Red Seal Millwright cheat sheet

Lockout/tagout isolates all energy sources-electrical, hydraulic, pneumatic, thermal, chemical, gravity, and stored spring energy-and zero-energy state is verified by test and attempted startup.

WHMIS/GHS supplier labels contain product identifier, hazard pictograms, signal word, hazard statements, precautionary statements, and supplier identification; workplace labels may be abbreviated.

Confined-space entry requires atmospheric testing before entry and during occupancy: oxygen typically 19.5–23% by volume and flammable gas below 10% LEL, with toxic gas limits set by jurisdiction.

A vernier least count equals one main-scale division divided by the number of vernier divisions; a metric micrometer least count is commonly 0.01 mm and an imperial micrometer 0.001 in.

Torque (T) equals force (F) times lever arm (r); bolt tension for a given torque depends on thread friction and head friction, and lubricated threads produce higher tension at the same torque.

A P&ID uses standard symbols for pumps, valves, instruments, and piping; instrument tag letters identify measured variable and function, such as PT for pressure transmitter and FC for flow controller.

Tagout tags identify the equipment, the reason for isolation, the person who applied the tag, and the date; removal is controlled by the person or procedure that applied the lockout.

Personal protective equipment is selected from the hazard assessment; electrical work requires arc-rated clothing and voltage-rated gloves when within the restricted approach boundary.

Symmetric two-leg lift: tension per leg = load ÷ (2 cos θ), where θ is the angle each leg makes with vertical; tension increases as legs move away from vertical.

Multi-leg sling vertical capacity = single-leg WLL × number of legs × cos θ (θ from vertical); at 60° from vertical each leg contributes half its rated capacity.

Horizontal sling angle: for a two-leg lift, tension per leg = load ÷ (2 sin α), where α is the angle from horizontal; at 30° tension equals load, and at 15° tension is about 1.93 times load.

Reject hooks with throat opening increased more than 10%, twist more than 10°, cracks, severe wear, or missing safety latch; hook latches prevent sling or load escape.

Wire rope is rejected for kinking, birdcaging, heat damage, severe corrosion, or broken-wire counts exceeding the applicable standard; diameter reduction and valley breaks also reduce strength.

The hook must be directly above the load center of gravity; an off-center hook causes the load to tilt until the center of gravity is vertically below the hook.

Crane hand signal for stop: extend one arm horizontally, palm down, and move the arm side to side; emergency stop uses both arms extended and waved.

Screw-pin shackles require the pin fully seated and tightened; bolt-type shackles are used where pins could loosen under vibration or repeated side loading.

Gear ratio = driven teeth ÷ driver teeth; output speed = input speed ÷ ratio; output torque = input torque × ratio (neglecting losses).

Open belt length L = 2C + π(D1 + D2)/2 + (D1 − D2)²/(4C), where C is center distance and D1, D2 are pulley diameters.

V-belt tension is checked by mid-span deflection, commonly about 1/64 in per inch of span; under-tension causes slip and heat, over-tension increases bearing load.

Roller chain is typically replaced when elongation exceeds about 2% of nominal pitch; worn chain rides high on sprocket teeth and damages the sprocket profile.

V-belt sheave grooves wear wider; when the belt bottoms in the groove, traction drops and the sheave must be replaced or resurfaced to specification.

Gear backlash is the circumferential clearance between meshing teeth; too little backlash causes overheating and seizure, too much causes impact and noise.

A fail-safe brake is spring-applied and power-released, so loss of electrical, hydraulic, or pneumatic power applies braking torque.

Belt drive output speed = input speed × (driver pulley diameter ÷ driven pulley diameter); torque changes inversely, ignoring slip and losses.

Bearing L10 life in millions of revolutions = (C/P)^p, where C is dynamic capacity, P is equivalent load, p = 3 for ball bearings and 10/3 for roller bearings.

For a rotating inner ring relative to load, the inner ring is mounted with interference on the shaft; a stationary outer ring may use a looser fit in the housing.

Grease fill for a bearing cavity is commonly one-third to one-half full; overfilling causes churning, heat, and grease breakdown.

Lip seals install with the lip facing the medium being retained; the lip is lubricated at assembly and the seal is pressed squarely to avoid cocking.

ISO VG grade is the nominal kinematic viscosity in centistokes at 40 °C; higher loads and temperatures generally require higher viscosity or appropriate additives.

Oil analysis reports viscosity, water content, particle count (ISO 4406), and wear metals; trends over time are more useful than a single sample.

Shaft critical speed is the speed at which a shaft's natural frequency matches running speed; continuous operation near it causes large vibration and possible failure.

Anti-wear and extreme-pressure additives form protective films; EP additives are used for high loads and slow speeds where boundary lubrication occurs.

Positive-displacement pump theoretical flow Q = displacement per revolution × shaft speed; volumetric efficiency = actual flow ÷ theoretical flow × 100%.

Centrifugal pump affinity laws at constant impeller diameter: Q ∝ N, H ∝ N², P ∝ N³.

NPSH available must exceed NPSH required by the manufacturer's margin; insufficient margin causes cavitation, noise, vibration, and impeller erosion.

Pump operating point is the intersection of the pump characteristic curve and the system curve; changing valve position or speed moves the operating point.

Hydraulic pressure P = force ÷ area; hydraulic power = pressure × flow, with units matched (W = Pa × m³/s).

A pressure-relief valve limits system pressure and is set below the rating of the weakest component; it is not a flow-control valve.

Compressor compression ratio = absolute discharge pressure ÷ absolute suction pressure; multi-stage compression with intercooling reduces power and discharge temperature.

ISO 1219 fluid power symbols show valve positions, ports, and actuation; a directional valve's center condition determines pump, load, and tank connections in neutral.

Belt conveyor capacity = material cross-sectional area × belt speed × bulk density; troughing angle and surcharge angle determine the effective area.

Conveyor belt tracking faults are corrected by adjusting take-up tension, squaring idlers and pulleys, centering the load, and removing buildup; damaged edges or seized idlers can prevent correction.

Screw conveyor capacity depends on screw diameter, pitch, speed, percent loading, and bulk density; sticky or abrasive materials reduce practical capacity.

Bucket elevator discharge is centrifugal at higher speeds and gravity at low speeds; bucket speed and head pulley diameter determine the discharge pattern.

Conveyor nip points between belt and pulley, chain and sprocket, and rotating shafts require guarding; pull cords and emergency stops must be accessible along the run.

Roller conveyor gravity slope depends on package weight and bottom surface; common practice is about 2–5% slope for free movement without excessive impact.

Belt splices are mechanical (fasteners) or vulcanized (heat/pressure); vulcanized splices are stronger and smoother but require more time and equipment.

Take-up devices maintain belt or chain tension; too little tension causes slip and snaking, too much tension overloads bearings and stretches the belt.

Vibration at 1× shaft speed with high radial and low axial amplitude typically indicates unbalance; 2× often indicates misalignment or looseness.

Gear mesh frequency = number of teeth × shaft speed; sidebands around mesh frequency can indicate tooth damage, eccentricity, or load modulation.

Bearing defect frequencies BPFO and BPFI are calculated from bearing geometry and shaft speed; they appear before visible spalling and are confirmed by spectral analysis.

FMEA risk priority number RPN = severity × occurrence × detection; higher RPN values identify failure modes to address first.

Thermography detects hot electrical connections, failing bearings, and blocked cooling; a temperature rise is compared with similar components under similar load.

Ultrasound detects compressed-air leaks, steam trap faults, and early bearing lubrication problems; high-frequency signals are translated to audible range.

Root-cause analysis uses techniques such as 5 Whys and fishbone diagrams to separate symptoms from the underlying failure mechanism.

Condition-based maintenance schedules work from measured condition-vibration, oil, temperature, ultrasound-rather than fixed calendar intervals.

Soft foot is checked by mounting an indicator on each foot and tightening bolts one at a time; shim the low foot until all feet carry load without vertical movement.

Shaft alignment has parallel offset and angular misalignment; laser or dial indicator methods measure both, and tolerance tightens as shaft speed increases.

Pipe connections are made after alignment and without forcing; piping must be independently supported so thermal growth and weight do not strain the machine casing.

Baseplate grout fills the space under the baseplate to provide rigid support and damping; epoxy grout is common for rotating equipment.

Pre-commissioning checks include rotation direction, lubrication, guard installation, control interlocks, and free movement before power is applied.

No-load run checks vibration, temperature, noise, and current; load is applied only after these readings are stable and within specification.

Total indicator reading (TIR) is the full movement of a dial indicator during one revolution; it equals twice the eccentricity for a round part rotating about its true center.

Flange bolt tightening follows a star or crossing pattern in stages to seat the gasket evenly and avoid uneven compression.