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# Mechanical Operations MCQ’s – Cyclone Separators

What is the speed of a horizontal belt filter?

a) 0.05 m/s

b) 0.1 m/s

c) 0.5 m/s

d) 10 m/s

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Answer: a

Explanation: The speed of the belt is about 0.05 m/s and the distance over which slurry is applied is so adjusted to produce a suitable thickness.

In liquid-liquid operations, centrifugal force is employed in

a) Settling

b) Filtration

c) Sedimentation

d) Both setting and filtration

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Answer: d

Explanation: In liquid-liquid operations, centrifugal force is employed in both settling and filtration, in both cases it replaces weaker force of gravity.

The prayon continuous filter, filters a surface of about ________

a) 1 to 20 m^{2}

b) 2 to 40 m^{2}

c) 30 to 40 m^{2}

d) 100 to 150 m^{2}

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Answer: b

Explanation: Prayon filter is made in five sizes providing filtering surfaces from about 2 to 40 m^{2} , it consists of a number of horizontal cells held in rotating frame.

Prayon filter has _______ percent of effective area.

a) 85

b) 48

c) 47

d) 50

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Answer: a

Explanation: A large filtering area, up to 85 percent of which is effective at any instant, low operating and maintenance cost and simple cloth replacement.

Any rotating machine in which centrifugal force is applied is called as _______

a) Mixer

b) Rotator

c) Centrifuge

d) Gravitate

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Answer: c

Explanation: Any rotating machine in which the centrifugal force is applied to achieve a phase separation is called as a centrifuge, it consists of a rotor bowl and a drive shaft.

The following equation represents the _______

F=0.000341 WrN^{2}

a) Magnitude of gravity

b) Magnitude of Centrifuge

c) Force of inertia

d) Force of tangent

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Answer: b

Explanation: Magnitude of centrifugal force is given by the above equation, where F is force developed in lb, W I sweight of rotating assembly and r is radius.

What does the following equation represents?

4.11*10^{-9} N^{2} D_{b}^{2} ρ_{m}

a) Diameter of basket

b) Stress force

c) Force of inertia

d) Force of tangent

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Answer: b

Explanation: Stress (S_{S}) in a centrifugal bowl is given by the above equation, where D_{b} is the diameter of the bowl, N is the rotations and p is the density.

Calculate F, if weight of assembly is 100 lb. and 5 ft. in radius having 20 rpm speed?

a) 3.41

b) 5.21

c) 6.82

d) 2.323

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Answer: a

Explanation: As we know that F = 0.000341 WrN^{2} = 0.000341*100*5*20 = 3.41 lb.

Calculate Ss, if Diameter is given as 10 inches and has 200 rpm also consider water as medium?

a) 0.005

b) 0.00822

c) 0.00026

d) 0.0058

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Answer: b

Explanation: We already know that density of water is 1000 kg/m^{3}, so 4.11*(10^{-9})*10*200 = 0.0082 p.s.i. i.e. self-stress Ss.

The speed at which frequency of rotation matches the natural frequency is called ____

a) Final speed

b) Optimum speed

c) Critical speed

d) Operating speed

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Answer: c

Explanation: The speed at which frequency of rotation matches the natural frequency of rotating part, at this speed vibrations induced by slight imbalance.