Ten original exam-style 5th Class Power Engineering questions from our free public sample, written to the public syllabus. Work them on paper, then check the answer key at the end. They are not questions from a real exam, and a score here does not predict your exam result.
1. What is identified as the primary disadvantage of electric boilers when compared to fuel-fired alternatives?
A. The low on-site energy conversion efficiency of electric heating
B. The frequent replacement of heating elements due to scale buildup on their surfaces
C. The more demanding water treatment programs required for the elements
D. The larger physical footprint needed to house the electrical switchgear
E. The relatively high operating cost of electricity compared to fuel
Question ID KE-501-C04-Q004 · Unit 5-1: Low Pressure Boiler Components and Operation · Report an error
2. Which type of burner control continuously adjusts the firing rate to keep boiler pressure at a steady value regardless of changing load?
A. Flame failure control
B. Modulating control
C. On-off control
D. High-low fire control
E. High limit control
Question ID KE-501-C08-Q001 · Unit 5-1: Low Pressure Boiler Components and Operation · Report an error
3. When an automatic gas valve opens too rapidly, a larger-than-normal combustible mixture accumulates in the furnace and ignites all at once, creating a momentarily high pressure. What is this event called?
A. Puff back
B. Furnace lockout
C. Backdraught
D. Light-off surge
E. Flashback
Question ID KE-501-C14-Q007 · Unit 5-1: Low Pressure Boiler Components and Operation · Report an error
4. Plug valves are listed as suitable for several industrial services, but one application falls outside their design limits. Which service is a plug valve NOT appropriate for?
A. Chemical industry isolation service
B. Low-pressure on/off cooling water service
C. Gas supply line quick-opening service
D. Water treatment plant flow control
E. High-pressure steam lines
Question ID KE-501-C18-Q004 · Unit 5-1: Low Pressure Boiler Components and Operation · Report an error
5. Which of the following is NOT a recognized reason for keeping an accurate boiler operating log?
A. To provide data used to schedule routine maintenance and improve operating efficiency
B. To remove the requirement for the boiler's annual jurisdictional inspection
C. To pass on a record of conditions from one operating shift to the next
D. To create a record that helps trace the cause of an abnormal condition
E. To reveal trends that may warn of a developing equipment problem
Question ID SUP5-51-Q016 · Unit 5-1: Low Pressure Boiler Components and Operation · Report an error
6. A trap is installed in a sanitary drainage system primarily to:
A. Capture hair and solid debris before they enter the waste stack
B. Slow the flow so grease can settle out before reaching the municipal main
C. Regulate flow velocity so solids remain in suspension in the pipe
D. Create a water seal that blocks sewer gases from entering the building
E. Provide an access point for rodding out blockages in the drain line
Question ID KE-502-C13-Q001 · Unit 5-2: Elements of Human Comfort in Facility Operation · Report an error
7. Which of the following correctly identifies the three general categories of refrigeration condensers?
A. Shell and tube, double tube, and shell and coil
B. Flooded, dry expansion, and plate surface
C. Air-cooled, water-cooled, and evaporative
D. Forced-draft, induced-draft, and natural-draft
E. Bare tube, finned tube, and evaporative
Question ID KE-502-C19-Q002 · Unit 5-2: Elements of Human Comfort in Facility Operation · Report an error
8. While water is being converted to steam at 100°C and atmospheric pressure, a thermometer placed in the water shows no temperature change even though heat is still being added. What term describes this added heat?
A. Sensible heat of the liquid
B. Heat of compression
C. Superheat
D. Specific heat
E. Latent heat of evaporation
Question ID KE-503-C08-Q004 · Unit 5-3: Basic Physical Science, Safety, and Regulation for Facility Operations · Report an error
9. CSA Z460 identifies two types of lockouts used in a heating plant. What are they?
A. Electrical lockouts and mechanical lockouts
B. Single-point lockouts and multi-point lockouts
C. Permanent lockouts and temporary lockouts
D. Supervisory lockouts and contractor lockouts
E. Personal lockouts and lockbox (group) lockouts
Question ID KE-503-C13-Q005 · Unit 5-3: Basic Physical Science, Safety, and Regulation for Facility Operations · Report an error
10. Which treatment method is most often applied after a settling tank to remove the suspended solids that remain in the water?
A. Lime-soda chemical softening
B. Reverse osmosis through a semi-permeable membrane
C. Filtration
D. Zeolite ion exchange softening
E. Deaeration
Question ID KE-503-C17-Q009 · Unit 5-3: Basic Physical Science, Safety, and Regulation for Facility Operations · Report an error
Answer key
1. E(KE-501-C04-Q004), Electricity usually costs more than fuel for the same heat, and that running cost is the main drawback of an electric boiler. The unit itself is compact: it needs no furnace, chimney, or fuel storage, and it turns about 98% of the incoming electricity into heat at the plant. Low efficiency and a large footprint are not fair criticisms. Immersion elements can need closer water treatment, but that is not the main reason to prefer a fuel-fired boiler.
2. B(KE-501-C08-Q001), A modulating control continuously varies the fuel and air supply to match the boiler load, keeping pressure at a constant value. On-off control only switches the burner fully on or off; high-low fire selects between two fixed rates; high limit control shuts down the burner as a safety measure rather than regulating firing rate.
3. A(KE-501-C14-Q007), A puff back occurs when an automatic gas valve opens too quickly, flooding the furnace with a larger-than-normal combustible mixture that ignites all at once, building a momentarily high pressure that blows back through air intakes and observation openings. This is why most larger gas valves are designed to open slowly. A flashback is a different event in which flame travels back into the burner body.
4. E(KE-501-C18-Q004), Plug valves are used for hot-water heating, chilled water, gas supply, low-pressure steam, water treatment, and in pulp, paper, and chemical plants. The steam duty named for them is low pressure only, so high-pressure steam is outside that service. The other duties in the question are ordinary plug-valve work.
5. B(SUP5-51-Q016), An operating log supports troubleshooting, trend analysis, and shift handover, but it does not substitute for the legally required inspection by the jurisdiction. That makes removing the requirement for the boiler's annual jurisdictional inspection the item that is not a valid reason.
6. D(KE-502-C13-Q001), The purpose of a trap is to hold a water seal that prevents sewer gases from backing up through the fixture outlet into the building. Capturing debris is the function of strainers; providing cleaning access is the function of cleanouts; flow velocity is maintained by correct pipe slope and sizing.
7. C(KE-502-C19-Q002), Refrigeration condensers fall into three groups: air-cooled, water-cooled, and evaporative. Shell-and-tube, double-tube, and shell-and-coil units are forms of water-cooled condenser, not extra groups. Flooded and dry-expansion describe how an evaporator is fed, not the type of condenser.
8. E(KE-503-C08-Q004), Latent heat is heat added or removed that causes a change of state at a constant temperature, so the thermometer shows no change. The specific form during liquid-to-vapour conversion is latent heat of evaporation. Sensible heat would produce a temperature rise; superheat is sensible heat added to steam already above the saturation temperature.
9. E(KE-503-C13-Q005), CSA Z460 defines two types of lockouts: personal lockouts, where an individual applies their own personal locks to equipment they will work on, and lockbox or group lockouts, where trained operators lock out equipment and secure all keys in a lockbox that other workers can each add a personal lock to. Electrical vs. mechanical and permanent vs. temporary are not the classification scheme used by CSA Z460.
10. C(KE-503-C17-Q009), Filters are frequently used in conjunction with settling tanks: the settling tank removes the bulk of the suspended impurities by gravity, and the water then passes through a filter to capture any remaining fine particles. Deaeration targets dissolved gases, and zeolite or lime-soda softening targets dissolved solids. Neither addresses the suspended-solids left after settling.
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