433A vibration, PM and commissioning practice questions.

Five free practice questions on vibration, PM and commissioning: block F of the Red Seal 433A Industrial Mechanic Millwright exam, about 16 of its 135 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.

01The questions

1. Procedural · Performs balancing procedures

   A vibration route flags a rising 1× peak on an induced-draft fan at a pulp mill. Before setting up to balance the wheel in place, what should the millwright do first?

   1. Clean the wheel and inspect for build-up, cracks, erosion and missing weights
   2. Add a trial weight at the heavy-spot location shown by the analyzer
   3. Check the alignment of the fan to the motor
   4. Send the wheel to a shop balancing machine
   Show the answer

   A. Correct. The RSOS lists inspecting and cleaning the equipment as the first balancing steps, to confirm balancing is actually necessary. Deposits on blades, eroded or broken fins, a lost balance weight, a loose hub or a bent shaft all produce 1× vibration; cleaning may remove the imbalance entirely, and a crack or loose fit must be repaired, not balanced over.

   Why not the others

   B. A trial weight before cleaning balances the dirt. When the build-up sheds later, the added weight becomes the new imbalance.

   C. Alignment is worth checking if 2× and axial vibration are present, but a rising 1× radial peak on a fan points first to the wheel's condition.

   D. Removing a large fan wheel is a major job. In-place (field) balancing is normal for installed fans, and only after cleaning and inspection show a true imbalance.

2. Procedural · Commissions systems and components

   A commissioning of a rebuilt reciprocating compressor at a water treatment plant is complete. What should the handover documentation contain so that later maintenance can rely on it?

   1. Only the baseline vibration readings, since that is what predictive maintenance uses
   2. A note that the machine ran satisfactorily
   3. The signed checklist, final alignment values, safety tests, settings and baseline readings
   4. The manufacturer's manual, filed with stores
   Show the answer

   C. Correct. Commissioning records are the starting point of the machine's history: the signed checklist proving each step was done, the final cold and hot alignment readings, results of safety device and relief valve tests, control and pressure settings, torque values, lubricant type and level, and the baseline vibration, temperature, pressure and current readings. These go into the CMMS against the equipment number so every later reading and repair has a reference.

   Why not the others

   A. Baseline vibration is one item. Without the alignment values, settings and safety test results, a later problem cannot be traced to a change from the commissioned state.

   B. A pass/fail note gives future millwrights nothing to compare against. The value of commissioning is in the recorded numbers.

   D. The manual describes the machine as designed, not how this machine was set up and how it ran on the day. Both are kept, but the commissioning record is the site-specific document.

3. Recall · Performs vibration analysis procedures

   A bump test on a fan pedestal at a mine shows a natural frequency very close to the fan's running speed, and the 1× vibration is amplified as a result. What is the accepted way to correct a resonance problem of this kind?

   1. Balance the fan to a finer tolerance
   2. Tighten the hold-down bolts to a higher torque
   3. Increase the bearing lubrication to damp the vibration
   4. Stiffen the structure or add mass to shift its natural frequency
   Show the answer

   D. Correct. Resonance occurs when a forcing frequency (here 1× rpm) coincides with a natural frequency. Balancing reduces the forcing but the amplification remains. The fix is to shift the natural frequency well away from running speed by stiffening the pedestal (bracing, thicker base, grouting) or adding mass, or, on a variable-speed drive, to lock out the resonant speed band. A bump test confirms the new natural frequency.

   Why not the others

   A. Balancing lowers the exciting force but does not remove the amplification. Any residual imbalance is still magnified at resonance; the natural frequency must move.

   B. Over-torquing bolts does not appreciably change the structure's stiffness and risks stripping them. Resonance needs a real change in stiffness or mass.

   C. Grease in a rolling bearing adds negligible damping to a structural resonance. Damping is not the practical millwright fix here.

4. Procedural · Decommissions systems and components

   A large pump set removed from a power station is to be kept as a strategic spare in a warehouse for two years. What preservation steps should the millwright take when decommissioning it for storage?

   1. Run it once a month on a test stand to keep it exercised
   2. Store it outdoors on timbers with a tarp over it
   3. Drain, coat, cap openings, add desiccant, and turn the shaft on a schedule
   4. Leave the oil in the bearings and wrap the whole unit in plastic
   Show the answer

   C. Correct. Storage preservation prevents corrosion and false brinelling. The casing is drained and flushed, machined surfaces and the shaft are coated with a preservative, ports and flanges are capped or blanked, desiccant is placed in the housing and cover, and the unit is tagged with its status and a schedule for turning the shaft periodically so bearings do not brinell and seals do not set. The preservation record goes into the CMMS with the equipment.

   Why not the others

   A. Monthly full runs are impractical and wear the machine. Rotating the shaft by hand on a schedule achieves the anti-brinelling purpose.

   B. Outdoor storage under a tarp exposes the unit to condensation and temperature swings; a strategic spare is stored indoors, preserved and inspected.

   D. Plastic traps moisture and causes condensation; old oil separates and acidifies. Preservative oil and desiccant with breathable covering are used instead.

5. Procedural · Performs non-destructive testing (NDT) procedures

   Before applying dye penetrant to a suspected crack on a gearbox housing at an auto plant, what must be done to the test area, and why?

   1. Apply developer first so the penetrant has something to soak into
   2. Heat it with a torch so the crack opens up
   3. Clean and degrease it and let it dry so penetrant can enter the crack
   4. Grind the surface smooth to remove any surface marks
   Show the answer

   C. Correct. The RSOS requires the component to be prepared so it does not give false readings. Oil, paint, scale and dirt fill or bridge a crack and block the penetrant, hiding a real defect; residual solvent or water in the crack prevents penetrant entering. After cleaning and drying, penetrant is applied, allowed its dwell time, excess is removed without flushing the crack, developer is applied and the indication is read and recorded.

   Why not the others

   A. Developer goes on last; it draws penetrant back out of the crack to form the visible indication. Applying it first blocks the crack.

   B. Flame heating can distort the part, drive off the penetrant and is unnecessary; capillary action draws penetrant into a clean crack at room temperature.

   D. Grinding smears metal over the crack mouth and can close it, producing a false clean result. Only cleaning is done; blending is a repair step after inspection.

02Answer key

03What block F covers

This block covers keeping equipment healthy and putting it into or out of service. It includes preventive, predictive and run-to-failure strategies, CMMS records and root cause analysis, vibration analysis and field balancing, dye penetrant, magnetic particle and ultrasonic testing, oil analysis, thermography and ultrasound, commissioning checks, run-in and baseline readings, and decommissioning, storage and disposal.

The Red Seal Occupational Standard names this block “Performs preventative and predictive maintenance, commissioning and decommissioning”. It carries 11.9% of the exam, about 16 of the 135 questions, split across two tasks. The share column is each task's weight within the block, as the standard publishes it.

04What the questions turn on

Vibration signatures

A dominant peak at 1x running speed in the radial directions is imbalance. A strong 2x peak with high axial vibration is misalignment. A long row of running-speed harmonics whose amplitude changes from reading to reading is mechanical looseness.

Bent shaft or imbalance

A bent shaft gives 1x vibration like imbalance, but also high axial 1x, with axial phase about 180 degrees apart at the two bearings. Balancing will not fix it. A long roll needs two-plane balancing; a narrow fan wheel needs one plane.

Reading an oil report

Silicon is the dirt marker, and rising iron and chromium alongside it mean abrasive wear, so seal the entry point before cleaning the oil. Viscosity and acid number rising together point to oxidation from heat and age.

Baselines and hot checks

Record baseline vibration and temperature after run-in, at normal load and temperature. Rising 2x and axial vibration as a new machine warms up means the cold alignment did not allow for thermal growth: check it hot and reset the offsets.

05The other blocks

The 433A exam has six blocks. Each has its own page of free questions:

The 433A Industrial Mechanic Millwright practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.