NCCER Industrial Maintenance Mechanic flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Zero energy verification

After lockout, confirm the machine will not start by attempting a normal start, then test for residual energy such as pressure, gravity, springs, and capacitors.

Confined space oxygen limits

Atmospheric testing for permit-required confined space entry must show oxygen between 19.5 and 23.5 percent by volume before entry and continuously during the work.

Fall protection trigger height

OSHA requires fall protection at 4 feet in general industry and 6 feet in construction; guardrails, personal fall arrest, or safety nets satisfy the requirement.

Safety Data Sheet sections

A GHS safety data sheet has 16 sections; Section 2 lists hazard identification and Section 8 lists exposure controls and required personal protective equipment.

Sling leg tension formula

For a two-leg sling, each leg carries the load divided by two times the cosine of the angle from vertical, so capacity drops as the legs spread wider.

SAE bolt grade markings

Grade 5 cap screws carry three radial lines on the head and grade 8 carries six; metric property class 8.8 and 10.9 are stamped numerically.

Grinder tool rest gap

On a bench or pedestal grinder, the tool rest must be set within 1/8 inch of the wheel face and the tongue guard within 1/4 inch.

Wire rope removal criteria

Remove a 6x19 wire rope sling from service at 10 broken wires in one lay or 5 in one strand, and for kinking, bird-caging, or heat damage.

Third-angle projection

In third-angle projection the top view sits above the front view and the right-side view sits to the right; first-angle projection reverses this arrangement.

P and ID tag letters

On a piping and instrumentation diagram, the first letter of an instrument tag is the measured variable (F flow, T temperature) and the second is the function (I indicator, C controller).

Isometric piping drawing

A single-line, non-scale piping drawing on 30-degree axes showing north, south, east, west, and vertical runs with coordinates, line numbers, and sizes.

Gate versus globe valve

Gate valves are for fully open or fully closed isolation and should not be throttled; globe valves use a plug and seat suited to throttling flow.

Spiral wound gasket use

Spiral-wound gaskets with a metal winding and soft filler are selected for high-pressure and high-temperature flanges where sheet gaskets would crush or fail.

Flange bolt tightening pattern

Tighten flange bolts in a star or crisscross pattern in stages of roughly 30, 70, and 100 percent of final torque so the gasket seats evenly.

Pipe schedule number

Schedule number equals 1000 times working pressure divided by allowable stress; a higher schedule means a thicker wall for the same nominal pipe size.

Sheave speed ratio

Driven rpm equals driver rpm times driver sheave diameter divided by driven sheave diameter; the ratio of the two diameters sets the speed change.

V-belt deflection check

Set tension so a straightedge laid across the sheaves shows about 1/64 inch of deflection per inch of span when the belt is pressed at mid-span.

Soft foot condition

A soft foot exists when one motor or pump foot does not sit flat, distorting the frame; correct it with shims before beginning shaft alignment.

Chain drive slack

A properly tensioned chain drive has about 1 to 2 percent of the sprocket center distance in slack, measured at the mid-span of the chain.

Bearing number 6205

In the 6205 designation, 62 identifies a light-series deep-groove ball bearing and 05 indicates a 25 mm bore, calculated as 5 times 5 mm.

Lip seal spring orientation

The garter spring side of a lip seal faces the medium being retained, so hydraulic oil or grease pressure pushes the lip tighter against the shaft.

Grease cavity fill amount

Fill a grease-lubricated bearing housing one-third to one-half full; overfilling raises operating temperature and can push seals out of position.

Pascal's law

Pressure applied to a confined fluid is transmitted undiminished in every direction, so the force produced equals system pressure multiplied by effective piston area.

Cylinder force formula

Force equals pressure times area; on the rod side, subtract the rod cross-sectional area from the bore area before multiplying by pressure.

FRL unit order

An air preparation unit is plumbed filter first, then regulator, then lubricator; the lubricator must be downstream of the regulator to meter oil correctly.

Accumulator precharge gas

Bladder and piston accumulators are precharged with dry nitrogen, typically to 60 to 80 percent of minimum system pressure; oxygen and compressed air are never used.

Three-phase power formula

Real power in a balanced three-phase circuit equals the square root of three times line voltage times line current times power factor.

Seal-in contact function

In three-wire control, a normally open auxiliary contact wired parallel to the start pushbutton keeps the starter coil energized after the button is released.

Reversing a three-phase motor

Interchange any two of the three motor supply leads to reverse rotation; a reversing starter requires both mechanical and electrical interlocks.

MTBF calculation

Mean time between failures equals total operating time divided by the number of failures in that period; it measures reliability, not repair speed.

Oil analysis wear metals

Spectrometric oil analysis reports iron, copper, chromium, lead, and silicon in parts per million, indicating wear of gears, bearings, bushings, or ingested dirt.

Infrared thermography

An infrared camera locates hot spots from loose electrical connections, overloaded circuits, and failing bearings by comparing temperature rise against similar loaded components.