Free NCCER Power Generation Maintenance Mechanic Knowledge Assessment Practice Questions

Sample Practice Questions

Try these 10 sample questions from the NCCER Power Generation Maintenance Mechanic Knowledge Assessment practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1On a construction maintenance job, a mechanic is about to use a powered tool designed to accept a guard. Which action meets the guarding requirement during use?

   1. A. Use the tool with its designed guard fitted.
   2. B. Use the tool without its guard when wearing eye protection.
   3. C. Fit the guard only after making a test cut.
   4. D. Fit the guard only when the cut produces sparks.

   Answer: A

   Explanation: OSHA states, "When power operated tools are designed to accommodate guards, they shall be equipped with such guards when in use." The guard is required during operation; eye protection, a preliminary cut, or the presence of sparks does not change that condition.

   Reference: OSHA 1926.300 General requirements — 29 CFR 1926.300(b)(1)

2. 2In a bolted flange joint, what is the expected result if hydrostatic end force exceeds the clamping force applied by the bolts?

   1. A. The flanges separate and the gasket leaks or blows out.
   2. B. The packing rings expand to restore the flange seal.
   3. C. The gasket automatically increases bolt preload.
   4. D. The flange joint becomes less sensitive to pressure.

   Answer: A

   Explanation: Garlock states, "If the hydrostatic end force exceeds the bolt force, the flanges will separate, and the gasket will leak or blow out." The pressure force challenges the bolt-created gasket compression; packing behavior and automatic preload cannot compensate.

   Reference: Garlock Product Selection Training — Forces Acting on a Gasket

3. 3A line needs an isolation valve with little pressure drop when fully open; flow regulation is not required. Which valve type matches that duty?

   1. A. Globe valve.
   2. B. Needle valve.
   3. C. Pressure-reducing valve.
   4. D. Gate valve.

   Answer: D

   Explanation: DOE states, "The disk of a gate valve is completely removed from the flow stream when the valve is fully open. This characteristic offers virtually no resistance to flow when the valve is open." It also says a gate valve does not regulate or throttle flow, matching the stated isolation duty.

   Reference: DOE Fundamentals Handbook: Mechanical Science, Volume 2 — Valves, Gate Valves, p. 8

4. 4Which task is a basic function of a rolling bearing in a machine?

   1. A. Increase friction while transmitting shaft load.
   2. B. Reduce friction without transmitting any load.
   3. C. Carry shaft load by direct shaft-to-housing rubbing.
   4. D. Reduce friction while transmitting load.

   Answer: D

   Explanation: SKF lists bearing functions as "reducing friction, transmitting loads, locating and guiding moving parts." A rolling bearing supports and guides the moving assembly while limiting friction.

   Reference: SKF Bearing Basics Training Transcript — Module 1, Summary, p. 5

5. 5Which pair of parts forms the primary sealing interface of a conventional pump mechanical seal?

   1. A. Two highly polished faces, one rotating and one stationary.
   2. B. Two packing rings compressed around the shaft.
   3. C. A rotating sleeve rubbing directly against the gland bore.
   4. D. The spring and shaft key pressing against one another.

   Answer: A

   Explanation: Chesterton describes "Two highly polished, spring-loaded “seal faces”" and says one face is stationary while the other rotates with the shaft. Their interface is the seal's central working contact.

   Reference: Chesterton Mechanical Seals and Equipment Conditions: Basic Rules — Mechanical Seals & Equipment Conditions—Basic Rules, introductory description

6. 6After cutting steel pipe and before hand-threading it, what should be done to the pipe end?

   1. A. Begin threading before removing the internal cutting burrs.
   2. B. Chamfer only the outside edge and leave the bore burr.
   3. C. Ream it to remove cutting burrs.
   4. D. Clean the outside wall but leave the cut-end burr.

   Answer: C

   Explanation: RIDGID instructs, "Ream the end of the pipe to remove any burrs that may have been produced during the cutting of the pipe." This restores a clean opening before threading.

   Reference: RIDGID Manual Pipe Threader Instructions — Threading procedure, step 3, p. 1

7. 7What does a superheater do to steam at a given pressure?

   1. A. Lowers its temperature below the condensate return.
   2. B. Removes only suspended solids.
   3. C. Reduces the boiler feedwater oxygen content.
   4. D. Raises its temperature above the saturation temperature.

   Answer: D

   Explanation: DOE defines the result of superheaters as "a steam temperature that exceeds the saturation temperature at a specific pressure". That is superheated steam.

   Reference: Improving Steam System Performance: A Sourcebook for Industry — Steam System Basics, Superheaters, p. 5

8. 8A hydraulic cylinder does not move and a pressure check at the cylinder shows pressure below circuit requirements. What should be investigated next?

   1. A. Replace the piston rod before tracing the low-pressure supply.
   2. B. The low supply pressure or its control path.
   3. C. Inspect only cylinder seals while ignoring upstream pressure.
   4. D. Increase relief setting immediately without checking the pressure path.

   Answer: B

   Explanation: Parker lists "Pressure too low" among reasons a cylinder will not move and directs, "Check pressure at cylinder to make sure it is to circuit requirements." The measured deficit points to supply or control pressure.

   Reference: Parker Standard Telescopic Service Manual — Troubleshooting Hints, Cylinder will not Operate or Move, p. 30

9. 9How does a reciprocating compressor raise the pressure of air in its cylinder?

   1. A. A diffuser increases the air velocity without changing volume.
   2. B. An air receiver removes water from the incoming air.
   3. C. An aftercooler adds heat to the cylinder air.
   4. D. A piston reduces the volume occupied by the air.

   Answer: D

   Explanation: "A piston, driven through a crankshaft and connecting rod by an electric motor, reduces the volume in the cylinder occupied by the air or gas, compressing it to a higher pressure." Introduction to Industrial Compressed Air Systems, Positive-Displacement Compressors, p. 5

   Reference: DOE, Improving Compressed Air System Performance: A Sourcebook for Industry — Introduction to Industrial Compressed Air Systems, Positive-Displacement Compressors, p. 5

10. 10A steam turbine diaphragm shows dishing and erosion during an outage. What does the manufacturer indicate may be necessary?

    1. A. Continue operation without addressing dishing or erosion.
    2. B. Repair only the casing while leaving the diaphragm damaged.
    3. C. Major repair or replacement of the diaphragm.
    4. D. Rebalance the rotor while leaving the eroded diaphragm in place.

    Answer: C

    Explanation: "Over time, some diaphragms may experience dishing and erosion, requiring major repairs or replacements." Dishing and erosion can require direct diaphragm repair or replacement.

    Reference: GE Vernova, Preparing for the Unexpected: A Guide to Steam Turbine Outage Planning — Key failure points and how to plan for them