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10 free 2B practice questions (printable)

Ten original exam-style 2nd Class Part B (2B) 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.

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1. A plant requires a steam turbine whose exhaust steam will be used for process heating. Which class of turbine is selected for this duty?

  • A. A noncondensing turbine that exhausts at or above atmospheric pressure
  • B. A regenerative bleeder turbine exhausting to a water-cooled surface condenser
  • C. A cross compound turbine exhausting to an air-cooled condenser under vacuum
  • D. A condensing turbine that exhausts below atmospheric pressure

Question ID 2B1-C01-Q001 · Unit §10: Heat Engines and Prime Movers · Report an error

2. Low carbon steel is the lowest-priced steel and is used extensively for steam, water, fuel oil and compressed air piping. Above what approximate temperature is low carbon steel NOT recommended because graphitization may occur within the pipe material?

  • A. 230°C
  • B. 525°C
  • C. 400°C
  • D. 540°C

Question ID 2B1-C10-Q001 · Unit §12: Piping · Report an error

3. In an orthographic drawing, what does the term 'orthographic' literally mean, and how many standard views does the most common orthographic drawing present?

  • A. "Pictorial snapshot": one combined three-dimensional view
  • B. "Description at right angles": three standard views (front, side, top)
  • C. "Description in section": four standard views including an auxiliary view
  • D. "Description in perspective": two standard views (front and side)

Question ID 2B1-C11-Q001 · Unit §13: Mechanical Drawing · Report an error

4. A refinery produces fuel oil by a process that uses heat and pressure to decompose heavier crude oil fractions, actually changing the hydrocarbon structure to yield more of the valuable lighter hydrocarbons such as gasoline. Which process is described?

  • A. Centrifuging
  • B. Cracking
  • C. Distillation
  • D. Sweetening

Question ID 2B2-C01-Q001 · Unit §14: Power Plant Systems · Report an error

5. Boiler feedwater can be used to supply steam desuperheaters only under what condition?

  • A. Only if the boiler feedwater conductivity exceeds 20 000 mmhos
  • B. Only if the boiler feedwater contains added polymers
  • C. Only if the boiler feedwater has been cycled up 50 to 100 times
  • D. Only if the boiler feedwater is phosphate free

Question ID 2B2-C02-Q023 · Unit §14: Power Plant Systems · Report an error

6. In a furnace, carbon combines with an insufficient supply of oxygen. What is the principal consequence?

  • A. The reaction becomes endothermic and absorbs heat from the surroundings
  • B. Complete combustion still occurs because carbon always forms CO2 regardless of oxygen supply
  • C. Incomplete combustion, producing carbon monoxide (CO) and wasting part of the available heat
  • D. Sulphur dioxide forms in place of carbon dioxide because the oxygen bonds with sulphur first

Question ID 2B2-C05-Q001 · Unit §16: Fuels and Combustion · Report an error

7. In the differentiation of fine particulate emissions, what does the designation 'PM10' specifically refer to?

  • A. Particulate matter less than 2.5 microns in diameter that penetrates deep into the lungs
  • B. Particulate matter that settles out within 10 metres of the stack base
  • C. Particulate matter less than 10 microns in diameter, readily inhaled into the lungs
  • D. Particulate concentration of 10 mg/m3 in the stack gases

Question ID 2B2-C08-Q001 · Unit §17: Environmental Protection · Report an error

8. A vector of length 1.0 is rotated counterclockwise to generate a sine wave. When the vector has rotated to an angle of 30 degrees, what is the magnitude of its vertical component (the instantaneous value plotted on the sine wave)?

  • A. 1.000
  • B. 0.707
  • C. 0.500
  • D. 0.866

Question ID 2B3-C01-Q001 · Unit §18: Electrotechnology · Report an error

9. Per the NEMA MG1 guideline cited for maximum-starts-over-time protection, how many starts are permitted with the motor initially at ambient temperature?

  • A. Two starts in succession, coasting to reset between starts
  • B. One start in succession, coasting to reset
  • C. Three starts in a row, coasting to reset between starts
  • D. Unlimited starts as long as cooling air is supplied

Question ID 2B3-C06-Q024 · Unit §18: Electrotechnology · Report an error

10. Which combination of properties best describes an ideal refrigerant?

  • A. Low boiling temperature at atmospheric pressure, high latent heat capacity, and a low specific volume at compressor suction pressure
  • B. High boiling temperature at atmospheric pressure, high latent heat capacity, and flammability when mixed with air
  • C. Low boiling temperature at atmospheric pressure, low latent heat capacity, and a high condensing pressure
  • D. High boiling temperature at atmospheric pressure, low latent heat capacity, and a high specific volume at compressor suction pressure

Question ID 2B3-C08-Q001 · Unit §20: Industrial/Commercial Refrigeration · Report an error

Answer key

  1. 1. A (2B1-C01-Q001), Turbines that exhaust at or above atmospheric pressure are noncondensing turbines, and they are used when the exhaust steam is to be utilized for process heating. Condensing turbines exhaust below atmospheric pressure and require a condenser, and are used where there is no need for process steam. A bleeder turbine extracts steam to heat feedwater (a regenerative cycle), and cross compounding refers to a shaft arrangement, neither of which defines the duty described.
  2. 2. C (2B1-C10-Q001), Low carbon steel is generally limited to service below about 400 to 425°C, depending on the reference (some codes flag prolonged service above about 425°C, or 800°F). Above that range it is not recommended because graphitization (the breaking down of steel into iron and carbon graphite, with failure occurring along lines of graphite concentration) may occur, so 400°C is the best answer here. 230°C is the steam temperature limit for grey cast iron, not the graphitization limit for low carbon steel. 525°C is the upper limit for certain low-chrome alloy steels, and 540°C is a typical central-station alloy steel steam piping temperature, both well above the carbon-steel limit.
  3. 3. B (2B1-C11-Q001), Orthographic is Greek for "Description at Right Angles," and the most commonly used orthographic drawing has three views: front, side, and top. A perspective or pictorial snapshot describes isometric/oblique pictorial drawings, not orthographic ones; an orthographic drawing is two-dimensional per view, not a single combined 3-D view; and while additional views (auxiliary, back, bottom, etc.) can be added, the standard orthographic set is three views, not four.
  4. 4. B (2B2-C01-Q001), The process that uses heat and pressure to decompose heavier crude fractions and actually change the hydrocarbon structure to produce more lighter hydrocarbons (gasoline) is cracking. Distillation only separates oil into its constituent parts by vaporizing the lighter fractions without changing the hydrocarbon structure. Centrifuging is used to detect water and sediment in a sample, not to refine oil. Sweetening is the removal of hydrogen sulphide from sour natural gas, not an oil-refining decomposition process.
  5. 5. D (2B2-C02-Q023), Boiler feedwater is a mixture of steam condensate and demineralized makeup containing amines and oxygen scavengers; it can be used to supply steam desuperheaters only if the water is phosphate free, since phosphate would carry into and deposit from the steam. Cycling up 50 to 100 times describes boiler blowdown, very high conductivity describes regen waste, and added polymers would disqualify rather than qualify the water for desuperheating.
  6. 6. C (2B2-C05-Q001), When carbon combines with insufficient oxygen it forms carbon monoxide (CO) instead of carbon dioxide (CO2); this is incomplete combustion and makes the process inefficient, losing a percentage of the available heat. Carbon does not always form CO2, because the product depends on the oxygen available. Combustion is exothermic (heat-releasing), never endothermic. Sulphur dioxide arises from sulphur, not from a shortage of oxygen on carbon.
  7. 7. C (2B2-C08-Q001), PM10 is defined as particulate that is less than 10 microns in diameter and is readily inhaled into the lungs, where a micron equals 10^-6 m. The 2.5-micron description belongs to PM2.5, which penetrates deeper into the lungs. The designation is a particle-size standard, not a concentration value (mg/m3) or a settling-distance specification.
  8. 8. C (2B3-C01-Q001), The instantaneous value equals the vector length multiplied by the sine of the rotation angle. With a length of 1.0 at 30 degrees, sin 30 = 0.5, so the vertical component is 0.5 x 1.0 = 0.5. The value 0.866 corresponds to 60 degrees (sin 60), 0.707 corresponds to 45 degrees, and 1.000 corresponds to 90 degrees where the full vector projects onto the vertical axis.
  9. 9. A (2B3-C06-Q024), The NEMA MG1 standard allows two starts in succession, coasting to reset between starts, with the motor initially at ambient temperature, and one start when the motor is already at its rated-load operating temperature. A single start applies only to the hot-motor case, three starts exceeds the guideline, and unlimited starts ignores the heat-buildup risk that the protection guards against.
  10. 10. A (2B3-C08-Q001), The ideal refrigerant should boil at a low temperature at atmospheric pressure so heat can be absorbed at a low enough temperature for cooling to occur, should have a high latent heat capacity to maximize the heat transferred per unit mass circulated, and should have a low specific volume at suction pressure to keep the required compressor size small. A high boiling temperature, low latent heat, high specific volume, high condensing pressure, or flammability with air are all undesirable traits, not ideal ones.

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