433A pumps, compressors and conveyors practice questions.

Five free practice questions on pumps, compressors and conveyors: block D of the Red Seal 433A Industrial Mechanic Millwright exam, about 24 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. Recall · Maintains pumps

   During a routine check, a millwright notes a small but steady stream of liquid from the seal chamber of a centrifugal pump fitted with a mechanical seal. How should this be interpreted?

   1. Normal; a slight steady drip cools the faces.
   2. The seal is failing; it should not leak visibly.
   3. The gland needs tightening.
   4. Acceptable until the leak rate doubles.
   Show the answer

   B. Correct. A mechanical seal runs on two lapped faces separated by a film so thin that its leakage is a vapour, invisible in normal service. A visible steady stream means the faces are worn, scored or heat-checked, the secondary seals (O-rings or bellows) have hardened, or the seal has been run dry or misaligned. Nothing can be adjusted on the seal; it is scheduled for replacement, and the cause (dry running, cavitation, pipe strain, flush failure) is found so the new seal lasts.

   Why not the others

   A. That is the rule for compression packing, which is lubricated and cooled by a controlled leak. A mechanical seal is cooled by the pumped liquid or a flush and is designed to be essentially leak-free.

   C. A mechanical seal gland clamps the stationary face and gasket; it is not an adjustment for leakage the way a packing gland is. Over-tightening it distorts the stationary face and makes the leak worse.

   D. Waiting on a leaking seal lets faces and sleeve deteriorate and risks a sudden failure with product loss. A visible leak is already the signal to plan the change.

2. Procedural · Maintains compressors

   As part of the weekly preventive maintenance on a plant air system, a millwright checks the air receiver. Which items on the receiver must be verified?

   1. That the outlet valve is throttled to limit flow.
   2. That the condensate drain works and that the relief valve lifts on test.
   3. That the receiver is painted and the pressure gauge reads zero.
   4. That the relief valve is wired shut so it cannot leak.
   Show the answer

   B. Correct. Water collects in the bottom of the receiver and must be drained daily by hand or by an automatic drain whose operation is confirmed (cycle it manually and watch it discharge); a receiver full of water loses storage capacity and corrodes. The relief valve is lifted by its lever with the receiver pressurized, at the interval the manufacturer and the provincial regulation call for, and must reseat cleanly; a valve that will not lift or will not reseat is replaced, never gagged. The RSOS names both checks.

   Why not the others

   A. The receiver outlet is fully open in service. Throttling it starves the plant and is not a maintenance item.

   C. Paint condition is a corrosion clue at best, and a gauge at zero on a working receiver would mean a failed gauge or an empty tank. Neither is the safety check.

   D. Gagging a relief valve removes the vessel's only over-pressure protection and is illegal under pressure-vessel regulations. A leaking relief valve is repaired or replaced.

3. Critical · Diagnoses conveying systems

   A 20 m (65 ft) screw conveyor moving wood chips at a pulp mill has developed a loud, intermittent knocking from the middle of its length. Throughput is unchanged, the drive end runs quietly, and the trough is not leaking. What is the most likely cause?

   1. The screw is turning the wrong direction.
   2. The conveyor is over-filled.
   3. A worn hanger bearing letting the screw sag.
   4. The drive sprocket is loose on its shaft.
   Show the answer

   C. Correct. A long screw conveyor is built in sections joined by coupling shafts, each supported by an intermediate hanger bearing. When a hanger bearing wears, the screw sags at that point and the flighting rubs and knocks against the trough as it turns, loudest under load. Hanger bearings (bronze, hardwood, UHMW or ball type) are wear items and the RSOS lists bearings among the components inspected and replaced. The coupling-shaft bolts at the same joint are checked, since a sheared or loose coupling bolt gives a similar knock.

   Why not the others

   A. Reverse rotation moves the chips the wrong way and throughput would collapse, not stay the same.

   B. Overfilling loads the drive and can jam the screw, but throughput is unchanged and the drive is running normally. A local knock at one point along the length is a mechanical fault there.

   D. A loose drive sprocket knocks at the drive end, where this machine is quiet. The noise is mid-length, at a hanger.

4. Procedural · Maintains fans and blowers

   A millwright is preparing to open the housing of a large centrifugal fan in a cement plant's kiln exhaust system to inspect the wheel. The motor has been locked out and tagged. What additional step is needed before anyone reaches into the housing?

   1. Remove the drive belts so the motor cannot turn the fan.
   2. Bleed the grease from the bearings.
   3. Secure the wheel so it cannot windmill from draft in the ductwork.
   4. Loosen the inlet cone to relieve pressure on the wheel.
   Show the answer

   C. Correct. A fan wheel connected to a duct system will turn on its own from natural draft or from air moved by other fans in the same system, even with its motor locked out. The wheel is blocked or chained and the isolating dampers closed and locked before hands go inside. This is the fan-specific part of reaching a zero-energy state: electrical lockout alone leaves the rotating hazard live.

   Why not the others

   A. The motor is already locked out. Removing belts does nothing about the real hazard, which is the wheel turning from airflow through the housing.

   B. Grease in a bearing is not stored energy and has no bearing on the wheel starting to turn. The wheel itself must be immobilized.

   D. There is no stored pressure in a fan housing once it stops. Loosening the cone only creates alignment work later; the hazard is windmilling.

5. Procedural · Maintains process tanks and containers

   A millwright is assigned to change the rubber liner in an agitated slurry tank at a mine concentrator. The tank has been emptied. What must be in place before anyone enters through the manway?

   1. The agitator motor switched off at the local stop button.
   2. Confined-space entry: blinding, atmosphere test, permit, attendant.
   3. A hard hat and safety glasses, with the lights on.
   4. Verbal permission from the operator on shift.
   Show the answer

   B. Correct. A tank is a confined space. Under the applicable provincial OH&S regulation and the site procedure, the feed, discharge and sparge lines are isolated and blinded (locked valves alone are not isolation for entry), the agitator and any other drive is locked out to a zero-energy state, the atmosphere is tested for oxygen, flammables and toxics and ventilated as needed, an entry permit is issued, and an attendant with a rescue plan is posted at the manway. Residual slurry, reagents and pH are on the RSOS hazard list for tanks.

   Why not the others

   A. A stop button is not a lockout; the agitator can be restarted from the control room. And the feed lines that can fill or gas the tank must be blinded, not just closed.

   C. PPE and lighting are needed but do not address the atmosphere, the energy sources feeding the tank or the rescue plan. Entry is controlled by the confined-space procedure, not by gear alone.

   D. A confined-space entry needs a written permit that records the isolation, the test results and the attendant. An operator's say-so is none of those.

02Answer key

03What block D covers

This block covers the process and material handling equipment a millwright keeps running. It includes centrifugal and positive displacement pumps, packing and mechanical seals, centrifugal and axial fans, reciprocating and rotary screw compressors, dryers and air receivers, process tanks, piping, valves and flanges, belt, screw, chain and pneumatic conveyors, and industrial robots and automated equipment.

The Red Seal Occupational Standard names this block “Services material handling / process systems”. It carries 17.8% of the exam, about 24 of the 135 questions, split across six tasks. The share column is each task's weight within the block, as the standard publishes it.

04What the questions turn on

Fan laws and speed changes

Fan power varies with the cube of speed. Raising a fan from 900 to 1 080 rpm, a 20 % speed increase, needs about 73 % more power. The same law is why a variable-frequency drive saves the most energy at part load.

Pump symptoms point to causes

A gravel noise with fluctuating discharge is cavitation, a suction-side problem such as a plugged strainer. Zero discharge with low motor amps means lost prime. A quiet pump giving about half its rated head may be running backwards.

Relief valves and throttling

A positive displacement pump delivers a fixed volume every revolution, so it needs a relief valve between the pump and the first shut-off valve. A centrifugal pump is throttled at its discharge valve, with the suction left fully open.

Training a conveyor belt

A belt moves toward the end of an idler it touches first, so train it by shifting idlers a little at a time, not by steering with the pulleys. Drift at the same point of the belt every revolution means a crooked splice or camber.

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.