CPE Mechanical Systems & Equipment 3 — Questions and Answers
Question 1: Which bearing type is most appropriate for applications with combined radial and axial (thrust) loads?
- Deep groove ball bearing
- Cylindrical roller bearing
- Angular contact ball bearing (Correct answer)
- Needle roller bearing
Correct answer: Angular contact ball bearing
Angular contact ball bearings are designed with a contact angle that allows them to carry significant combined radial and axial loads simultaneously.
Question 2: A pneumatic system uses a filter-regulator-lubricator (FRL) unit. What is the function of the regulator?
- Remove particulates and moisture from compressed air
- Maintain consistent downstream air pressure (Correct answer)
- Add oil mist to lubricate downstream actuators
- Measure air flow rate to control consumption
Correct answer: Maintain consistent downstream air pressure
The regulator reduces and stabilizes compressed air pressure to the set downstream value regardless of upstream pressure fluctuations.
Question 3: When aligning a flexible shaft coupling, which type of misalignment involves the shaft centerlines being parallel but offset?
- Angular misalignment
- Parallel (offset) misalignment (Correct answer)
- Axial misalignment
- Torsional misalignment
Correct answer: Parallel (offset) misalignment
Parallel misalignment occurs when two shaft centerlines are parallel but displaced laterally from each other.
Question 4: The Affinity Laws state that when pump speed doubles, the pump head changes by a factor of:
- 2 (doubles)
- 4 (quadruples) (Correct answer)
- 8 (increases 8-fold)
- 1.41 (square root of 2)
Correct answer: 4 (quadruples)
Per the Affinity Laws, pump head varies as the square of the speed ratio, so doubling speed quadruples the head.
Question 5: A compressed air receiver tank serves which primary function in a plant air system?
- Dries compressed air to reduce moisture content
- Stores air to buffer demand peaks and reduce compressor cycling (Correct answer)
- Filters oil carryover from the compressor
- Regulates downstream pressure to point-of-use equipment
Correct answer: Stores air to buffer demand peaks and reduce compressor cycling
The receiver tank acts as an air reservoir, smoothing out fluctuating demand and reducing compressor start-stop cycling.
Question 6: What does a high vibration reading at 2× running speed typically indicate in rotating machinery?
- Unbalance in the rotating element
- Misalignment of the coupling or bearings (Correct answer)
- Looseness of the foundation or base plate
- Resonance at the natural frequency
Correct answer: Misalignment of the coupling or bearings
A dominant 2× running speed frequency component is a classic vibration signature of shaft or coupling misalignment.
Question 7: Which type of compressor is classified as a positive-displacement machine?
- Centrifugal compressor
- Axial flow compressor
- Reciprocating piston compressor (Correct answer)
- Mixed-flow compressor
Correct answer: Reciprocating piston compressor
Reciprocating piston compressors trap and compress a fixed volume of gas per stroke, making them positive-displacement machines.
CPE Mechanical Systems & Equipment 3
Which bearing type is most appropriate for applications with combined radial and axial (thrust) loads?