MECHANICAL OPERATION

Question 1

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

Answer 1

Screw

Question 2

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

Answer 2

ratio of surface to volume as the actual volume.

Question 3

If Dp is the equivalent diameter of a non-spherical particle, Vp its volume and SAp its surface area, then its sphericity is Φs is defined by

Answer 3

Φs = 6 Vp/(Dp ⋅ SAp)

Question 4

Power required to drive a ball mill with a particular ball load is proportional to (where, D = diameter of ball mill )

Answer 4

D^2.5

Question 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.

Answer 5

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

Question 6

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

Answer 6

square root of the velocity.

Question 7

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

Answer 7

vibrating screen

Question 8

Which of the following is not categorised as a “mechanical operation” ?
Agitation
Filtration
Size enlargement
Humidification

Answer 8

Humidification

Question 9

Which of the following is a pressure filter ?

Leaf filter (Moore filter).
Plate and flame filter.
Rotary drum filter.
Sand filter.

Answer 9

Plate and Frame Filter

Question 10

Tabular bowl centrifuges as compared to disk bowl centrifuges

Answer 10

operate at higher speed.

Question 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

Answer 11

flint or porcelain

Question 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

Answer 12

added to the feed slurry.

precoated on the filter medium prior to filtration.

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

(all of these)

Question 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 ?

Answer 13

μ ≥ tan α

Question 14

Pick out the wrong statement pertaining to the roll crushers.

Maximum feed size determines the required roll diameter.

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

Both the rolls run necessarily at the same speed.

Reduction ratio and differential roll speed affect production rate & energy consumed per unit of surface produced.

Answer 14

Both the rolls run necessarily at the same speed.

Question 15

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

Answer 15

Toothed roll crusher

Question 16

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

Answer 16

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

Question 17

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

Answer 17

Cone type agitator

Question 18

__________ centrifuge is normally used in sugar mills.

Answer 18

Suspended batch basket

Question 19

Solid particles separation based on the difference in their flow velocities through fluids is termed as the

Answer 19

classification

Question 20

Diatomaceous earth is a/an

Answer 20

filter aid

Question 21

The distribution given by microscopic analysis of powder is

Answer 21

number

Question 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)

Answer 22

m/(ρ . Vp)

Question 23

For a non-spherical particle, the sphericity

Answer 23

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.

Question 24

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

Answer 24

1/4

Question 25

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

Answer 25

non-metallic ores

Question 26

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

Answer 26

hard rubber

Question 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.

Answer 27

speed

Question 28

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

Answer 28

Hanger

Question 29

If a force greater than that of gravity is used to separate solids & fluids of different densities, the process is termed as the

Answer 29

centrifugation

Question 30

Filter aid is used to

Answer 30

increase the porosity of the cake.

Question 31

Which of the following mineral dressing operations is termed as 'comminution'? Panning Spiralling Tabling None of these

Answer 31

None of these

Question 32

The capacity of a pneumatic conveying system depends upon the bulk density of materials. pressure of the conveying air. diameter of the conveying line. all of these

Answer 32

all of these

Question 33

Pick out the wrong statement. Close circuit grinding is more economical than open circuit grinding. Cod oil, beef tallow or aluminium stearates are used as grinding aids in cement 'industries'. The equipment used for the removal of traces of solids from a liquid is called a classifier. Size enlargement is a mechanical operation exemplified by medicinal tablet making.

Answer 33

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

Question 34

Gravity settling process is not involved in the working of a hydrocyclone classifier dorr-thickener sedimentation tank

Answer 34

hydrocyclone

Question 35

Froth floatation is the most suitable for treating

Answer 35

sulphide ores

Question 36

Which of the following is the most suitable for cleaning of fine coal dust (<0.5 mm) ?

Answer 36

Froth floatation

Question 37

Pick out the correct statement: Removal of iron from ceramic material is necessitated (by magnetic separation method) so as to avoid discolouration of ceramic products. The operating cost of shaking screen is more than that of a vibrating screen. Screen capacity does not depend upon the specific gravity of the minerals. Asphalt is best crushed using toothed roll crusher.

Answer 37

Removal of iron from ceramic material is necessitated (by magnetic separation method) so as to avoid discolouration of ceramic products.

Question 38

Range of compressibility co-efficient of the commercial compressible cake obtained in filtration operation is

Answer 38

0.2 to 0.8

Question 39

Highly viscous liquids & pastes are agitated by

Answer 39

multiple blade paddles

Question 40

The value of 'angle of nip' is generally about

Answer 40

32°

Question 41

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

Answer 41

metalliferrous ores

Question 42

Sulphuric acid mist is arrested by using a __________ scrubber.

Answer 42

venturi

Question 43

The main size reduction operation in ultrafine grinders is

Answer 43

attrition

Question 44

In case of a hammer crusher, crushing takes place by impact breaking. maximum acceptable feed size is 30 cms. reduction ratio can be varied by adjusting the distance from cage to hammers. all of the above

Answer 44

all of the above

Question 45

Jigging is a technique by which different particles can be

Answer 45

separated by particle size.

Question 46

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.

Answer 46

impact

Question 47

Balls for ball mills are never made of

Answer 47

Lead

Question 48

__________ is the most commonly used 'filter aid'.

Answer 48

Diatomaceous earth

Question 49

Energy consumed for crushing one ton of material ranges from __________ kWh. 0.01 to 0.1 0.5 to 1.5 2 to 3.5 4 to 5.

Answer 49

0.5 to 1.5

Question 50

For transporting pasty material, one will use a/an

Answer 50

screw colaveyor

Question 51

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 disc bowl centrifuge. sharpies supercentrifuge. batch basket centrifuge. sparkler filter.

Answer 51

disc bowl centrifuge.

Question 52

A tube mill compared to a ball mill has a higher length/diameter ratio. produces a coarser product. has a higher diameter/length ratio. uses much larger balls.

Answer 52

has a higher length/diameter ratio.

Question 53

Trommels separate a mixture of particles depending on their size density wettability electrical & magnetic properties

Answer 53

size

Question 54

Basic slag is not ground in jaw crushers ball mills compartment mills tube mills

Answer 54

jaw crushers

Question 55

Grindability of a material does not depend upon its elasticity hardness toughness size

Answer 55

size

Question 56

Shape factor for a cylinder whose length equals its diameter is 1.5 0.5 1.0 2.0

Answer 56

1.5

Question 57

In case of a hammer crusher, the feed may be highly abrasive (Moh's scale >5). minimum product size is 3 mm. maximum feed size may be 50 mm. rotor shaft carrying hammers can be vertical or horizontal.

Answer 57

rotor shaft carrying hammers can be vertical or horizontal.

Question 58

Dust laden air can be purified using a cyclone separator bag filter gravity settler tubular centrifuge

Answer 58

cyclone separator

Question 59

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 easier grindability poor grindability high power consumption in grinding

Answer 59

easier grindability

Question 60

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) 0.01 L.S 0.087 L.S L.S L.S/0.087

Answer 60

0.087 L.S

Question 61

Bond's crushing law isobtained by solving this equation for n = __________ and feed of infinite size. 1 1.5 2 2.5

Answer 61

1.5

Question 62

Which of the follwoing mechanical conveyors does not come under the division 'scrapers' ?

Answer 62

Bucket elevators

Question 63

__________ mixer is used for devulcanisation of rubber scrap & making water dispersion & rubber solution. Tumbler Banbery Muller Rubbon blender

Answer 63

Banbery

Question 64

Which of the following mechanical conveyors does not come under the division 'carriers' Belt conveyor Bucket elevator Screw conveyor Apron conveyor.

Answer 64

Screw conveyor

Question 65

Screen capacity is not a function of its openings size. screening mechanism. screening surface. atmospheric humidity.

Answer 65

atmospheric humidity.

Question 66

Which of the following is a vacuum filter ? Filter press Rotary disc filter Batch basket centrifuge Tank filter (Nutsch filter)

Answer 66

Rotary disc filter

Question 67

Pine oil used in froth floatation technique acts as a/an collector modifier frother activator

Answer 67

frother

Question 68

Feed size of ≥ 25 cms can be accepted by

Answer 68

jaw crusher

Question 69

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

Answer 69

Screw conveyor

Question 70

The most suitable equipment for removing the fine dust particle (< 1 micron dia.) from air below its dew point will be a/an

Answer 70

electrostatic precipitator

Question 71

Laminar flow region is said to exist during agitation of a liquid in an agitator, when the value of Reynolds number is

Answer 71

<10

Question 72

Filtration of water in a paper mill is done by a/an __________ filter. open sand plate and frame vacuum leaf sparkler

Answer 72

open sand

Question 73

Moore filter is a __________ filter.

Answer 73

leaf

Question 74

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

Answer 74

1

Question 75

Ball mill is used for crushing coarse grinding fine grinding attrition

Answer 75

fine grinding

Question 76

In case of a ball mill, coarse feed requires a larger ball. fine feed requires a larger ball. operating speed should be more than the critical speed. none of these

Answer 76

coarse feed requires a larger ball.

Question 77

Maximum size reduction in a ball mill is done by the, __________ action. attrition compression impact cutting

Answer 77

impact

Question 78

increasing the capacity of a screen __________ the screen effectiveness.

Answer 78

Decreases

Question 79

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

Answer 79

N^2

Question 80

Bond crushing law calls for relatively less energy for the smaller product particles, than does the Rittinger law. is less realistic in estimating the power requirements of commercial crushers. 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. states that the work required for the crushing is proportional to the new surface created.

Answer 80

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

Question 81

Flow of filtrate through the cake in a plate and frame filter press is best described by the __________ equation. Kozney-Karman Hagen-Poiseulle's Fanning's Kremser

Answer 81

Kozney-Karman

Question 82

The controlling resistance in a rotary drum vacuum filter is the __________ resistance. piping cake filter medium none of these

Answer 82

cake

Question 83

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

Answer 83

Gyratory crusher

Question 84

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

Answer 84

ball mill

Question 85

Crushing efficiency is the ratio of the surface energy created by crushing to the energy absorbed by the solid. energy absorbed by the solid to that fed to the machine. energy fed to the machine to the surface energy created by crushing. energy absorbed by the solid to the surface energy created by crushing.

Answer 85

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

Question 86

The resistance offered by the filter used in a bag filter is proportional to (where, c = dust concentration, and s = particle size ) c/s s/c s . c 1/s . c

Answer 86

c/s

Question 87

Cement clinker is reduced to fine size by a

Answer 87

tube mill

Question 88

The crushed material received for separation is called feed or

Answer 88

heading

Question 89

For spheres, volume shape factor is given by

Answer 89

π/6(=V/D3)

Question 90

Which of the following agitators having a large blade area, rotating at slow speed is used for mixing high viscosity liquids ( > 50000 centipoise) ? Propeller Helical screw Flat blade turbine Curved blade turbine

Answer 90

Helical screw

Question 91

The operating speed of a ball mill should be __________ the critical speed. less than much more than at least equal to slightly more than

Answer 91

less than

Question 92

Use of baffles in agitators help in minimising the __________ tendency. swirling vortexing both (a) & (b)

Answer 92

both (a) & (b)

Question 92

__________ are used for the separation of coarse particles from a slurry of fine particles. Thickeners Classifiers Hydrocyclones Decanters

Answer 92

Classifiers

Question 93

Fibrous material is broken by a

Answer 93

squirrel-cage disintegrator

Question 94

_________ is the most suitable for compounding rubber and plastic solids.

Answer 94

Banbery mixer