| AGA (Australian Gas Association) | The Australian Gas Association – a body that governs rules, regulations, and approvals for gas appliances and components in Australia |
| ANSI (American National Standards Institute) | A U.S. standards organization. In valves, “ANSI” often refers to US standard dimensions or classes (e.g. ANSI Class 150 flanges) |
| API (American Petroleum Institute) | Refers to API’s industry standards for valves. Example: API 6D for pipeline valves, API 600 for gate valves, API 607 fire-test for valves. |
| AS (Australian Standard) | National standards specifications issued by Standards Australia. Many valve designs and testing requirements in Australia follow AS or AS/NZS standards. |
| ASME (American Society of Mechanical Engineers) | An engineering society known for codes & standards. In valve context, ASME standards (e.g. ASME B16.34 for valves) define design, materials, and pressure ratings. |
| Bar | A unit of pressure. 1 bar ≈ 14.5 psi and ≈ 100 kPa (). Often used in valve pressure ratings (e.g. PN16 = 16 bar). |
| BSP (British Standard Pipe [thread]) | A standard pipe thread form (typically BSPT taper male, BSPP parallel female) used on many valve fittings in Australia for low-pressure applications. |
| Ball Valve (BV) | A quarter-turn valve that uses a hollow, perforated pivoting ball as the closure element. When the ball’s bore aligns with the pipeline, flow passes; a 90° turn blocks flow. It provides quick on-off control and tight sealing. |
| Bonnet | The cover on a valve body that encloses the internal parts. It’s usually made of the same material as the body and is bolted or welded in place to contain pressure, holding the stem and closure assembly inside. |
| Butterfly Valve (BFV) | A quarter-turn valve that uses a flat circular disc as the closing mechanism. Rotating the disc 90° within the pipe bore opens or closes flow. Butterfly valves are lightweight and offer quick shutoff or throttling. |
| Cavitation | The formation and collapse of vapor bubbles in a flowing liquid when local pressure drops below vapor pressure. Cavitation can cause noise and damage (pitting) to valve components when the bubbles implode. |
| Check Valve (Non-Return Valve, NRV) | A one-way valve that allows fluid to flow in only one direction and automatically prevents backflow. The valve opens with forward flow and closes if flow reverses ([What is a Check Valve and How Does it Work? |
| Choke Valve | A heavy-duty control valve designed to restrict flow and drop pressure, typically used at wellheads in oil & gas. It forces fluid through a narrow orifice (“choke”) to control production flow and downstream pressure . |
| Class (Pressure Class) | Refers to ANSI/ASME pressure rating classes for valves and flanges (e.g. Class 150, 300, 600). The class indicates the valve’s pressure-temperature rating (higher class = higher pressure capability). |
| Control Valve | A power-actuated valve that modulates flow to control process conditions (pressure, temperature, flow, level). It varies the size of the opening in response to a controller’s signal, allowing precise flow regulation in industrial processes. |
| DBB (Double Block and Bleed) Valve | A valve assembly that provides two isolation barriers in series plus a bleed point between them. In practice, it has two block valves and a bleed valve to vent the cavity between, enhancing isolation safety during maintenance. |
| Diaphragm Valve | A valve that uses a flexible diaphragm (membrane) pressed against a seat to stop flow. Lifting or lowering the diaphragm controls flow. This design isolates the working parts from the fluid, making it ideal for corrosive or slurry service. |
| DIN | Deutsches Institut für Normung, the German standards organization. “DIN” is often used to denote German standard dimensions or specifications (e.g. DIN flange dimensions). |
| DN (Diameter Nominal) | The nominal pipe size (in millimeters) used in metric standards for pipes and valves. For example, DN50 designates a nominal 50 mm bore (approximately 2″). It is a nominal reference, not an exact measurement of ID or OD. |
| ESDV (Emergency Shut Down Valve) | An emergency shutdown valve – a fast-acting actuated valve designed to stop the flow of hazardous fluid upon detection of an unsafe event. It is typically fail-safe (spring-closed) and part of a safety instrumented system. |
| EPDM (Ethylene Propylene Diene Monomer) | A type of synthetic rubber commonly used for valve seats and O-ring seals. EPDM is known for good resistance to water, weathering, and many chemicals (not petroleum oils). It’s widely used in water industry valves. |
| FF (Flat Face) | A type of flange face that is completely flat (no raised surface). It uses a full-face gasket for sealing and is common on cast iron or PVC valves and flanges in low-pressure service. |
| Foot Valve | A check valve with an integrated strainer, installed at the bottom (inlet) of a pump suction line. It permits flow into the suction line but prevents backflow when the pump stops, thus keeping the pump primed |
| Full Port (Full Bore) | Describes a valve (often a ball valve) whose internal flow passage is as large as the connecting pipe’s inner diameter. A full-port valve imposes no restriction on flow (no reduction in bore), minimizing pressure drop |
| Gate Valve (Sluice Valve) | A linear motion isolation valve that stops or allows flow by raising or lowering a flat gate (or wedge) into the path of the fluid. When the gate is lifted, flow passes through; when lowered, it seals against seats to shut off. Gate valves provide low resistance when fully open and are mainly used for on/off (not throttling). |
| Globe Valve | A type of valve with a usually spherical body and an internal movable disc (or plug) that moves perpendicular to the seat to regulate flow. Globe valves are used to start, stop, or throttle flow; they offer good flow control precision due to the disk-and-seat design. |
| Hydrostatic Test | (See “Pressure Test”) A testing procedure where a valve or piping is filled with water (or another liquid) and pressurized to check for leaks and verify integrity. Commonly required by standards for new or repaired valves. |
| ISO | International Organization for Standardization, a global standards body. ISO standards (e.g. ISO 5208 for valve testing) are often adopted in Australia/NZ for valve design, testing, and quality |
| Knife Gate Valve | A specialised gate valve with a thin, sharpened “knife-like” gate that can cut through heavy slurries or solids. Used in mining and wastewater, it provides on-off isolation for fluids with high solid content. (Not suited for throttling, as a partially open knife gate can cause vibration and wear.) |
| kPa (kilopascal) | A metric unit of pressure. 100 kPa = 1 bar. Often used in specifications – e.g. Australian standards might rate a valve to 1600 kPa (which is 16 bar) (). (1 kPa ≈ 0.145 psi.) |
| Lugged (Lug-Type Valve) | A style of valve body (commonly for butterfly or check valves) that has threaded “lug” holes matching the flange bolt pattern. A lugged valve can be bolted to one flange at a time, allowing the downstream flange to be removed while maintaining sealing on the upstream side (useful for dead-end service). |
| NACE | Refers to NACE International standards for corrosion. In valves, NACE compliance usually means meeting NACE MR0175/ISO 15156 material requirements for sour service (H₂S environments) ([What is Sour Service and Q&A on Material Selection |
| NB (Nominal Bore) | An older term for nominal pipe size, referring to the approximate bore (inside diameter). It’s used to quickly describe standard pipe/valve size (e.g. “50 NB” ~ 2 inch), but is not the exact measured ID or OD (). (Largely interchangeable with “Nominal Diameter” in context.) |
| NBR (Nitrile Butadiene Rubber) | A common elastomer (also known as Buna-N) used for O-rings and seals in valves. NBR is valued for its oil and fuel resistance, making it suitable for petroleum applications, and is also used in water valves. |
| Needle Valve | A small valve with a very fine, threaded stem (needle-like plunger) and a small orifice. It allows precise regulation of flow at low rates by gradual movement of the needle into or out of the orifice. Often used for calibration, metering, or in instrumentation lines. |
| NPT (National Pipe Taper) | A U.S. standard tapered pipe thread used for threaded valve ends and fittings (often in high-pressure or oilfield applications). NPT threads provide a seal by wedge-tightening and use thread sealant/tape. Common in 3000# and 6000# rated valves. |
| NRS (Non-Rising Stem) | Describes a gate valve design where the stem does not move up or down externally when the valve is operated. The stem’s thread is inside the valve, so the gate travels internally. NRS gate valves are used where vertical space is limited (e.g. underground); the position of the gate is not visible from the outside. |
| OS&Y (Outside Screw & Yoke) | A gate valve design with an exposed rising stem. The stem threads are external to the valve body, and the stem visibly moves up when opening. This gives a quick visual indication of the valve position (open/closed). OS&Y valves are common in firefighting systems and industrial services where monitoring valve status is important. |
| Pinch Valve | A valve that controls flow by pinching a flexible tube or sleeve to obstruct flow. When open, the sleeve is unrestricted (full bore); when closed, it is pinched shut. Pinch valves handle slurries or corrosive fluids well because the fluid contacts only the flexible sleeve |
| Plug Valve | A quarter-turn valve that uses a cylindrical or tapered plug with a hole through it as the closure element. Rotating the plug aligns the hole with the flow (open) or blocks the flow (closed). Plug valves (also called cock valves) provide quick shutoff and are often used for fuels, gases, and some slurries. |
| PN (Pressure Nominal) | A pressure rating system (in bar) used internationally (metric). PN followed by a number (e.g. PN16) indicates the approximate maximum working pressure in bars for a valve/flange at a reference temperature (). (PN16 is ~16 bar, PN20 ~20 bar, etc., analogous to ANSI class but in metric terms.) |
| Pressure Reducing Valve (PRV) | A valve that automatically reduces a higher inlet pressure to a steady lower outlet pressure. It maintains downstream pressure at a set level regardless of upstream fluctuations. PRVs (pressure regulators) are commonly used in water distribution (to prevent over-pressure to homes) and steam systems. |
| Pressure Relief Valve / Safety Valve (PRV / PSV) | A safety valve designed to open at a preset pressure to protect equipment from overpressure. When system pressure exceeds the setpoint, the valve opens and vents fluid (liquid or gas) until pressure drops to safe levels . It then re-closes. (PSV typically refers to a pressure safety valve for compressible fluids like steam or gas, which “pop” fully open at set pressure.) |
| psi (pounds per square inch) | An imperial unit of pressure. 1 psi = 6.895 kPa. For reference, 14.7 psi = 1 atmosphere ≈ 101 kPa. In valve specs, ANSI pressure classes are often given in psi (e.g. 150 psi class). Australia/NZ mostly use kPa/bar, but psi is seen in international specs. |
| PTFE (Polytetrafluoroethylene) | A highly inert, low-friction fluoropolymer used for valve seats, seals, and linings – best known by the brand name Teflon. PTFE has exceptional chemical resistance and a very low coefficient of friction (), making it ideal for tight sealing. It’s usable up to around 260°C. |
| Raised Face (RF) | A flange face type where the gasket-seating area is raised above the bolt circle. Most steel flanged valves have a raised face to concentrate gasket pressure. An RF flange is used with ring gaskets (not full-face) (). (Typical for ANSI/ASME flanges in Class 150 and above.) |
| Reduced Port (Reduced Bore) | A valve whose flow port is smaller than the pipe’s inner diameter (usually one size smaller). For example, a reduced-port ball valve in a 2″ line might have an internal bore equivalent to a 1½″ pipe. This causes a bit more friction loss compared to a full-port valve (). (Also called standard port in ball valves when one size reduction.) |
| Ring Type Joint (RTJ) | A metal-to-metal flange sealing method using a precision metal gasket ring and grooved flange faces. An RTJ flange has a circular groove; a soft metal ring gasket is crushed into the groove as bolts tighten, creating a high-pressure leak-tight seal. Common in high-pressure oil/gas service . |
| Seat (Valve Seat) | The sealing surface inside a valve on which the closure element (gate, disc, ball, etc.) rests to form a tight shut-off. Many valves have replaceable seats. The seat can be metal or a softer material (like PTFE or rubber) depending on the design – metal seats handle high temperature, soft seats provide zero leakage in low-temperature service. |
| Slurry Valve | A general term for any valve specifically engineered to handle slurries (fluids with suspended solids) in mining or mineral processing. Slurry valves often use robust designs and materials to resist abrasion – e.g. knife gate valves, pinch valves, or heavy-duty ball valves with liners are employed . |
| Socket Weld (SW) | An end connection type where the valve has a socket recess to accept a pipe end. The pipe is inserted and fillet-welded around the rim of the socket. Socket-weld valves are used for small bore high-pressure piping (common in stainless steel lines) to provide a strong, leak-free joint. |
| Solenoid Valve | An electrically actuated valve that uses a solenoid (electromagnetic coil) to move an internal plunger or diaphragm, opening or closing the orifice. When the coil is energized, the valve changes state. Solenoid valves enable automatic on/off control of fluids and are widely used in irrigation, pneumatic systems, and industrial automation. |
| Stem | The shaft that connects the valve’s handle or actuator to the internal closure element. Turning or moving the stem opens or closes the valve. In rising-stem valves, the stem moves linearly; in quarter-turn valves, it rotates. The stem typically passes through a packing gland in the bonnet to prevent leakage. |
| Trim | The collective term for a valve’s internal parts that contact the fluid and can be replaced. Valve trim usually includes the disc or plug, seat rings, stem, and other small internal pieces. Different trim materials (e.g. stainless steel, Monel, etc.) are chosen for compatibility with the fluid. |
| Two-piece Valve | Commonly refers to a two-piece ball valve design where the valve’s body is made in two halves (usually threaded or bolted together). This design is economical and sturdy, but the valve must be removed from the line to disassemble (not easily serviced in-line). |
| Three-piece Valve | A valve (often a ball valve) made of three sections: two end caps and a central body held together by bolts or screws. This allows the center section (with ball and seats) to be removed for maintenance without disturbing the pipe connections (). Three-piece valves are typically easier to service (rebuild/clean) but are more costly than two-piece designs. |
| Valve (general) | A mechanical device that controls the flow and pressure of fluids (liquids, gases, slurries) in a system. By moving a closure element (gate, ball, disk, plug, etc.), a valve can start/stop flow, throttle flow rate, or relieve pressure. Valves come in many types (as listed above), each suited to specific functions and industries. |
| Viton | A brand name for FKM, which is a fluoroelastomer (fluorinated rubber) often used for O-rings and seals in valves. Viton seals have excellent high-temperature stability and chemical resistance, making them suitable for aggressive fluids and temperatures up to ~200°C. |
| Wafer (Wafer-Style Valve) | A valve designed with a compact body that fits between two pipe flanges (held in place by the flange bolting, but without its own bolt holes). Many butterfly valves and some check valves are wafer-style. This design saves weight and space, but typically requires flange bolts to secure it in the pipeline (and usually does not allow one end disconnection like a lug type). |
| Water Hammer | A pressure surge or shock wave in a pipeline caused by a sudden change in flow velocity, such as quickly closing a valve. The kinetic energy of moving fluid is abruptly converted to a pressure spike, which can damage valves or pipes (). (Example: a loud “bang” in pipes when a tap is turned off quickly). |
| WaterMark | An Australian certification mark indicating a plumbing product is approved for potable (drinking water) use. A valve with WaterMark approval has been tested and meets the requirements for safe water supply. WaterMark certification is mandatory for plumbing products connected to the water mains in Australia. |
| Yoke | The yoke is the external structure on a valve (often part of the bonnet assembly) that supports top-mounted actuators or the screw mechanism of an OS&Y gate valve. In an OS&Y gate valve, the yoke holds the nut through which the stem threads, and often includes mounting for a handwheel or actuator. (Part of the term “Outside Screw and Yoke”). |
