NCCER Industrial Maintenance Mechanic key terms

A documented procedure in which energy sources are isolated, locked, and tagged so equipment cannot be started or release stored energy while a worker services or repairs it.

An enclosed area with limited entry and exit, not designed for continuous occupancy, that may hold a hazardous atmosphere, engulfment risk, or other serious danger and therefore needs a written entry permit.

A standardized document supplied with a chemical product that lists its hazards, safe handling rules, first-aid steps, and spill response, so workers understand the risks before use.

The anchors, harnesses, lanyards, and guardrails used together to arrest or prevent a fall when someone works above a set height or near an unprotected edge.

A hand tool that signals or clicks when a preset twisting force is reached, used to tighten fasteners to a specified value so joints are neither loose nor overstressed.

The distance from one thread form to the next, stated as threads per inch or as millimeters of lead, which sets how far a fastener advances with each full turn.

Raised or stamped symbols on a fastener head that identify its strength grade and therefore the tightening torque and load it can safely carry.

The maximum load a sling, shackle, or other rigging component is rated to lift safely in normal service; it is marked on the hardware and must never be exceeded.

The measured angle between a sling leg and the horizontal; smaller angles raise tension in each leg sharply, so assembly capacity must be reduced using a load angle factor.

A drawing method that shows an object from several perpendicular directions, such as front, top, and side, so each view gives true shape and size along its axis.

The bordered area, usually at the lower right of a drawing, that records the part name, drawing number, scale, revision level, and approval signatures.

A theoretically exact point, line, or surface established on a drawing from which dimensions and measurements are taken, so parts mate and inspect consistently.

A symbolic drawing language that sets allowable form, orientation, and location variation for features, telling the fabricator exactly what must be controlled and how much deviation is acceptable.

A standard size label, such as 2-inch, that identifies a pipe's outside diameter; actual wall thickness is set separately by the pipe schedule number.

A compressible sealing element placed between two mating surfaces to fill small imperfections and stop liquid or gas from leaking out of the joint.

A valve whose wedge-shaped disc slides across the flow path; it is intended to be fully open or fully closed and should not be used for throttling.

A pressure test in which a system is filled with liquid and pressurized above its working pressure to prove joints and components are leak-free before service.

A device joining two shafts that transmits torque while absorbing small amounts of misalignment, vibration, or end float so the connected bearings are not overloaded.

A shaft alignment method using dial indicators to measure offset and angular error between two machines, with one reading taken on the rim and one on the face.

A condition where a machine foot does not sit flat on its base, distorting the frame when the bolt is tightened and making alignment readings unreliable.

The distance a drive belt sags or can be pushed at the middle of its span under a known force, used to check and set correct tension.

The small gap between rolling elements and raceways, or between shaft and bushing, that lets a lubricant film form and allows for thermal expansion.

A measure of how thick a fluid is and how easily it flows; it changes with temperature and must match the speed and load of the machine being lubricated.

A numbered scale from 000 to 6 describing grease stiffness, based on how far a standard cone sinks into a sample; higher numbers mean firmer grease.

A shaft-sealing assembly that holds a stationary face against a spring-loaded rotating face, allowing only very slight leakage on pumps and mixers.

A valve that opens automatically at a set pressure and discharges fluid to tank or atmosphere, protecting the system from damage caused by overpressure.

A pressure vessel that stores hydraulic fluid against a gas charge, absorbing shock, supplying extra flow during demand peaks, and holding pressure when the pump stops.

A combined air-preparation assembly for pneumatic systems containing a filter, a pressure regulator, and a lubricator, installed upstream of the equipment it serves.

A measure of filter element pore size that states the largest particle the element is designed to capture, and therefore how clean the fluid or air becomes.

A protective device in a motor starter that senses excess current and opens the control circuit, stopping the motor before sustained overloading damages the windings.

An electronic controller that varies the frequency and voltage fed to an AC motor, giving adjustable speed, softer starts, and lower starting current.

A conductor tying metal equipment frames to earth so fault current has a low-resistance path back to the source and protective devices trip quickly.

A check that applies high direct voltage to motor or cable insulation and measures leakage, revealing moisture, contamination, or deterioration before a failure occurs.

A predictive technique that measures the frequency and amplitude of machine vibration to detect imbalance, misalignment, looseness, or a failing bearing before breakdown.

A predictive inspection that uses a thermal camera to find abnormal hot spots in electrical panels, bearings, and piping caused by resistance, friction, or failing insulation.

Software that stores equipment history, schedules preventive tasks, and issues numbered work orders so labor, parts, and repair records stay traceable.

The average operating time between one failure and the next for a repairable asset, used to judge reliability and compare maintenance strategies.