Day 6 Boilers – ECET 2026 Mechanical

Why This Topic is Important for ECET

Boilers are a core part of Thermal Engineering and are directly linked to steam power plants, IC engines, and energy systems. Questions from boilers are very frequent in ECET because they involve conceptual understanding, definitions, classification, efficiency formulas, and numerical problems. Mastering boilers will help you score marks quickly and strengthen your fundamentals for both exams and future industry roles.

📘 Concept Notes

🔹 Definition of Boiler

A boiler is a closed vessel in which water is heated to produce steam using the heat energy released by combustion of fuels.

Steam generated is used for power generation, heating, and industrial applications.

🔹 Classification of Boilers

Based on Contents

Fire Tube Boiler → Hot gases pass through tubes, water surrounds them. Example: Cochran, Lancashire.
Water Tube Boiler → Water flows inside tubes, hot gases surround them. Example: Babcock & Wilcox.

Based on Firing

Internally Fired (furnace inside boiler shell).
Externally Fired (furnace outside).

Based on Circulation

Natural Circulation (Cochran, Babcock & Wilcox).
Forced Circulation (La-Mont, Benson, Velox).

Based on Pressure

Low-pressure (< 15 bar).
High-pressure (> 80 bar).

🔹 Examples of Boilers

Cochran Boiler (Vertical Fire Tube) → Compact, used for small power requirements.
Lancashire Boiler (Horizontal Fire Tube) → Long horizontal shell, used in industries.
Babcock & Wilcox Boiler (Water Tube) → High pressure, widely used in power plants.
La-Mont Boiler (Water Tube, Forced Circulation) → High-pressure modern boiler.

🔹 Boiler Mountings & Accessories

Mountings (safety devices, compulsory): Safety valve, Pressure gauge, Water level indicator, Fusible plug.
Accessories (efficiency-improving): Economizer, Superheater, Air preheater, Feed pump.

🔹 Merits of Water Tube Boilers (over Fire Tube)

Higher pressure & higher efficiency.
Steam generation is faster.
Safer in operation.

🔹 Applications

Power plants (electricity generation).
Marine engines.
Industrial heating and processing.

⚙️ Formulas

Boiler Efficiency:

$\eta_{boiler} = \frac{\text{Heat Output}}{\text{Heat Input}} \times 100$

Equivalent Evaporation:

$EE = \frac{m \times (h_{steam} - h_{water})}{2257} \quad (kg/hr)$

Heat Supplied by Fuel:
$Q = m_f \times CV$
where mfm_fmf = mass of fuel, CVCVCV = calorific value

Factor of Evaporation:

$FE = \frac{h_{steam} - h_{water}}{2257}$

🔟 10 MCQs

Q1. Which of the following is a fire tube boiler?
a) Babcock & Wilcox
b) La-Mont
c) Lancashire
d) Benson

Q2. In a water tube boiler:
a) Hot gases pass inside the tubes
b) Water flows inside the tubes
c) Fuel is outside the tubes
d) Steam passes inside the shell

Q3. Cochran boiler is:
a) Vertical fire tube boiler
b) Horizontal water tube boiler
c) High pressure boiler
d) None of these

Q4. Boiler efficiency is given by:
a) Heat input / Heat output
b) Heat output / Heat input
c) Work output / Heat input
d) Heat input / Work output

Q5. Which of the following is NOT a boiler mounting?
a) Safety valve
b) Economizer
c) Pressure gauge
d) Fusible plug

Q6. Equivalent evaporation of a boiler producing 1800 kg/hr of steam with enthalpy difference 2200 kJ/kg is:
$EE = \frac{1800 \times 2200}{2257}$
a) 1753 kg/hr
b) 1652 kg/hr
c) 1800 kg/hr
d) 2000 kg/hr

Q7. The main function of an economizer in a boiler is:
a) Superheat the steam
b) Reduce boiler weight
c) Preheat the feed water
d) Store steam

Q8. La-Mont boiler is:
a) Low pressure fire tube boiler
b) Natural circulation boiler
c) Forced circulation boiler
d) None of these

Q9. The calorific value of coal is 28,000 kJ/kg. If 200 kg of coal is burnt per hour, heat supplied is:
a) 4,800,000 kJ/hr
b) 5,600,000 kJ/hr
c) 3,200,000 kJ/hr
d) 2,800,000 kJ/hr

Q10. Which one of the following increases boiler efficiency?
a) Safety valve
b) Superheater
c) Fusible plug
d) Pressure gauge

✅ Answer Key

Q	Ans
1	c
2	b
3	a
4	b
5	b
6	a
7	c
8	c
9	a
10	b

🧠 Explanations

Q1: Lancashire is a fire tube boiler → (c).
Q2: In water tube boilers, water flows inside tubes → (b).
Q3: Cochran is a vertical fire tube boiler → (a).
Q4: Boiler efficiency = Heat output / Heat input → (b).
Q5: Economizer is an accessory, not a mounting → (b).
Q6: $EE = \frac{1800 \times 2200}{2257} = 1753 , kg/hr$ → (a).
Q7: Economizer preheats feed water → (c).
Q8: La-Mont is a forced circulation boiler → (c).
Q9: $Q = 200 \times 28000 = 5,600,000 , kJ/hr$ → (b).
Q10: Superheater improves efficiency by raising steam temperature → (b).

🎯 Motivation / Why Practice Matters

Boilers are one of the most repeated topics in ECET Thermal Engineering. By solving problems daily, you’ll quickly improve your accuracy, calculation speed, and memory recall. In exams, even 1–2 marks make a huge difference in ranking, and boiler questions are usually direct + high scoring if practiced well.

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Day 6 Boilers – ECET 2026 Mechanical

Why This Topic is Important for ECET