Valve Glossary

Understanding the Valve Glossary

1 Piece Ball Valve - Inexpensive and having few potential leak paths (end connections and stem), they are a light-weight and difficult to repair. Often a reduced port design, typical of OEM and commercial-duty ball valves.

2 Piece Ball Valve - Industrial standard for flanged ball valves, having only one body joint (potential leak path), they are easier to repair but are more expensive than 1 piece designs due to the increased complexity of the design.

3 Piece Ball Valve - Industrial standard for threaded and welded connections, the central body can be removed without removing the end connections from the pipeline, thus repair is easier. They can also be supplied with different end configurations. Having two body joints (potential leak paths), some designs utilize through bolts and others studs with nuts.

Adjustable Stem Packing - A stem seal is used to seal between the shaft of the handle stem and the valve body. This seal is then compressed around the stem by means of a packing gland, which forms a watertight seal around the handle stem assembly. Over time, due to various environmental conditions, the seal material may expand or contract; thereby affecting the quality of this seal. To combat this (if a leak should occur) you can adjust the packing gland by tightening it slightly.

Anti-static device (ball valve feature) - Ensures an electrical continuity between valve ball, stem, and body thereby reducing static electricity which may exist in the ball or stem of the valve.

Ball Valve - A ¼ turn valve using a hollow sphere used to close, open or control fluid flow.

Blow Out Proof Stem - Ensures the top packing rings can be replaced while the valve is under pressure, without the stem being pushed out.

Bubble Tight Design - A phrase describing the sealing ability of a valve. During air pressure testing of a new valve in the closed position, leakage past the seats is collected and bubbled through water. To qualify as bubble-tight, no bubbles should be observed in a prescribed time span.

Butterfly Valve - Enables quick shut-off of pipeline flow similar to a ball valve, except they typically cost less and more compact than comparable ball valves.

Chain Wheel - Type of manual actuator for difficult to reach (typically high) valves. The chain wheels can be supplied in a variety of materials.

Control Valve - A valve used to control fluid flow by varying the size of the flow passage, which is accomplished via manual or automated actuation, thus enables the direct control of flow rate and the consequential control of process quantities such as pressure, temperature, and liquid level.

Cv (Flow Coefficient) - Refers to a scientific standard for volume of water at 60ºF which can pass through a pipe, valve or other pipeline fitting and have a loss or differential pressure drop of 1 PSI. Therefore the higher the Cv value for a given flow rate, the lower the pressure drop will be across the valve/fitting.

Double Acting Pneumatic Valve Actuator - This type of valve actuator has two compressed air ports; when air is applied to one port and vented by the other, it causes the internal pinion assembly to rotate clockwise. Just the opposite occurs when air is applied to the other port with the rotation being counter-clockwise.

Double Offset Butterfly Valve - Refers to the position of the valve stem in relation to the centreline of the disc and bore, they are used for higher pressures and fluids with particulate, reduces contact between the valve disc and seat, prolonging the seat life.

Fire Safe - A valve design that is capable of passing a fire test with specified limits on leakage to the atmosphere and downstream after being closed subsequent to fire exposure.

Floating (ball valve (ball moves to seat) - Its diverting ball is not anchored to the valve body; rather it floats against the seat to form a seal. Compared to a Trunnion Valve the sealing is improved and its design is more compact, however they generally have higher torque requirements and thus used for lower pressure applications.

Lug (Butterfly) Valve - Has threaded flange holes to enable removing piping from one side of the valve without affecting its sealing.

Metal Seat - The valve ball or disc interfaces directly against a metal seat. This style of valve requires periodic operation and maintenance to ensure a leak-free seal. These types of valves are better for high pressures, extreme temperatures, sanitary/pure fluids and applications with a high percentage of particulates in the fluid. Metal seats are commonly used for control valves due to higher fluid velocities and related erosion. Special alloys can be used for enhanced fluid compatibility.

MSS - Manufacturers Standardization Society of the Valve and Fittings Industry

• SP-6:Standard Finishes for Contact Faces of Pipe Flanges and Connecting-End Flanges of Valves and Fittings
• SP-25: Standard marking system for valves, fittings, flanges and unions
• SP-44:covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for steel pipeline flanges
• SP-55:Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components – Visual Method for Evaluation of Surface Irregularities
• SP-67: Butterfly valves
• SP-72:General purpose ball valves

Multi-Port (Ball Valve design) Valves - which have more than one inlet or outlet, used for diverting flow.

Pigging - Devices sent through pipelines for cleaning and inspection purposes. Cleaning could be maintenance or process (cross contamination) related. Pigging devices are often used during production and only full port ball valves are compatible with pigging processes.

PTFE - Made from Virgin Teflon, this is the most common sealing material; its chemical compatibility is excellent for almost all media. Temperature -50°F to 400°F.

PTFE Cavity filled Seats Available on request (CF), suitable for filling the void between the body and ball eliminating product build up. Cavity filled seats are standard on our sanitary line of ball valves in both two and three way.

Seal Weld - Eliminates potential leakage at body joints to ensure pressure containment. Accomplished using automatic welding equipment to create uniform weld penetrations; during the welding procedure a continuous water flow passes through the valve to protect the valve seats and seals from damage.

Spring Return Pneumatic Valve Actuators - Designed to ensure the actuator "fails safe", compressed air is used to compress springs and a counter-clockwise rotation. Upon venting or loss of pressure, the spring forces clockwise rotation of the valve positioner.

Full Port (Bore) - The bore or ID of the valve matches the ID of the pipe it is connected to, minimizing differential pressure drop.

TFM (valve seat material) - Considered to be an upgrade from PTFE material, having an improved thermo-mechanical properties resulting in lower torque and less permeability, cold flow deformation. In addition deformation recovery is enhanced.

Triple Offset Butterfly Valve ( high pressure, dirty fluids, bubble tight performance) - Designed like a Double Offset butterfly valve with the addition of having a tapered shaped seat which matches the sealing disc, eliminating rubbing altogether and enables tight sealing with a metal-to-metal interface. Due to their compact size, triple offset valves are sometimes a better choice than gate valves due to reduced weight, cost and ease of operation (ergonomics).

Trunnion (ball valve (seat moves to ball) - Has a diverting ball which is physically connected to both the upper and lower parts of the valve body, utilizing line pressure to move the seat against the ball for sealing. This is typical for larger valves and higher pressure valves.

Two-way/Bi-Directional (ball valve ) - Whichever side has the higher pressure, the seat or ball moves accordingly for sealing.

Wafer (butterfly) valve Has smooth bore flange holes such that the valve is sandwiched between opposing pipe flanges and thus removing one side of the piping and leaving the valve in-place is not possible.

ACCUMULATOR - A vessel in which a gas is trapped and compressed by the liquid in a hydraulic system, thus storing energy to supply liquid under pressure to the system when needed.

ACTUATOR - Device used to operate a valve using electric, pneumatic or hydraulic means. Often used for remote control or sequencing of valve operations.

ADAPTER SPOOL - An extension which is added to a short face-to-face valve, to conform to standard API 6D face-to-face dimensions.

ALLOY STEEL - A steel consisting primarily of iron with some percentage of one or more other elements such as chromium, nickel, manganese, or vanadium deliberately added to enhance its properties.

AMBIENT TEMPERATURE - The prevailing temperature of the environment immediately surrounding an object.

ANCHOR PIN - A pin welded onto the body of ball valves. This pin aligns the adapter plate and restrains the plate and gear operator from moving while the valve is being operated.

ANGLE VALVE - A variation of the globe valve, in which the end connections are at right angles to each other, rather than being inline.

ATMOSPHERIC PRESSURE - The external pressure exerted on a body by the atmosphere: 14.7 psi (absolute) at sea level.

BACK PRESSURE REGULATOR - Regulator designed to control upstream pressure. See "REGULATOR."

BACKSEAT - A Shoulder on the stem of a valve which seals against a mating surface inside the bonnet to permit replacement, under pressure, of stem seals or packing.

BALL CHECK - A fitting with a small ball that seals against a seat preventing flow in one direction and allowing flow in the other direction.

BAR - A metric unit of pressure. One bar equals 14.5 psi.

BDV - BLOW DOWN VALVE A small ball valve that is installed on the above ground end of an extended drain line. This valve also serves to vent body cavity pressure in the "block and bleed" mode. See "Block and Bleed;" "Extended BDV."

BELLEVILLE SPRING - A spring resembling a dished washer, used in some ball valves to push the seats against the ball.

BEVEL GEAR OPERATOR - Device facilitating operation of a gate or globe valve by means of a set of bevel gears having the axis of the pinion gear at right angles to that of the larger ring gear. The reduction ratio of this gear set determines the multiplication of torque achieved.

BODY - The principal pressure containing part of a valve, in which the closure element and seats are located.

BOLTED BONNET - A bonnet which is connected to a valve body with bolts or studs and nuts.

BOLTED CONSTRUCTION - Describes a valve construction in which the pressure shell elements are bolted together, and thus can be taken apart and repaired in the field.

BOLTING SETS - Bolts, or studs, and nuts sometimes supplied with flanged valves to install the valve between line flanges.

BONNET - The top part of a valve, attached to the body, which contains the packing gland, guides the stem, and adapts to extensions or operators.

BORE (OR PORT) - The inside diameter of the smallest opening through a valve, e. g., inside diameter of a seat ring, diameter of hole through ball in a ball valve.

BURST PRESSURE - That pressure (PSI) at which rupture of a stressed element or pressure-containing vessel takes place. See "Ultimate Strength."

BUTT WELD END (BWE) - The end connection of a valve suitably prepared for butt welding to a connecting pipe.

BYPASS - A system of pipes and valves permitting the diversion of flow or pressure around a line valve.

CARBON STEEL (CS) - Iron containing carbon in the form of carbides, about 0.1 to 0.3 percent carbon with no other alloying elements other than the sulphur, phosphorus, and other elements present in almost all steels.

CAST IRON - The common term for cast grey iron or iron containing flake carbon. Cast iron is brittle, exhibiting very little ductility before fracturing.

CAST - The form of a particular part of a valve, where the basic shape is formed by moulding rather than fabricating.

CAVITATION - The rapid formation and collapse of vapor pockets in a flowing liquid in localized regions of very low pressure; often a cause of erosive damage to pumps, throttling type valves, and to the piping itself. Can be the cause of excessive noise.

CHAIN WHEEL OPERATED VALVE - An overhead valve operated by a chain drive wheel instead of a handwheel.

CHECK VALVE - A one-directional valve which is opened by the fluid flow in one direction and closed automatically when the flow stops or is reversed.

CLAPPER - The hinged closure element of a swing check valve.

CLEVIS - A "U" shaped connecting yoke at the end of a stem or rod, between the ends of which a gate or other part may be pinned or bolted.

CLOSURE ELEMENT - The moving part of a valve, positioned in the flow stream which controls flow thru the valve. Ball. Gate, Plug, Clapper, Disc, etc., are specific names for closure elements.

CLOSURE - The ends of a ball valve, bolted to the body, which often contain the seat rings. Often referred to as part of the body.

COMPRESSOR - A device which converts mechanical energy into gas pressure.

CONCENTRIC - Having the same centres.

CONTAMINANT - A particle or material which is foreign to the fluid media.

CONTROL VALVE - A valve that controls a process variable, such as pressure, flow or temperature by modulating its opening in response to a signal from a controller. See "Controller"

CONTROLLER - A device that measures a controlled variable, compares it with a predetermined setting and signals the actuator to read just the opening of the valve in order to re-establish the original control setting.

CORROSION - The deterioration of a material due to chemical action.

CRYOGENIC TEMPERATURE - Any temperature below about -240°F.

CRYOGENIC VALVE - A valve capable of functioning at cryogenic temperatures.

CYCLE - A single complete operation or process returning to the starting point. A valve, stroked from full open to full close and back to full open, has undergone one cycle.

CYLINDER OPERATOR - A power-piston valve operator using either hydraulic or pneumatic pressure. A sealed piston converts applied pressure into a linear piston rod (stem) motion. See "Power Operators."

DEZINCIFICATION - A form of pitting corrosion which attacks certain zinc.

DIAPHRAGM - A round, thin flexible sealing device secured and sealed around its outer edge - and sometimes around a central hole in the diaphragm - with its unsupported area free to move by flexing.

DIFFERENTIAL PRESSURE - The difference in pressure across a valve in a pressurized line. The difference in pressure between any two points in a pressurized system under flowing conditions.

DISC - The closure element of a globe angle or small regulator valve. The disc (sometimes referred to as "valve," "poppet" or "plug") moves to and from the seat in a direction perpendicular to the seat face. Depends on stem force for tight shutoff.

DISTRIBUTION LINE - A pipeline which distributes gas to the service lines of individual consumers. Most generally it is small in diameter (6 inch and under) and low pressure (under 150 psi).

DRAIN PLUG - A fitting at the bottom of a valve, the removal of which permits draining and flushing the body cavity.

DRIVE PINS - The two pins which fit into the bottom of a ball valve stem and engage corresponding holes in the ball. As the operator turns the stem, the drive pins turn the ball.

ECCENTRIC - Not having the same centre.

ELASTOMER - A natural or synthetic elastic material often used for o-ring seals. Typical materials are viton, buna-n, EPDM (ethylene propylene dimonomer), etc.

ELBOW - A female threaded, or socket fitting used for changing direction in a run of pipe or tubing. See "Ell," "Street Ell."

ELECTROLESS NICKEL PLATING - A plating process which requires no external electrical power and is the result of a chemical reaction between the part and the plating solution. A uniform consistent deposit and plating rate can be produced by controlling and adjusting the chemistry of the plating bath.

ELL - A pipe or tubing fitting that has the shape of an "L."

EMERGENCY SEAT SEAL - To obtain tight shut off in an emergency situation, a sealant can be injected into a specially designed groove in the seat rings. Available for most ball valves and gate valves.

EMO - ELECTRIC MOTOR OPERATED - The actuation of a valve by electric motor. See "Power Operator."

END BEVEL Weld end preparations for butt welding. Governed by ASME B16.25.

END CONNECTION - The type of connection supplied on the ends of a valve which allows it to be installed in a pipeline. Weld end (WE), raised face flange (RF), ring type joint (RTJ), screwed end (SC).

EROSION - The mechanical wearing away of a metal surface or part due to fluid impingement. The presence of entrained solid particles accelerates this process.

ESDV - EMERGENCY SHUT DOWN VALVES - A valve or a system of valves which, when activated, initiate a shut-down of the plant, process, or platform they are tied to.

EXPANDING GATE VALVE - A gate valve that is comprised of a separate gate and segment that as the valve operates the gate and segment move without touching the seats, permitting the valve to be opened and closed without wear. In the closed position the gate and segment are forced against the seat. Continued downward movement of the gate causes the gate and segment to expand against the seats. When the valve reaches its fully open position, the gate and segment seal off against the seats while the flow is isolated from the valve body.

EXPLOSION PROOF - The prevention of explosion, triggered by electrical components, through containment in special housings. A requirement for electrical devices, such as solenoids and switches, when exposed to a potentially explosive environment.

EXTENSIONS - The equipment applied to buried valves to provide above ground accessibility to operating gear, blowdown and seat lubrication systems.

EXTERNAL COATING - Coating applied to protect valves against various environments - sea air, salt water, earth buried, normal air exposure.

FABRICATED VALVE - One in which the body and hub parts are not cast - but rather are formed from plate or pipe and the welded or bolted together.

FACE-TO-FACE - The overall dimension from the inlet face of a valve to the outlet face of the valve (one end to the other). This dimension is governed by ASME B16.10 and API-6D to ensure that such valves are mutually inter changeable, regardless of the manufacturer.

FACING - The finish of the contact surface of flanged fittings.

FAIL SAFE VALVE - A valve designed to fail in a preferred position (open or closed) in order to avoid an undesirable consequence in a piping system.

FEMALE THREAD - An internal screw thread designed to mate with a component having male (external) threads of the same size and type.

FIRE GATE A gate or ball valve which is positioned in a pipeline at the entrance to a compressor station. This valve is closed in case of fire in the compressor station. Closing the valve prevents the gas in the pipeline from feeding the fire.

FIRE SAFE - A statement associated with a valve design which is capable of passing certain specified leakage and operational tests after exposure to fire. Must be referenced to a particular specification. See API Spec. 6FA and BS Spec 6755.

FITTING - Any component, other than valves, used with pipe as part of the pressure system and normally referring to items covered by a national standard.

FLANGE - A cast or formed pipe fitting consisting of a projecting radial collar with bolt holes to provide means of attachment to piping components having a similar fitting. The end piece of flanged-end valves.

FLAT FACE (FF) - A flange surface in which the gasket sealing area is the entire surface from the ID to the outside edge. Usually used for class 125 cast iron valves.

FLEXIBLE TUBE VALVE - A special valve using a flexible sleeve or tube which acts as the closure element. Pressure applied to the jacket space surrounding the outside of the tube, controls the opening and closing of the valve.

FLOAT VALVE - A valve which automatically opens or closes as the level of a liquid changes. The valve is operated mechanically by a float which rests on the top of the liquid.

FLOATING BALL - A ball valve having a non-trunnion mounted ball. The ball is free to float between the seat rings, and thus causes higher torques.

FLOW COEFFICIENT - The number of gallons of water per minute that will flow through a valve with a pressure drop of 1 psi. Also referred to as the Cv of the valve.

FLOW LAMINAR - The flow of a viscous fluid in which the fluid moves in parallel layers with a fixed velocity gradient from the centreline to the containing walls of the conduit. Sometimes referred to as "streamline" flow.

FLOW METER - An instrument used to measure flow rate or total flow or both.

FLOW RATE - The volume or weight of a fluid passing thru a pipeline or conductor per unit of time, i.e., 3000 barrels of oil per day; 4 MMCF of gas per hour.

FLOW, TURBULENT - The random flow of a fluid in which the velocity at a certain point in the fluid varies irregularly.

FLOW - A fluid in motion in a conducting line.

FLUID - Any non-solid substance that can be made to flow. Both liquids and gases are fluids.

FORCE - The intensity of an influence tending to produce motion, distortion or change of shape. The product of unit force (PSI) and the area over which it acts. Usually expressed in pounds.

FORGING - A metalworking process that involves hammering or squeezing, with or without a die, at hot working temperatures to form a specific shape.

FRICTION - The resistance to motion between two contacting surfaces or substances. Friction is also developed between a flowing fluid and the inner wall of the conducting pipe - resulting in a drop in pressure.

FULL BORE (FULL PORT) - Describes a valve in which the bore (port) is nominally equal to the bore of the connecting pipe.

FULL OPENING - Describes a valve whose bore (port) is nominally equal to the bore of the connecting pipe.

GALLING - The tearing of metal when two elements rub against each other. Usually caused by lack of lubrication or extreme contact pressure.

GAS - A compressible fluid - such as air, hydrogen, nitrogen, etc.

GASKET - A component whose purpose is to seal a joint between two larger components, softer than the surfaces of the joint being sealed and usually squeezed by means of bolting to affect the seal.

GATE VALVE - A straight-thru pattern valve whose closure element is a wedge or parallel-sided slab, situated between two fixed seating surfaces, with means to move it in or out of the flow stream in a direction perpendicular to the pipeline axis.

GATE - The closure element of a gate valve (sometimes called wedge or disc).

GAUGE, PRESSURE - An instrument, usually with a threaded connection, for measuring and indicating the pressure in a piping system at the point at which it is connected.

GLAND FOLLOWER OR GLAND FLANGE - The component used to hold down or retain the gland in the stuffing box.

GLAND OR GLAND BUSHING - That part of a valve which retains or compresses the stem packing in a stuffing box (where used) or retains a stem O-ring, lip seal, or stem O-ring bushing. Sometimes manually adjustable. See "Packing," "StuffingBox."

GLAND PLATE - The plate in a valve which retains the gland, gland bushing or stem seals and sometimes guides the stem.

GLOBE VALVE - A valve whose closure element is a flat disc or conical plug sealing on a seat which is usually parallel to the flow axis. Can be used for throttling services.

GO - GEAR OPERATED - The actuation of a valve thru a gear set which multiplies the torque applied to the valve stem. See "BGO," "MGO."

GRAPHITE - Flexible carbon material used to make gaskets and packing. The gaskets may be flat graphite sheet or have metal inserts for added strength. The packing is a combination of lattice braided rings used as anti-extrusion or wiper rings and die-formed rings which are compressed to affect the seal.

GREASE FITTING - A fitting through which lubricant or sealant is injected.

HAND WHEEL - A wheel-shaped valve operating device intended to be grasped with one or both hands which allows turning the valve stem or operator shaft to which it is attached.

HARD FACING - A surface preparation in which an alloy is deposited on a metal surface usually by weld overlay to increase resistance to abrasion and or corrosion.

HUBS - The end connection tubes on a gate valve.

HUEY TEST - A corrosion resistance test for stainless steels, most useful for predicting resistance to intergranular corrosion.

HWO - HANDWHEEL OPERATED - A valve on which the handwheel drives the stem directly to operate the valve.