Process Equipment and Plant Design (Set 2)

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

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 2

600

Question 3

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.

Answer 3

both(b) & (c).

Question 4

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. and is directly proportional to the radius of the dust particle path.
d. 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

Answer 5

1

Question 6

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

Answer 6

A vapor phase reactor.

Question 7

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

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.

Answer 8

all multipass

Question 9

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

Answer 9

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

expansion joint, changes in its direction, change in the shape of pipeline

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

Answer 10

decreases upwards.

Question 11

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

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.

Answer 12

damaging

Question 13

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

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.

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

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

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.

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

Answer 18

D/5 or minimum 2” to 5D.

Question 19

Brass valves are usually made for pipe sizes ____ inches.

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

Answer 20

remains same

Question 21

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

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.

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
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.

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.

Answer 24

(1/n)th

Question 25

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 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.

a. It is unsuitable for concentrating those liquids, which form a scale or deposit salt.
b. It is suitable for process, in which the final product is a liquor instead of solid.
c. Its usual dimensions are: tube dia = 2-3 cms; evaporator body dia = 1-4 metres and evaporator height = 2.5-4 metres.
d. 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

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.

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

Answer 28

high latent heat.

Question 29

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

Answer 29

Conical

Question 30

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

a. Diameter of Horton sphere is normally 6 to 25 metres and it is supported by 6 to 12 nos. tubular or rolled section column.
b. 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.
c. Horton sphere is used for the storage of gases and volatile liquid at a moderate pressure of 1 to 10 kg/cm2.
d. 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

Answer 31

plug flow.

Question 32

Le/D for a Tee (used as elbow, entering branch) would be
a. less than that for Tee (used as elbow, entering run).
b. more than that for Tee (used as elbow, entering run).
c. around 90.

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.

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.

Answer 34

1.3 to 2

Question 35

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.

Answer 35

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

Question 36

Accidents in chemical plants are mostly due to

Answer 36

faulty operating procedures.

Question 37

For identical operating conditions, the pressure drop over ____ tray is the highest out of the following.
a. sieve
b. valve
c. counterflow
d. 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

Answer 38

(ph - dt)/ph

Question 39

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

Answer 39

Permissible slot velocity

Question 40

Pick out the wrong statement about distillation operation

a. Distillation under vacuum is a substitute for steam distillation.
b. In differential (simple) distillation, the vapour is removed as soon as it is formed without appreciable condensation.
c. 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.
d. 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).

Answer 41

650

Question 42

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

Answer 42

Copper

Question 43

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

Answer 43

3

Question 44

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

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

Answer 45

upper limit of the vapour velocity.

Question 46

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

Answer 46

decreases.

Question 47

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

Answer 47

12.5

Question 48

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

Answer 48

> 10

Question 49

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

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

Answer 50

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

Question 51

In common bubble cap distillation column design practice, riser area is approximately equal to (where, Aa = Annular passage area, and Sa = Slot area)

Answer 51

Aa = Sa

Question 52

Heat transfer co-efficient, hG(Kcal/hr.m2 .°C) and mass velocity of air, G (kg/hr.m2 ) for air flow parallel to the surface in case of constant drying rate in batch drying is related as hG = 0.0176G0.8. But when the flow of air perpendicular to the surface is encountered, this equation changes to

Answer 52

hG = 1.004G^0.37

Question 53

In the agitators, the power required will be changed with the increase of diameter of agitator (D) as

Answer 53

D^5

Question 54

Apex angle of conical heads used in the bottom heads of chemical process equipments is usually

Answer 54

60°

Question 55

Pressure drop due to pipe fittings can be estimated by the equation, https://www.indiabix.com/_files/images/chemical-engineering/process-equipment-and-plant-design/561-40-1.png
, where, Le = equivalent length of straight pipeline which will incur the same frictional loss as the fitting and D = diameter of the fitting. The value of Le/D (dimensionless) for 45° elbow and 180° close return bends would be respectively around

Answer 55

45 and 75

Question 56

A pressure vessel is said to be made of ‘thick’ shell, if the ratio of its diameter to wall thickness is

Answer 56

10

Question 57

Rate of filtrate delivery is inversely proportional to the
a. filtering area & the pressure difference driving force.
b. viscosity of filtrate.
c. cake & filter medium resistance.

Answer 57

both (a) and (b)

Question 58

Tube side heat transfer co-efficient for turbulent flow of liquid through tubes is proportional to

Answer 58

G^0.8

Question 59

Circumferential (hoop) stress in a thin cylindrical vessel under internal pressure is ____ the longitudinal stress.

Answer 59

twice

Question 60

The dust collection efficiency of electrostatic precipitator increases with increase in the

Answer 60

electrode area.

Question 61

For storing hazardous chemicals in large storage tanks, the minimum safe distance between the two tanks should range between ____ times the tank diameter.

Answer 61

1 to 1.5

Question 62

Which of the following factors determine the amount of entrainment in a distillation column?
a. Plate spacing.
b. Depth of liquid above the bubble cap slots.
c. Vapour velocity in the volume between the plates.

Answer 62

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

Question 63

The absorption factor is defined as (where, S1 = slope of the equilibrium curve, S2 = slope of the operating line)

Answer 63

S1/S2

Question 64

In shell and tube heat exchangers, straight tie rods are used to

Answer 64

hold baffle in space.

Question 65

In a rotary drier, the average retention time of solid is(where Z = length of the drier, metres ρ = apparent solid density, kg/m3 L = flow rate of dry solids, kg/see. m2 drier cross-section H = hold up of solid.)

Answer 65

Z.H.p/L

Question 66

In case of design of a shell and tube heat exchanger,

a. minimum cleaning lane of 6.5 mm is provided, when tubes are on a square pitch.

b. minimum tube sheet thickness (in which tubes are fixed) is equal to the O.D. of the tube upto 15 mm tube diameter; and for > 15 mm tube diameter, tube sheet thickness is smaller than tube diameter.

c. O.D. of the tube is 6 to 40 mm while the tube lengths used are 0.5, 2.5, 3.0, 4.0, 5.0, 6 metres.

Answer 66

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

Question 67

In a cylinderical vessel subjected to internal pressure, the longitudinal stress σL and the circumferential stress, σn are related by

Answer 67

σh = 2 σL

Question 68

Nominal size of a pipe is an indication of its ____ diameter.

Answer 68

approximate

Question 69

Excessive liquid gradient on a tray may result in the

a. maldistribution of gas.
b. back trapping.
c. gas blowing beneath cap skit.

Answer 69

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

Question 70

The ratio of tube length to shell diameter in case of liquid shell and tube heat exchanger ranges from

Answer 70

4 to 8

Question 71

In a double pipe concentric heat exchanger, the equivalent diameter of annulus for heat transfer would be (where, D1 and D2 are I.D. of inner and outer pipes)

Answer 71

https://www.indiabix.com/_files/images/chemical-engineering/process-equipment-and-plant-design/566-92-1.png

Question 72

What is the slope of the operating line in the stripping section of a distillation column?

Answer 72

> 1

Question 73

____ shaped roof is most commonly used for cylindrical tanks.

Answer 73

Cone

Question 74

In a thin cylindrical shell, the hoop stress is ____ stress.

Answer 74

circumferential tensile

Question 75

Commercial packed scrubbers are normally designed for a pressure drop range of ____ mm water coloumn per metre of packed height.

Answer 75

17-34

Question 76

The retention time of material in a rotary dryer depends upon its

a. rpm
b. slope & length
c. flights arrangement

Answer 76

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

Question 77

In actual operation of a bubble cap distillation tower, the ____ at the bottom of the tower is more than that at the top of the tower.

a. molal flow rate of vapour
b. vapour molecular weight
c. pressure and temperature

Answer 77

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

Question 78

Rotary driers are most economically designed for the number of heat transfer units (HTU) from

Answer 78

1.5 to 2.5

Question 79

The difficulty of liquid distribution in packed towers is accentuated, when the ratio of tower diameter to packing diameter is

Answer 79

< 7

Question 80

A forced circulation long tube vertical evaporator as compared to the natural circulation evaporator

a. is economical in operation.
b. employs high velocity, high heat transfer rate and less heating surface requirement.
c. employs a centrifugal pump placed between external downtake from vapor drum and inlet to tube bundle.

Answer 80

both (b) & (c).

Question 81

An increase in the liquid resistance to interphase mass transfer and a resultant reduction in plate efficiency is caused by

a. an increase in liquid viscosity.
b. an increase in relatived volatility for rectification columns.
c. decrease in gas solubility for absorbers.

Answer 81

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

Question 82

In the design of a bag filter, the gas temperature is an important consideration, as it affects the
a. gas density
b. gas viscosity
c. fibre selection

Answer 82

all (a), (b) & (c)

Question 83

With increase in temperature drop (in a shell and tube heat exchanger), the LMTD correction factor, FT

Answer 83

decreases very rapidly

Question 84

The normal range of velocity of steam in pipes is ____ m/sec.

Answer 84

80-100

Question 85

____ dished head is the strongest of all.

Answer 85

Hemispherical

Question 86

Pick out the correct statement.

a. It is preferred to use a vertical condenser for condensation of vapor from a distillation column without sub-cooling
b. Draining of residual liquid on tray during shut down of distillation column is facilitated by weep holes.
c. Random packing a packed tower offers the advantage of lower pressure drop and higher throughput of fluids as compared to regular/stacked packing.
d. Risers are generally not connected to the plate in a distillation coloumn by bolts, rivets or welding.

Answer 86

Risers are generally not connected to the plate in a distillation coloumn by bolts, rivets or welding.

Question 87

“A claming section” before the liquid flows into the downcomer is privided to

Answer 87

permit release of entrained vapour in the liquid.

Question 88

The units of Young’s modulus of elasticity and ____ are the same.

Answer 88

stress

Question 89

In the design of a shell and tube heat exchanger, the corrosion allowance

a. need not be provided for non-pressure parts like tie rods, spacers, baffles, supports etc.
b. for carbon steel and cast iron pressure parts is 1.5 mm (except for tubes) and for severe conditions it is 3 mm.
c. for internal cover and tube sheet is provided on both the sides.

Answer 89

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

Question 90

Vertical condenser is advantageous to the horizontal condenser from operation point of view, when

Answer 90

both the functions of condensation & sub cooling are carried out in a single unit.

Question 91

Hazards associated with the relief valve leakage for extremely hazardous material storage can be taken care of by providing

Answer 91

rupture diaphragm

Question 92

Minimum baffle spacing recommended in a shell and tube heat exchanger is equal to

Answer 92

5 cms

Question 93

____ liquor is best handled in a long tube vertical evaporator.

Answer 93

Foamy

Question 94

Theoretically calculated diameter of the stripping section of the continuous rectification column is ____ that of the enriching section.

Answer 94

more than

Question 95

Hold up of material in a operating rotary drier is in the range of

Answer 95

0.05 to 0.15

Question 96

A binary liquid azeotropic mixture has boiling point higher than either of the components, when it shows ____ deviation from Raoult’s Law.

Answer 96

negative

Question 97

The testing pressure of storage tanks and pressure vessels designed as per Indian standard codes should be about ____ times.the design pressure.

Answer 97

1.5 to 2

Question 98

Flanges are connected to pipes by
a. screwing
b. welding
c. brazing

Answer 98

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

Question 99

The ratio of down take area to cross-sectional area of the tube, for calendria type evaporator ranges from

Answer 99

0.5 to 1

Question 100

Shortest distance between two tubes is

Answer 100

called tube clearance.