January 12, 2022

Industrial Valve Glossary (A–Z) | VAMECA

Industrial stainless steel and brass valves, fittings, and actuators forming the letters A to Z — industrial valve glossary by VAMECA

Discover the definitions of the terms, components and standards used in industrial valve, control and sealing applications.

(A VAMECA project – continuously updated.)

A

Actuator : Device that mechanically controls the opening or closing of a valve (pneumatic, electric or hydraulic).

Water hammer absorber : Device that absorbs pressure surges in a fluid network.

Flange anchoring – support that prevents mechanical stresses on the piping.

Shaft – rod connecting the actuator to the closure element.

Manual operation – direct actuation by lever or handwheel.

ANSI – American National Standards Institute (basis for many pressure classes).

API 607 / 608 – fire test requirements

API 598 : American standard defining leak-tightness tests for industrial valves.

ASME B16.34 : Valve design standard for pressure-containing valves in accordance with North American standards.

ATEX : European certification for equipment used in explosive atmospheres.

AISI – American Iron and Steel Institute (classification of stainless steels).

Learn more about standards in our various articles: Standards & Certifications

Venting – device for air discharge in a closed network or controlled air introduction into a circuit.

Compressed air – fluid used for pneumatic actuation.

Opening angle – operating position of a quarter-turn valve.

Abrasive – fluid containing solid particles.

Fluid acceleration – phenomenon related to a reduction in cross-section.

Upstream / Downstream – refer respectively to the inlet and outlet of the flow.

Carbon steel (CS) – Robust material used for steam and hydrocarbon networks.

Stainless steel (SS / Inox) – corrosion resistant.

Aluminium – lightweight, used for actuator bodies.

Alloy – combination of metals improving mechanical properties.

Anodizing – surface treatment that increases corrosion resistance.

AC/DC – type of electrical power supply for an actuator.

Actuator torque – operating torque of an actuator.

Priming – initial charging of a fluid network.

B

Ball or plug: Rotating element of a ball valve, allowing passage or shutoff of the fluid.

Tapered plug : variant suited to viscous or loaded fluids.

Flange : Mechanical part used to join two pipes by bolting with a gasket in between.

Position locking : Function ensuring that a valve remains in position in the event of a power failure.

Mechanical stop : Physical limit preventing excessive rotation of the stem or actuator.

Limit switch box : control accessory indicating the open/closed position of an automated valve.

By-pass : Secondary circuit allowing fluid diversion for maintenance or balancing.

Control loop : System combining sensor, valve and controller to maintain a process setpoint.

Pressure balancing : mechanism that reduces operating effort on certain high-pressure valves.

Bronze : Copper-tin alloy, used for its resistance to corrosion and seawater.

Two-piece / Single-piece : refers to the body structure of a valve (2 bolted pieces or 1 machined piece).

Brushed (steel) : typical metallic surface finish for premium stainless steel equipment.

B16.5 / B16.47 (ASME) : standards defining pipe flanges (dimensions, tolerances, pressure classes).

BSP (British Standard Pipe) : parallel thread standard used mainly in Europe.

Bar : unit of pressure measurement (1 bar = 14.5 psi).

Bore (passage) : internal diameter of the fluid passage (full bore / reduced bore).

Bleed valve (purge) : small valve used to vent trapped air or fluid.

Test bench : machine used for leak-tightness and pressure tests (hydrostatic or pneumatic test).

Bidirectional : valve providing sealing in both flow directions.

Block and bleed : installation configuration combining an isolation valve and a bleed valve.

Line flushing : operation consisting of purging a fluid network before commissioning.

Local control box : operating interface located close to the valve.

Stuffing box leakage : leakage or wear of the sealing packing around the stem.

Thermal lock : overpressure caused by expansion of a fluid trapped between two closed valves.

C

Check valve : Prevents the fluid from flowing in reverse.

Pressure class (Class) : Indicates the maximum allowable pressure according to ANSI standards (Class 150, 300, 600…).

CRN (Canadian Registration Number) : Mandatory registration number for any pressure equipment in Canada.

Cv / Kv : Flow coefficients representing a valve's capacity to pass fluid.

Valve body : Main part containing the fluid passage and internal components.

Condensate : Steam that has cooled and turned back into liquid in a steam network.

D

DN (Nominal Diameter) : Indicates the standard internal diameter of a piping component.

Double-acting : Operating mode of a pneumatic actuator without a return spring.

Flow meter : Instrument for measuring fluid flow rate.

Stem failure : Breakage or twisting of a valve operating stem.

Differential pressure : Pressure difference between the inlet and outlet of a component.

Gear reducer : Torque reducer enabling manual operation of a large-diameter valve.

E

Leak-tightness : Ability of a system to prevent any fluid leakage.

EPDM / PTFE / Graphite : Materials used for gaskets depending on temperature and fluid chemistry.

Solenoid valve : Electrically actuated device controlling air or fluid supply.

Hydrostatic test : Pressure test used to verify the mechanical strength of equipment.

Condensate removal : Process aimed at removing water formed in a steam network.

Envelope dimensions : Space occupied by a valve or a valve/actuator assembly.

F

Failsafe : Function ensuring the safe position of a valve during a power failure.

NPT / BSP threading : Thread types (American tapered or European parallel).

Full bore / Full passage : Valve whose internal passage matches the pipe diameter.

Control function : Ability of a valve to modulate fluid flow.

Shutoff function : Valve providing full opening or closing of the passage.

Corrosive fluid : Substance that attacks materials that are not chemically compatible.

G

Globe valve : Valve designed for precise flow control.
Graphite : Sealing material resistant to high temperatures.
Packing : Element ensuring dynamic sealing around the stem.
Knife gate valve : Sliding blade valve used for slurries and loaded media.
Stem guide : Part that stabilizes the axial movement of a valve stem.
Lubrication : Application of lubricant to mechanical components to reduce wear.

H

High pressure : Application range above 50 bar.
Hydraulic : Actuation type using pressurized oil.
Hot tap : Connection made on an in-service line without interrupting flow.
Hysteresis : Difference between the effective opening and closing positions of a control valve.
Handwheel : Manual operating wheel.

I

ISO 5211 : Standard defining the interface between valve and actuator.
Position indicator : Accessory that visually indicates the open state of a valve.
Stainless steel : Steel alloy resistant to corrosion.
Instrumentation : Set of sensors and measuring devices connected to valves and piping.
Isolation : Function of shutting off part of a network.

J

Flat gasket : Sealing element between two flanges.
Spiral-wound gasket : Metallic gasket for high pressures and temperatures.
Valve skirt : Lower part of the body, protecting the closure element.
O-ring : Elastomer ring ensuring dynamic sealing.

K

Kv : Flow coefficient expressed in m³/h for a 1 bar pressure drop.
Mounting kit : Set of parts used to adapt an actuator to a valve.
Maintenance kit : Set of seals and wear parts for maintenance.

L

Liner : Internal lining providing corrosion protection.
Torque limiter : Mechanism preventing excessive torque on the actuator.
Brass : Copper-zinc alloy used for small equipment.
Linearity : Proportional relationship between valve opening and flow rate.

M

Pressure gauge : Instrument measuring fluid pressure.
Preventive maintenance : Regular servicing to prevent failures.
Modulating : Progressive control function of a valve.
Wafer / Lug mounting : Types of connections for butterfly valves.
Membrane (diaphragm) : Flexible element separating two pressure zones.

N

NPS (Nominal Pipe Size) : Standardized pipe diameter in inches according to North American standards.

CSA standard : Canadian organization that publishes safety standards, including CSA B51 for pressure equipment and CSA C22.2 for electrical devices in hazardous locations.

Leakage class : Sealing classification according to ISO 5208 / API 598.

Neutralization : Process for treating an acidic fluid before discharge.

O

Orifice : Internal passage through which the fluid flows.
Open/Close time : Time required to open or close the valve.
Overtorque : Applied torque above the design tolerance.
Orientation : Installation position affecting performance (horizontal/vertical).

P

PN (Nominal Pressure) : Indicates the maximum pressure in bar.
Operating pressure : Maximum continuous working pressure.
PS Automation : German manufacturer of electric actuators distributed by VAMECA.
Drain : Removes condensate or air bubbles from a network.
Reduced bore : Internal section smaller than the nominal diameter.

Q

Quick exhaust valve : Rapid relief valve in a pneumatic circuit.
Surface finish quality : Level of finish influencing leak-tightness.
Quadrant : Standard rotation angle of a quarter-turn valve (90°).

R

Control : Continuous adjustment of flow to maintain a setpoint.
Pressure reducer : Device stabilizing downstream pressure.
Position feedback : Signal indicating the open/closed state of an automated valve.
Stem breakage : Mechanical failure due to excessive torque.

S

Safety valve : Safety device that relieves overpressure.
Seat : Sealing surface between the closure element and the body.
Smart positioner : Intelligent positioner with digital communication.
SIL (Safety Integrity Level) : Certified functional safety level.
Shutoff : Function providing complete fluid isolation.

T

Torque : Force required to operate a valve.
Thermal : Relating to the operating temperature of the fluid.
Visual indicator : Status indicator on a motorized valve.
Tapping : Machining of an internal thread for connection.

U

UL / FM : North American safety and fire certifications.
Unidirectional : Valve providing sealing in one direction only.
Industrial utilities : Set of auxiliary plant fluids (water, air, steam).

V

VAMECA : Canadian distributor of industrial valves and sealing solutions.
Valve : Shutoff, control or safety component in a fluid circuit.
3-way valve : Allows a fluid to be mixed or distributed between two circuits.
Vexve : Finnish manufacturer of district heating valves.

W

Wafer : Compact mounting type between two flanges.
WCB : Material designation (ASTM A216 cast steel).
Water hammer : Pressure wave caused by the sudden closing of a valve.

X

Xylan® : fluoropolymer coating (often blue) applied to bolts, flanges and valve components to improve corrosion resistance and reduce tightening torque.

X-type strainer (X-strainer) : inclined basket filter providing effective filtration in a compact footprint, often used in steam or liquid process service.

X-block manifold : cross-shaped valve block used in instrumentation to centralize multiple functions (isolation, purge, test).

X-flow : term used to describe cross-flow configurations in multi-way valve systems or leak-testing circuits.