MCQ and SAQ from Maharashtra BOE Exam 2018

MCQ

(i) An increase in steam pressure of a boiler during start-up from 4 bar (g) to 12 bar (g), will result in decrease of ____.

(a) enthalpy of steam

(b) sensible heat of steam

(c) specific volume of steam*

(d) saturation temperature of steam.

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(ii) Combustible elements in the fuel are ____.

(a) carbon and hydrogen

(b) carbon, hydrogen and sulphur*

(c) carbon, hydrogen and nitrogen

(d) carbon, hydrogen and ash.

 

(iii) The two basic properties enable control valves to 'control' are ____.

(a) temperature and pressure

(b) temperature and flow rate

(c) pressure and valve movement

(d) pressure and flow rate*

 

(iv) The basic job of boiler feed water treatment is to overcome the problems of ____.

(a) corrosion

(b) scale

(c) carryover

(d) all the above*

 

(v) Dissolved CO₂ in boiler feed water when left untreated would result in occurrence of ____ in boiler tubes.

(a) scale

(b) water side corrosion*

(c) creep

(d) water hammer.

 

(vi) ____ fired steam boiler will have the least evaporation ratio.

(a) Bagasse

(b) Coal

(c) LSHS*

(d) Natural gas.

 

(vii) Once-through boiler is named as such because ____.

(a) flue gases pass only in one direction

(b) steam is sent out only in one direction

(c) air is sent through same direction

(d) there is no recirculation of water*

 

(viii) Low combustion temperature minimizes ____ in FBC boilers.

(a) NOx*

(b) SOx

(c) CO

(d) Suspended particulate matter.

 

(ix) ____ is a carbon-neutral fuel.

(a) Coal

(b) Hydrogen

(e) Natural gas

(d) Biomass*

 

(x) Proper sizing of steam pipeline helps in minimizing ____.

(a) steam requirement.

(b) pressure drop*

(c) temperature drop.

(d) boiler efficiency

True/False

(i) An increase in the steam pressure from 7 kg/cm² to 10 kg/cm², will result in an increase of specific volume.

False (Specific volume decreases as pressure increases).

(ii) A device used to convert low pressure steam to high pressure steam is called a thermo compressor.

True

(iii) Lower excess air resulting in lesser stack loss is not true with respect to improper sizing of coal.

False (Lower excess air does reduce stack loss; the statement is confusingly worded but generally false as written).

(iv) Sulphur is measured in proximate analysis.

False (Sulphur is measured in ultimate analysis, not proximate).

(v) The density of a substance relative to water is called viscosity.

False (That is specific gravity; viscosity is resistance to flow).

(vi) The head loss due to friction in a steam pipe is directly proportional to the diameter of the pipe.

False (Head loss is inversely proportional to diameter, not directly).

(vii) Carpet loss is associated with storage of furnace oil.

True (Carpet loss refers to slow leakage/spreading of oil on storage surfaces).

(viii) Water softening process reduces TDS but not hardness.

False (Softening primarily reduces hardness; it may not significantly reduce TDS).

(ix) Steam at 4 kg/cm² has sensible heat of 144 kCal/kg and latent heat of 510 kCal/kg. If the steam is 90% dry, then the total enthalpy of steam in kCal/kg is 603.

True (Calculation: 144 + 0.9 × 510 = 144 + 459 = 603 kCal/kg).

(x) The balanced draught furnace is one that is operated with only natural draught.

False (Balanced draught uses both forced and induced draught fans to maintain near-atmospheric pressure in the furnace).

Unit Conversion

(a) 175 MTOE → kCal

1 MTOE (Million Tonnes of Oil Equivalent) = 10⁶ tonnes × 10³ kg/tonne = 10⁹ kg

1 kg OE = 10,000 kCal (approx., standard value)

So, 1 MTOE = 10⁹ × 10⁴ = 10¹³ kCal

175 MTOE = 175 × 10¹³ kCal = 1.75 × 10¹⁵ kCal

(b) 175 mmwc → PSI

1 mmwc = 0.001422 PSI (approx.)

175 mmwc = 175 × 0.001422 = 0.24885 PSI

(c) 175 kCal → HP (horsepower)

1 HP (metric) = 641.186 kCal/h

175 kCal/h = 175 ÷ 641.186 = 0.2729 HP

(d) 175 m/sec → km/hr

1 m/s = 3.6 km/h

175 m/s = 175 × 3.6 = 630 km/h

(e) 175 °C → °F

°F = (°C × 9/5) + 32

°F = (175 × 9/5) + 32 = (315) + 32 = 347

Full Forms

(a) MEDA

Maharashtra Energy Development Agency

(b) ASME

American Society of Mechanical Engineers

(c) LSHS

Low Sulphur Heavy Stock

(d) MTOE

Million Tonnes of Oil Equivalent

Define in short

(i) Co-generation

The simultaneous production of electrical energy (or mechanical power) and useful thermal energy (like steam or hot water) from the same fuel source.

(ii) Vacuum and condenser efficiency

Vacuum efficiency: The ratio of the actual vacuum pressure in the condenser to the ideal vacuum (perfect vacuum) achievable, expressed as a percentage.

Condenser efficiency: The ratio of the actual temperature rise of the cooling water to the maximum possible temperature rise (if the steam were cooled to the cooling water inlet temperature).

(iii) 'Boiler' as per The Indian Boiler Act, 1923

A closed pressure vessel in which steam or other vapor is generated at a pressure greater than atmospheric pressure by the application of heat, including any pipe or fitting attached to it for its proper functioning.

(iv) Degree of superheat

The difference between the actual temperature of superheated steam and the saturation temperature corresponding to its pressure.

(v) Maximum continuous rating (MCR)

The maximum power output or steam generation rate that a boiler or power plant can sustain continuously under specified operating conditions without overloading or damaging the equipment.

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