Red Seal Millwright key terms

A procedure that isolates and de-energizes every energy source feeding a machine, then locks and tags each isolation point so the equipment cannot be started or re-energized while people are working on it.

Specialized clothing and gear worn to shield the body from workplace hazards, such as safety glasses, gloves, hearing protection, respirators and fall-arrest harnesses; the selection follows a task hazard assessment.

An enclosed or partly enclosed area with limited entry and exit, poor natural ventilation and no design for continuous occupancy; entry requires hazard assessment, atmospheric testing and a standby attendant.

A standardized document listing a product's hazards, safe handling, first-aid measures, spill response and required protective equipment, kept accessible so workers can identify and control exposure risks.

A precision gauge with a spring-loaded plunger that displays small linear movements on a graduated dial, used to measure shaft runout, end play, flatness and machine alignment.

A hand tool that signals or slips once a set twisting force is reached, letting a fastener be tightened to a specified value so the joint is neither loose nor overstressed.

The maximum load a sling, shackle or other lifting component is rated to carry in a stated configuration, set by the manufacturer and reduced when rigging is used off vertical.

A multiplier used to find the true tension in a sling leg, which rises sharply as the leg moves away from vertical; flat slings therefore carry far more tension than their share of the load.

The point at which an object's weight is considered to act; a stable lift requires the hoist hook to hang directly above this point so the load does not tip.

The pattern and direction in which strands are twisted around a wire rope core, described as regular or lang lay, right or left hand; choosing the lay controls wear and load rotation.

A sling arrangement in which the sling passes around the load and back through an eye or sliding fitting, so the loop tightens around the load as lifting force is applied.

A U-shaped metal lifting fitting closed by a pin or bolt, used to join slings to loads, eyes and hooks; its rated capacity is marked on the body and must not be exceeded.

A grooved wheel that guides and supports a rope or cable in a block, or a grooved pulley that drives or guides a belt; groove condition and diameter affect rope and belt life.

The small clearance between the teeth of two meshed gears, felt as rotational play; too little causes heat and scoring, while too much produces noise, impact and uneven motion.

Permanent growth in the pitch of a roller chain from wear between pins and bushings; measured across a set number of links, it shows when the chain must be replaced.

The distance a V-belt or synchronous belt yields when a known force is applied at mid-span; comparing the reading to a tension specification tells whether the drive is correctly tightened.

The total distance the inner ring can move relative to the outer ring, radially or axially, before the rolling elements are pinched; it influences heat, noise and how load is shared.

A mating condition in which the shaft is slightly larger than the bore, so the parts must be pressed, shrunk or heated together; the resulting grip transmits torque and resists fretting.

A fluid's resistance to flow, stated at a reference temperature; it governs how well a lubricant builds a film and is the main basis for choosing an oil grade.

A numbered scale describing grease stiffness, from very soft to very hard, based on how far a standard cone sinks into a sample; it predicts how the grease feeds and stays in a bearing.

A rotary shaft seal with a flexible elastomeric lip that rides on the shaft, holding a thin film of oil in place while excluding dirt and moisture from the bearing housing.

The total movement of a shaft surface toward and away from a fixed reference during one revolution, measured with a dial indicator and revealing bend, eccentricity or bad seating.

An intentional axial force applied to a bearing, fastener or spring to remove internal clearance and increase stiffness, giving accurate positioning and resistance to load reversal.

Formation and violent collapse of vapour bubbles where liquid pressure drops below vapour pressure; the collapse creates noise, vibration and pitting of pump impellers and casings.

The margin by which absolute pressure at a pump inlet exceeds the liquid's vapour pressure, expressed as head; too small a margin causes cavitation and lost capacity.

A spring-loaded valve that opens at a set pressure and bypasses or dumps flow, preventing system pressure from climbing high enough to damage components, seals or piping.

A pressure vessel holding fluid against compressed gas to store energy, absorb shock or supply short-term flow; it must be fully discharged before any work on the circuit.

A statement of the particle size a filter element captures, given as nominal or absolute; it shows how well a fluid system is shielded from abrasive contamination.

The alignment of a belt on its pulleys and idlers, judged by where the belt edges sit; drift to one side is corrected by adjusting pulleys, idlers and loading conditions.

A movable tail pulley or frame that maintains tension on a conveyor belt and compensates for stretch, letting the belt be adjusted as it settles and wears.

The joint joining the ends of a conveyor belt, made by vulcanizing, mechanical fasteners or hinge pins; splice quality determines belt strength and how smoothly it runs.

Condition monitoring that measures vibration amplitude and frequency to expose unbalance, misalignment, looseness and bearing defects while they are still developing.

Laboratory testing of lubricant samples for wear metals, water, dirt and additive depletion; trends in the results guide maintenance timing and reveal hidden component damage.

A non-contact method that images surface temperatures to reveal overloaded electrical connections, failing bearings, blocked cooling passages and other abnormal heat before breakdown.

A structured method of tracing a failure back to the underlying conditions and decisions that allowed it, so corrective action prevents repeat events rather than only repairing the symptom.

Setting two coupled shafts on a common centreline using a laser emitter and detector that measure offset and angular error, then calculating the shim and side corrections needed.

A condition where a machine foot does not sit flat on its base, so tightening the hold-down bolt springs the frame and twists the shaft; found with a dial indicator or feeler gauge.

Offset, angular or combined error between the centrelines of two connected shafts, which adds load to bearings and couplings and shows up as vibration at one or two times running speed.