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4

The most prominent single cause of corrosion in boiler-tubes, drums, economisers and steam superheaters in a thermal power plant boiler is the

A. Water alkalinity & leakage

B. Hydrazine addition during feed water treatment

C. Release of non-condensable gas from water in the boiler

D. Scale formation

Correct Answer :

C. Release of non-condensable gas from water in the boiler


Related Questions

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Name the safety device used to protect the boiler, when the water level falls below a minimum level.

A. Blow down valve

B. Blow off cock

C. Fusible plug

D. Safety valve

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4

A high pressure boiler generates steam at a pressure greater than __________ kg/cm2.

A. 10

B. 30

C. 50

D. 80

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4

Most of the phosphorous present in the blast furnace burden enters into

A. Hot metal

B. Flue gases

C. Slag

D. Refractory lining

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4

Steel rods are normally used for concrete reinforcement because concrete and steel have almost equal

A. Tensile strength

B. Compressive strength

C. Young's modulus

D. Thermal co-efficient of expansion

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4

In a forced draft cooling tower, water is cooled from 95 to 80°F by exposure to air with a wet bulb temperature of 70°F. In this case, the

A. Range is 15°F

B. Approach is 10°F

C. Both (A) & (B)

D. Neither (A) nor (B)

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4

Function of gear box is to

A. Reduce the speed

B. Obtain variable speed

C. Increase the speed

D. Produce high torque

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4

During decarburising of a plain carbon steel, the thickness of ferrite layer growth is proportional to

A. Time

B. Square root of time

C. Square of time

D. Cube of time

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4

In case of condensers & evaporators operating under given terminal conditions, LMTD (logarithmic mean temperature difference) for counter flow as compared to that for parallel flow is

A. More

B. Less

C. Equal

D. Much more

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4

The swift cup test evaluates the following property of a sheet metal.

A. Stretchability

B. Drawability

C. Bendability

D. None of these

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4

The pressure drop per unit length for laminar flow of fluid through a long pipe is proportional to (where, A = cross-sectional area of the pipe & D = Diameter of the pipe)

A. A

B. D

C. 1/A

D. 1/A2

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4

Water-tube boiler is the one, in which

A. Water passes through tubes and flue gases around it

B. Tube carrying hot flue gases are immersed in a pool of water

C. Tubes are placed in vertical position

D. None of these

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4

Thermodynamic cycle involved in the working of a thermal power plant is the __________ cycle.

A. Joule

B. Carnot

C. Rankine

D. Brayton

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4

The transition temperature at which all the ferromagnetic materials become paramagnetic materials is termed as the 'Curie temperature'. Its value for cobalt is __________ °C.

A. 768

B. 1127

C. 1359

D. 1480

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4

Softening of hardened steel is done by its

A. Normalising

B. Tempering

C. Annealing

D. Carburising

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4

For separating small pieces of metal from engine oil of a car, the best separating technique is the

A. Chromatography

B. Evaporation

C. Filtration

D. Fractional distillation

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Work done by a/an __________ process is determined by ∫p. dv

A. Adiabatic

B. Quasi-static

C. Isothermal

D. Isentropic

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With increase in temperature, the electrical conductivity of a __________ decreases.

A. Semi-conductor

B. Metal or alloy

C. Dielectric

D. None of these

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4

__________ joint is usually used for joining cast iron pipes mostly used for temporary pipelines, where it may be necessary to dismantle & reassemble the pipeline very frequently.

A. Collar

B. Flanged

C. Bell and Spigot

D. Expansion

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4

In case of water (Prandtl number ≈ 6) flowing over a flat plate heated over the entire length, the thermal boundary layer thickness as compared to hydrodynamic boundary layer thickness is

A. Less

B. More

C. Equal

D. Unpredictable

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4

Which of the following pairs is not correctly matched?

A. Uranium - 233 : Fertile material

B. Binding energy : Mass defect

C. Scattering: Absorption cross-section

D. Number of nucleons : Mass number

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Which of the following processes follows the hardening process for reducing the hardening strains & increasing the toughness of the steel part?

A. Anodising

B. Tempering

C. Carburising

D. Annealing

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4

Encyclopaedia of Chemical Technology has been

A. Authored by Kirk Othmer

B. Edited by Perry and Chilton

C. Edited by Kirk Othmer

D. Authored by Perry and Chilton

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4

Lap joints are preferred over butt joints in soldering/brazing, because these joints are

A. Weaker in tension but stronger in shear

B. Weaker in shear but stronger in tension

C. Stronger in both shear and tension

D. The lap joints are easily made

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4

In multipass welds, shot peening is done after each pass to

A. Close the surface porosity

B. Break the continuity of columnar grains

C. Flatten the weldment

D. Introduce texture in the weld

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4

Fatigue resistance of a material is measured by the

A. Elastic limit

B. Ultimate tensile strength

C. Young's modulus

D. Endurance limit

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In case of a, centrifugal pump, the ratio h1/h2 is termed as the __________ efficiency (where, h1 = actual measured head & h2 = head imparted to the fluid by impeller).

A. Mechanical

B. Overall

C. Volumetric

D. Impeller

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4

Pick out the correct combination about the role of various additives used in polymers.

A. Plasticiser: increases the polymer strength

B. Heat stabiliser: increases the maximum service temperature

C. Fillers: Does not affect the property of polymer but increases its weight

D. Lubricants: increases the flexibility of polymers

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4

Pick out the wrong statement.

A. Ductile fracture of a stressed material, which exhibits a large plastic deformation is commonly caused by the formation and coalescence of voids in the necked region

B. Brittle fracture is caused by the propagation of pre-existing cracks in the material and involves minimum plastic deformation

C. Fatigue fracture of a material is always brittle in nature and takes place due to the existence of line imperfections

D. Brittle materials are generally tested in tension

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4

The condition of diffraction from a crystal is given by

A. nλ = 2d Sin θ

B. λ = d Sin 2θ

C. λ = 2d Sin 2θ

D. nλ = d Sin θ

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4

If a nuclear reactor produces more fissile nuclear fuel than it consumes, then it is called a __________ reactor.

A. Critical

B. Breeder

C. Fertile

D. Heterogeneous