Section 3

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.

16
19
28
38

Answer 1

19

Question 2

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.

300
600
1000
1500

Answer 2

600

Question 3

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

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

Answer 3

both(b) & (c).

Question 4

The dust collection efficiency of a cyclone separator

decreases with increase in gas flow rate.
is inversely proportional to the mass of the dust particle.
is directly proportional to the radius of the dust particle path.
none of these.

Answer 4

none of these.

Question 5

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

∞
1
20.8
2

Answer 5

1

Question 6

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

A vapor phase reactor.
Pot type reactor.
A liquid phase reactor.
A liquid phase catalytic reactor.

Answer 6

A vapor phase reactor.

Question 7

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

density of the gas, but is independent of the viscosity of the gas.
density of the gas and inversely as viscosity of the gas.
viscosity of the gas and inversely as density of the gas.
none of these.

Answer 7

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

Question 8

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

1-1 cocurrent
double pipe
all multipass
all (involving liquid/liquid heat transfer)

Answer 8

all multipass

Question 9

Movement of pipeline caused by thermal expansion is taken care by providing

expansion joint.
changes in its direction.
change in the shape of pipeline.
all (a), (b) and (c).

Answer 9

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

Question 10

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

decreases upwards.
increases upwards.
remains same throughout.
may decrease or increase upwards depending upon whether vacuum or positive pressure would be maintained inside the shell.

Answer 10

decreases upwards.

Question 11

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

0.1
0.8
0.25
0.5

Answer 11

0.8

Question 12

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.

working
damaging
allowable
none of these

Answer 12

damaging

Question 13

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

lto3
4 to 8
3 to 12.5
12.5 to 18.5

Answer 13

3 to 12.5

Question 14

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

5-10
15-20
30-35
35-40

Answer 14

15-20

Question 15

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

A. d1 / (d1+d2)
B. d2 / (d1+ d2)
C. (d2+d2) / d1
D. (d2+d2) / d2

Answer 15

d1 / (d1+d2)

Question 16

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

liquid gradient on the tray.
lower skirt clearance.
lower static submergence.
small downcomer liquid seal.

Answer 16

liquid gradient on the tray.

Question 17

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

2
5
10
15

Answer 17

5

Question 18

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

D/2 or minimum 2” to 5D.
D/5 or minimum 2” to 5D.
D/5 or minimum 2” to D.
none of these.

Answer 18

D/5 or minimum 2” to 5D.

Question 19

Brass valves are usually made for pipe sizes __________ inches.

≤1
≤2
>2.5
>3.5

Answer 19

≤2

Question 20

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

increases
decreases
remains same
may increase or decrease depending upon the solubility of the gas in the liquid

Answer 20

remains same

Question 21

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

results in higher shell side pressure drop.

can accomodate less number of tubes for a given shell diameter.

facilitates easier shell side cleaning; hence is more suitable for handling high dirt factor shell side fluid.

creates relatively lower turbulence on the shell side resulting in lower shell side heat transfer co-efficient.

Answer 21

results in higher shell side pressure drop.

Question 22

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

The corrosive and fouling fluid should be preferably routed through the tubes.

The viscous fluid should be routed through the shell side.

Lower flow rate fluid should be routed through the shell side.

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

Answer 22

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

Question 23

The necessary wall thickness for a metallic storage vessel is a function of the

ultimate tensile strength (or yield point) of the material and operating temperature.

operating pressure and welding/joint efficiency.

diameter of the vessel.

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

Answer 23

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

Question 24

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.

‘n’th
(1/n)th
0.5 nth
1.5 nth

Answer 24

(1/n)th

Question 25

Pick out the wrong statement

In a flanged and standard dished head, the crown radius is ≤ shell outside diameter.

In a flanged and shallow dished head, the crown radius is > shell outside diameter.

Flat head covers are most suitable for larger vessels operating at very high pressure.

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 25

Flat head covers are most suitable for larger vessels operating at very high pressure.

Question 26

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

It is unsuitable for concentrating those liquids, which form a scale or deposit salt.

It is suitable for process, in which the final product is a liquor instead of solid.

Its usual dimensions are: tube dia = 2-3 cms; evaporator body dia = 1-4 metres and evaporator height = 2.5-4 metres.

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

Answer 26

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

Question 27

Weep holes provided in the plates of a distillation column

facilitate draining out liquid from a tray when the unit is not in operation.

are normally located near the overflow weir so that any delivery of liquid during operation follows approximately the same path as the overflow fluid.

must be large enough (usually 1/4” to 5/8” dia) to prevent plugging but should not deliver excessive amount of fluid during operation.

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

Answer 27

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

Question 28

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

low cost.
high latent heat.
non-corrosive condensate.
high film co-efficient.

Answer 28

high latent heat.

Question 29

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

Conical
Flat
Dome
Umbrella

Answer 29

Conical

Question 30

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

Diameter of Horton sphere is normally 6 to 25 metres and it is supported by 6 to 12 nos. tubular or rolled section column.

Thickness of spherical shell is half that of the cylinderical vessel under same operating pressure condition. Besides, the ratio of surface area to volume is less for sphere than any other shape ; hence insulation required is less.

Horton sphere is used for the storage of gases and volatile liquid at a moderate pressure of 1 to 10 kg/cm2 .

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

Answer 30

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

Question 31

Value of Peclet number = ∞, is the representative of

laminar flow.
complete back mixing,
plug flow.
eddy diffusivity = 0.

Answer 31

plug flow.

Question 32

Le/D for a Tee (used as elbow, entering branch) would be

less than that for Tee (used as elbow, entering run).

more than that for Tee (used as elbow, entering run).

around 90.

both (b) and (c).

Answer 32

both (b) and (c).

Question 33

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

less than
1.25-1.50 times
2.5 times
one-fourth of

Answer 33

1.25-1.50 times

Question 34

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

1.3 to 2
1.6 to 2
2.5
1.5 to 3

Answer 34

1.3 to 2

Question 35

1.2 to 3.8 cms is the value of the

downcomer liquid seal in case of a balanced tray design.

static submergence in case of a bubble cap tray for column operating under pressure (≥ 1 atm.).

skirt clearance for bubble caps.

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

Answer 35

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

Question 36

Accidents in chemical plants are mostly due to

inadequate equipment design.
faulty operating procedures.
improper layout of the equipments.
failure of equipments.

Answer 36

faulty operating procedures.

Question 37

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

sieve
valve
counterflow
bubble cap

Answer 37

bubble cap

Question 38

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

(ph - dh)/ph
(ph - dh . dt/2)/ph
(ph - dt)/ph
(ph - dh)/dh

Answer 38

(ph - dt)/ph

Question 39

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

Permissible slot velocity
Tray diameter
Liquid load
Vapor load

Answer 39

Permissible slot velocity

Question 40

Pick out the wrong statement about distillation operation

Distillation under vacuum is a substitute for steam distillation.

In differential (simple) distillation, the vapour is removed as soon as it is formed without appreciable condensation.

In flash (equilibrium) distillation, a definite fraction of liquid is vaporised in such a way that the evolved vapour & residual liquids are in equilibrium with each other.

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

Answer 40

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

Question 41

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).

250
450
650
750

Answer 41

650

Question 42

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

Aluminium
Stainless steel
Copper
Carbon steel

Answer 42

Copper

Question 43

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

1.5
3
5
7

Answer 43

3

Question 44

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

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

more than the tube diameter.

equal to the tube diameter.

more in case of triangular pitch as compared to the square pitch tube layout.

Answer 44

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

Question 45

Diameter of the seive tray column is determined by the

lower limit of vapour velocity.
upper limit of the vapour velocity.
hole diameter of the seive tray.
height of the plate spacing.

Answer 45

upper limit of the vapour velocity.

Question 46

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

decreases.

increases.

remains unaffected.

may increase or decreaes depending upon whether the fluid is Newtonian or non-Newtonion.

Answer 46

decreases.

Question 47

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

5.5
12.5
30.5
45.5

Answer 47

12.5

Question 48

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

< 10
> 10
> 20
30

Answer 48

> 10

Question 49

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

tubes to avoid the expansion of high pressure shell construction.

shell side for smaller total pressure drop.

shell side, if the flow is counter-current and tube side if the flow is co-current.

shell side for large overall heat transfer co-efficient.

Answer 49

tubes to avoid the expansion of high pressure shell construction.

Question 50

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

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

it incurs less pressure drop as compared to any other try designed for the same duty.

it eliminates the foaming and entrain-ment tendency during operation.

none of these.

Answer 50

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