Section 3

Question 1

Angled baffles are preferred in the agitation tank to control the swirling action; if the viscosity of the liquid to be mixed is about 200 poise. However, the baffle may be completely eliminated for mixing liquids having viscoisty above __________ poise.

Answer 1

600

Question 1

Tube wall thickness depends on the cor-rosiveness of the fluids and their operating pressure & temperature and is specified by Birmingham wire gauge (B.W.G)-a number which varies from 8 to 18 with the numbers 14 and 16 being more commonly used. Outside diameter of tubes varies from about 15 to 50 mm; however a tube of less than __________ mm outside diameter is generally not recommended for fouling fluids.

Answer 1

19

Question 2

Ratio of tube length to shell diameter for a shell and tube heat exchanger is

A. 8 : 1 to 12 : 1 for both liquid-liquid and gas-gas heat exchangers.
B. 4 : 1 to 8 : 1 for liquid-liquid exchanger.
C. < 4 : 1 for gas-gas exchangers.
D. both(b) & (c).

Answer 2

D

Question 3

The dust collection efficiency of a cyclone separator
A decreases with increase in gas flow rate.
B is inversely proportional to the mass of the dust particle.
C is directly proportional to the radius of the dust particle path.
D none of these.

Answer 3

D

Question 4

In a shell and tube heat exchanger, the overall heat transfer co-efficient is proportional to the tube side (volumetric flow rate)0.8. This is valid, only when the ratio of the tube side film resistance to the total resistance is almost equal to

Answer 4

1

Question 5

Which of the following types of reactors is the safest from operation point of view ?

Answer 5

A vapor phase reactor.

Question 6

In a bag filter, the pressure drop increases directly as the

Answer 6

density of the gas and inversely as viscosity of the gas.

Question 7

The LMTD correction factor (FT) is applied in __________ heat exchangers.

Answer 7

all multipass

Question 8

Movement of pipeline caused by thermal expansion is taken care by providing
A. expansion joint.
B. changes in its direction.
C. change in the shape of pipeline.
D. all (a), (b) and (c).

Answer 8

all (a), (b) and (c).

Question 9

For a cylindrical shell, (subject to the thickness of uppermost course being more than the minimum for diaofthe tank in question), the thickness of the courses of shell

Answer 9

decreases upwards.

Question 10

In the design of a paddle agitator, the ratio (paddle diameter)/(tank diameter) is normally taken as

Answer 10

0.80

Question 11

The design stress, which is more than the damaging stress, is the least unit stress that will render a member unfit for service before the end of its normal life. The design stress factor or factor of safety indicates the margin between design stress and the __________ stress.

Answer 11

damaging

Question 12

Hole diameter of the seive trays in the distillation column ranges from __________ mm.

Answer 12

3 to 12.5

Question 13

Factor of safety (i.e., overdesign factor) in heat transfer equipments is about __________ percent more than the actual/theoretical design factor.

Answer 13

15-20

Question 14

For annular flow of a fluid, the ratio of the equivalent diameter for pressure drop calculation to the equivalent diameter for heat transfer calculation is

Answer 14

(d1)/(d1+d2)

Question 15

In actual operation of distillation column, the vapour is not distributed uniformly among the bubble caps, primarily because of the

Answer 15

liquid gradient on the tray.

Question 16

The minimum shell thickness for tank ≤ 15 metres diameter is limited to __________ mm, for reasons of elastic stability.

Answer 16

5

Question 17

If ‘D’ is the inside diameter of the shell of a shell and tube heat exchanger, then the baffle spacing is usually in the range of

Answer 17

D/5 or minimum 2” to 5D.

Question 18

Brass valves are usually made for pipe sizes __________ inches.

Answer 18

≤2

Question 19

At the following point for a given packing and set of fluids, the pressure drop per metre of packed height, with variation in fluid rates and operating pressure

Answer 19

remains same

Question 20

In a shell and tube heat exchanger, triangular pitch arrangement as compared to square pitch arrangement

Answer 20

results in higher shell side pressure drop.

Question 21

Pick out the wrong statement about routing of fluids in a shell and tube heat exchanger.

Answer 21

Higher pressure fluid stream should be routed through the shell side.

Question 22

The necessary wall thickness for a metallic storage vessel is a function of the
A ultimate tensile strength (or yield point) of the material and operating temperature.
B operating pressure and welding/joint efficiency.
C diameter of the vessel.
D all (a); (b) and (c).

Answer 22

all (a); (b) and (c).

Question 23

In a multiple effect evaporator system having ‘n’ effects, the amount of water evaporated per unit surface area in approximately equal to __________ times that in a single effect.

Answer 23

(1/n)th

Question 24

Pick out the wrong statement
A. In a flanged and standard dished head, the crown radius is ≤ shell outside diameter.
B. In a flanged and shallow dished head, the crown radius is > shell outside diameter.
C. Flat head covers are most suitable for larger vessels operating at very high pressure.
D. Flanged only head is a type of flat head in which gradual change in the shape at the centre results in reduced local stresses.

Answer 24

C

Question 25

Pick out the wrong statement pertaining to the design of a horizontal tube evaporator.

Answer 25

Liquor flows inside the tube, while the steam is outside submerging the tube.

Question 26

Weep holes provided in the plates of a distillation column
A. facilitate draining out liquid from a tray when the unit is not in operation.
B. are normally located near the overflow weir so that any delivery of liquid during operation follows approximately the same path as the overflow fluid.
C. must be large enough (usually 1/4” to 5/8” dia) to prevent plugging but should not deliver excessive amount of fluid during operation.
D. all (a), (b) and (c).

Answer 26

D

Question 27

Steam is preferred to be used as a heating medium in heat exchangers, because of its

Answer 27

high latent heat.

Question 28

__________ shapedroof is the most commonly used roof for cylinderical storage tanks.

Answer 28

Conical

Question 29

Pick out the wrong statement pertaining to ‘Horton sphere’ used for the storage of liquid ammonia.

Answer 29

Horton sphere is used for the storage of liquid at sub-zero temperature at very high pressure upto 200 kg/cm2.

Question 30

Value of Peclet number = ∞, is the representative of

Answer 30

plug flow.

Question 31

In most of the shell and tube heat exchangers, the tube pitch is generally __________ the tube diameter.

Answer 31

1.25-1.50 times

Question 32

Accidents in chemical plants are mostly due to

Answer 32

faulty operating procedures.

Question 33

In a distillation column, bubble caps are located on trays with a pitch of __________ times the outside diameter of the caps.

Answer 33

1.3 to 2

Question 34

1.2 to 3.8 cms is the value of the
A. downcomer liquid seal in case of a balanced tray design.
B. static submergence in case of a bubble cap tray for column operating under pressure (≥ 1 atm.).
C. skirt clearance for bubble caps.
D. all (a), (b) and (c).

Answer 34

D

Question 35

For identical operating conditions, the pressure drop over __________ tray is the highest out of the following.

Answer 35

bubble cap

Question 36

A perforated plate has holes of diameter dn arranged in a pitch ph. Each hole has a tube of I.D. dt passing through it. The ligament efficiency is given by

Answer 36

(ph - dt)/ph

Question 37

__________ is the determining factor for the number of bubble caps to be used per tray.

Answer 37

Permissible slot velocity

Question 38

Pick out the wrong statement about distillation operation

Answer 38

Flash distillation, differential distillation & steam distillation are all continuous distillation processes.

Question 39

Low pressure steam (with saturation temperature between 105 to 120°C) is usually used in the vacuum evaporators, which normally employ a vacuum of about __________ mm Hg (referred to a 760 mm mercury barometer).

Answer 39

650

Question 40

Which of the following is the best tube material from thermal conductivity point of view alone?

Answer 40

Copper

Question 41

Normal screwed fittings are used for pipes upto a diameter of __________ inches.

Answer 41

3

Question 42

In a shell and tube heat exchanger, the clearance of the tube is generally

Answer 42

not less than one-fourth of the tube diameter or 3/16”.

Question 43

Diameter of the seive tray column is determined by the

Answer 43

upper limit of the vapour velocity.

Question 44

For a given fluid, as the pipe diameter increases, the pumping cost

Answer 44

decreases.

Question 45

Maximum acceptable total liquid gradient over a tray is about __________ mm.

Answer 45

12.5

Question 46

In case of a ‘thin’ pressure vessel, the ratio of its diameter to wall thickness is

Answer 46

> 10

Question 47

High pressure fluid in a shell and tube heat exchanger should preferably be routed through the

Answer 47

tubes to avoid the expansion of high pressure shell construction.

Question 48

Bubble cap tray is the most commonly used tray in large distillation column, because

Answer 48

of its flexibility and nearly constant efficiency under varying conditions of operation.