The NDT Dictionary

Couplant (n.): A gel that spends all night on the part and all weekend on your jacket.

Back Wall (n.): The one reliable thing on an Ultrasonic Testing screen, and the first to disappear when you need it.

Grass (n.): What grows on the A-scan when nobody mows the gain.

Dead Zone (n.): The area near the surface where discontinuities go to be ignored.

Angle Beam (n.): A probe that reaches the weld root without ever facing it head-on.

Skip Distance (n.): How far the beam travels before it bounces off the back wall. The only skipping allowed in Ultrasonic Testing.

Time-of-Flight Diffraction (n.): A method that ignores the big reflections and listens to the gossip from the crack tips.

Calibration Block (n.): A piece of steel that has been told it is perfect and believes it.

Lift-Off (n.): What a rocket and an eddy current probe have in common. Both ruin the day when they happen by accident.

Skin Depth (n.): How far into a metal an eddy current will go before it loses interest.

Impedance Plane (n.): A screen where every flaw gets a squiggle and every squiggle gets an opinion.

Frequency (n.): The setting you change when the flaw is deeper than your confidence.

Null (n.): The state of calm in which an eddy current instrument has nothing to say. Rare.

Acoustic Impedance (n.): A material's resistance to being pushed around by sound, and the reason air gaps get all the reflection and none of the credit.

Half-Life (n.): The time it takes for half of anything to disappear: atoms, patience, or the last donut at a safety meeting.

Inverse Square Law (n.): The reason standing twice as far away makes you four times as comfortable.

Latent Image (n.): A radiograph's best-kept secret, until the developer tells all.

Barricade (n.): A rope, some tape, and a surprising amount of authority.

Exposure Time (n.): The only period during which everyone on site becomes a patient person.

Densitometer (n.): A device that tells you, to two decimal places, how wrong your guess was.

Artifact (n.): Any mark on the film that was not there when you started and is definitely there now.

Half-Life (n.): The point at which your source and your patience are both at fifty percent.

Leakage Field (n.): The only leak the customer is glad you found.

Residual Field (n.): A magnetized part's way of saying, 'I'll never forget you.'

Particle Concentration (n.): The one number in the bath that takes thirty minutes in a settling tube to tell you the truth.

Black Light (n.): A UV-A lamp that makes indications glow, white socks glow, and the inspector's dignity dim.

Prods (n.): Two handheld electrodes that create a circular field and, occasionally, a lesson about arc strikes.

Dwell Time (n.): The penetrant's turn to work, refereed by an inspector with a stopwatch.

Developer (n.): A fine white coating that turns a part into a canvas and an inspector into a critic.

Relevant Indication (n.): Something you can't wipe off, explain away, or blame on the previous shift.

Nonrelevant Indication (n.): A glowing, dramatic mark that has no business in your report, like a coworker's opinion about the weather.

Pre-Cleaning (n.): The least glamorous step in the inspection and the one that decides everything.

Looks Fine (phrase): The first guess of every bystander, and the last thing an inspector will write without a measurement.

Weld Gauge (n.): A small metal ruler with strong opinions about the sixteenth of an inch.

Borescope (n.): A tool that lets you look into a hole without the hole looking back. Usually.

Parallax (n.): Why you and the person next to you read the same gauge differently, and each think the other needs glasses.

Disbond (n.): Two layers that once promised to stick together and now sound dull when tapped.

Emissivity (n.): How much a surface is willing to admit about its own temperature.

Flux Leakage (n.): The only kind of leak the inspector is happy to find.

Bubble Solution (n.): Soap with a career.

Reference Block (n.): The only piece of steel on site whose flaws were ordered in advance.

Firmware Update (n.): A surprise redecoration of the instrument menu, scheduled for the day before the biggest job.

Couplant (n.): The only thing in the field that is applied liberally and still runs out.

Cable Wiggle (n.): The traditional diagnostic procedure for a probe that works only sometimes.

Discontinuity (n.): What it's called when you find something and haven't opened the code book yet.

Defect (n.): A discontinuity that lost the argument with the acceptance criteria.

Nonrelevant Indication (n.): A signal with no connection to the discontinuity you wanted, like a stranger at a family reunion.

Porosity (n.): A weld with more holes than a colander and the same confidence about holding things together.

Level III (n.): A person who knows the answer, the exception to the answer, and the committee that argued about the exception.

Experience Hours (n.): The only measurement in NDT that has no calibration block and is still expected to be accurate to the quarter hour.

Recertification (n.): The five-year reminder that you are not as current as you remember.

Eye Exam (n.): A test proving you can read fine print, a skill you will use for the rest of your career against your will.

Addendum (n.): The code's way of saying 'We improved it. Please check the effective date.'

Code Case (n.): An exception wearing a code number.

Scope (n.): The first paragraph of a standard, and the one that tells you whether the other four hundred pages apply.

Informative (adj.): Describes any code material nobody is required to follow and everybody is expected to know.

Fit-Up (n.): The stage of welding where a gap is a root opening if it's within tolerance and a story if it isn't.

Preheat (n.): The part of welding where the metal warms up and everyone else wishes they could.

Undercut (n.): A groove at the weld toe, and what your confidence gets when the inspector arrives.

Heat-Affected Zone (n.): The area near the weld that was fine until someone got too close. Also, the break room.

Report (n.): The only part of the inspection read by people who weren't there.

Revision Letter (n.): A single capital that means someone read the procedure very carefully.

Data File (n.): The one record that remembers every scan you've forgotten.

Sign-Off (n.): The moment a stack of pages becomes official, which is why you read it one more time.

Per Diem (n.): A daily meal allowance, and the reason every technician knows the best diner within ten miles.

Area Release (n.): Official word that the hazards have checked out, so you can check in.

Standby (n.): Paid waiting, during which the technician's most-used instrument is the clock.

Hot Work Permit (n.): The one piece of paper on site that can tell the schedule 'not yet' and be right.

Turnaround (n.): A scheduled shutdown during which the plant stands still so that everyone else can run around.

Tailgate Meeting (n.): A safety discussion held in a parking lot, where the first hazard is usually the weather.

Graveyard Shift (n.): The hours between midnight and dawn, when the thing most likely to go out of tolerance is you.

First Article (n.): The one part inspected as if the whole order depends on it, because it does.

Shutdown (n.): A short word for a long schedule.

Pre-Job Meeting (n.): A gathering in which everyone learns where the muster point is.

Deliverable (n.): A binder with an answer for every question the client hasn't asked yet.

Dwell Time (n.): The only wait in the trade that everyone agrees is necessary.

Scope of Work (n.): A short document that answers every question except the one you have on site.

Status Update (n.): A weekly summary with more colors than a C-scan.

Corrosion Allowance (n.): The extra wall thickness a vessel is born with, which the plant spends like an allowance on a Saturday.

Turnaround (n.): A month of planned work that begins with a vessel full of surprises.

Outage (n.): The only time a power plant is happy to be producing nothing.

Refueling Floor (n.): The one place in the plant where everyone talks quietly, walks slowly, and still runs out of time.

Foreign Object Debris (n.): Anything on the hangar floor that wasn't there the last time the inspector looked.

Heavy Check (n.): An inspection so thorough that the airplane gets to see parts of itself it has never seen.

Audit Finding (n.): A free second pair of eyes, delivered with a form number.

Right-of-Way (n.): The narrow strip of land where everything must fit, including the truck, the pipe, and the plan.

Holiday (n.): A gap in the pipe coating. Unlike the other kind, nobody is happy to see it.

Weather Window (n.): A short period of acceptable conditions, always one hour shorter than the weld.

Void Space (n.): A compartment that is empty by name and full of inspection by nature.

Dry Dock (n.): Where a ship goes to find out what the water has been saying about it.

Fracture-Critical Member (n.): A bridge part with no backup plan, which is why the inspector has several.

Weather Window (n.): A brief period of acceptable wind, announced just after the crew has left.

Rework (n.): A part's second chance to make a first impression.

Track Window (n.): A scheduled block of time on the rail, minus the time it takes to get there, set up, wait, and leave.

Resolution (n.): A January promise to read the new edition cover to cover, and the one promise that comes with an index.

Couplant, Winter Edition (n.): A gel that has decided to be a solid until further notice.

Hydration Break (n.): A scheduled pause, and the only item on the schedule the crew has ever finished ahead of time.

Traveler (n.): The one document that follows a part everywhere and still has more stamps than a passport.

Observation (n.): An audit finding that isn't a nonconformance yet, but has the energy of one.

Turnaround (n.): A planned shutdown in which a refinery opens everything, looks inside, and finds out what the last one was hinting at.

Critical Path (n.): The chain of jobs that can't slip, and the one the inspection always lands on.

Holiday Schedule (n.): A calendar that lists every day off and every deadline that moved into the day before.

Return to Service (n.): The date everyone circles on the calendar, and the inspector circles twice.

Task Card (n.): The shortest document in the hangar that begins with the word 'Inspect' and means every word.

Dry Dock (n.): A place where the ship finally holds still and everyone else finally doesn't.

Undocking Date (n.): The one measurement on the project that was never taken with a gauge.

Right-of-Way (n.): The land a pipeline crosses, and what mud has over everything on it.

Weather Day (n.): A day when the welding spread is paid to watch the sky, and the inspector is paid to watch the spread watch the sky.

Snooper Truck (n.): A vehicle with an arm that lets the inspector see the underside of the bridge without leaving the road.

Lane Closure (n.): A traffic restriction that gives the inspector eight hours and gives every driver eight opinions.

Weather Window (n.): A short stretch of good weather, scheduled around the crew's availability, which has not read the schedule.

Rope Access (n.): A method of reaching the blade in which the inspector hangs around and the wind hangs on.

Track Window (n.): A block of time on the railroad that the schedule gives, the dispatcher shortens, and the inspector spends racing.

Track Time (n.): The window between trains when the inspection happens. It is always fifteen minutes shorter than the work.

Revision History (n.): The page where a document shows its homework.

First-Article Inspection (n.): The one part that gets looked at more closely than every part that follows combined.