Exam Practice Test Questions And

3rd Class Stationary Engineer License Exam Practice Test Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

Q1 What is the primary purpose of a steam boiler?

• To circulate feedwater
• To store steam
• To convert water into steam
• To cool condensate

Rationale: Boilers apply heat to water to create steam for power, heating,

or process use.Q2 Which device prevents boiler pressure from exceeding safe limits?

• Steam trap 1 / 4

• Blowdown valve
• Safety valve
• Check valve

Rationale: The safety valve is the final protective device against

overpressure.Q3 What causes boiler corrosion?

• High pH
• Oxygen in the water
• Softened water
• High pressure

Rationale: Dissolved oxygen leads to pitting and metal loss inside boilers.

Q4 Which test measures boiler water alkalinity?

• Hardness test
• Conductivity test
• P-alkalinity test
• Silica test

Rationale: P-alkalinity identifies carbonate/bicarbonate levels controlling

scaling/caustic issues.

Q5 2 / 4

A steam trap removes:

• Oil
• Condensate
• Insoluble solids
• Water treatment chemicals

Rationale: Steam traps discharge condensate while retaining steam.

Q6 Which pump feeds water directly into a boiler?

• Sump pump
• Circulator pump
• Feedwater pump
• Lubrication pump

Rationale: Feedwater pumps maintain boiler water level under pressure.

Q7

Foaming in a boiler is most commonly caused by:

• High pressure
• High total dissolved solids
• Low alkalinity
• Excess blowdown

Rationale: High TDS causes unstable water surfaces leading to foam and

carryover.

Q8 3 / 4

What is the purpose of bottom blowdown?

• Reduce pH
• Remove scale
• Remove sludge and sediment
• Increase water level

Rationale: Bottom blowdown purges settled solids from the mud drum.

Q9 Which of the following best describes superheated steam?

• Moist steam
• Steam heated above saturation temperature
• Steam with water droplets
• Steam at low pressure

Rationale: Superheated steam contains additional heat with no moisture

present.Q10

A pressure gauge is connected to the boiler using a:

• Blowdown tank
• Fusible plug
• Siphon
• Injector

Rationale: Siphons protect gauges from high-temperature steam by

trapping water.

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