Mechanical Operations

231. Production rate _________ with increased fineness, with a given energy input to the size reduction machine.

  1. Decreases
  2. Increases
  3. Remains unchanged
  4. May increase or decrease; depends on the machine

Correct answer: (A)
Decreases

232. Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of _________ mm.

  1. 0.007
  2. 0.3
  3. 50
  4. 0.014

Correct answer: (B)
0.3

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

  1. 0.01 to 0.1
  2. 0.1 to 0.3
  3. 0.2 to 0.8
  4. 0.2 to 0.4

Correct answer: (C)
0.2 to 0.8

234. Raw materials are charged in the iron blast furnace using

  1. Bucket elevator
  2. Skip hoist
  3. Screw conveyor
  4. None of these

Correct answer: (B)
Skip hoist

235. Reciprocal of sphericity is termed as the

  1. Specific surface ratio
  2. Shape factor
  3. Sauter diameter
  4. Surface area per unit mass

Correct answer: (B)
Shape factor

236. Reciprocating screens are normally inclined at an angle of 5° with the horizontal and employ gyratory motion at feed end & reciprocating motion at the discharge end. They are not suitable for the screening of the

  1. Light metal powder down upto 4 mesh size
  2. Dry chemicals
  3. Heavy tonnages of rocks or gravel
  4. Powdered food & granular materials

Correct answer: (C)
Heavy tonnages of rocks or gravel

237. Reduction ratio of crushers is the

  1. Ratio of feed opening to discharge opening
  2. Ratio of discharge opening to feed opening
  3. Determining factor for minimum dia of the feed and the product
  4. None of these

Correct answer: (A)
Ratio of feed opening to discharge opening

238. Removal of activated carbon from glycerine is done by

  1. Plate and frame filter
  2. Rotary vacuum filter
  3. Batch basket centrifuge
  4. None of these

Correct answer: (A)
Plate and frame filter

239. Ribbon blenders are exclusively meant for

  1. Blending miscible liquids
  2. Non-flowing powder and thin pastes
  3. Bath mixing
  4. Continuous mixing

Correct answer: (B)
Non-flowing powder and thin pastes

240. Rittinger number which designates the new surface produced per unit of mechanical energy absorbed by the material being crushed, depends on the

  1. State or manner of application of the crushing force
  2. Ultimate strength of the material
  3. Elastic constant of the material
  4. All (A), (B) and (C)

Correct answer: (D)
All (A), (B) and (C)

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