Terms starting with D

Measurement setup with diffuse illumination of the sample and viewing perpendicular to its surface.

Diffuse blue reflectance at 457 nm measured with the instrument's UV content tuned to daylight illuminant D65.

Digital Addressable Lighting Interface: a two-wire digital lighting control bus where each driver has its own address.

The maximum fluence or power density an optic can take before it is permanently damaged.

A blade or set of blades in a duct or opening that controls, balances or shuts off airflow.

A thin coating that slows soil moisture through a foundation wall but cannot resist water under pressure.

Installed fiber with no transmission equipment attached, either spare or leased bare to a customer who lights it.

To bring a drain or drainage layer out to open ground lower down so its water can escape by gravity. Shop talk

Optical power in decibels relative to one milliwatt, the unit of power meters and transceiver specs.

Unwanted earth fault on a substation battery or DC control supply, which normally floats free of earth. Shop talk

Direct current electrode positive: welding polarity with the electrode on the positive terminal.

Demand-controlled ventilation: adjusting outdoor air in real time to match how many people are actually in a space.

Direct current voltage gradient survey that locates and sizes coating holidays on buried pipe.

Isolated from every source, proven free of voltage and safe to work on. Shop talk

Mounting an IC upside down with its legs in the air and wiring straight to the pins, like an insect on its back. Shop talk

Magnesia fired so hard it barely reacts with water, the main raw material of basic refractories.

Busbar with no voltage on it, the condition that lets a breaker close without synchronising checks. Shop talk

The very bottom of low water, when the tide has stopped falling and not yet started to rise. Shop talk

Steam heating slang for the long-gone engineers and fitters who designed and piped the steam systems that remain in service. Shop talk

Shop slang for exactly on size or perfectly aligned, with no measurable error left. Shop talk

Out of legal working hours under the hours of service rule, and required to stop work wherever the train sits. Shop talk

Fully annealed to the lowest hardness the metal can reach, with no work hardening left in it. Shop talk

To travel as a passenger to or from an assignment, paid but not working the train. Shop talk

A pressurized feedwater heater that strips dissolved oxygen and carbon dioxide out of boiler feedwater with steam.

Selective leaching of one element from an alloy, leaving a weak, porous remnant that still looks intact.

To remove the sharp raised edges and slivers that machining leaves on a part.

Loss of carbon from the surface of steel during heating, leaving a soft skin that will not fully harden.

Heat produced by radioactive decay of fission products after a reactor shuts down, which must be removed.

The agreed method for factoring measurement uncertainty into a pass or fail call against a spec.

The angle of the Moon or Sun north or south of the celestial equator, which makes the two daily tides unequal.

Removal of radioactive contamination from people, tools, surfaces or systems to reduce dose and spread.

Solid-state device that blocks DC but passes AC and fault current, grounding a pipeline without losing CP.

The depth of a tooth space below the pitch circle, slightly larger than the addendum to give tip clearance.

Impressed-current groundbed with anodes stacked in a vertical hole drilled tens of metres deep or more.

Number of yield-killing defects per unit area of wafer or panel, the main input to yield models.

The safety strategy of stacking independent layers of protection so no single failure can lead to harm.

Uncertainty that exists because the measurand itself is not defined precisely enough to have one single value.

A cycle that melts frost off a heat pump's outdoor coil or a refrigerated evaporator so it can keep moving heat.

To heat a gauge's electrodes hard in vacuum so they release adsorbed gas that would otherwise skew the reading.

A count of the independent information behind an uncertainty estimate, showing how reliable that estimate is.

A surface layer that has split away from the concrete below it, found by the hollow sound it makes when tapped.

Separation of the layers of a laminate or multilayer nonwoven, such as an SMS or a film composite.

Separation between layers of a board's laminate or between laminate and copper, usually from heat or moisture.

Separation of a coating from its substrate or of one coating layer from another.

Single number for the total color difference between a sample and its target, usually in CIELAB units.

A single number for how far a color is from its standard, read by a spectrophotometer.

The temperature difference between supply and return water in a hydronic system. Shop talk

How quickly an oil sheds water and settles into clean layers after being churned with it.

Unit of fiber fineness equal to the mass in grams of 9,000 meters of fiber or filament.

How tightly a compacted asphalt layer is packed, reported as a percentage of its maximum theoretical density.

Unrolling and positioning geosynthetic rolls in their final location before seaming or covering.

The percentage of the feedstock sprayed that actually ends up as coating on the part.

A chart line that follows a single depth below chart datum across the seabed.

A device on a rail that lifts a rolling car's wheels off the track before it can reach another track.

Vent filter packed with drying beads that cleans and dries the air a gearbox or tank breathes in.

A postulated accident that a nuclear plant is explicitly designed to withstand without exceeding set safety limits.

The outdoor weather and indoor targets a heating or cooling system is sized to handle.

Installer shorthand for a destructive seam sample, and for the job of cutting one out. Shop talk

Testing seam samples cut from installed geomembrane in peel and shear to prove seam strength.

An extra reinforced layer of membrane at corners, cracks, drains and penetrations before the main coat goes on.

Metal-based additive that keeps hot engine parts clean and neutralizes acids from combustion.

Radiation injuries that appear only above a threshold dose and become more severe as dose increases.

Process that fires powder from a long barrel using repeated explosions of oxygen and acetylene.

Extra survey work over a feature or shoal to pin down its least depth, shape and extent.

Temperature at which moisture condenses from air; specs keep steel at least 3 C above it for blasting and painting.

The temperature at which water vapor in a furnace atmosphere condenses, used as a gauge of carbon potential.

The temperature at which air becomes saturated and water starts condensing out when it is cooled.

Design for manufacturability: checking and adjusting a design so it can be built reliably at sensible cost.

Dry film thickness: the thickness of a cured coating layer, measured in mils or microns.

Ideal critical diameter: the largest bar that would reach 50 percent martensite at its center in a perfect quench.

Deionized water rinse, the final stage that washes salts off the part so they do not end up trapped under powder.

To fine-tune a burner with a combustion analyzer until oxygen, CO and stack temperature land where they belong. Shop talk

The inch measure of gear tooth size: number of teeth per inch of pitch diameter, larger number for finer teeth.

A valve that closes by pressing a flexible diaphragm down onto a weir or the body floor, with no stem packing.

The gap between the point where a control turns the burner on and the point where it turns it off.

Two traces carrying equal and opposite signals, routed tightly together at matched length and impedance.

Scheme that compares current entering and leaving a protected zone and trips when the two disagree.

A supply air outlet, usually in the ceiling, that spreads air into the room in a set pattern and mixes it with room air.

High vacuum pump with no moving parts that drives gas toward the exhaust with downward jets of hot oil vapour.

Diagonal cutting pliers, used for snipping small wire and cable ties close to a surface. Shop talk

Rebuilding worn or mis-machined surfaces to original size with thermal spray, then machining to finish.

The relationship between a dimmer or control signal and the light output it produces.

Joking name for conventional mineral oil refined from crude, used to set it apart from synthetics. Shop talk

TIG slang for touching the tungsten into the weld pool or filler, contaminating it and stopping the work. Shop talk

Measure of visible dark specks in pulp or paper, reported as equivalent black area per unit area.

A capped vertical stub of pipe below the gas inlet tee that traps scale, dirt and liquid before they reach the gas valve. Shop talk

A musty, sweaty-sock odor blown out by an air conditioner or heat pump, caused by microbial growth on the indoor coil. Shop talk

The movable closure element that seats to stop flow in globe, check, safety and butterfly valves.

Off-load switch that provides a visible isolating gap but is not built to make or break load current.

Any break in the normal makeup of a weld, such as a pore or inclusion, that becomes a defect only when it exceeds code limits.

Ashless additive that keeps soot, sludge and oxidation products suspended so they drain out with the oil.

Survey work proving that a charted feature does not exist, so it can be removed from the chart.

Line protection that measures impedance to a fault and trips fastest for faults close to the relay.

Unwanted change in shape or size of a part during heat treatment, such as bowing, warping or ovality.

How much the day's two high waters, or its two low waters, differ in height from each other.

A tide with a single high water and a single low water in each lunar day.

How fast a laser beam spreads with distance far from its waist, given as an angle in milliradians.

Using different designs, technologies or physical principles for the same safety function to guard against common-cause failure.

Dielectric constant: how much a board material slows signals and sets trace impedance, relative to vacuum.

DMX512: the digital control protocol for stage and architectural lighting, carrying 512 channels per universe.

A small precast concrete block, often with tie wire cast in, used to hold rebar up off the ground. Shop talk

Insulation power factor test on transformers, bushings and breakers, named after a well-known test set maker. Shop talk

Design of experiments: planning a set of runs that vary several factors at once so their effects can be separated.

To take a finished roll off a winder and start winding on a fresh core or shaft. Shop talk

A small steel lug tacked to a part so a wedge or bolt can pull pieces into alignment during fit-up. Shop talk

A cast or cut tensile specimen with wide ends and a narrow middle, used to test bulk adhesive properties. Shop talk

Short trace from a surface mount pad to a nearby via, shaped like a cartoon bone, used to fan out parts. Shop talk

To relieve a crew that has run out of legal hours; the relief crew are the dog catchers. Shop talk

A corner of flashing or membrane folded into shape without cutting, so the corner stays watertight. Shop talk

Crooked bend where two bends in one conduit end up out of plane, so the run will not lie flat. Shop talk

A complete mess: a badly organized job, a tangled setup or a botched piece of work. Shop talk

Dumbbell-shaped specimen punched from geomembrane sheet for tensile and stress crack tests. Shop talk

Small extension on a glass melting furnace where the batch is charged into the tank. Shop talk

Bend in a Weibull plot where the data change slope, a sign of two failure modes or two populations mixed together. Shop talk

Shop name for the chunky engagement teeth on a gear or sliding collar that lock a gear to its shaft. Shop talk

Pipeline slang for hot-applied coal tar or asphalt enamel coating, poured over the pipe and wrapped. Shop talk

Approval for a worker to exceed the plant's administrative dose level, still below the legal limit. Shop talk

The maximum dose a worker or member of the public may legally receive from regulated sources in a set period.

A device worn by a person to measure the radiation dose they receive.

Describes an actuator that uses air or oil pressure to drive in both directions, with no return spring.

Isolation using two closed seats in series with a vent or drain between them to prove the isolation holds.

Fiber with a small doped core for the laser light inside a much larger inner cladding that guides multimode pump light.

Budget slang for entering the same physical effect twice under different names, which inflates the uncertainty. Shop talk

Rolling a gear in tight mesh against a master gear and recording how the center distance varies.

Locking two nuts together on a stud so a wrench on one of them can screw the stud in or out. Shop talk

A fault where a pulsed laser emits two pulses where it should emit one, from too much gain or bad switch timing. Shop talk

Two conductors under a breaker or lug terminal listed for only one, a classic inspection writeup. Shop talk

Tempering a part twice, cooling to room temperature in between, to temper martensite formed after the first.

Lab slang for the frequency-doubling crystal or module that turns an infrared laser into its second harmonic. Shop talk

A ring-shaped laser mode with a dark center, usually a sign of misalignment or overheating in a TEM00 laser. Shop talk

A smooth steel bar across a slab joint that transfers load while letting the joint open and close.

Welding vertically from the top down, fast and with less heat, as done on cross-country pipelines. Shop talk

A ceiling luminaire, usually recessed, that directs its light downward, known regionally as a can or pot light.

Defects per million opportunities: defect count scaled by the number of chances for a defect in each unit.

Distributed power unit: a locomotive placed mid-train or on the rear and controlled by radio from the lead unit.

The pressure difference that pulls or pushes combustion gases through the boiler and out the chimney.

A slow, heavy, low-priority freight train, often of bulk loads or empties. Shop talk

The pan under a cooling coil that catches condensate and routes it to a drain line.

Carrying water along the plane of a geosynthetic to an outlet, as in wall backdrains and leak detection layers.

A dimpled or ribbed plastic core with filter fabric that carries water down to drains instead of letting it sit on the membrane.

How readily a fabric hangs and folds under its own weight, a comfort property for gowns, drapes and wipes.

Shop word for tempering, as in drawing hardened steel back to a softer, tougher hardness. Shop talk

Design rule check: automated scan of a layout for spacing, width, drill and connectivity violations.

To put on the protective clothing required by an RWP before entering a contaminated area. Shop talk

Gradual change in an instrument's readings over time that comes from the instrument itself, not from what it measures.

Slow, steady creep of a process or gauge reading in one direction as something wears, depletes or ages.

Machine file listing the size and position of every hole to be drilled in a board.

Lump of polymer that falls from a spinneret or die and lands in the web as a hard, often glassy spot. Shop talk

The tooth flank that carries load when power flows in the normal direction; the opposite flank is the coast side.

The electronic power supply that converts line voltage into the regulated current or voltage an LED needs.

Royal Navy slang for a hydrographic surveyor, from a clipped form of hydrographer. Shop talk

The fall in an LED's efficiency as drive current or temperature rises, so extra power yields proportionally less light.

The final fiber cable run from a distribution terminal on the street to a single customer building.

A vertical strip of facade worked from top to bottom on one setup of a swing stage or bosun's chair. Shop talk

Missing pings or beams where the sonar failed to record a valid depth, leaving gaps in the data. Shop talk

Temperature at which a heated grease turns fluid enough to drip from a test cup.

A large cylindrical vessel in a watertube boiler where steam separates from water or where sediment collects.

The rotating mixing barrel on a ready-mix truck, turning one way to mix and the other to discharge.

A continuous asphalt plant that dries the aggregate and mixes it with binder in one rotating drum.

Describes mix short on binder: dull brown, harsh to rake and likely to ravel early. Shop talk

Powder in which additives such as metallic flake are mixed in loose after milling rather than fused on.

Plain air temperature as an ordinary thermometer reads it, kept dry and out of direct sun.

Storage of cooled spent fuel in sealed steel canisters inside concrete or steel casks, cooled passively by air.

Back section of a paper machine, from the dryers through calender and reel, where the sheet is finished. Shop talk

To run the burner on a boiler that has lost its water, overheating and often destroying the heating surfaces.

Visible line on a Fourdrinier table where the wet sheet's surface turns from glossy water to dull matte. Shop talk

The oven after the washer that drives off rinse water before parts reach the powder booth.

Controlled first heat-up of a new monolithic lining to drive off water without cracking or spalling.

To let a boat settle deliberately on the bottom as the tide falls, against a wall, on legs or on twin keels. Shop talk

Vacuum pump with no oil or liquid in its pumping chamber, used where oil vapour would contaminate the process.

Abrasion test that feeds sand between a coated sample and a spinning rubber wheel, then measures volume loss.

Machine start-up before oil has reached the contacts, when a big share of lifetime wear happens. Shop talk

Tooling sealant without water, soap or solvent on the tool, as most manufacturers require.

Dry granular refractory compacted by vibration without water and sintered in place by heat.

Height above chart datum of a rock, bank or flat that dries at low tide, shown on charts as an underlined figure.

The volume loss of hardened concrete as it gives up moisture over months and years.

Describes webs formed from dry staple fibers, chiefly by carding and by air laying.

Dispatcher, as said on the radio: the person who controls train movements over a territory. Shop talk

Dynamic shear rheometer: the instrument that measures a binder's stiffness and elasticity by twisting a thin disk of it.

Direct traffic control: authority granted by named blocks of track on unsignaled lines.

Decitex: fiber fineness unit equal to the mass in grams of 10,000 meters of fiber, the European standard.

Direct tension indicator: a hardened washer with bumps that flatten when the bolt reaches required tension.

Danger to navigation: a newly found hazard reported urgently so charts and warnings change before the survey ends.

A twin-barrel package that holds both parts of an adhesive and pushes them through a static mixer in fixed ratio.

Air lost from supply ducts or pulled into return ducts through gaps at joints, seams and connections.

Shop name for a micro-ohmmeter used to measure very low contact and joint resistances. Shop talk

A slide-rule style duct sizing calculator that matches airflow and friction rate to round and rectangular duct sizes. Shop talk

The paving crew member who guides trucks to the paver, signals the dump and collects load tickets. Shop talk

Heat-treat slang for quenching a part, especially by hand into an open oil or water tank. Shop talk

A soft, powdery concrete surface that rubs off under traffic or a scraped fingernail.

A light, quick pass of powder that barely covers, or the first thin pass before building film. Shop talk

Fine, cooled overspray that settles on a surface as loose powder and weakens the next layer sprayed over it. Shop talk

A short filler piece of pipe cut in to close a gap or correct a misfit between two spools. Shop talk

A patch of new stone, brick or wood cut and set into a damaged area of an original piece. Shop talk

How far a white light's color sits above or below the blackbody line, giving it a green or pink tint.

Dense vertically cracked: a thermal barrier sprayed hot so it forms deliberate through-thickness cracks.

The time a pressure-sensitive bond sits after application while it builds toward full strength.

Shop name, from a trade name, for blue layout fluid painted on metal so scribed lines show up bright. Shop talk

Retarding force made by turning a locomotive's traction motors into generators and burning the energy off as heat.

A marker filled with test fluid of known surface tension, used to check a surface's treatment level. Shop talk