NCCER Industrial Maintenance Mechanic cheat sheet

OSHA 1910.147 governs lockout/tagout; after locking, verify the zero-energy state by attempting a normal start and by testing stored energy sources (pressure, gravity, springs, capacitors).

Fall protection is triggered at 4 ft in general industry (1910.28) and 6 ft in construction (1926.501); guardrails, nets, or personal fall arrest systems satisfy the requirement.

Permit-required confined space entry requires atmospheric testing: oxygen 19.5 to 23.5 percent, flammable gas below 10 percent LEL, and toxics below exposure limits before and during entry.

Portable ladder setup follows the 4:1 rule: the base sits 1 ft out from the wall for every 4 ft of working height, and the ladder extends 3 ft above a landing.

Extinguisher classes: A ordinary combustibles, B flammable liquids, C energized electrical, D combustible metals, K commercial cooking oils.

PASS technique: Pull the pin, Aim at the base of the fire, Squeeze the handle, Sweep side to side.

Hearing conservation programs are required at an 8-hour TWA of 85 dBA; the general-industry permissible exposure limit is 90 dBA.

A GHS safety data sheet has 16 sections; Section 2 covers hazards and Section 8 covers exposure controls and PPE; eye protection must meet ANSI Z87.1.

Torque is force times lever length (T = F x L); a torque wrench is a measuring instrument and must be returned to its lowest setting after use.

SAE grade 5 cap screws have three radial marks and grade 8 has six; metric property class 8.8 and 10.9 are stamped on the head.

Two-leg sling: tension per leg = (load / 2) divided by the cosine of the angle from vertical; capacity multipliers are 0.866 at 30 degrees, 0.707 at 45 degrees, and 0.5 at 60 degrees from vertical.

Never exceed a hook's rated working load limit; remove hooks showing more than 10 percent throat opening increase, more than 10 degrees twist, or missing safety latches.

Bench and pedestal grinders: the tool rest gap must not exceed 1/8 in and the tongue guard must not exceed 1/4 in from the abrasive wheel.

Ring-test a vitrified wheel before mounting and never exceed the maximum RPM marked on the wheel blotter.

Use a box-end wrench or socket for breaking fasteners loose, and pull toward the body rather than pushing, to avoid knuckle injury on slip.

Remove a 6x19 wire rope sling from service for 10 broken wires in one lay, 5 broken wires in one strand, kinking, bird-caging, or heat damage; chain slings are grade 80 or 100.

Third-angle projection places the top view above the front view and the right-side view to the right; first-angle projection places the top view below the front view.

Line conventions: hidden features are dashed, centerlines are long-short-long, phantom lines show alternate positions or motion, and cutting-plane lines mark section views.

A scale of 1/4 in = 1 ft 0 in means 1 in on the drawing represents 4 ft of actual length.

The title block carries drawing number, scale, company, and approval; the revision block records changes and is identified on the drawing by a triangle or cloud.

On a P&ID, the first letter of an instrument tag is the measured variable (F flow, P pressure, T temperature, L level) and the second letter is the function (I indicator, C controller, T transmitter).

An isometric piping drawing is single-line and not to scale; it shows north, south, east, west, and vertical runs with coordinates, line numbers, and sizes.

GD&T feature control frames state the geometric characteristic, tolerance zone, and datum references; datums are the reference origin for all measurements.

A bill of materials lists item number, quantity, part number, and description for every component called out on the drawing.

Schedule number = 1000 x (internal working pressure / allowable stress); for a given nominal pipe size, a higher schedule means a thicker wall.

Pipe outside diameter is standardized and does not equal nominal size: NPS 1 is 1.315 in OD, NPS 2 is 2.375 in OD, and NPS 4 is 4.500 in OD.

Gate valves are for fully open or fully closed isolation and should not be throttled; globe valves are built for throttling; ball and butterfly valves are quarter-turn; check valves allow flow in one direction only.

Spiral-wound gaskets with metal windings suit high pressure and temperature; compressed sheet gaskets suit low pressure and temperature service with compatible fluids.

Flange bolts are tightened in a star or crisscross pattern in stages (about 30, 70, and 100 percent of final torque) so the gasket seats evenly.

37-degree JIC flare fittings and SAE 45-degree fittings seal metal-to-metal and need no thread sealant; NPT pipe threads require PTFE tape or pipe dope applied to the male threads.

Tubing is specified by outside diameter and wall thickness, while pipe is specified by nominal size and schedule.

A relief valve set pressure must not exceed the maximum allowable working pressure of the weakest component in the protected system.

Driven rpm = driver rpm x (driver sheave diameter / driven sheave diameter); the speed ratio is driven speed divided by driver speed.

V-belt tension is set by deflection: roughly 1/64 in of deflection per inch of span at mid-span, and multi-belt drives require a matched belt set.

Chain drives are tensioned to about 1 to 2 percent of the sprocket center distance in slack at mid-span.

Correct soft foot before alignment; then correct angular (face) misalignment before parallel (rim) offset, re-checking each step.

Precision alignment targets are commonly 0.002 in or less parallel offset and 0.0005 in per inch or less angularity; thermal growth offsets are applied at cold alignment.

Gear types: spur for parallel shafts and straight teeth, helical for smoother quieter parallel service, bevel for intersecting shafts, worm for high reduction and self-locking at low lead angles.

Backlash is measured with a dial indicator at the pitch circle; too little backlash causes overheating and tooth failure, too much causes impact and noise.

Gear couplings tolerate misalignment and need lubrication; elastomeric jaw, grid, and tire couplings tolerate misalignment without lubrication but have lower torque density.

In a bearing designation such as 6205, the 62 indicates a light-series deep-groove ball bearing and 05 indicates a bore of 25 mm (5 x 5 mm).

A rotating inner ring under a stationary load direction requires an interference fit on the shaft; a stationary inner ring uses a transition or line-to-line fit.

Fill a grease-lubricated bearing cavity one-third to one-half full of grease; overfilling raises operating temperature and can displace seals.

NLGI grease grade indicates consistency: NLGI 2, the most common, has a worked penetration of 265 to 295.

ISO VG numbers equal the lubricant's nominal kinematic viscosity in centistokes at 40 degrees C.

Install a lip seal with the garter spring facing the medium being retained, so pressure assists the sealing lip.

Tapered roller bearings carry combined radial and thrust loads and are mounted with a specified end play or preload, never with zero clearance left to chance.

Bearing defect frequencies (BPFO, BPFI, BSF, FTF) are non-synchronous; peaks at these frequencies in a vibration spectrum indicate raceway, ball, or cage damage rather than unbalance.

Pascal's law: pressure applied to a confined fluid is transmitted undiminished in all directions, so F = P x A.

Cylinder force equals system pressure times effective area; on the rod side, subtract the rod cross-sectional area from the bore area first.

Cylinder speed = pump flow divided by effective piston area; flow controls set speed by restricting flow, not by limiting pressure.

The relief valve sets maximum system pressure and is normally set above the maximum working pressure but below the rating of the weakest component; it protects the circuit and is not a speed control.

An air preparation unit is plumbed filter first, then regulator, then lubricator (FRL), with the lubricator downstream of the regulator.

Meter-out flow control gives smoother control of a cylinder with an overrunning or gravity load than meter-in control.

Accumulators are precharged with dry nitrogen, typically to 60 to 80 percent of minimum system pressure; oxygen, air, or acetylene must never be used.

Fluid cleanliness is rated by ISO 4406 particle counts; a common target for industrial hydraulic systems is around 18/16/13, achieved with return and pressure filters near 10 microns.

Ohm's law: E = I x R; single-phase power P = E x I = I squared x R; three-phase real power P = 1.732 x E x I x power factor.

Motor branch-circuit conductors and short-circuit protection are sized from NEC Table 430.250 full-load current, while overload heaters are sized from the motor nameplate current.

Three-wire start/stop control uses a normally open auxiliary contact in parallel with the start pushbutton to seal in the starter coil after the button is released.

Reverse a three-phase motor by interchanging any two of the three supply leads; a reversing starter needs both mechanical and electrical interlocks.

Overload protection guards the motor against sustained overcurrent; fuses and circuit breakers guard the circuit against short circuits and ground faults.

Insulation resistance is measured with a megohmmeter; the IEEE 43 minimum for random-wound motors is approximately one megohm plus one megohm per kilovolt of rated voltage.

NEMA enclosure types: 1 indoor general purpose, 4 and 4X weathertight, 7 and 9 hazardous-location gas and dust, 12 industrial dust-tight.

VFD outputs are pulse-width modulated; use inverter-duty motors and shielded motor cable, and never open the motor circuit while the drive is running.

PM intervals are set by manufacturer hours, cycles, or calendar time; predictive tasks are triggered by condition data rather than schedule.

Overall vibration velocity (in/s RMS) is compared to ISO 10816 severity bands, but trend direction against the machine's own baseline is more useful than a single reading.

Spectrometric oil analysis reports iron, copper, chromium, lead, and silicon in ppm; viscosity at 40 degrees C, water content, and ISO 4406 particle count complete the picture.

Infrared thermography finds loose electrical connections, overloaded circuits, and failing bearings by comparing temperature rise with similarly loaded components.

Ultrasound detects compressed-air and gas leaks, steam trap failures, and early bearing or lubrication problems that are not yet visible as heat.

MTBF = total operating time divided by number of failures; MTTR = total repair time divided by number of repairs.

Unbalance and misalignment are the two most common causes of excessive 1x running-speed vibration; looseness produces harmonics of running speed.

Precision maintenance basics that drive reliability: correct lubrication, correct fastener torque, precision alignment and balance, and contamination control.