The reduction ratio for grinders is defined as(where, Df and Dp are average diam

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Question
The reduction ratio for grinders is defined as(where, D_f and D_p are average diameters of feed and product respectively).
Options
A. D_f/D_p
B. D_p/D_f
C. D_f - D_p
D. none of these

Correct Answer

D_f/D_p

Mechanical Operations problems

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1. Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the __________ filtration.
Options
A. constant rate
B. varying pressure
C. varying rate
D. constant pressure

2. Filter medium resistance is that offered by the
Options
A. filter cloth.
B. embedded particles in the septum.
C. filter cloth and the embedded particle collectively.
D. none of these.

3. During washing of filter at the end of constant pressure filtration, the rate of washing equals the rate of filtration
Options
A. at time zero.
B. at the end of filtration.
C. when half the filtrate has been obtained.
D. at the end of filtration, but decreases with time subsequently.

7. Pick out the wrong statement pertaining to the turbine agitator.
Options
A. Recommended peripheral speed for the turbine agitator is 200-250 metres/minute.
B. Pitched blade turbine agitator gives only radial flow with complete absence of the axial flow.
C. Generally, the diameter of the agitator is kept between l/3rd to l/6th of the tank diameter while the blade length is l/4th of agitator diameter (with central disc, it is l/8th of the agitator diameter).
D. Turbine agitator should be located at a height not less than one agitator diameter length from the bottom. If the depth of liquid in the tank is more than twice the agitator diameter, two agitators should be used.

8. Rittinger number which designates the new surface prduced per unit of mechanical energy absorbed by the material being crushed, depends on the
Options
A. state or manner of application of the crushing force.
B. ultimate strength of the material.
C. elastic constant of the material.
D. all (a), (b) and (c).

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