Red Seal Millwright flashcards

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

Zero-energy verification

After isolating and locking a machine, confirm no stored energy remains by testing for voltage, pressure, gravity, thermal, and spring energy, then attempt startup.

WHMIS supplier label

A Canadian supplier label must show product identifier, hazard pictograms, signal word, hazard statements, precautionary statements, and supplier contact information; workplace labels may use abbreviated information.

Micrometer reading

Read the barrel main scale, add the thimble scale value multiplied by the least count, and include the vernier if present; least count is usually 0.01 mm or 0.001 in.

Torque and bolt tension

Applied torque equals force times lever arm and is converted to bolt tension through thread and head friction; lubricated threads reduce friction and can increase tension for the same torque.

Two-leg sling tension

For a symmetric two-leg lift, tension per leg equals load divided by two times the cosine of the angle each leg makes with vertical; larger angle from vertical increases tension.

Sling capacity at angle

A multi-leg sling's vertical capacity equals single-leg working load limit times number of legs times cosine of angle from vertical; at 60 degrees from vertical capacity is halved.

Hook rejection criteria

Reject a hook if the throat opening has increased more than 10 percent, if it is twisted more than 10 degrees, or if it has cracks, excessive wear, or a missing safety latch.

Center of gravity lift

The hook must be positioned above the load's center of gravity; if the center of gravity is off to one side, the load will tilt until the lifting point is vertically above it.

Gear ratio formula

Gear ratio equals number of teeth on the driven gear divided by teeth on the driver; output speed is input speed divided by ratio, and output torque is input torque multiplied by ratio.

Open belt length

For two pulleys on parallel shafts, open belt length is twice center distance plus pi times the sum of diameters divided by two plus the square of the diameter difference divided by four times center distance.

V-belt deflection rule

Check V-belt tension at mid-span by applying force and measuring deflection; a common rule is about 1/64 inch deflection per inch of span, with exact values from the drive manufacturer.

Roller chain elongation

Roller chain is typically replaced when elongation exceeds about 2 percent of the nominal pitch over the measured span, because further elongation damages sprocket teeth and increases shock loading.

Bearing L10 life

Basic rating life L10 in millions of revolutions equals the dynamic capacity divided by equivalent load, raised to exponent 3 for ball bearings or 10/3 for roller bearings.

Grease fill amount

A bearing cavity is commonly filled to about one-third to one-half full with grease; overfilling causes churning, overheating, and grease breakdown, especially at high speed.

Lip seal orientation

Install a lip seal with the sealing lip facing the medium being retained, and lubricate the lip during assembly so it does not run dry or fold over on the shaft.

ISO viscosity grade

ISO VG number is the lubricant's nominal kinematic viscosity in centistokes at 40 degrees Celsius; selection depends on bearing speed, load, and operating temperature.

Pump volumetric efficiency

Volumetric efficiency equals actual flow divided by theoretical flow times 100 percent; theoretical flow for a positive-displacement pump equals displacement per revolution times shaft speed.

Centrifugal affinity laws

For a centrifugal pump at constant impeller diameter, flow varies directly with speed, head varies with speed squared, and power varies with speed cubed.

NPSH margin

Net positive suction head available must exceed the pump's required NPSH by a margin set by the manufacturer; insufficient margin causes cavitation, noise, vibration, and impeller damage.

Hydraulic power formula

Hydraulic power equals pressure multiplied by flow; in SI units, watts equal pascals times cubic metres per second, and in imperial units horsepower equals pressure times flow divided by a constant.

Belt conveyor capacity

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

Conveyor belt tracking

Belt tracking deviations are corrected by adjusting take-up tension, squaring idlers and pulleys, centering the load, and cleaning buildup; persistent faults can indicate damaged belt edges or seized idlers.

Screw conveyor capacity

Screw conveyor capacity depends on screw diameter, pitch, speed, percent loading, and material bulk density; decrease capacity for sticky, abrasive, or easily fluidized materials.

Bucket elevator discharge

Bucket elevators discharge by centrifugal action at higher speeds or by gravity at low speeds; speed and pulley diameter determine the discharge type and bucket selection.

Vibration 1X unbalance

A dominant vibration at one times shaft speed, with high radial amplitude and low axial amplitude, typically indicates rotor unbalance rather than misalignment or bearing damage.

Gear mesh frequency

Gear mesh frequency equals number of teeth on a gear multiplied by its shaft rotational speed; sidebands around mesh frequency can indicate tooth damage or modulation.

FMEA risk priority number

Risk priority number equals severity times occurrence times detection, each rated on a defined scale; higher RPN values identify failure modes that should be addressed first.

Bearing defect frequencies

BPFO and BPFI are bearing ball pass frequencies for outer and inner races; they are calculated from bearing geometry and shaft speed and appear as vibration peaks before visible damage.

Soft foot check

With the machine unbolted and indicator on the foot, check each foot for vertical movement as bolts are tightened; shim the low foot so all feet carry load without strain.

Shaft alignment tolerance

Alignment tolerances for offset and angularity depend on shaft speed and coupling type; higher speed requires tighter tolerance, and final alignment is done at operating temperature when specified.

Pipe strain alignment

Piping connected to a pump or compressor must be independently supported and aligned without forcing; pipe strain can distort the casing and destroy shaft alignment after commissioning.

Commissioning no-load run

Before loaded operation, verify rotation direction, lubrication, guards, and controls, then run unloaded and check vibration, temperature, noise, and current before applying load.