MCQ
(i) Following part is not included in Boiler accessories ____.
(a) ESP
(b) Economiser
(c) Chimney*
(d) Air pre-heater
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(ii) The following are the water tube boilers except ____.
(a) Stirling
(b) Lancashire*
(c) Yarrow
(d) Babcock and Wilcox
(iii) ____ is generally placed after the economizer.
(a) Air pre-heater*
(b) Superheater
(c) Evaporator
(d) None of the above
(iv) An economiser in a boiler ____.
(a) Increases steam pressure
(b) Increases steam temp
(c) Decreases fuel consumption*
(v) Size of boiler tubes is specified by ____.
(a) Mean diameter and thickness
(b) Inside diameter and thickness
(c) *Outside diameter and thickness
(d) Outside diameter and inside diameter
(vi) The number of fire tubes in Lancashire boiler is ____.
(a) Zero
(b) One
(c) Two*
(d) Four
(vii) The biggest loss in the boiler is ____.
(a) Moisture in fuel
(b) Dry flue gases*
(c) Steam formation
(d) Unburnt carbon
(viii) Which of the following can be measured by 'Bolometer'?
(a) Thermal radiations*
(b) Electrical signals
(c) Optical inputs
(d) Temperature inputs
(ix) 'M' Alkalinity represents ____.
(a) Total alkalinity*
(b) Partial alkalinity
(c) Total hardness
(d) None of the above
(x) Which loss is not considered while evaluating boiler efficiency by "Indirect Method"?
(a) Blow down Loss
(b) Un-burnt loss
(c) Air infiltration loss*
(d) Stack Temp loss
True/False
(i) The smallest size of the coal (less than 75 micron) is required in pressurized fluidized bed combustion boiler for firing.
False (PFBC typically uses coal in the range of 1–6 mm, not <75 micron; pulverized coal firing uses <75 micron)
(ii) The Major axis of elliptical manholes on the shell should be provided circumferentially.
False (Major axis should be provided longitudinally / along the shell axis, not circumferentially)
(iii) Fusible plug for boilers is made of fusible metal containing tin, lead and copper.
True
(iv) Boiler stays are used to prevent flat surfaces from tearing apart.
True
(v) Vacuum efficiency of a condenser would be 100% if the condenser is of surface type and temperature of condensate falls below saturation temperature.
False (Vacuum efficiency = (Actual vacuum / Ideal vacuum) × 100; it cannot be 100% if condensate temperature is below saturation because that implies sub cooling, but vacuum efficiency relates to pressure, not condensate temp alone; also 100% is rarely achieved)
A vessel having vacuum of 60 cm of Hg will have absolute pressure equal to 150 mm of Hg when barometer reads 750 mm of Hg.
True (Barometer 750 mm Hg – Vacuum 600 mm Hg = 150 mm Hg absolute
(vii) Abrasiveness index gives idea about hardness of coal and caking index is a measure of binding property of coal.
True
(viii) Junker's calorimeter is used to determine calorific value of liquid fuel and also gaseous fuels.
True
(ix) 1 kg of CO needs 1.57 kg of O₂ and produces 2.57 CO₂.
False (Correct: 2CO + O₂ → 2CO₂; 1 kg CO needs ~0.57 kg O₂, produces ~1.57 kg CO₂, not 2.57)
On the basis of boiler pressure, medium pressure boiler is operated in between 10.54 to 15.5 kg/cm².
False (Medium pressure boiler range is typically 5–10 kg/cm²; 10.54–15.5 kg/cm² falls under high pressure in many classifications)
Fill in the gaps (Answer are given in the bracket)
(i) Hydrogen reacts with oxygen produces ____ and release heat ____ kCal / kg. (water (H₂O), 34,000)
(ii) Carbon reacts with Oxygen produces ____ and release heat ____ kCal / kg. (carbon dioxide (CO₂), 8,080)
(iii) Carbon monoxide reacts oxygen produces ____ and release heat ____ kCal / kg. (carbon dioxide (CO₂), 2,430)
(iv) Sulphur reacts with oxygen produces ____ and release heat ____ kCal/kg. (sulfur dioxide (SO₂), 2,220)
(v) Methane reacts with oxygen produces ____ and release heat ____ kCal/kg. (carbon dioxide (CO₂) and water (H₂O), 13,250)
Define
(i) pH and conductivity of boiler feed water
pH – A measure of the acidity or alkalinity of feed water (scale 0–14). For boiler feed water, pH is typically maintained between 8.5 and 9.5 to prevent corrosion and scale formation.
Conductivity – A measure of the water's ability to conduct electricity, indicating the concentration of dissolved ions (salts, minerals). High conductivity leads to scaling and foaming in the boiler. It is used to control blowdown.
(ii) Boiler circulation ratio and mention its value for natural circulation
Circulation ratio – The ratio of mass of water-steam mixture circulating through the boiler tubes to the mass of steam produced per unit time.
Circulation Ratio=Total mass of mixture/Mass of steam generated
Value for natural circulation – Typically between 5:1 and 30:1.
Common design value: around 10:1 to 20:1.
(iii) 'Steam pipe' as per The Boiler Act, 1923
As per the Boiler Act, 1923 (India), a steam pipe is defined as:
"Any pipe through which steam passes from a boiler to a prime mover or other user, or both, if pressure inside exceeds atmospheric pressure, and includes any fitting or other appliance attached thereto."
Note: This Act has been replaced by the Boilers Act, 2025, but the definition remains substantially similar.
(iv) Specific heat at constant volume
Specific heat at constant volume (Cv) – The amount of heat required to raise the temperature of 1 kg of a substance by 1°C (or 1 K) when the volume is held constant. In this process, no expansion work is done; all heat goes into increasing internal energy.
For ideal gases, Cv = R/(γ − 1), where γ=Cp/Cv.
(v) Volatile matter in coal
Volatile matter (VM) – The portion of coal that is released as gases and vapours (such as methane, hydrogen, hydrocarbons, tar) when coal is heated in absence of air under standardized conditions. It does not include moisture. High VM means coal ignites easily, burns with a long flame, but may produce smoke. VM is a key parameter in coal classification (e.g., lignite has high VM; anthracite has low VM).
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