Abbreviations

Acronyms and abbreviations

343 abbreviations insiders use without thinking, expanded and explained.

• AAMA 2604Powder Coating
  The mid-tier North American architectural coating spec, requiring five years of Florida exposure with limited fade.
• ACAsphalt
  Asphalt cement: the binder itself, and in pavement design talk, shorthand for the asphalt concrete layer.
• ACHHVAC
  Air changes per hour: how many times a space's full air volume is replaced in one hour.
• ADCPTides
  Acoustic Doppler current profiler: an instrument that measures current speed and direction at many depths at once.
• ADLNonwovens
  Acquisition distribution layer: the lofty layer under a diaper topsheet that takes in liquid and spreads it to the core.
• AES woolRefractories
  Alkaline earth silicate wool, a body-soluble high-temperature fiber used in place of ceramic fiber.
• AHUHVAC
  Air handling unit: the cabinet of fans, coils, filters and dampers that conditions and moves air through a building's ducts.
• ALARANuclear
  As low as reasonably achievable: the principle of keeping doses as low as practical, not just below limits.
• ALBHydrography
  Airborne lidar bathymetry: depth measured from an aircraft with green laser pulses that pass through the water.
• ANOVAStatistics
  Analysis of variance: splitting total variation into parts from each factor and from error, then testing which parts are real.
• AOIPCBs
  Automated optical inspection: camera system that checks boards for missing, shifted or badly soldered parts.
• AOSGeosynthetics
  Apparent opening size: an index of the largest openings in a geotextile, given as a US sieve number or in millimeters.
• APCFiber Optics
  Angled Physical Contact: a singlemode connector polish with an 8 degree angle that sends reflections into the cladding.
• AQLStatistics
  Acceptable quality level: the defect rate a sampling plan is built to pass most of the time, the good end of its OC curve.
• ASEPhotonics
  Amplified Spontaneous Emission: random spontaneous photons amplified in a gain medium, a broadband noise background.
• ASRConcrete
  Alkali-silica reaction, a slow internal reaction between cement alkalis and certain aggregates that cracks concrete.
• AWTribology
  Antiwear: additives or oils that build protective films to cut wear under moderate boundary contact.
• AZSRefractories
  Alumina-zirconia-silica fused-cast refractory, the standard glass-contact material in glass melting furnaces.
• BBRAsphalt
  Bending beam rheometer: the test that checks how stiff and brittle a binder gets at low temperature.
• BFENonwovens
  Bacterial filtration efficiency: the percentage of a bacteria-laden aerosol that a mask or filter fabric stops.
• BFVValves
  Butterfly valve: the clipped form used on valve tags, takeoff sheets and HVAC and fire protection drawings. Shop talk
• BILElectrotechnology
  Basic lightning impulse insulation level: the peak impulse voltage equipment must withstand without breakdown.
• BMSBoilers
  Burner management system: the safety controls that handle purge, ignition, flame proving and trips on larger boilers.
• BOMPCBs
  Bill of materials: list of every part on an assembly with designators, values and part numbers.
• CAFPCBs
  Conductive anodic filament: copper growth along glass fibers inside a board that shorts holes under voltage.
• CATZOCHydrography
  Category of zone of confidence: the ENC quality code that tells mariners how far to trust the depth data.
• CCSRefractories
  Cold crushing strength: the room-temperature compressive strength of a refractory, in MPa or psi.
• CCTLighting
  Correlated Color Temperature: the warm-to-cool appearance of white light, stated in kelvin.
• CDNonwovens
  Cross direction: the direction across the width of a nonwoven roll, at right angles to machine travel.
• CDFNuclear
  Core damage frequency: the estimated likelihood per reactor-year of an accident that damages the core.
• CFMHVAC
  Cubic feet per minute: the standard unit of airflow through equipment, ducts and outlets.
• CIELABPaper Optics
  Color space describing a color by lightness L* plus a* for red-green and b* for yellow-blue.
• CISCorrosion
  Close interval survey: potential readings taken every metre or so along a pipeline to find protection gaps.
• CJPWelding
  Complete joint penetration: a groove weld that fuses through the full thickness of the joint.
• CLSMConcrete
  Controlled low-strength material, the soupy flowable fill poured into trenches and voids instead of compacted soil.
• CMCMetrology
  Calibration and measurement capability, the best uncertainty a lab can routinely deliver for a given calibration.
• COBLighting
  Chip-on-Board: an LED array with many dies mounted closely under one phosphor layer, acting as a single compact source.
• COPHVAC
  Coefficient of performance: heat moved or delivered for each unit of energy put in, with both measured in the same units.
• CpStatistics
  Process capability ratio: the specification width divided by six process standard deviations, ignoring centering.
• CPAPhotonics
  Chirped Pulse Amplification: stretching a short pulse before amplifying it, then recompressing it afterwards.
• CpkStatistics
  Process capability index that accounts for centering: distance from the mean to the nearest spec limit in units of 3 sigma.
• CQAGeosynthetics
  Construction quality assurance: independent monitoring and testing that a geosynthetic system was built as designed.
• CRILighting
  Color Rendering Index: a score up to 100 for how true surface colors look under a source compared with a reference light.
• CSECorrosion
  Copper-copper sulfate electrode, the standard reference for pipe-to-soil potential readings.
• CSPWaterproofing
  Concrete surface profile, a 1 to 10 scale of how rough a prepared concrete surface is.
• CTElectrotechnology
  Current transformer: an instrument transformer that scales large primary currents down to a standard secondary.
• CTCRailroad
  Centralized traffic control: signals and switches controlled remotely by a dispatcher who routes every train.
• CTE mismatchAdhesives
  Coefficient of thermal expansion mismatch, the different growth of bonded materials with heat that stresses the bond.
• CTIElectrotechnology
  Comparative tracking index: voltage an insulating material withstands before tracking under a wet contamination test.
• CTOLighting
  Color Temperature Orange: a correction gel that warms daylight-balanced light toward tungsten color temperature.
• CUBEHydrography
  Combined Uncertainty and Bathymetry Estimator: an algorithm that builds a depth surface by weighting soundings by uncertainty.
• CUICorrosion
  Corrosion under insulation: hidden external corrosion of piping and vessels beneath wet thermal insulation.
• CUSUMStatistics
  Cumulative sum chart: adds up deviations from target so that a small persistent shift builds into a clear signal.
• CVNonwovens
  Coefficient of variation: standard deviation divided by the mean, the yardstick of nonwoven uniformity.
• CvValves
  Flow coefficient: US gallons per minute of 60 degree F water a valve passes with a 1 psi pressure drop.
• CWPhotonics
  Continuous Wave: laser operation with a steady output beam rather than pulses.
• CWIWelding
  Certified Welding Inspector: the AWS inspection credential, and the usual job title for the person checking welds.
• DALILighting
  Digital Addressable Lighting Interface: a two-wire digital lighting control bus where each driver has its own address.
• DCEPWelding
  Direct current electrode positive: welding polarity with the electrode on the positive terminal.
• DCVHVAC
  Demand-controlled ventilation: adjusting outdoor air in real time to match how many people are actually in a space.
• DCVGCorrosion
  Direct current voltage gradient survey that locates and sizes coating holidays on buried pipe.
• DFMPCBs
  Design for manufacturability: checking and adjusting a design so it can be built reliably at sensible cost.
• DFTCorrosion
  Dry film thickness: the thickness of a cured coating layer, measured in mils or microns.
• DIHeat Treating
  Ideal critical diameter: the largest bar that would reach 50 percent martensite at its center in a perfect quench.
• DI rinsePowder Coating
  Deionized water rinse, the final stage that washes salts off the part so they do not end up trapped under powder.
• DkPCBs
  Dielectric constant: how much a board material slows signals and sets trace impedance, relative to vacuum.
• DMXLighting
  DMX512: the digital control protocol for stage and architectural lighting, carrying 512 channels per universe.
• DOEStatistics
  Design of experiments: planning a set of runs that vary several factors at once so their effects can be separated.
• DPMOStatistics
  Defects per million opportunities: defect count scaled by the number of chances for a defect in each unit.
• DPURailroad
  Distributed power unit: a locomotive placed mid-train or on the rear and controlled by radio from the lead unit.
• DRCPCBs
  Design rule check: automated scan of a layout for spacing, width, drill and connectivity violations.
• DSRailroad
  Dispatcher, as said on the radio: the person who controls train movements over a territory. Shop talk
• DSRAsphalt
  Dynamic shear rheometer: the instrument that measures a binder's stiffness and elasticity by twisting a thin disk of it.
• DTCRailroad
  Direct traffic control: authority granted by named blocks of track on unsignaled lines.
• DTIFasteners
  Direct tension indicator: a hardened washer with bumps that flatten when the bolt reaches required tension.
• DtoNHydrography
  Danger to navigation: a newly found hazard reported urgently so charts and warnings change before the survey ends.
• DVCThermal Spray
  Dense vertically cracked: a thermal barrier sprayed hot so it forms deliberate through-thickness cracks.
• ECCSNuclear
  Emergency core cooling system: the set of safety systems that inject water to keep the core covered after a loss of coolant.
• ECDISHydrography
  Electronic Chart Display and Information System: the type-approved chart system a ship can carry in place of paper charts.
• EDFAPhotonics
  Erbium-Doped Fiber Amplifier: the optical amplifier that boosts signals near 1550 nm without converting them to electronics.
• EDRBoilers
  Equivalent direct radiation: the square-foot rating of heating radiators, used to size steam boilers.
• EERHVAC
  Energy efficiency ratio: cooling output in Btu per hour divided by watts of input at one hot, full-load test point.
• ELDWaterproofing
  Electronic leak detection, using a small electric current to pinpoint breaches in a membrane.
• ELLGeosynthetics
  Electrical leak location: surveys that find holes in an installed geomembrane by tracing current through them.
• EMCElectrotechnology
  Electromagnetic compatibility: a product neither upsets nearby equipment with its noise nor gets upset by theirs.
• EMIElectrotechnology
  Electromagnetic interference: unwanted electrical noise that disturbs the operation of a circuit or system.
• EMTElectricians
  Electrical metallic tubing: thin-wall, unthreaded steel conduit joined with set-screw or compression fittings.
• ENCHydrography
  Electronic navigational chart: an official vector chart database used in ECDIS, built from objects with attributes.
• ENIGPCBs
  Electroless nickel immersion gold: flat surface finish of nickel topped with a very thin layer of gold.
• EOTRailroad
  End-of-train device: a unit hung on the last car's coupler that reports rear brake pipe pressure and motion to the head end.
• EPTribology
  Extreme pressure: additives or oils that react with metal under heavy load to prevent welding and scuffing.
• EPDNuclear
  Electronic personal dosimeter: a worn device that shows dose and dose rate live and alarms at set points.
• EPZNuclear
  Emergency planning zone: the area around a nuclear plant where protective actions are pre-planned.
• ER probeCorrosion
  Electrical resistance probe that tracks corrosion by measuring the rising resistance of a thinning metal element.
• ERSHydrography
  Ellipsoidally referenced survey: depths taken from GNSS ellipsoid heights and converted to chart datum with a separation model.
• ERVHVAC
  Energy recovery ventilator: a unit that swaps heat and moisture between outgoing exhaust air and incoming fresh air.
• ESDElectrotechnology
  Electrostatic discharge: sudden flow of built-up static charge that can destroy or upset electronics.
• EWMAStatistics
  Exponentially weighted moving average: a chart or controller that blends each reading with the past to catch small, slow shifts.
• FBECorrosion
  Fusion-bonded epoxy: a powder coating fused onto heated pipe, the standard external line pipe coating.
• FBEPowder Coating
  Fusion-bonded epoxy, a fast-curing epoxy powder applied to preheated pipe, rebar and valves for corrosion protection.
• FCAWWelding
  Flux-cored arc welding: arc welding with a tubular wire filled with flux, with or without shielding gas.
• FITStatistics
  Failures in time: one failure per billion device-hours, the standard unit for semiconductor failure rates.
• FNCHeat Treating
  Ferritic nitrocarburizing: adding nitrogen and carbon below the critical temperature for a thin, hard layer.
• FRARailroad
  Federal Railroad Administration: the federal agency that sets and enforces railroad safety rules.
• FTBGeosynthetics
  Film tear bond: a seam coupon that breaks in the sheet beside the weld rather than through the weld itself.
• FTIRTribology
  Fourier transform infrared spectroscopy, an oil test that fingerprints oxidation, contamination and additive loss.
• FTTHFiber Optics
  Fiber to the Home: access networks that run fiber all the way into each residence.
• GCLGeosynthetics
  Geosynthetic clay liner: a factory-made barrier of sodium bentonite held between two geotextiles.
• GMAWWelding
  Gas metal arc welding: a continuously fed wire electrode shielded by gas, known in the shop as MIG.
• GMFGears
  Gear mesh frequency: tooth count times shaft speed, the frequency at which teeth enter mesh.
• GNSSHydrography
  Global navigation satellite systems: satellite positioning such as GPS, GLONASS, Galileo and BeiDou, used together.
• gsmNonwovens
  Grams per square meter, the shorthand unit for nonwoven basis weight on specs, labels and the line.
• GTAWWelding
  Gas tungsten arc welding: an arc from a non-consumable tungsten electrode under inert gas, known as TIG.
• GUMMetrology
  Guide to the Expression of Uncertainty in Measurement, the core reference method for evaluating measurement uncertainty.
• GVDPhotonics
  Group Velocity Dispersion: how strongly a material's group velocity changes with wavelength, which stretches short pulses.
• HAAPowder Coating
  Hydroxyalkylamide, the TGIC-free crosslinker used to cure carboxyl polyester powders.
• HASLPCBs
  Hot air solder leveling: finish made by dipping a board in molten solder and blowing off the excess.
• HAZWelding
  Heat-affected zone: base metal next to a weld whose structure changed from the heat but did not melt.
• HDGFasteners
  Hot-dip galvanized: coated by dipping in molten zinc, leaving a thick, rugged layer for outdoor steel.
• HDIPCBs
  High-density interconnect: boards built with microvias, fine lines and sequential lamination for dense parts.
• HDPEGeosynthetics
  High-density polyethylene: the stiff, chemically resistant polymer used for most landfill and mining geomembranes.
• HIDLighting
  High-Intensity Discharge: lamps such as metal halide and high-pressure sodium that make light from an electric arc in a pressurized tube.
• HMAAsphalt
  Hot mix asphalt: aggregate and binder mixed hot at a plant, hauled hot and compacted before it cools.
• HMORRefractories
  Hot modulus of rupture: the bending strength of a refractory measured at high temperature.
• HRWRConcrete
  High-range water reducer, the superplasticizer that makes concrete flow without adding water.
• HSPFHVAC
  Heating seasonal performance factor: a heat pump's seasonal heating output in Btu divided by its electricity use in watt-hours.
• HSSMachine Shop
  High-speed steel: the tough, hand-grindable tool steel used for drills, taps, lathe bits and some endmills.
• HVAFThermal Spray
  High-velocity air fuel: an HVOF-style process that burns fuel with compressed air instead of oxygen.
• HVOFThermal Spray
  High-velocity oxygen fuel: burning fuel and oxygen under pressure to fire powder at supersonic speed.
• I-MR chartStatistics
  Individuals and moving range chart: the control chart for one measurement per period, such as one batch or one lot.
• IAQHVAC
  Indoor air quality: how clean and healthy indoor air is, judged by contaminants, ventilation, humidity and comfort.
• ICCPCorrosion
  Impressed current cathodic protection: CP powered by a rectifier pushing current through long-life anodes.
• IDMTElectrotechnology
  Inverse definite minimum time: an overcurrent curve that trips faster as current rises, down to a set minimum.
• IFBRefractories
  Insulating firebrick: light, porous brick rated by the maximum temperature it can face, such as group 23 or 26.
• IGUWaterproofing
  Insulating glass unit, two or more lites sealed around a spacer with a dry air or gas space between.
• ILICorrosion
  In-line inspection: sending instrumented tools through a pipeline to measure wall loss, dents and cracks.
• IPLVHVAC
  Integrated part load value: a single weighted chiller efficiency figure that reflects operation at 100, 75, 50 and 25 percent load.
• ipRGCLighting
  Intrinsically photosensitive retinal ganglion cells: eye cells that sense light for the body clock rather than for vision.
• IRIAsphalt
  International Roughness Index: a measure of ride quality in inches per mile, collected with a laser profiler.
• ISO VGTribology
  ISO viscosity grade, the number on an industrial oil that names its kinematic viscosity in cSt at 40 C.
• JMFAsphalt
  Job mix formula: the approved recipe of gradation and binder content a plant must produce on a project.
• KINuclear
  Potassium iodide: stable iodine tablets taken to block the thyroid from absorbing radioactive iodine.
• KOElectricians
  Knockout: a partly punched disc in a box or panel that is removed to make a hole for a conduit or cable fitting. Shop talk
• kVPowder Coating
  Kilovolts, the voltage setting on a corona gun that governs how hard it charges the powder.
• LATTides
  Lowest Astronomical Tide: the lowest level that tide predictions reach when the weather is held at average.
• LBElectricians
  L-shaped conduit body with its outlet on the back, used to turn a conduit run straight through a wall.
• LCFiber Optics
  Lucent Connector: the small latching connector with a 1.25 mm ferrule used on most transceivers and data center panels.
• LCONuclear
  Limiting condition for operation: a technical specification requirement for equipment or conditions needed to run the plant.
• LEDLighting
  Light-Emitting Diode: a semiconductor light source, made white for lighting by coating a blue chip with phosphor.
• LLDPEGeosynthetics
  Linear low-density polyethylene: a softer, more flexible geomembrane polymer that follows uneven ground better than HDPE.
• LMAPhotonics
  Large Mode Area: fiber with an enlarged core that spreads light out to raise nonlinear and damage limits.
• LNTNuclear
  Linear no-threshold model: the assumption that cancer risk rises in direct proportion to dose, with no safe threshold.
• LOCANuclear
  Loss of coolant accident: a break or leak in the reactor coolant system that lets coolant escape faster than it can be replaced.
• LPRCorrosion
  Linear polarization resistance: an electrochemical method that reads corrosion rate in minutes in conductive liquids.
• LRAHVAC
  Locked rotor amps: the current a motor draws at the instant of starting, before it turns, listed on the nameplate.
• LSEAdhesives
  Low surface energy, describing plastics and coatings that most adhesives cannot wet or bond without help.
• LTDSGeosynthetics
  Long-term design strength: reinforcement strength left after reductions for creep, installation damage and aging.
• LTPDStatistics
  Lot tolerance percent defective: the poor quality level that a sampling plan should reject with high probability.
• MARVGeosynthetics
  Minimum average roll value: the lowest average test result a product guarantees for any roll it ships.
• MAWPBoilers
  Maximum allowable working pressure: the highest pressure a boiler is approved to operate at, stamped on its nameplate.
• MBESHydrography
  Multibeam echo sounder: a sonar that measures a fan of depths across the track on every ping, covering a wide swath.
• MBHBoilers
  Thousands of Btu per hour: the everyday unit for rating heating boilers, burners and heating loads.
• MDNonwovens
  Machine direction: the direction a nonwoven travels through the line, along the length of the roll.
• MERVHVAC
  Minimum efficiency reporting value: a 1 to 16 rating of how well an air filter captures particles of different sizes.
• MHHWTides
  Mean Higher High Water: the average height of the higher of each day's two high waters over the datum epoch.
• MHWTides
  Mean High Water: the mean height of every high tide across the datum epoch, often the line that defines the legal shoreline.
• MICCorrosion
  Microbiologically influenced corrosion: corrosion started or sped up by bacteria and other microbes.
• MLLWTides
  Mean Lower Low Water: the average height of the lower of each day's two low waters, used as chart datum in the United States.
• MLOElectricians
  Main lugs only: a panel with no main breaker, fed through lugs from a breaker or fuse somewhere upstream.
• MMAAdhesives
  Methyl methacrylate, the monomer behind most structural acrylic adhesives and the shorthand name for them.
• MMOCorrosion
  Mixed metal oxide anode: titanium coated with precious-metal oxides, the standard long-life ICCP anode.
• MOPAPhotonics
  Master Oscillator Power Amplifier: a low-power seed laser followed by amplifier stages that bring it to full power.
• MOVValves
  Motor-operated valve: a valve driven by an electric actuator with a motor, gearbox, torque switch and limit switches.
• MOWRailroad
  Maintenance of way: the department and crews that build and maintain track, bridges and roadbed.
• MPRailroad
  Milepost: the numbered marker that fixes every location on a railroad by distance along the line.
• MPCTribology
  Membrane patch colorimetry, a test that measures varnish-forming material in turbine and hydraulic oils.
• MPEMetrology
  Maximum permissible error: the error limit an instrument must stay inside to conform, set by its spec, a standard or the law.
• MPOFiber Optics
  Multi-fiber Push-On: a single connector that terminates 8, 12, 16 or 24 fibers in one rectangular ferrule.
• MRUHydrography
  Motion reference unit: the sensor that measures a vessel's roll, pitch and heave to correct sonar data.
• MSAStatistics
  Measurement systems analysis: the set of studies that prove a gauge is fit for the decisions its data will drive.
• MSCRAsphalt
  Multiple stress creep recovery: a high-temperature binder test measuring how much of a deformation the binder recovers.
• MSLTides
  Mean Sea Level: the plain average of a station's hourly water levels across the tidal datum epoch.
• MTWelding
  Magnetic particle testing: finding surface and near-surface cracks in steel with a magnetic field and iron powder.
• MTBFStatistics
  Mean time between failures: average operating time between successive failures of a repairable system.
• MTLTides
  Mean Tide Level: the height midway between the mean high water and mean low water datums.
• MTTFStatistics
  Mean time to failure: expected life of a non-repairable item, the average time until its first and only failure.
• MTVAsphalt
  Material transfer vehicle: a machine between the trucks and the paver that remixes hot mix and feeds it nonstop.
• MWBCElectricians
  Multiwire branch circuit: two or three hot conductors on different phases sharing one neutral.
• NAVDTides
  North American Vertical Datum: the geodetic height reference used for land elevations across the United States.
• NEGVacuum
  Non-evaporable getter: a porous alloy that pumps active gases once it has been activated by heating in vacuum.
• NMASAsphalt
  Nominal maximum aggregate size: the sieve size used to name a mix, such as a 9.5 mm or 19 mm mix.
• NMIMetrology
  National metrology institute, the body that realizes a country's measurement units at the top of its traceability chain.
• NPTValves
  National Pipe Taper: the tapered pipe thread used for threaded valves and fittings in North America.
• OBAPaper Optics
  Optical brightening agent: a dye that absorbs UV light and re-emits it as blue, making paper look whiter.
• OCAPStatistics
  Out-of-control action plan: the scripted checklist that tells operators exactly what to do when an SPC chart fires.
• ODPhotonics
  Optical Density: a logarithmic measure of how strongly a filter or laser eyewear blocks light at a given wavelength.
• ODB++PCBs
  Structured CAD-to-fabrication data format that packs layers, drills, netlist and part data into one package.
• OFATStatistics
  One factor at a time: changing a single input while holding the rest fixed, the habit designed experiments replace. Shop talk
• OITGeosynthetics
  Oxidative induction time: a measure of how much antioxidant protection remains in a polyolefin geosynthetic.
• OLTCElectrotechnology
  On-load tap changer: a transformer switch that changes the turns ratio under load to regulate voltage.
• OLTSFiber Optics
  Optical Loss Test Set: a light source and power meter used together to measure end-to-end link loss.
• OOCStatistics
  Out of control: shorthand for a point or chart that has violated a control limit or run rule. Shop talk
• OOSStatistics
  Out of specification: a measured result outside the spec limits, meaning the product itself is nonconforming.
• OOTMetrology
  Out of tolerance, an as-found calibration result outside the instrument's allowed limits. Shop talk
• OPOPhotonics
  Optical Parametric Oscillator: a tunable source that splits pump photons into two longer-wavelength beams in a nonlinear crystal.
• OSRailroad
  On sheet: a report of the time a train passed a station, or the act of reporting it. Shop talk
• OS&YValves
  Outside screw and yoke: a rising-stem valve design with its stem threads above the packing, out of the fluid.
• OS2Fiber Optics
  Optical Singlemode 2: the low-water-peak cabled singlemode grade used for most indoor and outdoor singlemode installs.
• OTDRFiber Optics
  Optical Time Domain Reflectometer: a tester that maps a fiber's loss and events by timing light reflected back along it.
• PAGTribology
  Polyalkylene glycol, a synthetic base oil prized for low friction and clean running but hostile to most other oils.
• PAOTribology
  Polyalphaolefin, the synthetic hydrocarbon base oil built from alpha-olefins and classed as Group IV.
• PAVAsphalt
  Pressure aging vessel: the test that ages binder under heat and pressure to simulate years of service on the road.
• PC numberPaper Optics
  Post color number: a Kubelka-Munk measure of how much a pulp yellows during an aging test.
• PCCPaper Optics
  Precipitated calcium carbonate: a synthetic filler, often made beside the mill, that raises brightness and opacity.
• PCERefractories
  Pyrometric cone equivalent: a refractory's softening point expressed as the number of a matching standard cone.
• PCENuclear
  Personnel contamination event: contamination found on a worker's skin or personal clothing above a set threshold. Shop talk
• PCMNuclear
  Personnel contamination monitor: a walk-in booth that scans the whole body for contamination at exits.
• PDFMetrology
  Probability density function, the curve describing how likely each possible value of a quantity is.
• PFAMetrology
  Probability of false accept, the chance that a nonconforming item is measured and passed as good.
• PFRMetrology
  Probability of false reject, the chance that an item actually in tolerance is measured and failed.
• PGAsphalt
  Performance Grade: the binder rating that names the hottest and coldest pavement temperatures a binder can handle.
• PLCRefractories
  Permanent linear change: the lasting shrinkage or growth of a refractory after heating and cooling.
• PMTPowder Coating
  Part metal temperature, the temperature of the substrate itself, which is what actually drives the cure.
• PNValves
  Pressure nominal: the metric rating series, such as PN 16 or PN 40, used for European and ISO valves and flanges.
• PONFiber Optics
  Passive Optical Network: a point-to-multipoint fiber network where unpowered splitters share one fiber among many users.
• PPNonwovens
  Polypropylene: the most widely used polymer in nonwovens, especially spunbond and meltblown fabrics.
• PPKHydrography
  Post-processed kinematic: GNSS positions computed after the survey from logged rover and base data, at centimetre level.
• PpkStatistics
  Process performance index: a Cpk-style figure computed with the overall standard deviation, capturing long-term variation.
• PQRWelding
  Procedure qualification record: the documented test weld and results that support a WPS.
• PRENCorrosion
  Pitting resistance equivalent number: an index of a stainless alloy's chloride pitting resistance from its chemistry.
• PSAAdhesives
  Pressure-sensitive adhesive, the always-tacky layer on tapes and labels that bonds under finger pressure with no cure step.
• PSANuclear
  Probabilistic safety assessment: a systematic model of how accidents could happen and how likely each outcome is.
• PTWelding
  Penetrant testing: revealing surface-breaking cracks by drawing colored or fluorescent dye out of them.
• PTConcrete
  Post-tensioning: reinforcing concrete with steel tendons that are stretched tight after the concrete hardens.
• PT chartHVAC
  Pressure-temperature chart: a table giving each refrigerant's saturation temperature at each pressure.
• PTCRailroad
  Positive train control: an onboard and wayside system that stops a train before it breaks a speed limit or authority.
• PTHPCBs
  Plated through-hole: a drilled hole whose walls are copper-plated to connect every layer it passes through.
• PURAdhesives
  Polyurethane reactive hot melt, applied molten like a hot melt, then moisture-cured into a heat-resistant bond.
• PVAAdhesives
  Polyvinyl acetate emulsion, the white or yellow wood glue that sets as its water soaks into the wood.
• PVCGeosynthetics
  Polyvinyl chloride: a flexible, plasticized geomembrane that folds and seams easily, used in ponds, canals and water features.
• PWHTWelding
  Postweld heat treatment: heating a finished weld to relieve stress and temper the heat-affected zone.
• PWLAsphalt
  Percent within limits: a statistical measure of how much of a lot falls inside the specification limits.
• Q&THeat Treating
  Quench and temper: hardening steel by quenching, then tempering it back to a set strength and toughness.
• QC/QAAsphalt
  Quality control and quality assurance: contractor testing to run production and agency testing to verify it.
• R&OTribology
  Rust and oxidation inhibited: a lightly additized oil with no antiwear or EP chemistry.
• R&RWaterproofing
  Remove and replace: cutting out old sealant completely and installing new sealant in the cleaned joint. Shop talk
• RadConNuclear
  Radiological controls: the radiation protection function, its rules and its technicians, in Navy and government usage. Shop talk
• RAPAsphalt
  Reclaimed asphalt pavement: old asphalt milled or crushed and fed back into new mix as aggregate and binder.
• RCDElectrotechnology
  Residual current device: trips when the current going out on the live conductors does not all come back.
• RefdesPCBs
  Reference designator: the label such as R12 or U3 that names one part on the schematic, board and BOM. Shop talk
• RGAVacuum
  Residual gas analyzer: a small mass spectrometer that identifies which gases remain in a vacuum chamber.
• RMSElectrotechnology
  Root mean square: the effective value of an alternating quantity, giving the same heating as that DC value.
• RPVOTTribology
  Rotating pressure vessel oxidation test, which rates how much oxidation life is left in an oil.
• RSMStatistics
  Response surface methodology: sequential experiments that fit curved models to find the settings that optimize a response.
• RSSGeosynthetics
  Reinforced soil slope: an embankment built steeper than its fill could stand alone by layering geogrid or geotextile in it.
• RSSMetrology
  Root sum of squares, combining independent uncertainty contributions by squaring, adding and taking the square root.
• RTWelding
  Radiographic testing: imaging a weld's interior with X-rays or gamma rays on film or a digital detector.
• RTFOAsphalt
  Rolling thin-film oven: the short-term aging test that mimics what plant mixing and paving do to a binder.
• RTJValves
  Ring type joint: a flange face with a machined groove that holds a solid metal ring gasket for high pressure.
• RTKHydrography
  Real-time kinematic: GNSS positioning that uses carrier-phase corrections from a base station to reach centimetres live.
• RTUHVAC
  Rooftop unit: a packaged air conditioner, often with gas heat, that sits on a roof curb and ducts straight down into the building.
• RTVAdhesives
  Room-temperature vulcanizing silicone, a rubbery adhesive-sealant that cures without heat, usually from air moisture.
• RULRefractories
  Refractoriness under load: the temperature at which a refractory starts to deform under a small steady load.
• RWPNuclear
  Radiation work permit: the document that sets radiological conditions, controls and dose limits for a specific job.
• SAWWelding
  Submerged arc welding: an arc buried under a blanket of granular flux, used for long, heavy welds.
• SBETHydrography
  Smoothed best estimate of trajectory: the post-processed position and attitude file applied to multibeam data. Shop talk
• SBONuclear
  Station blackout: complete loss of offsite and onsite AC power at a nuclear plant.
• SBSPhotonics
  Stimulated Brillouin Scattering: narrow-linewidth light scattering backward off sound waves it creates in fiber.
• SCFiber Optics
  Subscriber Connector: a square push-pull connector with a 2.5 mm ferrule, common in telecom and FTTH.
• SCADAElectrotechnology
  Supervisory control and data acquisition: the system that lets a control room watch and switch remote plant.
• SCCCorrosion
  Stress corrosion cracking: brittle cracking caused by tensile stress acting together with a specific corrosive environment.
• SCCConcrete
  Self-consolidating concrete, a highly fluid mix that fills forms and wraps rebar under its own weight.
• sccmVacuum
  Standard cubic centimetres per minute: a mass flow unit for process gases, referred to 0 °C and 1 atm.
• SCMConcrete
  Supplementary cementitious material: fly ash, slag cement or silica fume used alongside portland cement in a mix.
• SDCMLighting
  Standard Deviation of Color Matching: the step size used to state how closely light sources match in color.
• SEERHVAC
  Seasonal energy efficiency ratio: an air conditioner's cooling output over a typical season divided by its electricity use.
• SFMMachine Shop
  Surface feet per minute: how fast the cutting edge moves across the work, the basis for spindle speed.
• SHCSFasteners
  Socket head cap screw: a round-headed, high-strength screw driven with a hex key into a tapped hole.
• SHGPhotonics
  Second Harmonic Generation: converting light to exactly double its frequency, half its wavelength, in a nonlinear crystal.
• SHRHVAC
  Sensible heat ratio: the share of a cooling load or coil capacity that is sensible rather than latent.
• SIMetrology
  International System of Units, the coherent set of seven base units on which all traceable measurement rests.
• SMAAsphalt
  Stone matrix asphalt: a gap-graded, binder-rich surface mix built on a stone-on-stone skeleton.
• SMAWWelding
  Shielded metal arc welding: arc welding with a flux-coated consumable electrode, known in the shop as stick.
• SMSNonwovens
  Spunbond-meltblown-spunbond: a three-layer composite of strong spunbond outer layers around a meltblown barrier core.
• SMTPCBs
  Surface mount technology: soldering components onto pads on the board surface instead of through holes.
• SPCStatistics
  Statistical process control: using control charts and run rules to tell routine process noise from real changes.
• SPDLighting
  Spectral Power Distribution: a graph of how much power a light source emits at each wavelength.
• SRBCorrosion
  Sulfate-reducing bacteria: oxygen-free microbes that make hydrogen sulfide and drive much MIC.
• SSGWaterproofing
  Structural silicone glazing, where glass is held to its frame by silicone instead of exterior caps or stops.
• STPEWaterproofing
  Silyl-terminated polyether, a moisture-curing hybrid sealant that is paintable, weather-resistant and free of isocyanates.
• SVPHydrography
  Sound velocity profile: how the speed of sound changes with depth through the water, measured to correct sonar depths.
• TABNonwovens
  Through-air bonded: shop and spec shorthand for fabrics bonded by hot air drawn through the web. Shop talk
• TANTribology
  Total acid number: milligrams of potassium hydroxide needed to neutralize the acids in one gram of oil.
• TARMetrology
  Test accuracy ratio, the UUT tolerance divided by the accuracy spec of the standard used to test it.
• TBNTribology
  Total base number: the alkaline reserve left in an engine oil to neutralize combustion acids.
• TDSBoilers
  Total dissolved solids: the concentration of dissolved minerals and salts in boiler water, held in range by blowdown.
• TgAdhesives
  Glass transition temperature, above which a cured adhesive turns from hard and glassy to soft and rubbery.
• TgPCBs
  Glass transition temperature: the point where a board's resin turns from rigid to rubbery and expands much faster.
• TGICPowder Coating
  Triglycidyl isocyanurate, the classic crosslinker that cures carboxyl polyesters into weather-resistant films.
• TGOThermal Spray
  Thermally grown oxide: the alumina layer that grows between bond coat and ceramic in hot service.
• THDElectrotechnology
  Total harmonic distortion: the combined size of all harmonics relative to the fundamental, as a percentage.
• THHNElectricians
  Thermoplastic high heat-resistant nylon-coated wire: the standard single conductor pulled into conduit.
• THUHydrography
  Total horizontal uncertainty: how far a sounding's true position could be from where it was recorded, at 95 percent confidence.
• TIFFGears
  Tooth interior fatigue fracture: a crack that starts deep inside a case-hardened tooth, not at its surface.
• TiO2Paper Optics
  Titanium dioxide: the most powerful white pigment for adding opacity, used where every point of opacity counts.
• TLDNuclear
  Thermoluminescent dosimeter: a passive badge whose crystals store radiation energy and release it as light when heated.
• TM-30Lighting
  A color rendition method that rates fidelity and saturation with 99 color samples, giving Rf, Rg and a color vector graphic.
• TPIFasteners
  Threads per inch: the count of thread crests in one inch of length, used to state the pitch of inch threads.
• TPUHydrography
  Total propagated uncertainty: the combined estimate of how far each sounding could be from the truth, at 95 percent confidence.
• TSAThermal Spray
  Thermally sprayed aluminum: arc- or flame-sprayed aluminum that protects steel from corrosion.
• TSPVacuum
  Titanium sublimation pump: a heated titanium filament that coats nearby walls with a fresh gettering film.
• TSRAsphalt
  Tensile strength ratio: a moisture-damage test comparing the strength of soaked mix specimens to dry ones.
• TURMetrology
  Test uncertainty ratio, the tolerance being checked divided by the expanded uncertainty of the measurement process.
• TUSHeat Treating
  Temperature uniformity survey: a test mapping how evenly a furnace holds temperature across its work zone.
• TVUHydrography
  Total vertical uncertainty: the depth part of a sounding's uncertainty, judged against a depth-dependent limit.
• TWCRailroad
  Track warrant control: running trains outside CTC on dispatcher-issued warrants with fixed limits.
• TXVHVAC
  Thermostatic expansion valve: a metering device that adjusts refrigerant flow to hold constant evaporator superheat.
• UCLStatistics
  Upper control limit: the top boundary on a control chart, paired with the lower control limit (LCL) below the centerline.
• UGRLighting
  Unified Glare Rating: a calculated index of discomfort glare from interior luminaires, where lower numbers mean less glare.
• UHVVacuum
  Ultra-high vacuum: pressures below about 10⁻⁷ mbar, reached only with baked, metal-sealed systems.
• UNCFasteners
  Unified National Coarse: the standard coarse inch thread series, such as 1/4-20, 3/8-16 and 1/2-13.
• UNFFasteners
  Unified National Fine: the inch thread series with more threads per inch, such as 1/4-28, 3/8-24 and 1/2-20.
• UNRFasteners
  Unified National Round root: an external inch thread with a required rounded root, for better fatigue life.
• UPCFiber Optics
  Ultra Physical Contact: a domed singlemode connector polish with no angle, color-coded blue.
• UTWelding
  Ultrasonic testing: finding internal flaws by sending high-frequency sound into a weld and reading echoes.
• UUTMetrology
  Unit under test, the instrument being calibrated or tested, as opposed to the standard used to check it.
• VAVHVAC
  Variable air volume: a system that holds supply air temperature steady and varies the amount of air to each zone.
• VFAAsphalt
  Voids filled with asphalt: the share of the aggregate voids occupied by binder rather than air.
• VFLFiber Optics
  Visual Fault Locator: a bright red laser pen that shows breaks, bends and bad connectors as visible glowing points.
• VMAAsphalt
  Voids in mineral aggregate: the space between aggregate particles available for binder and air.
• VPSThermal Spray
  Vacuum plasma spray: plasma spraying inside a low-pressure inert chamber to make oxide-free metal coatings.
• VTWelding
  Visual testing: inspecting welds by eye with gauges, lights and magnifiers, the first and most-used NDE method.
• VTElectrotechnology
  Voltage transformer: an instrument transformer that steps high voltage down to a standard level for relays and meters.
• w/cmConcrete
  Water-to-cementitious-materials ratio: the weight of mix water divided by the weight of cement plus SCMs.
• WDMFiber Optics
  Wavelength Division Multiplexing: sending several signals on different wavelengths over the same fiber.
• WMAAsphalt
  Warm mix asphalt: mix produced and placed about 30 to 100 F cooler than hot mix using additives or foaming.
• WOGValves
  Water, oil, gas: a cold working pressure rating stamped on small threaded valves, such as 600 WOG.
• WPSWelding
  Welding procedure specification: the written instructions that tell welders exactly how to make a weld.
• WRBWaterproofing
  Water-resistive barrier, the layer behind cladding that sheds water that gets past the outer skin.
• WWRConcrete
  Welded wire reinforcement, a grid of steel wires welded at every crossing and sold in sheets or rolls.
• YAGPhotonics
  Shorthand for yttrium aluminum garnet, and in practice for the Nd:YAG laser at 1064 nm. Shop talk
• YSZThermal Spray
  Yttria-stabilized zirconia: the standard ceramic for thermal barrier top coats.
• ZDDPTribology
  Zinc dialkyldithiophosphate, the classic antiwear and antioxidant additive in engine and hydraulic oils.