, enabling battery and two-wire field valve networks.
Read → GlossaryWhat Is a Needle Valve?
The fine-metering valve for instrument, sample, and gauge lines.
Read → GlossaryWhat Is a Partial Stroke Test (PST)?
The online test that moves an ESD valve partway to prove it is not stuck, without shutting the process down.
Read → GlossaryWhat Is a Pinch Valve?
The rubber-sleeve valve with a full-bore path and no metal in the flow - built for abrasive slurries, sand, and frac fluid.
Read → GlossaryWhat Is a Plug Valve?
The quarter-turn tapered-plug isolation valve - lubricated vs sleeved types and why it suits gathering and slurry service.
Read → GlossaryWhat Is a Valve Positioner?
The device that makes a control valve hit its target - closed-loop positioning and smart valve diagnostics.
Read → GlossaryWhat Is a Pressure Reducing Regulator?
The self-contained spring-and-diaphragm valve that holds downstream pressure with no power or controller.
Read → GlossaryWhat Is a Pressure Sustaining Valve?
The valve that holds a minimum upstream pressure, opening only to bleed off the excess.
Read → GlossaryWhat Is a PRV Station?
The vault-mounted control valve that holds a fixed downstream pressure feeding a lower zone.
Read → GlossaryWhat Is a Rack and Pinion Actuator?
The constant-torque pneumatic actuator that is the standard automator for on-off ball and butterfly valves.
Read → GlossaryWhat Is a Remote Shut-In Valve?
The actuated wellhead valve that fails safe closed and can be commanded shut from the control room.
Read → GlossaryWhat Is a Pressure Safety Valve?
The pop-action safety valve that fully vents gas overpressure instantly.
Read → GlossaryWhat Is a Scotch Yoke Actuator?
The quarter-turn actuator whose yoke delivers high breakaway torque for large valves and ESD service.
Read → GlossaryWhat Is a Smart Valve Positioner?
The digital HART or fieldbus positioner that adds valve diagnostics and partial-stroke testing to a control valve.
Read → GlossaryWhat Is a Solenoid Valve?
The electrically switched on/off valve that pilots actuators and enforces ESD - how it works, NO vs NC.
Read → GlossaryWhat Is a Subsurface Safety Valve (SSSV)?
The fail-safe downhole valve that closes to isolate a well on loss of control-line pressure - types and integrity monitoring.
Read → GlossaryWhat Is a Surface Safety Valve (SSV)?
The actuated fail-safe valve on the wellhead tree, tied into the well's shutdown system for surface isolation.
Read → GlossaryWhat Is a Surge Anticipator Valve?
The valve that opens on the pump-trip low-pressure wave to relieve the returning surge.
Read → GlossaryWhat Is a Three-Way Valve?
The three-port valve that diverts or mixes flow, using L-port or T-port ball bores to route among ports.
Read → GlossaryWhat Is Valve Cavitation?
How vapor bubbles form and collapse across a valve, the damage they cause, and anti-cavitation trim.
Read → GlossaryWhat Is a Valve Flow Characteristic?
Linear, equal-percentage, and quick-opening curves - and why the wrong one makes a loop hunt at part-stroke.
Read → GlossaryWhat Is Valve Position Control (Optimizing Valve Control)?
A slow outer loop that watches the most-open valve and nudges a shared setpoint to cut pumping and compression energy.
Read → GlossaryValve Rangeability & Turndown
Inherent vs installed rangeability, why control fails near the seat, and how oversizing wastes it.
Read → GlossaryWhat Is Valve Seat Leakage Class?
ANSI/FCI 70-2 classes I to VI, what each permits, and when Class V or VI shutoff is required.
Read → GlossaryWhat Is a Valve Signature Test?
Plotting actuator pressure against travel to expose valve friction, bench set, and dead band.
Read → GlossaryWhat Is Valve Stiction?
The stick-slip friction that makes loops oscillate no matter how you tune them - how to spot it and fix it.
Read → GlossaryWhat Is Control Valve Trim?
The plug, seat, and cage that shape a control valve's flow characteristic.
Read →One Platform for the Field
Merobix is cloud SCADA for oil & gas - it reads the instruments and protocols defined here into one dashboard.