MMAW NC II flashcards
MMAW NC II · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Lockout/tagout purpose
- Prevents unexpected energization or release of stored energy during service by isolating every energy source, dissipating residual energy, and applying a personal lock and tag.
- 5S red tag
- A marker placed on an item in the sort step to identify it as unnecessary, moving it to a holding area for review and disposition by a set date.
- Hazardous waste container rule
- Containers holding spent solvent, oily rags, or used filters stay closed, labeled with contents and start date, and are never mixed with general trash.
- Arc flash boundary
- The distance at which incident energy equals 1.2 cal/cm²; unqualified persons stay outside it and qualified persons wear PPE rated for the labeled incident energy.
- First-angle projection rule
- The view placed below the front view is the top view, and the view to the right is the left-side view; the projection symbol on the drawing confirms the convention.
- Drawing scale precedence
- A dimension printed on the drawing always overrides a length measured from the paper; scaling a print gives an estimate only, never an acceptance value.
- Clearance fit designation
- In a fit such as H7/g6 the uppercase letter is the hole and the lowercase letter is the shaft; H hole with a g shaft always produces clearance.
- Directional valve ways and positions
- The number of boxes is the number of positions and the number of ports in one box is the number of ways, so a 5/2 valve has five ports and two positions.
- Vernier caliper reading step
- Read the main scale at the vernier zero, then add the coinciding vernier line multiplied by the resolution, for example 0.02 mm on a 50-division vernier.
- Micrometer thimble division
- On a metric micrometer each full thimble turn advances 0.5 mm and the thimble is divided into 50 parts, so one division equals 0.01 mm.
- Instrument resolution rule
- Choose a measuring instrument whose resolution is about one tenth of the tolerance being checked, so measurement uncertainty does not consume the whole tolerance zone.
- Torque wrench storage
- Store a torque wrench at its lowest scale setting and recalibrate after a drop or at the set interval, because a compressed spring drifts out of calibration.
- Ohm's law and power
- V equals I times R, and power equals V times I, which also equals I squared times R or V squared divided by R for a resistive load.
- Parallel resistance rule
- The reciprocal of total resistance equals the sum of the reciprocals of the branch resistances; total resistance is always lower than the smallest branch.
- Three-phase power formula
- For a balanced three-phase load, power equals the square root of three times line voltage times line current times power factor.
- Silicon diode forward drop
- A conducting silicon diode drops about 0.7 V in the forward direction; a germanium diode drops about 0.3 V; reverse bias blocks current until breakdown.
- Cylinder retract force
- Retract force equals pressure times the annulus area, calculated as pi times bore squared minus rod squared, all divided by four.
- Meter-out speed control
- Throttling the exhaust flow from a cylinder gives stable speed control for a load that tends to run away, because the oil or air column stays under pressure.
- Relief valve function
- A hydraulic relief valve limits maximum system pressure by diverting pump flow to tank; pump displacement sets flow, while the load and relief setting create pressure.
- FRL unit order
- The air preparation unit is arranged filter, then regulator, then lubricator in the direction of flow, with the regulator setting downstream working pressure.
- PNP sensor output
- A PNP sensor sources current by switching the positive supply to its output when triggered, so the PLC input common must be connected to 0 V.
- Inductive versus capacitive sensor
- An inductive sensor detects metallic targets only, while a capacitive sensor detects most materials including liquids and granular solids at slightly longer range.
- Incremental encoder channels
- Channels A and B in quadrature give both pulse count and direction, and counting all four edges multiplies the base resolution by four.
- Live-zero analog signal
- A 4-20 mA loop uses 4 mA for 0 % of span, so a current below about 3.6 mA indicates a broken wire or failed transmitter.
- PLC scan cycle
- The controller reads inputs, executes the program from top to bottom, then updates outputs; response to a pulse shorter than the scan time can be missed.
- Sinking input module
- A sinking DC input module expects the field device to supply positive voltage to the terminal, which matches a PNP sensor output configuration.
- Ladder latch instructions
- OTL sets a bit and holds it after the rung goes false; OTU resets it; the latch survives a power cycle unless the retentive memory is cleared.
- Forced output hazard
- A forced PLC output overrides the program in run mode and can energize an actuator unexpectedly; all forces must be removed and recorded before handover.
- Bearing mounting force rule
- Apply mounting force to the race with the interference fit, the inner race on a rotating shaft, and never transmit force through the rolling elements.
- Soft foot check
- Before shaft alignment, check that all machine feet sit flat; a soft foot distorts the frame when bolts are tightened and ruins alignment readings.
- Unbalance vibration signature
- Mass unbalance produces vibration mainly at one times running speed, while misalignment shows a strong two times component and looseness shows harmonics.
- Half-split fault method
- Test at the midpoint of the signal chain, then continue into the half that still shows the fault; each test must confirm or eliminate a section.