Name: Vajra Industrial Solutions
Address: 3rd Floor, 348, Aristo Complex, Opp. Sanghani Skyz, Navrachna University Road, Bhayali TP-2, Vadodara, Gujarat, 391410, IN
Telephone: +91-9979774557
Price range: $$

A

Actuator: A device that moves or controls a valve using an external power source — pneumatic (compressed air), electric (motor), or hydraulic (fluid pressure). Replaces manual operation for remote, automated, or fail-safe control.
API: American Petroleum Institute. Issues valve standards widely used in oil & gas: API 6D (pipeline valves), API 600 (gate valves), API 602 (small steel gate valves), API 609 (butterfly valves), API 526 (flanged safety relief valves), API 598 (valve testing and inspection).
API 6D: The API standard for pipeline and piping valves — gate, globe, check, ball, and plug valves used in oil & gas transmission pipelines. Covers design, materials, dimensions, testing (pressure test, seat leakage, shell test), and marking requirements. Considered the benchmark for oil & gas valve quality.
API 598: API standard for valve testing and inspection — shell (body) pressure test, seat leakage test, and backseat test. Defines acceptance criteria for leakage rates during hydrostatic and pneumatic tests. Most industrial valves are tested to API 598.
API 600: API standard for steel gate valves — flanged and butt-welding ends, NPS 1/2" to 60", Class 150 to 2500. Heavier-wall design than ASME B16.34 minimum; required for refinery and petrochemical gate valves.
API 602: API standard for compact steel gate valves — NPS 1/2" to 4", designed for smaller bore, higher-pressure instrument and process applications. Shorter face-to-face dimensions than API 600.
API 607: API standard for fire testing of soft-seated quarter-turn valves. Tests whether a valve maintains acceptable leakage after exposure to a fire event (fireproof integrity). Required for ball and butterfly valves in hydrocarbon service.
API 609: API standard for butterfly valves — lug- and wafer-style, Category A (concentric/resilient seat) and Category B (double or triple offset/metal seat). Covers design, materials, pressure-temperature ratings, and testing.
ASME: American Society of Mechanical Engineers. Issues B16 standards for valve dimensions and ratings: B16.34 (valves — flanged, threaded, and welding end), B16.5 (pipe flanges and flanged fittings), B16.10 (face-to-face dimensions), B16.25 (butt-welding ends).
ASME B16.34: The primary ASME standard for pressure-temperature ratings of valves with flanged, threaded, and welding ends. Defines allowable operating pressures at various temperatures for each material group and pressure class (Class 150 to 4500). Every industrial valve supplier must reference B16.34 ratings.
ASME B16.5: ASME standard for pipe flanges and flanged fittings — NPS 1/2" to 24", Class 150 to 2500. Defines flange dimensions: bolt circle, bolts, OD, raised-face dimensions. Used on valve flanged ends.

B

Backseat: A secondary sealing surface inside the valve body that seats against the stem when the valve is fully open. The backseat prevents leakage out through the stuffing box when the valve is fully open, allowing packing replacement under pressure. Required by API 600/602 for gate valves.
Ball Valve: A quarter-turn valve with a spherical ball as the obturator. The ball has a bore: when aligned with the pipeline the valve is open; rotated 90° it is closed. Available as floating ball (1/2"–6", Class 150–900) or trunnion-mounted (2"–48", Class 150–2500). Preferred for on-off and isolation service.
BEP (Best Efficiency Point): For pump/valve system design, the operating point at which a pump runs at maximum efficiency. Valve Cv sizing should account for system BEP to avoid excessive pressure drop.
Body: The main pressure-containing shell of the valve. Can be cast (WCB, CF8M), forged (A105, F316), or fabricated. Body material must be compatible with the process fluid and rated for the design temperature and pressure.
Bonnet: The top cover of the valve body that houses the stem and packing/seal arrangement. Can be bolted (standard), pressure-sealed (high-pressure), extended (cryogenic or high-temp), or welded (forged body valves). Also called the 'cover' or 'cap'.
Bore: The inside diameter of the valve flow passage. Full bore (full port): the bore equals the pipe ID, minimising pressure drop — preferred for pigging and high-flow services. Reduced bore (standard port): the bore is smaller than the pipe ID, used where pressure drop is acceptable and cost savings desired.
BTO (Breakaway Torque): The torque required to unseat a valve from its fully closed position — the highest torque the actuator must produce. BTO is the critical parameter for actuator sizing. Typically 1.5–2× the running torque for ball valves in clean service.
Butterfly Valve: A quarter-turn valve using a disc (butterfly) as the obturator. The disc rotates in the flow stream. Types: concentric (resilient seat, Class 150), double-offset (metal seat, Class 150–600), triple-offset (metal seat, tight shutoff, Class 150–900). Used in large-diameter (DN50–DN2000) on-off and throttling service.
Butt Weld (BW): A valve end connection where the valve body ends are welded directly to the pipeline. Provides the highest integrity, leak-free connection. Used for high-pressure, high-temperature, or critical service where flange joint leakage is unacceptable.

C

Cavitation: A damaging phenomenon in liquid service where the local pressure drops below the liquid's vapour pressure, forming vapour bubbles that then collapse violently as pressure recovers. Causes severe noise, vibration, and erosion of valve trim. Prevented by using anti-cavitation trim, multiple-stage pressure reduction, or changing valve location in the system.
Check Valve: A self-actuating valve that allows flow in one direction only, preventing backflow. Types include swing check (hinged disc), dual-plate (two spring-loaded half-discs, wafer pattern), tilting-disc, and piston-lift. Used after pumps, compressors, and in any line where backflow would damage equipment.
Class (Pressure Class): ASME/ANSI designation for a valve's pressure-temperature capability: Class 150, 300, 600, 900, 1500, 2500, 4500. Higher class = higher allowable pressure at temperature. Class 150 (~20 bar at ambient) to Class 2500 (~345 bar at ambient) for carbon steel WCB material. Select class based on maximum operating pressure at maximum temperature from B16.34 tables.
Concentric Butterfly Valve: The simplest butterfly valve design — the stem runs through the centre of the disc and the seat is a resilient (rubber or EPDM) ring. Suitable for water, HVAC, and low-pressure process up to Class 150. Also called 'centric' or 'rubber-seated' butterfly valve.
Control Valve: A valve used to regulate (modulate) flow, pressure, temperature, or liquid level. Uses an actuator and positioner to move the valve to any position between fully open and fully closed in response to a controller signal. Sized by Cv for the required flow range.
Cv (Flow Coefficient): The numerical measure of a valve's capacity to pass flow. Defined as the flow in US gal/min of water at 60°F (15.6°C) with a 1 psi pressure drop. Higher Cv = larger valve capacity. Formula for liquids: Cv = Q × √(SG / ΔP). European equivalent: Kv (m³/h at 1 bar ΔP). Relationship: Cv = 1.156 × Kv.
Cryogenic Valve: A valve designed for service at very low temperatures, typically below −46°C (−50°F). Features an extended bonnet (cold box) to keep the packing and stuffing box warm, preventing ice formation and packing failure. Used in LNG, liquid nitrogen, liquid oxygen, and liquid CO2 service.

D

DBB (Double Block and Bleed): A valve arrangement (or single valve body) providing two independent seating surfaces that isolate from both the upstream and downstream sides, with a bleed/vent port between them to confirm isolation and drain the cavity. Required by API 6D and many oil & gas plant procedures for safe isolation of equipment for maintenance.
Diaphragm Valve: A valve where a flexible diaphragm (EPDM, PTFE, or natural rubber) acts as the seating element. The diaphragm is pushed against a weir or straight-through body to close. No stem-to-fluid contact — ideal for sterile pharmaceutical, food, and corrosive chemical service. Certified to USP Class VI for pharma applications.
Double-Offset Butterfly Valve: A butterfly valve with two geometric offsets of the disc stem from the centreline and the pipe bore centreline. The offsets allow the disc to cam in and out of the seat, reducing friction and wear compared to concentric design. Suitable for tight shutoff in Class 150–300, temperatures to 200°C with metal seats.
Double-Seated Globe Valve: A globe valve with two seats and a plug that seats on both simultaneously. Provides inherently unbalanced forces at low pressure drops but allows smaller actuator because net pressure force on plug is low. Used for large flow control valves.
Dual-Plate Check Valve: A wafer-pattern check valve with two spring-loaded half-disc plates that open with forward flow and snap closed when flow stops. Much shorter face-to-face length than swing check; lower slam potential. Common in water, HVAC, and gas pipelines.
Duplex Stainless Steel: A family of stainless steels with a mixed austenitic-ferritic microstructure (≈50/50). Common grades: 2205 (UNS S31803/S32205), 2507 (super-duplex, UNS S32750). Offers approximately double the strength of 316L with better corrosion resistance in chloride environments. Used in offshore, seawater desalination, and chemical service.

E

E-Body (Eccentric Plug Valve): A plug valve variant where the plug has an eccentric (off-centre) seat that cams in and out during operation, reducing friction and wear. Used in slurry, sewage, and abrasive service.
EPDM: Ethylene Propylene Diene Monomer rubber. A common elastomer for valve seats and seals. Good resistance to hot water, steam (to 120°C), ozone, weathering. Not suitable for oils, fuels, or aromatic hydrocarbons. Used in water treatment, HVAC, and food-grade butterfly and diaphragm valves.
ESD (Emergency Shutdown) Valve: A safety-instrumented valve that closes automatically in an emergency (detected by gas sensors, fire detectors, or high-pressure switches) to isolate a section of process plant. Required by IEC 61511 for Safety Instrumented Systems (SIS). Typically a ball or globe valve with a spring-return pneumatic actuator, SIL-rated.
ETO (End-to-Open Torque): The torque required to unseat a valve from its fully open position when initiating a closing stroke. Usually lower than BTO for ball valves but can be the critical value for butterfly valves depending on disc geometry.
Extended Bonnet: An elongated bonnet that places the packing/stuffing box away from the extreme temperature of the process fluid. Used for cryogenic valves (cold box prevents ice bridging the stem) and high-temperature valves (heat dissipation protects packing). Standard for LNG and boiler applications.

F

Face-to-Face (F-F): The dimension from one flange face to the opposite flange face of a valve. Standardised by ASME B16.10 for all valve types and classes. Matching face-to-face allows replacement of one valve with another of the same type and class without cutting pipe. Critical for plant maintenance.
Fail-Closed (FC): An actuated valve that closes automatically on loss of instrument air (pneumatic) or electrical power. A spring-return actuator forces the valve closed. Used where the safe failure mode is to stop flow: e.g., fuel gas to burners, steam to reactors.
Fail-Open (FO): An actuated valve that opens automatically on loss of instrument air or power. Used where the safe failure mode is to maintain flow: e.g., cooling water supply to heat exchangers, quench water to fired coils.
Fire Safe (Fire Tested): A valve design tested to maintain acceptable leakage after exposure to a fire event as defined by API 607 or ISO 10497. Requires a secondary (usually graphite or metal) backup seat that seals when the primary soft seat is destroyed by fire. Mandatory for ball and butterfly valves in hydrocarbon service.
Flange: A projecting rim with bolt holes used to connect a valve to piping. Raised Face (RF) is standard for most services. Ring Type Joint (RTJ) is used for high-pressure Class 600+. Flat Face (FF) is used with cast iron to prevent flange cracking. Dimensions per ASME B16.5 (NPS 1/2"–24") or B16.47 (NPS 26"–60").
Flashing: When liquid flowing through a valve experiences a pressure drop below its vapour pressure and partly vaporises, and the downstream pressure is too low to allow re-condensation. Unlike cavitation, the vapour remains — causing severe erosion, noise, and vibration. Requires special trim (anti-flash) and materials.
Floating Ball Valve: A ball valve where the ball is not fixed to the body — it 'floats' between two seat rings and is pushed against the downstream seat by line pressure to seal. Suitable for NPS 1/2"–6", Class 150–900. Above 6" or Class 900+, trunnion-mounted design is preferred for lower operating torque.
Fugitive Emissions: Unintended leakage of process fluid to atmosphere through a valve's stem packing or shaft seal. Regulated by ISO 15848-1 (industrial valves) and EPA Method 21. Class A (≤10 ppm), Class B (≤100 ppm), Class C (≤500 ppm) per ISO 15848. Low-emission packing (graphite + anti-extrusion rings) required for LDAR compliance.
Full Bore (Full Port): A valve where the internal bore diameter equals the nominal pipe bore, resulting in minimal pressure drop (Cv approaches infinity relative to the pipe). Required for pig-launching lines, slurry service, viscous fluids, and systems with tight pressure budgets. Opposite: Reduced Bore.

G

Gate Valve: A multi-turn valve where a flat or wedge-shaped gate (disc) slides perpendicular to the flow to open or close. Provides minimal pressure drop when fully open. Not suitable for throttling. Types: solid wedge, flexible wedge, split wedge, slab gate (through-conduit), parallel slide. Standard for on-off isolation in pipelines.
Globe Valve: A multi-turn valve with a disc (plug) that moves perpendicular to the seat. Excellent for throttling due to the gradual change in flow area with disc position. High pressure drop compared to gate or ball valves. Used for flow control, steam service, feedwater, and chemical dosing. Available as T-pattern, Y-pattern, and angle body.
Graphite Packing: Stem packing made from flexible graphite, offering wide temperature range (−200°C to +550°C), good chemical resistance, and self-lubricating properties. Standard for fire-safe and high-temperature applications. Flexible graphite packing achieves low fugitive emissions per ISO 15848.

H

Handwheel: A manual wheel-shaped device attached to the valve stem for opening and closing by hand. Clockwise rotation typically closes the valve (right-hand thread). Gear operators (gearboxes) are added for large valves where manual force would be excessive.
Hastelloy: A family of nickel-based alloys with exceptional corrosion resistance. Most common valve grade: Hastelloy C-276 (UNS N10276) — resists concentrated sulfuric acid, hydrochloric acid, chlorine, and oxidising acids. Used where 316 SS fails. Other grades: C-22, B-3 (hydrochloric acid), G-30 (phosphoric acid).
HIPPS (High Integrity Pressure Protection System): A safety instrumented system designed to prevent overpressure in a vessel or pipeline, typically instead of or in addition to a conventional safety relief valve. Uses SIL-rated fast-closing valves, logic solvers, and pressure transmitters. Requires IEC 61511 functional safety assessment.
HMI (Hand-Manual Interface): Manual override capability on an actuated valve, allowing hand operation when power/air is unavailable. Quarter-turn valves use a lever declutch; multi-turn valves use a handwheel or gear operator. Required for plant startup and maintenance.

I

Inconel: A family of nickel-chromium superalloys used for extreme temperature and corrosion environments. Inconel 625 (UNS N06625): weld overlay for valve trim, sour service, and seawater. Inconel 718: high-strength fasteners and stem material. Used where Hastelloy and 316SS are insufficient.
ISO 5208: International standard for industrial valves — pressure testing of metallic valves. Defines test procedures for shell (body) test, seat leakage test, backseat test, and extended closure test. Rate A (zero leakage) through Rate F (max allowable rates). Commonly referenced alongside or instead of API 598.
ISO 15848: ISO standard for measurement, test, and qualification procedures for fugitive emissions from industrial valves. Part 1 for classification of production tightness (Class A/B/C) and types of tests; Part 2 for production acceptance tests. Used by refineries and chemical plants for environmental compliance.
Isolation Valve: A valve whose primary purpose is to fully open or fully close to isolate equipment or pipe sections for maintenance or emergencies. Must achieve tight shutoff (ANSI/FCI 70-2 Class IV, V, or VI). Ball, gate, and butterfly valves are common isolation types.

K

Knife Gate Valve: A gate valve variant with a thin, sharp-edged gate that slices through slurry, pulp, wastewater, or bulk solids. Unidirectional (one-direction shutoff) unless double-disc design. Used in water treatment, pulp & paper, mining, and sewage. Low cost for large DN (DN50–DN1000) applications.
Kv (Flow Factor): European equivalent of Cv. Defined as the flow in m³/h of water at 5–40°C with 1 bar pressure drop. Conversion: Cv = 1.156 × Kv, or Kv = 0.865 × Cv. Used in EN/DIN valve specifications and European process plants.

L

LDAR (Leak Detection and Repair): A regulatory programme (EPA Method 21 in the USA; EU IED in Europe) requiring periodic monitoring of valves, pumps, and flanges for fugitive hydrocarbon emissions, followed by repair when emissions exceed thresholds. Low-emission valves (ISO 15848 Class A) minimise LDAR repair frequency.
Limit Switch: An electrical device mounted on a valve to signal when the valve has reached its fully open or fully closed position. Sends feedback to the DCS or SCADA. Required for ESD valves and all valves in automated safety loops.
LNG (Liquefied Natural Gas): Natural gas cooled to −162°C to liquefy for transport. LNG service valves must be cryogenic-rated (extended bonnet), made from austenitic stainless steel or 9% nickel steel which remains ductile at −162°C. Carbon steel becomes brittle at these temperatures.
Lug Butterfly Valve: A butterfly valve with threaded inserts (lugs) in the body flange, allowing it to be bolted from both sides. Unlike wafer style, the lug design allows either side to be disconnected from the pipe independently — essential for end-of-line service. Also called 'tapped lug' or 'lug type'.

M

Metal Seat: A valve seat made from metal (hard-faced Stellite, stainless steel, or Inconel alloy overlay) rather than soft materials (PTFE or elastomer). Handles temperatures beyond the limits of soft seats (typically above 200°C or below −46°C) and abrasive services. Leakage rate is higher than soft seat (ANSI Class IV vs Class VI).
MTC (Material Test Certificate): A document (mill certificate) confirming the chemical composition and mechanical properties (tensile strength, yield strength, elongation, Charpy impact, hardness) of the material used in a valve component, traceable to the heat number. Required for all pressure-retaining valve components. EN 10204 Type 3.1 (manufacturer-certified) and 3.2 (third-party witnessed) are the standard MTC types.
MOP (Maximum Operating Pressure): The highest pressure at which a valve will be operated under normal conditions. Must be below the maximum allowable operating pressure (MAOP) at the operating temperature as defined by ASME B16.34 for the valve's pressure class and material group.
Multi-Turn Valve: A valve that requires multiple rotations of the handwheel or actuator to travel from fully open to fully closed. Includes gate, globe, diaphragm, and pinch valves. Opposite of quarter-turn valves (ball, butterfly, plug).

N

NACE MR0175: NACE International (now AMPP) standard for materials for use in H2S-containing (sour) oil and gas environments, to prevent sulfide stress cracking (SSC). Specifies maximum hardness limits for carbon steel (22 HRC max), low-alloy steel, and CRA (corrosion-resistant alloy) materials. Equivalent ISO standard: ISO 15156.
NBR (Nitrile Rubber): A synthetic rubber with good resistance to petroleum-based oils and fuels, making it common for valve O-rings and seats in hydrocarbon service. Temperature range: −40°C to +120°C. Not suitable for steam, hot water, or oxygenated solvents.
Needle Valve: A valve with a slender, tapered needle-shaped plug that mates with a conical seat. Provides precise, fine-control of small flows at high pressures. Used in instrument impulse lines, sampling systems, gauge isolation, and hydraulic circuits. Available in 1/4"–2", rated to 6,000–20,000 psi (415–1380 bar).
Non-Return Valve (NRV): Another term for check valve — a valve that allows flow in one direction and prevents reverse flow. 'Non-return valve' is the common term in UK/Commonwealth countries; 'check valve' is preferred in North America.

O

O-Ring: A circular cross-section elastomeric seal used in valve bore seals, stem seals, and body joints. Material selection (NBR, EPDM, Viton, PTFE, Kalrez) depends on the fluid, temperature, and pressure. O-ring materials are the first consideration in valve material selection for chemical compatibility.
OS&Y (Outside Screw and Yoke): A gate valve design where the stem threads are external to the valve body, outside the packing area. The rising handwheel visually indicates valve position — stem rising = valve opening. Preferred for critical services because the stem threads are not exposed to the process fluid.

P

Packing (Stem Packing): Sealing material compressed around the valve stem in the stuffing box to prevent leakage to atmosphere. Common types: PTFE (clean service, to 200°C), graphite (fire-safe, high-temperature, low-emission), and proprietary spiral-wound graphite for ISO 15848 Class A compliance.
Piggable Valve: A valve (usually ball or gate) designed with a full-bore opening and geometry that allows an inspection or cleaning pig to pass through without obstruction. Required on pig-launcher/receiver sections of oil and gas pipelines. Must be full-bore and have no body cavities that trap the pig.
Pilot-Operated Safety Valve (POSV): A pressure relief valve where a small pilot valve senses system pressure and controls a larger main valve. Provides tighter set-pressure accuracy (±0.5% vs ±3% for spring-loaded) and can be set closer to operating pressure (up to 98% of set pressure vs 90% for spring-loaded). Used where blowdown and tighter tolerances are needed.
Pinch Valve: A valve that controls flow by pinching a flexible rubber sleeve closed. The sleeve is the only wetted component — ideal for abrasive, corrosive, or sticky media (slurry, cement, fly ash, pulp) where metal trim would erode rapidly. Available DN25–DN400. Sleeve life is the limiting factor.
Plug Valve: A quarter-turn valve using a tapered or cylindrical plug with a through-bore as the obturator. Types: lubricated (sealant injected to reduce friction, used in dirty gas and oil service) and non-lubricated (PTFE-sleeved, clean service). Also eccentric plug type for slurry/sewage.
PMI (Positive Material Identification): Non-destructive testing to verify that valve materials match the specification. Typically done with handheld XRF (X-ray fluorescence) analysers that give elemental composition. Required on CRA (high-alloy) materials and in piping classes where material mix-up could cause catastrophic failure (e.g., 316L in chloride service where carbon steel was intended).
Positioner: A device mounted on a control valve actuator that receives the controller signal (4–20 mA or HART) and precisely positions the valve to achieve the required Cv. Pneumatic positioners supply air to the actuator; digital (SMART) positioners add diagnostics (valve signature, friction measurement, I/P conversion).
PRV / PSV (Pressure Relief Valve / Pressure Safety Valve): A valve that automatically opens when system pressure exceeds a set point, relieving excess pressure to protect vessels and pipelines from overpressure failure. PRV = modulating; PSV = snap-acting (full-lift). Designed to API 526 (flanged) or ASME Section VIII. Must be sized for the worst-case relief scenario.
PTFE (Polytetrafluoroethylene): A fluoropolymer with near-universal chemical resistance and very low friction coefficient. Used in valve seats (soft seat ball valves), stem packing, seat rings, and diaphragms. Temperature range: −200°C to +260°C. Creeps under load at high temperatures — use filled PTFE (glass, carbon, or graphite-filled) for better dimensional stability.

Q

Quarter-Turn Valve: A valve that requires only 90° rotation of the operator (handwheel, lever, or actuator) to travel from fully open to fully closed. Includes ball, butterfly, and plug valves. Fast operation; simple automation. Opposite: multi-turn valves (gate, globe).

R

Raised Face (RF): The most common flange face type — a raised ring concentric with the bore that concentrates gasket load on a narrow ring area, improving sealing efficiency. Standard for Class 150–600. RTJ is preferred at Class 900+.
Reduced Bore (Standard Port): A ball or gate valve where the internal bore is smaller than the nominal pipe size, creating a venturi-like restriction. Results in higher pressure drop but smaller, lighter, and cheaper valve than full bore equivalent. Suitable where pigging is not required and pressure drop is acceptable.
Rising Stem: A valve design where the stem moves upward as the valve opens, providing a visual indication of valve position. Standard on OS&Y gate valves. 'Non-rising stem' keeps the stem in place while a nut rises — used where headroom is limited.
RTJ (Ring Type Joint): A high-pressure flange face type using a metallic oval or octagonal ring gasket in a machined groove. Provides superior sealing at Class 900 and above. More expensive than raised-face and requires precise machining. Standard on high-pressure API 6D valves in Class 900–2500.
RTO (Run-to-Close Torque): The torque required to continue rotating a valve from partway open toward the fully closed position. Usually less than BTO. The actuator must sustain RTO throughout the entire stroke, not just at the seat.

S

Safety Valve: A type of pressure relief valve with a 'pop-action' (snap-open) mechanism that fully opens when set pressure is reached and remains open until pressure drops below the reseat pressure. Used on steam boilers (ASME Section I) and pressure vessels (ASME Section VIII). Sized to API 520/526.
Seat: The sealing surface inside the valve body against which the disc, ball, gate, or plug closes to achieve shutoff. Seat leakage class (ANSI/FCI 70-2) defines acceptable leakage: Class IV (metal seat, ≤0.01% of max Cv), Class V (metal, ≤0.0005% of max Cv), Class VI (soft seat, zero leakage per ANSI tables).
SIL (Safety Integrity Level): A measurement of the performance required for a safety instrumented function (SIF), defined by IEC 61508/61511. SIL 1 through SIL 4 (highest). ESD valves and final elements in safety loops must achieve the required SIL level through design and proof testing. SIL certificates are issued by independent bodies (TÜV, Exida).
Slab Gate Valve (Through-Conduit): A gate valve where the gate is a flat slab with a bore through it. When open, the bore aligns with the pipeline providing a full, unrestricted bore. No body cavity — ideal for piggable pipelines, slurry, and viscous oil. Standard for transmission pipelines to API 6D.
Soft Seat: A valve seat or seat ring made from resilient materials — PTFE, RPTFE (reinforced), DEVLON, or elastomers (EPDM, Viton, NBR). Achieves bubble-tight shutoff (ANSI Class VI). Temperature limited to the seat material rating (PTFE to 200°C). Susceptible to fire damage — paired with metal backup seat for fire-safe designs.
Solenoid Valve: An electromechanical valve using a magnetic coil to directly or indirectly control fluid flow. In valve automation, solenoid valves control the instrument air supply to pneumatic actuators — energising/de-energising the solenoid opens or closes the air path, driving the valve open or closed.
Sour Service: Fluid service containing hydrogen sulphide (H2S) at conditions that can cause sulfide stress cracking (SSC) of susceptible materials. Defined by NACE MR0175 / ISO 15156. All valve materials (body, trim, bolting, packing) must meet hardness limits and material qualifications for sour service.
Stellite: A cobalt-chromium alloy (e.g., Stellite 6, Stellite 21) used as a hard-facing overlay on valve seats and trim. Provides excellent resistance to wear, erosion, galling, and high-temperature oxidation. Applied by welding overlay on metal-seated ball, gate, and globe valves.
Strainer: A device installed upstream of valves, pumps, meters, and instruments to remove particulate from the fluid. Types: Y-type (in-line, small sizes), basket (larger sizes, side-entry for cleaning), duplex (two-basket with isolation for online basket change). Screen mesh from 10 mesh (coarse) to 100 mesh (fine) depends on the equipment to be protected.
Stuffing Box: The chamber in the valve body that houses and compresses the stem packing (gland packing). The gland follower (gland flange) is tightened to increase packing compression and stop leakage. Over-tightening increases stem friction and actuator torque; under-tightening allows fugitive emissions.
Super Duplex: High-alloy duplex stainless steels — 2507 (UNS S32750) and Zeron 100 (UNS S32760) — with PREN (Pitting Resistance Equivalent Number) > 40. Extremely resistant to chloride pitting, crevice corrosion, and stress corrosion cracking. Used in seawater injection, offshore, and subsea service where 2205 duplex is insufficient.
Swing Check Valve: A check valve with a hinged disc (clapper) that swings open on forward flow and swings closed on reverse flow. Simple and robust. Prone to slam on sudden flow reversal. Used in large water, steam, and gas lines where slam is manageable or where disc-assisted closing (spring or counterweight) is fitted.

T

Throttling: Partially opening a valve to restrict flow and create a pressure drop, used to regulate flow rate, pressure, or level. Globe valves are the best isolation valve design for throttling. Ball valves can throttle but create uneven seat wear. Gate valves must NOT be used for throttling — vibration destroys the seat.
Traceability: The ability to trace a valve component back to the original heat of material through documentation — MTCs, PMI, heat numbers stamped on components, and quality records. Required by ASME, API, and PED for all pressure-retaining components. Essential for critical service and ASME Code stamp valves.
Trim: The internal components of a valve that are in contact with the process fluid — seat rings, disc/gate/ball, stem, and packing. Trim material selection is critical for corrosion resistance, wear resistance, and temperature rating. Common trims: No. 8 (13Cr), No. 5 (Stellite), SS316, Monel, Hastelloy, and duplex stainless.
Triple-Offset Butterfly Valve (TOBV): The most advanced butterfly valve design with three geometric offsets: two on the disc/stem axis and one on the seat cone angle. The cone geometry means the disc and seat make contact only at the final moment of closing (zero friction during most of the stroke), achieving metal-to-metal shutoff equivalent to Class IV/V. Used for high-temperature steam, hydrocarbons, and critical isolation where zero leakage is needed. Rated to Class 150–2500, −196°C to +850°C.
Trunnion Ball Valve: A ball valve where the ball is fixed (supported) by upper and lower trunnion shafts, independent of pipeline pressure. Upstream and downstream seat rings are spring-loaded against the ball. Above NPS 4" or Class 600+, trunnion design is preferred because the ball is not displaced by line pressure — giving lower BTO and better seat life.

U

USP Class VI: United States Pharmacopeia standard for materials that contact food, pharmaceutical, or drug products. USP Class VI is the highest biocompatibility rating — tests include systemic toxicity, intracutaneous reactivity, and implantation. Required for elastomers (EPDM, Viton, silicone) and PTFE used in pharmaceutical diaphragm and ball valves.

V

Viton (FKM): Fluoroelastomer rubber with excellent resistance to hydrocarbons, fuels, solvents, and elevated temperatures (−20°C to +200°C, short excursions to 250°C). Common for valve O-rings and seats in oil & gas, chemical, and refinery service. Not suitable for steam, hot water, or ketones. Trade name: Viton® (Chemours).

W

Wafer Butterfly Valve: A butterfly valve designed to fit between two pipe flanges without its own flange bolting — the pipe bolts pass around the outside of the valve body. Lowest cost and lightest style. Cannot be used at end-of-line (pipe must be flanged on both sides). Lug design is needed for end-of-line service.
Water Hammer: A pressure surge caused by the sudden change in fluid velocity in a pipeline — most commonly when a valve closes rapidly and the kinetic energy of the moving fluid converts to a pressure wave. Can cause pipe, valve, and fitting failure. Prevented by slow-closing valves, water hammer arrestors, or air vessels.
Wedge: The closure element (gate) of a wedge gate valve. Types: solid wedge (most common, rigid), flexible wedge (machined groove on periphery allows slight flexing to compensate for thermal distortion — preferred in steam service), split wedge (two-piece, self-aligning). Flexible wedge is standard on steam line gate valves.

Y

Y-Pattern Valve: A globe valve (or strainer) design where the flow path is angled at approximately 45° through the body, creating a straighter flow path than a standard T-pattern globe, giving lower pressure drop and Cv. Used for high-pressure steam and where pressure drop must be minimised while still achieving throttling/isolation.
Yoke: The structural frame connecting the valve body to the actuator or handwheel. On OS&Y gate valves, the yoke carries the stem nut and provides the mechanical support for multi-turn operation. On actuated valves, the yoke or bracket transfers actuator forces to the valve body.

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