Q: Safety valve function in boilers: select the correct purpose. Context: Overpressure protection is mandatory to prevent boiler explosions and protect equipment and personnel. Choose the correct function of a safety valve.

Concept The safety valve is a pressure-relief device that automatically releases steam if the boiler pressure exceeds the set working (or design) limit, preventing catastrophic overpressure. Not to be confused with Water level indication (gauge glass or water level indicator). Pressure measurement (Bourdon pressure gauge).

Q: Boiler performance statements: identify the incorrect statement among the following. Context: Factor of evaporation (FE), equivalent evaporation, and boiler efficiency are standard boiler performance terms. Select the statement that is wrong.

Concept check Factor of evaporation (FE) adjusts actual evaporation to an equivalent basis (from and at 100°C). It is not necessarily always > 1. FE can be less than, equal to, or greater than 1 depending on feedwater temperature and final steam state. Equivalent evaporation expresses evaporation on the standard basis “from and at 100°C”. It may be reported per hour or per kg of fuel (i.e., equivalent evaporation per kg fuel). Boiler efficiency is correctly defined as useful heat to steam / heat released in the furnace. Therefore Option A is wrong because FE is not always greater than unity.

Question 1

Boiler type for fluctuating steam demand: identify the most suitable option.  Context: Rapid changes in steam load require boilers that respond quickly and handle variable draught and firing conditions.  Choose the boiler best suited to fluctuating …

Accepted Answer

Concept Among classic fire-tube and water-tube designs, the locomotive boiler is specifically designed for rapidly varying loads with strong, controllable draught (blast pipe) and large heating surface, making it well suited for fluctuating steam demand in mobile service. Why others are less suitable Lancashire/Cornish boilers have large water volumes and slow response to rapid load changes. Babcock and Wilcox (water-tube) are excellent for high pressure and high rates but the classic exam key for “fluctuating demand” favors the locomotive boiler’s on-off, quick-response operation.

Question 2

Single-acting vs double-acting steam engine: comparative power output.  Context: In a double-acting engine, steam performs work on both sides of the piston each cycle; in a single-acting engine, only one side.  Choose the correct comparison of power…

Accepted Answer

Concept With identical cylinder size and speed, a single-acting steam engine admits steam to only one side of the piston, producing work on one stroke. A double-acting engine produces work on both strokes. Hence, ideal power of a single-acting unit is about half that of a similar double-acting unit (neglecting small differences in rod area, etc.).

Question 3

Speed classification of steam engines: categorize an engine running between 100 and 250 r.p.m.  Context: Slow, medium, and high-speed steam engines are classified by crankshaft rpm bands in classic practice.  Select the correct class for 100–250 r.p…

Accepted Answer

Concept Typical classification places engines of about 100–250 r.p.m. in the medium-speed category. Slower machines (e.g., < 100 r.p.m.) are slow-speed; much faster units are high-speed types.

Question 4

Safety valve function in boilers: select the correct purpose.  Context: Overpressure protection is mandatory to prevent boiler explosions and protect equipment and personnel.  Choose the correct function of a safety valve.

Accepted Answer

Concept The safety valve is a pressure-relief device that automatically releases steam if the boiler pressure exceeds the set working (or design) limit, preventing catastrophic overpressure. Not to be confused with Water level indication (gauge glass or water level indicator). Pressure measurement (Bourdon pressure gauge).

Question 5

Boiler performance statements: identify the incorrect statement among the following.  Context: Factor of evaporation (FE), equivalent evaporation, and boiler efficiency are standard boiler performance terms.  Select the statement that is wrong.

Accepted Answer

Concept check Factor of evaporation (FE) adjusts actual evaporation to an equivalent basis (from and at 100°C). It is not necessarily always > 1. FE can be less than, equal to, or greater than 1 depending on feedwater temperature and final steam state. Equivalent evaporation expresses evaporation on the standard basis “from and at 100°C”. It may be reported per hour or per kg of fuel (i.e., equivalent evaporation per kg fuel). Boiler efficiency is correctly defined as useful heat to steam / heat released in the furnace. Therefore Option A is wrong because FE is not always greater than unity.

Question 6

Compound steam engine: choose the correct statement about advantages/design features.  Context: Compounding expands steam in multiple cylinders to improve economy and reduce temperature range per cylinder.  Select the correct statement for a compoun…

Accepted Answer

Concept Compound engines divide expansion across multiple cylinders (HP→IP→LP), improving efficiency and reducing thermal stresses. They are generally more costly than simple engines of the same power due to added cylinders and components. Why the others are incorrect Forces are shared across stages; they are not “increased” as per Option B. Overall expansion ratio is increased, not reduced (Option C). Per-cylinder temperature range is decreased, reducing condensation (Option D).

Question 7

Boiler efficiency calculation from operating data: compute percentage efficiency.  Data given: Feed water supplied = 205 kg/h Coal fired = 23 kg/h Net enthalpy rise per kg of water = 145 kJ/kg Calorific value of coal = 2050 kJ/kg  Calculate the boil…

Accepted Answer

Given Feedwater mass flow = 205 kg/h Coal firing rate = 23 kg/h Net enthalpy rise per kg water = 145 kJ/kg Coal calorific value (CV) = 2050 kJ/kg Approach Boiler efficiency = (Useful heat added to water per hour) / (Fuel energy input per hour). Step-by-step Useful heat rate = (205 kg/h) × (145 kJ/kg) = 29,725 kJ/h Fuel heat input rate = (23 kg/h) × (2050 kJ/kg) = 47,150 kJ/h Efficiency = 29,725 / 47,150 = 0.6304 ≈ 63% Common pitfalls Forgetting to multiply by the hourly mass flow before taking the ratio. Confusing equivalent evaporation with efficiency; efficiency always compares useful output energy to input fuel energy. Final Answer 63%

Question 8

Boilers: identify the correct statement for a water-tube boiler  In water-tube designs, compare the path of water versus the path of hot gases and flames.  Choose the correct option.

Accepted Answer

Concept and identification In a water-tube boiler, the water/steam flows inside the tubes while the hot gases flow externally over the tube bank. This is the core distinction from fire-tube boilers, where hot gases are inside the tubes and water surrounds them. Why the other options are incorrect (b) describes a fire-tube boiler, not a water-tube boiler. (c) is too strong: many water-tube boilers use natural circulation (e.g., Babcock & Wilcox); forced circulation exists but is not universal. Final Answer Water passes through tubes surrounded by flames and hot gases

Question 9

Boilers: select the statement(s) that are wrong among common classifications  Evaluate each claim about locomotive, water-tube, and La-Mont boilers for correctness.  Choose the option that best identifies the wrong statement(s).

Accepted Answer

Check each statement (a) Wrong: A locomotive boiler is a fire-tube boiler (shell with tubes carrying hot gases). (b) Wrong: Classic water-tube boilers (e.g., Babcock & Wilcox, Stirling) are typically externally fired (separate furnace); some modern designs can be internally fired, but the blanket statement is incorrect. (c) Wrong: The La-Mont boiler is a high-pressure, forced-circulation water-tube boiler, not low pressure. Conclusion Each listed statement is wrong, so the correct choice is All of the above statements are wrong.

Question 10

Fire-tube boilers: firing arrangement for typical designs  Determine whether common fire-tube boilers are internally or externally fired, based on furnace location.  Choose the correct option.

Accepted Answer

Concept Fire-tube boilers such as Cornish, Lancashire, Scotch marine, and locomotive typically have the furnace inside the shell, i.e., are internally fired. Water surrounds the furnace and tubes within the shell. Final Answer Internally fired

Question 11

Locomotive boiler: typical shell diameter range  Recall the standard shell diameter used in classic locomotive boilers used on railways.  Choose the correct value.

Accepted Answer

Typical dimensioning Locomotive fire-tube boilers usually have shell diameters in the vicinity of about 1.5 m (order of magnitude 1–2 m), balancing grate area, tube bundle, and envelope constraints between frames. Final Answer 1.5 m

Question 12

Scotch marine boiler: orientation of its fire tubes  Scotch (Scots) marine boilers are compact fire-tube marine units. Identify how the fire tubes are arranged between the furnace/combustion chamber and the uptake.  Choose the correct option.

Accepted Answer

Horizontal tubes

Question 13

Boiler draught: primary objectives of producing draught  List the functions served by draught in a steam generator, from air supply to gas discharge.  Choose the correct option.

Accepted Answer

Concept Draught (natural via chimney or mechanical via fans/steam jet) creates the pressure differential to: • Supply sufficient combustion air, • Carry products of combustion through the passes, and • Discharge them safely to atmosphere. Final Answer All of the above

Question 14

Simple vertical and fire-tube boilers: identify the correct statement  Evaluate each claim about space requirement, achievable steam pressure/quantity, and tube count in a simple vertical boiler.  Choose the correct option.

Accepted Answer

Verification (a) Incorrect: For the same capacity, water-tube boilers typically occupy less space and hold less water than fire-tube units. (b) Incorrect: Simple vertical boilers are low capacity, low pressure units. (c) Correct: The classic simple vertical boiler has a single, central fire (flue) tube within the vertical shell (distinct from the vertical cross-tube type that adds cross tubes). Final Answer A simple vertical boiler has one fire tube.

Question 15

Boiler components: function of the grate  Confirm the definition of a grate located within the combustion chamber of a solid-fuel boiler (coal/wood).  Choose the correct truth value.

Accepted Answer

Definition A grate is the bed of bars in the furnace on which solid fuel (coal/wood) rests and burns; ash falls through to an ash pit while air flows through the grate for combustion. Final Answer True: it is the support on which solid fuel is burned

Question 16

Condensing plant: condensate temperature relative to cooling-water inlet  In a surface condenser, compare the temperature of condensate leaving the condenser to that of the circulating water at inlet.  Choose the correct relation.

Accepted Answer

Concept Condensate in a surface condenser is approximately at the saturation temperature corresponding to condenser pressure (often ~30–45 °C under vacuum). The cooling water enters at a lower temperature and exits warmer after absorbing latent and sensible heat. Therefore At the outlet of the condenser, the condensate is hotter than the cooling-water inlet temperature. Final Answer Higher than the cooling-water inlet temperature

Question 17

Stationary land boilers: commonly used main safety valve type  Select the safety valve design typically employed on stationary boilers, where orientation is fixed and compactness is less critical than reliability and constancy of set pressure.  Choo…

Accepted Answer

Concept For stationary land boilers, the classic choice is the dead-weight safety valve, which maintains an accurate set pressure by calibrated weights and is unaffected by vibration/tilt (suitable when the boiler is fixed in place). Locomotive/marine boilers usually employ spring-loaded valves due to motion and space constraints. Clarifications A high-steam/low-water device is a protective combined valve/sensor but not the standard main safety valve type across stationary plant. Final Answer Dead-weight safety valve

Question 18

LaMont boiler: identify whether the statement about type and circulation is correct.  Statement: The LaMont boiler is a high-pressure, water-tube steam boiler that operates with forced circulation driven by a pump.  Choose the correct option (True/F…

Accepted Answer

Concept & identification The LaMont boiler is a high-pressure water-tube boiler that uses forced circulation. A circulating pump drives water through the economiser and evaporator tubes, improving heat transfer and preventing overheating of tubes. Why True Water flows inside tubes (water-tube construction). A pump forces circulation (not natural circulation). Designed for high pressures and high steaming rates. Common pitfalls Do not confuse LaMont with natural-circulation types (e.g., Babcock & Wilcox). LaMont explicitly employs a pump. Final Answer True

Question 19

Economiser effect on boiler output: complete the sentence with the correct engineering impact.  An economiser __________ the steam-raising capacity of a boiler by preheating the incoming feedwater using waste flue-gas heat.  Choose the correct word …

Accepted Answer

Concept An economiser transfers residual heat from flue gases to the feedwater. This raises feedwater temperature before it enters the boiler, which reduces the fuel required per kg of steam and effectively increases the steam-raising capacity for a given firing rate. Why 'increases' Lower enthalpy rise needed in the boiler proper. Improved overall efficiency allows higher evaporation rate with the same fuel input. Final Answer increases

Question 20

Benson (once-through, supercritical) boiler: typical steaming capacity.  Choose the approximate rate of steam production commonly associated with Benson boilers in standard references and exam data.

Accepted Answer

Concept The Benson boiler is a once-through, high-pressure (often supercritical) water-tube boiler. Standard objective-type references commonly quote a typical steaming capacity around 135 tonnes per hour for benchmark problems. Notes Although practical designs may span a wide range, 135 t/h is the widely accepted figure for textbook MCQs. Final Answer 135 tonnes/h

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