In ball mill operation, the feed size (Df
in meters) and the ball diameter
(Db
in metres) are related as (where, K = grindability constant (varying from
0.9 to 1.4 in increasing order of hardness))
(A) Db
2 = K.Df
(B) Db = K.Df
(C) Db
3 = K.Df
(D) Db
2 = K.Df

1 Answer

Answer :

(A) Db
2 = K.Df

Related questions

Description : Grindability of a material does not depend upon its (A) Elasticity (B) Hardness (C) Toughness (D) Size

Last Answer : (D) Size

Description : Out of the following size reduction equipments, the maximum feed size can be accepted by the (A) Tube mill (B) Ball mill (C) Jaw crusher (D) Jet pulveriser

Last Answer : (C) Jaw crusher

Description : __________ balls capable of grinding the feed in a ball mill gives the maximum efficiency. (A) Cast iron (B) Minimum size (C) Maximum size (D) Elliptical

Last Answer : (B) Minimum size

Description : Feed size of ≥ 25 cms can be accepted by (A) Ball mill (B) Rod mill (C) Fluid energy mill (D) Jaw crusher

Last Answer : (D) Jaw crusher

Description : In case of grinding in a ball mill (A) Wet grinding achieves a finer product size than dry grinding (B) Its capacity decreases with increasing fineness of the products (C) Grinding cost and power requirement increases with increasing fineness of the products (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Description : A tube mill as compared to a ball mill (A) Employs smaller balls (B) Gives finer size reduction but consumes more power (C) Has larger length/diameter ratio (>2 as compared to 1 for ball mill) (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Description : The main differentiation factor between tube mill and ball mill is the (A) Length to diameter ratio (B) Size of the grinding media (C) Final product size (D) Operating speed

Last Answer : (A) Length to diameter ratio

Description : What is the critical rotation speed in revolutions per second, for a ball mill of 1.2 m diameter charged with 70 mm dia balls? (A) 0.5 (B) 1.0 (C) 2.76 (D) 0.66

Last Answer : (D) 0.66

Description : Arrange the following size reduction equipment in the decreasing order of the average particle size produced by each of them. (A) Jaw crusher, Ball mill, Fluid energy mill (B) Ball mill, Jaw crusher, Fluid ... C) Fluid energy mill, Jaw crusher, Ball mill (D) Fluid energy mill, Ball mill, Jaw crusher

Last Answer : (A) Jaw crusher, Ball mill, Fluid energy mill

Description : 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

Last Answer : (A) Coarse feed requires a larger ball

Description : Half the angle of nip, (α), for a roll crusher is given by (where, dr, dp and df are diameters of crushing rolls, feed particles and rolls gap respectively). (A) cos α = (dr + dp)/(dr + df) (B) cos α = (dr + df)/(dr + dp) (C) tan α = (dr + dp)/(dr + df) (D) sin α = (dr + dp)/(dr + df)

Last Answer : (A) cos α = (dr + dp)/(dr + df)

Description : The reduction ratio for grinders is defined as (where, Df and Dp are average diameters of feed and product respectively). (A) Df /Dp (B) Dp /Df (C) Df - Dp (D) None of these

Last Answer : (A) Df /Dp

Description : . Which of the following equations is Rittinger's crushing law? (Where P = power required by the machine, m = feed rate, k = a constant, Ds̅a & D̅sb = volume surface mean diameter of feed & product respectively.) (A) P/m = K/ ... K . ln D̅sa /D̅sb (C) P/m = K . (1/ D̅sb - 1/Ds̅a ) (D) None of these

Last Answer : (C) P/m = K . (1/ D̅sb - 1/Ds̅a )

Description : 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

Last Answer : (C) D2.5 (D) 1/D2

Description : Tube mill compared to ball mill (A) Produces finer products (B) Is long in comparison with its diameter (C) Uses smaller balls (D) All (A), (B) & (C)

Last Answer : (D) All (A), (B) & (C)

Description : 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

Last Answer : (A) Has a higher length/diameter ratio

Description : Length/diameter ratio of a ball mill is (A) 1.5 (B) 1 (C) < 1 (D) > 1

Last Answer : (C) < 1

Description : Pick out the wrong statement. (A) Packed towers are preferred for vacuum operation, because the pressure drop through the packing is less and they (packings) also lessen the ... of liquid, problem of channelling, loading & flooding is generally encountered in packed towers

Last Answer : (C) Diameter of randomly packed tower is normally more than 1.2 metres

Description : During size reduction by a jaw crusher, the energy consumed decreases with the (A) Decreasing size of product at constant size of feed (B) Decreasing machine capacity (C) Increasing size of feed at constant reduction ratio (D) None of these

Last Answer : (C) Increasing size of feed at constant reduction ratio

Description : Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the __________ filtration. (A) Constant rate (B) Varying pressure (C) Varying rate (D) Constant pressure

Last Answer : (A) Constant rate

Description : The mechanism of size reduction by a hammer mill is by impact and attrition between the (A) Grinding element & the housing (B) Feed particles (C) Both (A) and (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) and (B)

Description : In the illustration, the contacts between terminals 26 and 27 should be closed when _________. EL-0046 A. using one generator in isochronous mode only B. using two or more generators in ... through varying loads in parallel or single operation D. the circuit breaker is closed for that generator

Last Answer : Answer: C

Description : Which of the following gives the work required for size reduction of coal to -200 mesh in a ball mill most accurately? (A) Rittinger's law (B) Kick's law (C) Bond's law (D) None of these

Last Answer : (A) Rittinger's law

Description : For grinding of cereals, grains, spices, pigments, saw dust, cork etc., the most extensively used size reduction equipment is a (A) Buhrstone mill (B) Ball mill (C) Crushing rolls (D) Hammer mill

Last Answer : (A) Buhrstone mill

Description : 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

Last Answer : (B) Ball mill

Description : Maximum size reduction in a ball mill is done by the, __________ action. (A) Attrition (B) Compression (C) Impact (D) Cutting

Last Answer : (C) Impact

Description : Cement clinker is reduced to fine size by a (A) Roll crusher (B) Ball mill (C) Tube mill (D) Hammer mill

Last Answer : (C) Tube mill

Description : Grinding efficiency of a ball mill is of the order of __________ percent. (A) 1-5 (B) 40-50 (C) 75-80 (D) 90-95

Last Answer : (A) 1-5

Description : Tractor drawn disc harrows have concave discs of size varying from… diameter. a. 55-90cm b. 60-100cm d. None of the above

Last Answer : Ans - c. 35-70cm

Description : 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

Last Answer : (A) Easier grindability

Description : Grindability index of a coal is 100. It implies that the (A) Coal can be pulverised with great difficulty (B) Coal can't be pulverised (C) Coal can be easily pulverised (D) Power consumption in grinding the coal will be very high

Last Answer : (C) Coal can be easily pulverised

Description : Hardgrove Grindability index of four coal samples are given below. Which of them is the easiest to grind? (A) 50 (B) 70 (C) 85 (D) 100

Last Answer : (D) 100

Description : The advantage of firing porcelain in vacuum:** A. Reduces size of air-bubbles incorporated thus decreasing porosity B. Removes water before firing, increasing the hardness of porcelain C. Significantly lowers firing temperature

Last Answer : A. Reduces size of air-bubbles incorporated thus decreasing porosity

Description : If a steel rod of 20 mm diameter and 5 metres long elongates by 2.275 mm when subjected to an  axial pull of 3000 kg, the stress developed, is  (A) 9.5541 kg/cm2 (B) 95.541 kg/cm2 (C) 955.41 kg/cm2 (D) 9554.1 kg/cm

Last Answer : (C) 955.41 kg/cm2

Description : If a steel rod of 20 mm diameter and 5 metres long elongates by 2.275 mm when subjected to an  axial pull of 3000 kg, the stress developed, is  (A) 9.5541 kg/cm2 (B) 95.541 kg/cm2 (C) 955.41 kg/cm2 (D) 9554.1 kg/cm

Last Answer : (C) 955.41 kg/cm2

Description : A girl throws a 0.1 kilogram ball at a wall. The ball hits the wall perpendicularly with a velocity of 5 meters per second and then bounces straight back with a velocity of 4 meters per second. The ... .4 kilogram-meters per second y) 0.5 kilogram-meters per second z) 0.9 kilogram-meters per second

Last Answer : ANSWER: Z -- 0.9 KILOGRAM-METERS PER SECOND 

Description : In reference to dB meters, 0 dBm represents 1 milliwatt into what value of load?

Last Answer : 600-ohm load.

Description : For maximum discharge through a chimney, its height should be (A) 200 meters (B) Infinitely long (C) More than 105.7 metres (D) Equal to the height of the hot gas column producing draught

Last Answer : (D) Equal to the height of the hot gas column producing draught

Description : A pressure head of 320 metres of water in meters of CCl4 (sp.gr = 1.6) will be (A) 100 (B) 200 (C) 320 (D) 160

Last Answer : (B) 200

Description : With increasing carbon percent in steel beyond 0.8%, its ultimate tensile strength (UTS) and __________ is not affected. (A) Impact strength (B) Percent elongation (C) Hardness (D) Both 'b' & 'c'

Last Answer : (A) Impact strength

Description : Packed column distillation is limited to the column __________ metres. (A) Height < 6 (B) Diameter < 0.6 (C) Both (A) & (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) & (B)

Description : Which of the following relationship is valid for the equilibrium position of the float in a Rotameter? (Where, Df= Drag force on the float Bf = Buoyant force on the float Wf = Weight of the float). (A) Df + Bf = Wf (B) Df = Bf + Wf (C) Df + Bf + Wf =0 (D) None of these

Last Answer : (A) Df + Bf = Wf

Description : For an irreversible process involving only pressure-volume work (A) (dF)T, p 0 (D) (dA)T, v >0

Last Answer : (A) (dF)T, p

Description : For a reversible process involving only pressure-volume work (A) (dF)T, p < 0 (B) (dF)T, p > 0 (C) (dF)T, p = 0 (D) (dA)T, v < 0

Last Answer : (C) (dF)T, p = 0

Description : Rod mills employed for grinding (A) Employ a steel shell having L/D ratio of 1.5 to 3.0 (B) Is useful for handling sticky materials (C) Employ steel rods of 2-12 cms diameter extending over full length of the mill (D) All 'a', 'b' & 'c'

Last Answer : (D) All 'a', 'b' & 'c'

Description : A boy is standing on an elevator which is traveling downward with a constant velocity of 30 meters per second. The boy throws a ball vertically upward with a velocity of 10 meters per second ... the ball, MAGNITUDE AND DIRECTION, relative to the elevator shaft the instant the boy releases the ball?

Last Answer : ANSWER: 20 METERS PER SECOND DOWN

Description : A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system ... What is the porosity of the fluidised bed? (A) 0.2 (B) 0.5 (C) 0.7 (D) 0.8

Last Answer : (C) 0.7

Description : An example of unsteady non uniform flow is the flow of liquid under pressure through a (A) Tapering pipe at constant flow rate (B) Tapering pipe at either decreasing or increasing flow rate (C) Long pipeline of constant diameter (D) None of these

Last Answer : (B) Tapering pipe at either decreasing or increasing flow rate