Mechanical Operations Indiabix 1 - 5

1. Short distance transportation of grain, gravel, sand, ash, asphalt etc. is done by using a

__________ conveyor.

a. flight

b. slat or drag

c. ribbon

d. screw

D

2. Equivalent diameter of a particle is the diameter of the sphere having the same

a. ratio of surface to volume as the actual volume.

b. ratio of volume to surface as the particle.

c. volume as the particle.

d. none of these.

A

3. If dp is the equivalent diameter of a non-spherical particle, Vp its volume and sp its

surface area, then its sphericity is Φs is defined by

a. Φs = 6 Vp/dp sp

b. Φs = Vp/dp sp

c. Φs = 6 dp Sp/Vp

d. Φs = dp Sp/Vp

A

4. Power required to drive a ball mill with a particular ball load is proportional to (where, D =

diameter of ball mill )

a. D

b. 1/D

c. D2.5

d. 1/D2.5

C

5. Pick out the wrong statement.

a. Recycled coarse material to the grinder by a classifier is termed as circulating

load.

b. Wear and tear in wet crushing is more than that in dry crushing of materials.

c. Size enlargement (opposite of size reduction) is not a mechanical operation.

d. A 'dust catcher' is simply an enlargement in a pipeline which permits the solids

to settle down due to reduction in velocity of the dust laden gas.

C

6. In continuous filtration (at a constant pressure drop), filtrate flow rate varies inversely as

the

a. square root of the velocity.

b. square of the viscosity.

c. filtration time only.

d. washing time only.

A

7. For sizing of fine materials, the most suitable equipment is a

a. trommel

b. grizzly

c. shaking screen

d. vibrating screen

D

8. Which of the following is not categorised as a "mechanical operation" ?

a. Agitation

b. Filtration

c. Size enlargement

d. Humidification

D

9. Which of the following is a pressure filter ?

a. Leaf filter (Moore filter).

b. Plate and flame filter.

c. Rotary drum filter.

d. Sand filter.

B

10. Tabular bowl centrifuges as compared to disk bowl centrifuges

a. operate at higher speed.

b. employ bowl of larger diameter.

c. can not be operated under pressure/vacuum.

d. can't be used for separation of fine suspended solids from a liquid.

A

11. Pebble mills are tumbling mills widely used for grinding in the manufacture of paints &

pigments and cosmetic industries, where iron contamination in the product is highly

objectionable. Pebbles used in pebble mill are made of

a. bronze

b. stainless steel

c. flint or porcelain

d. concrete

C

12. Filter aids like asbestos, kieselguhr, diatomaceous earth etc. are used to increase the

porosity of the final filter cake & reducing the cake resistance during filtration. Filter aid is

a. added to the feed slurry.

b. precoated on the filter medium prior to filtration.

c. separated from the cake by dissolving solids or by burning it off.

d. all 'a', 'b'&'c'.

D

13. Which of the following relationships between co-efficinet of friction (μ) between rock &

roll and a (half of the angle of nip) of the particle to be crushed is correct ?

a. μ > tan α

b. μ ≥ tan α

c. μ > tan 2α

d. μ ≤ tan α

B

14. Pick out the wrong statement pertaining to the roll crushers.

a. Maximum feed size determines the required roll diameter.

b. For hard material's crushing, the reduction ratio should not exceed 4.

c. Both the rolls run necessarily at the same speed.

d. Reduction ratio and differential roll speed affect production rate & energy

consumed per unit of surface produced.

C

15. Which of the following is not an ultrafine grinder (colloid mill)?

a. Micronizers

b. Agitated mills and fluid energy mills

c. Toothed roll crusher

d. Hammer mills with internal classification

C

16. Two particles are called to be equal settling, if they are having the same.

a. size.

b. specific gravity.

c. terminal velocities in the same fluid & in the same field of force.

d. none of these.

C

17. Which of the following is the most suitable for handling fibrous and dense slurries ?

a. Propeller agitator

b. Cone type agitator

c. Turbine agitator

d. Radial propeller agitator

B

18. __________ centrifuge is normally used in sugar mills.

a. Tubular bowl

b. Disc-bowl

c. Suspended batch basket

d. Perforated horizontal basket continuous

C

19. Solid particles separation based on the difference in their flow velocities through fluids

is termed as the

a. clarification

b. classification

c. elutriation

d. sedimentation

B

20. Diatomaceous earth is a/an

a. explosive

b. filter aid

c. filter medium

d. catalyst

B

21. The distribution given by microscopic analysis of powder is

a. number

b. length

c. area

d. volume

A

22. Number of particles in a crushed solid sample is given by (where, m = mass of particles

in a sample, Vp = volume of one particle, ρ= density of particles)

a. m/ρ . Vp

b. m. ρ/Vp

c. m . Vp/ρ

d. Vp/m . ρ

A

23. For a non-spherical particle, the sphericity

a. is defined as the ratio of surface area of a sphere having the same volume as

the particle to the actual surface area of the particle.

b. has the dimension of length.

c. is always less than 1.

d. is the ratio of volume of a sphere having the same surface area as the particle

to the actual volume of the particle.

A

24. In washing type plate and frame filter press, the ratio of washing rate to the final filtrate

rate is

a. 4

b. 1/4

c. 1

d. 1/2

B

25. Ball mills and tube mills with flint or porcelain balls are used for size reduction of

a. asbestos

b. rubber

c. non-metallic ores

d. limestone

C

26. Size reduction of __________ is accomplished in steam heated rollers and roll

crushers.

a. resins

b. gums

c. hard rubber

d. waxes

C

27. The capacity of a belt conveyor depends upon two factors. If one is the cross-section of

the load, the other is the __________ of the belt.

a. speed

b. thickness

c. length

d. none of these

A

28. Which of the following is not a part of the Blake jaw crusher?

a. Hanger

b. Check plates

c. Toggles

d. Pitman

A

29. If a force greater than that of gravity is used to separate solids & fluids of different

densities, the process is termed as the

a. sedimentation

b. flocculation

c. dispersion

d. centrifugation

D

30. Filter aid is used to

a. increase the rate of filtration.

b. decrease the pressure drop.

c. increase the porosity of the cake.

d. act as a support base for the septum.

C

31. Which of the following mineral dressing operations is termed as 'comminution'?

a. Panning

b. Spiralling

c. Tabling

d. None of these

D

32. The capacity of a pneumatic conveying system depends upon the

a. bulk density of materials.

b. pressure of the conveying air.

c. diameter of the conveying line.

d. all (a), (b) and (c).

D

33. Pick out the wrong statement.

a. Close circuit grinding is more economical than open circuit grinding.

b. Cod oil, beef tallow or aluminium stearates are used as grinding aids in cement

'industries'.

c. The equipment used for the removal of traces of solids from a liquid is called a

classifier.

d. Size enlargement is a mechanical operation exemplified by medicinal tablet

making.

C

34. Gravity settling process is not involved in the working of a

a. hydrocyclone

b. classifier

c. dorr-thickener

d. sedimentation tank

A

35. Froth floatation is the most suitable for treating

a. iron ores

b. sulphide ores

c. quartzite

d. none of these

B

36. The energy required per unit mass to grind limestone particles of very large size to 100

μm is 12.7 kWh/ton. An estimate (using Bond's law) of the energy to grind the particles

from a very large size to 50 μrn is

a. 6.35 kWh/ton

b. 9.0 kWh/ton

c. 18 kWh/ton

d. 25.4 kWh/ton

C

37. Which of the following is the most suitable for cleaning of fine coal dust (

D

38. Pick out the correct statement:

a. Removal of iron from ceramic material is necessitated (by magnetic separation

method) so as to avoid discolouration of ceramic products.

b. The operating cost of shaking screen is more than that of a vibrating screen.

c. Screen capacity does not depend upon the specific gravity of the minerals.

d. Asphalt is best crushed using toothed roll crusher.

A

39. Range of compressibility co-efficient of the commercial compressible cake obtained in

filtration operation is

a. 0.01 to 0.1

b. 0.1 to 0.3

c. 0.2 to 0.8

d. 0.2 to 0.4

C

40. Highly viscous liquids & pastes are agitated by

a. propellers

b. turbine agitators

c. multiple blade paddles

d. none of these

C

41. The value of 'angle of nip' is generally about

a. 16°

b. 32°

c. 52°

d. 64°

B

42. Size reduction of the __________ can be suitably done by ball mills, crushing rolls and

rod mills.

a. metalliferrous ores

b. non-metallic ores

c. basic slags

d. asbestos & mica

A

43. Sulphuric acid mist is arrested by using a __________ scrubber.

a. packed wet

b. hollow wet

c. venturi

d. co-current

C

44. The main size reduction operation in ultrafine grinders is

a. cutting

b. attrition

c. compression

d. impact

B

45. In case of a hammer crusher,

a. crushing takes place by impact breaking.

b. maximum acceptable feed size is 30 cms.

c. reduction ratio can be varied by adjusting the distance from cage to hammers.

d. all (a), (b) and (c).

D

46. Jigging is a technique by which different particles can be

a. separated by particle size.

b. separated by particle density.

c. separated by particle shape.

d. mixed.

A

47. Crushing of mineral particles is accomplished in a 'cage mill', when one or more alloy

steel bars are revolved in opposite directions. It is a type of __________ mill.

a. impact

b. roll

c. vibratory

d. none of these

A

48. Balls for ball mills are never made of

a. forged/cast steel

b. lead

c. cast iron

d. alloy steel

B

49. 200 mesh screen means 200 openings per

a. cm2

b. cm

c. inch

d. inch2

C

50. __________ is the most commonly used 'filter aid'.

a. Diatomaceous earth

b. Fuller's earth

c. Vermiculite

d. Semi-plastic clay

A

1. Energy consumed for crushing one ton of material ranges from __________ kWh.

a. 0.01 to 0.1

b. 0.5 to 1.5

c. 2 to 3.5

d. 4 to 5.

B

2. For transporting pasty material, one will use a/an

a. apron conveyor

b. belt conveyor

c. screw colaveyor

d. bucket elevator

C

3. Where the density difference of the two liquid phase to be separated is very small (as in

milk cream separator), the most suitable separator is a

a. disc bowl centrifuge.

b. sharpies supercentrifuge.

c. batch basket centrifuge.

d. sparkler filter.

A

4. A tube mill compared to a ball mill

a. has a higher length/diameter ratio.

b. produces a coarser product.

c. has a higher diameter/length ratio.

d. uses much larger balls.

A

5. Trommels separate a mixture of particles depending on their

a. size

b. density

c. wettability

d. electrical & magnetic properties

A

6. Basic slag is not ground in

a. jaw crushers

b. ball mills

c. compartment mills

d. tube mills

A

7. Grindability of a material does not depend upon its

a. elasticity

b. hardness

c. toughness

d. size

D

8. Shape factor for a cylinder whose length equals its diameter is

a. 1.5

b. 0.5

c. 1.0

d. 2.0

A

9. In case of a hammer crusher, the

a. feed may be highly abrasive (Moh's scale >5).

b. minimum product size is 3 mm.

c. maximum feed size may be 50 mm.

d. rotor shaft carrying hammers can be vertical or horizontal.

D

10. Dust laden air can be purified using a

a. cyclone separator

b. bag filter

c. gravity settler

d. tubular centrifuge

A

11. Rittinger's number designates the new surface created per unit mechanical energy

absorbed by the material being crushed. Larger value of Rittinger's number of a material

indicates its

a. easier grindability

b. poor grindability

c. high power consumption in grinding

d. none of these

A

12. Capacity (in tons/hr) of jaw/gyratory crusher is equal to (where, L = length of the

receiving opening, cm S = greater width of the discharge opening, cm)

a. 0.01 L.S

b. 0.087 L.S

c. L.S

d. L.S/0.087

B

13. Vacuum is applied in __________ zone, in case of a general type continuous rotary

drum vacuum filter.

a. filtering

b. washing

c. drying

d. all (a), (b) & (c)

D

b. 1.5

15. Which of the follwoing mechanical conveyors does not come under the division

'scrapers' ?

a. Ribbon conveyor

b. Flight conveyor

c. Bucket elevators

d. Drag conveyor.

C

16. __________ mixer is used for devulcanisation of rubber scrap & making water

dispersion & rubber solution.

a. Tumbler

b. Banbery

c. Muller

d. Rubbon blender

B

17. Which of the following mechanical conveyors does not come under the division

'carriers' ?

a. Belt conveyor

b. Bucket elevator

c. Screw conveyor

d. Apron conveyor.

C

18. Screen capacity is not a function of

a. its openings size.

b. screening mechanism.

c. screening surface.

d. atmospheric humidity.

D

19. Which of the following is a vacuum filter?

a. Filter press

b. Rotary disc filter

c. Batch basket centrifuge

d. Tank filter (Nutsch filter)

B

20. Pine oil used in froth floatation technique acts as a/an

a. collector

b. modifier

c. frother

d. activator

C

21. Length/diameter ratio of a ball mill is

a. 1.5

b. 1

c. < 1

d. > 1

C

22. Feed size of ≥ 25 cms can be accepted by

a. ball mill

b. rod mill

c. fluid energy mill

d. jaw crusher

D

23. Which is the most suitable conveyor for transportation of sticky material ?

a. Apron conveyor

b. Belt conveyor

c. Screw conveyor

d. Pneumatic conveyor

C

24. The most suitable equipment for removing the fine dust particle (< 1 micron dia.) from

air below its dew point will be a/an

a. bag filter

b. electrostatic precipitator

c. cyclone separator

d. wet scrubber

B

25. Laminar flow region is said to exist during agitation of a liquid in an agitator, when the

value of Reynolds number is

a. >10

b.

B

26. Filtration of water in a paper mill is done by a/an __________ filter.

a. open sand

b. plate and frame

c. vacuum leaf

d. sparkler

A

27. Moore filter is a __________ filter.

a. leaf

b. press

c. rotary

d. sand

A

28. Sphericity of a cubical particle, when its equivalent diameter is taken as the height of

the cube, is

a. 0.5

b. 1

c. 2

d. 3

B

29. Ball mill is used for

a. crushing

b. coarse grinding

c. fine grinding

d. attrition

C

30. In case of a ball mill,

a. coarse feed requires a larger ball.

b. fine feed requires a larger ball.

c. operating speed should be more than the critical speed.

d. none of these

A

31. Maximum size reduction in a ball mill is done by the, __________ action.

a. attrition

b. compression

c. impact

d. cutting

C

32. increasing the capacity of a screen __________ the screen effectiveness.

a. decreases.

b. increases

c. does not effect

d. none of these

A

33. The power number for a stirred tank becomes constant at high Reynolds number. In

this limit, the variation of power input with impeller rotational speed (N) is proportional to

a. N°

b. N1

c. N2

d. N3

C

34. Bond crushing law

a. calls for relatively less energy for the smaller product particles, than does the

Rittinger law.

b. is less realistic in estimating the power requirements of commercial crushers.

c. states that the work required to form particle of any size from very large feed is

proportional to the square root of the volume to surface ratio of the product.

d. states that the work required for the crushing is proportional to the new surface

created.

A

35. Flow of filtrate through the cake in a plate and frame filter press is best described by the

__________ equation.

a. Kozney-Karman

b. Hagen-Poiseulle's

c. Fanning's

d. Kremser

A

36. The controlling resistance in a rotary drum vacuum filter is the __________ resistance.

a. piping

b. cake

c. filter medium

d. none of these

B

37. Which of the following is used for primary crushing of very hard lumpy materials ?

a. Toothed roll crusher

b. Gyratory crusher

c. Ball mill

d. Tube mill

B

38. Coal is finally pulverised to 200 mesh size for burning in boilers by a

a. hammer crusher

b. ball mill

c. roll crusher

d. gyratory crusher

B

39. Crushing efficiency is the ratio of the

a. surface energy created by crushing to the energy absorbed by the solid.

b. energy absorbed by the solid to that fed to the machine.

c. energy fed to the machine to the surface energy created by crushing.

d. energy absorbed by the solid to the surface energy created by crushing.

A

40. The resistance offered by the filter used in a bag filter is proportional to (where, c = dust concentration, and s = particle size )

a. c/s

b. s/c

c. s . c

d. 1/s . c

A

41. ement clinker is reduced to fine size by a

a. roll crusher

b. ball mill

c. tube mill

d. hammer mill

C

42. The crushed material received for separation is called feed or

a. tailing

b. heading

c. concentrate

d. middling

B

43. For spheres, volume shape factor is given by

a. π(=A/D2)

b. 2π(=2A/D2)

c. π/6(=V/D3)

d. AD/V

C

44. Which of the following agitators having a large blade area, rotating at slow speed is

used for mixing high viscosity liquids ( > 50000 centipoise) ?

a. Propeller

b. Helical screw

c. Flat blade turbine

d. Curved blade turbine

B

45. __________ is defined as the geometric mean of the relative rejections and the relative

recoveries of two minerals.

a. Separation efficiency

b. Selectivity index

c. Concentration ratio

d. none of these

B

46. The operating speed of a ball mill should be __________ the critical speed.

a. less than

b. much more than

c. at least equal to

d. slightly more than

A

47. Use of baffles in agitators help in minimising the __________ tendency.

a. swirling

b. vortexing

c. both (a) & (b)

d. neither (a) nor (b)

C

48. __________ are used for the separation of coarse particles from a slurry of fine

particles.

a. Thickeners

b. Classifiers

c. Hydrocyclones

d. Decanters

B

49. Fibrous material is broken by a

a. rollcrusher

b. squirrel-cage disintegrator

c. ball mill

d. tube mill

B

50. __________ is the most suitable for compounding rubber and plastic solids.

a. Banbery mixer

b. Pan mixer

c. Pug mill

d. Charge can mixer

A