Process Equipment Design

Question 1

Fresh water carrying pipelines in chemical industries are coloured with __________ color.

Answer 1

sea green

Question 2

Which of the following material is seldom used for pressure vessel construction?
a. Rimmed steel
b. Mild steel
c. Killed steel
d. Semi-killed steel

Answer 2

Rimmed steel

Question 3

The ratio of shear stress to shear strain is called

Answer 3

shear modulus

Question 4

25 per cent cut segmental baffle means that the baffle

Answer 4

height is 75% of the I.D. of the shell.

Question 5

Liquid/petroleum fuel storage tanks are built underground (as in case of petrol pumps), when the storage capacity is less than __________ kilolitres.

Answer 5

45

Question 6

Le/D for fully open globe value may be around

Answer 6

300

Question 7

Lug support is
a. the most suitable for thick vertical vessel.
b. same as bracket support.
c. provided usually for vessels of much smaller height than skirt supported vessels.
d. all (a), (b) and (c).

Answer 7

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

Question 8

Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column.
a. Bubble cap trays though most expensive are the best in situations, where low vapour rates is to be handled and a positive liquid seal is essential at all flow rates.
b. Murphree efficiency of all the three trays are nearly equal, however the peak efficiency is generally higher for seive and valve trays than the bubble cap.
c. Maintenance cost for valve and seive trays are comparatively more than bubble cap tray due to their relatively complicated construction features.
d. Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provides the maximum flexible operating range.

Answer 8

Maintenance cost for valve and seive trays are comparatively more than bubble cap tray due to their relatively complicated construction features.

Question 9

With increase in the number of shell passes, the value of FT

Answer 9

increases

Question 10

Holes of a sieve tray are arranged in triangular pitch of __________ times the hole diameter.

Answer 10

2.5 to 5

Question 11

In case of a shell and tube heat exchanger, the minimum shell thickness for carbon steel (inclusive of corrosion allowance) depends on shell diameter and is in the range of __________ mm.

Answer 11

5 - 11

Question 12

The stress developed in a material without any permanent set is called the

Answer 12

elastic limit

Question 13

In a shell and tube heat exchanger, the ‘tube pitch’ is defined as the

Answer 13

shortest centre to centre distance between adjacent tubes.

Question 14

Which of the following is not a valid assumption in continuous binary distillation for calculating the number of equilibrium stages by Mc-Cabe-Thiele’s method?
a. Sensible heat changes for vapour & liquid are negligibly small.
b. Reflux is not a saturated liquid.
c. Molar latent heat of the two components are equal.
d. Heat of mixing of normal liquid is assumed to be zero.

Answer 14

Reflux is not a saturated liquid.

Question 15

Overall distillation column efficiency for most of the refinery columns can be given by (for μ = 0.07 - 1.4 cp and relative volatility < 4) (where η = overall column efficiency, % μ = molal average viscosity of feed at average column temperature and pressure, cp Δp = pressure drop per tray, psi)

Answer 15

η = 17 - 61.1 log μ

Question 16

The value of fouling factor depends upon the
a. characteristic of process fluid.
b. velocity of process fluid containing suspended solids.
c. suspended solids in the fluid.
d. all (a), (b) and (c).

Answer 16

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

Question 17

In case of bubble cap distillation column of diameter greater than 1.2 metres, the cap diameter is roughly about __________ cms.

Answer 17

10

Question 18

Tube side pressure drop in a 1-2 heat exchanger (for turbulent flow of fluids through the tubes) is about __________ times, that in a 1-1 heat exchanger having the same size & number of tubes and operated at the same liquid flow rate.

Answer 18

8

Question 19

To keep the power input constant for a stirred vessel operating under fully developed turbulent flow conditions (constant power number), if the impeller diameter is increased by 20%, the impeller speed should be decreased by a factor of

Answer 19

(1.2)^5/3

Question 20

Where does the maximum tensile strength occur in a thick cylindrical vessel subjected to internal pressure?

Answer 20

At the inner surface.

Question 21

It is not desirable to design a heat exchanger for LMTD correction factor, FT, of less than

Answer 21

0.8

Question 22

A rivetted joint does not fail by __________ of rivets.
a. tearing
b. shearing
c. tearing of the plate across a row
d. none of these

Answer 22

none of these

Question 23

Triangular pitch tube layout as compared to square pitch in a shell and tube heat exchanger

Answer 23

permits the use of more tubes in a given shell diameter.

Question 24

Bracket supports are the most suitable for supporting __________ vessels.

Answer 24

thick walled vertical

Question 25

In a multipass shell and tube heat exchanger, the shell side cross flow area does not depend upon

Answer 25

none of these

Question 26

Two iron pipes of the same nominal diameter but different schedule numbers will have the same

Answer 26

inside diameter

Question 27

Steam side heat transfer co-efficient for design consideration under ordinary condition can be assumed to be about __________ kcal/hr.m2.°C.

Answer 27

7500

Question 28

Lessing ring is formed by the addition of a partition across the centre of a raschig ring, which results in an area increase of about __________ percent.

Answer 28

20

Question 29

In chemical process equipments, the conical bottom heads used, usually has an apex angle of

Answer 29

60°

Question 30

Smaller sized packings are generally dumped to the packed columns, and the large ones of size greater than __________ mm are stacked individually, which provides better control over bed porosity and offers lower gas pressure drop.

Answer 30

75

Question 31

Shell side heat transfer co-efficient in case of square pitch as compared to the triangular pitch under similar condition of fluid flow and tube size is

Answer 31

less

Question 32

Correct use of ‘factor of safety’ is very important in equipment design. It is defined as the ratio of the

Answer 32

ultimate stress to working stress.

Question 33

The operating velocity in the absorption tower is usually 40-50% of the flooding velocity. Packed absorption towers are normally designed for a pressure drop of about __________ mm of water column per metre height of packing.

Answer 33

20-40

Question 34

__________ tray arrangement is recommended for distillation column having diameter upto 4 ft.

Answer 34

Cross flow

Question 35

What is the value of ‘q’ for saturated liquid feed to a distillation column?

Answer 35

1

Question 36

In perforated plate towers, the
a. hole sizes may be around 1/8” or 3/16”.
b. total hole area may be around 6 to 15% of tower cross-sectional area.
c. pressure drop is less compared is similar bubble cap towers.
d. all (a), (b) and (c).

Answer 36

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

Question 37

The main purpose of providing stepping on the trays is to

Answer 37

facilitate handling of large flow rate of liquid.

Question 38

The operating pressure drop range in a bag filter is about __________ mm water gauge.

Answer 38

50-150

Question 39

The ends of a cylinderical vessel can be closed by a head, which can be one of the four shapes. For the same thickness, choose the one which can withstand the highest pressure.

Answer 39

Ellipsoidal

Question 40

For laminar flow (NRe < 2100) in steel pipe, the optimum inside pipe diameter is given by

Answer 40

Di, opt = 3 Q^0.36 ρ^0.18

Question 41

Pick out the correct statement.
a. When highly corrosive fluids are to be handled, the plate towers prove to be cheaper and easier to construct than packed tower.
b. Packed towers are generally preferred over plate towers, if the liquids have a foaming tendency.
c. The pressure drop through the packed towers is generally more than the pressure drop through plate towers designed for same duty.
d. none of these.

Answer 41

Packed towers are generally preferred over plate towers, if the liquids have a foaming tendency.

Question 42

Wall thickness of schedule 40 pipe as compared to that of schedule 80 pipe is

Answer 42

less

Question 43

Pick out the wrong statement pertaining to the design of a basket type evaporator.
a. It is used for high viscosity liquor having large rate of scaling.
b. The tube bundle is suspended on bracket.
c. There is no central downtake.
d. Downtake is formed by the annular space between the bundle and the shell.

Answer 43

It is used for high viscosity liquor having large rate of scaling.

Question 44

Pick out the wrong statement pertaining to the design of the bubble cap tray of a distillation column to give stable operation and even vapour distribution.
a. The pressure drop due to the caps & slots and the static submergence should be as high as practicable for reasonable operation.
b. Tendency towards stable operation is increased by increasing the skirt clearance of the caps, lowering the rate of liquid flow per unit plate width or increasing the spacing between the caps.
c. The dimensionless ratio of liquid gradient to pressure drop head caused by the bubble cap assembly should be less than 0.4.
d. none of these.

Answer 44

none of these.

Question 45

Speed of the drum of the rotary vacuum filter normally ranges from __________ rpm.

Answer 45

0.1 to 2

Question 46

A stuffing box is used for

Answer 46

prevention of fluid leakage around moving parts.

Question 47

Pressure drop (Δp) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as

Answer 47

Δp = G^2

Question 48

Pick out the wrong statement.
In an agitated vertical cylinderical reaction vessel, the
a. ratio of liquid depth to tank diameter (i.e. the filling ratio) recommended for most purposes is 1.
b. filling ratio for dispersing gas in a liquid is 2 for sufficiently long contact period.
c. flat bottom and conical bottom vessels have low agitation efficiency for agitation of heavy solids in liquids.
d. dished bottom vessel has very high power consumption.

Answer 48

dished bottom vessel has very high power consumption.

Question 49

Needle valves are generally not used for

Answer 49

very large diameter pipes.

Question 50

Height equivalent to a theoretical plate (HETP) is the height of packing that will give the same separation as one theoretical plate in gas-liquid mass transfer operations like distillation, absorption/stripping and humidification/dehumidification. HETP which is experimentally determined, depends upon the

a. flow rates of each fluid.
b. type and size of packing.
c. concentration of each fluid.
d. all a, b & c.

Answer 50

all a, b & c.

Question 51

Pick out the wrong statement.
a. Safety valves are provided in heat exchangers for removal of non-conden-sables.
b. Liquid metals and dowtherm are used for very high temperature heating.
c. In a shell and tube heat exchanger, high pressure fluid is generally routed through the tube.
d. A loop seal or U-seal is provided in a vertical condenser sub-cooler to prevent quick draining of the condensate.

Answer 51

Safety valves are provided in heat exchangers for removal of non-conden-sables.

Question 52

With increase in gas flow rate to fabric surface area ratio (Nm3/hr/m2 fabric surface area), the size & the cost of a bag filter

Answer 52

decreases

Question 53

A head comprises of straight flange section, corner torus, section and central dished section. Crown radius and knuckle radius in a head is related respectively to the

Answer 53

central dished section and corner torus section.

Question 54

Which of the following is used to set the diameter of the distillation column?
a. Number of theorectical plates.
b. Static submergence.
c. Allowable vapour velocity.
d. Length of straight rectangular weir on cross-flow tray.

Answer 54

Allowable vapour velocity.

Question 55

Ponchon Savarit method is based on the use of enthalpy concentration diagram, which contains the bubble point curve (saturated liquid curve), dew point curve (saturated vapour curve) and equilibrium tie lines. As compared to McCabe-Thiele’s method, this method

a. is more accurate in finding the number of equilibrium stages.
b. accounts for the enthalpy changes in the process.
c. facilitates direct calculation of heat load on reboiler & condenser from, the diagram used in this method.
d. all ‘a’, ‘b’ & ‘c’.

Answer 55

all ‘a’, ‘b’ & ‘c’.

Question 56

The optimum size ratio for two mixed reactors in series depends on the kinetics of the reaction and the conversion level. For reaction orders more than one, the

Answer 56

smaller reactor should come first.

Question 57

Which of the following is not a graphical method (but is an analytical method) for the calculation of theoretical number of stages in case of continuous binary distillation?
a. Sorel-Lewis method.
b. McCabe-Thiele’s method.
c. Ponchon-Savarit method.
d. none of these.

Answer 57

Sorel-Lewis method.

Question 58

Saddle supports are used for supporting __________ vessels.

Answer 58

horizontal cylinderical

Question 59

The diameter of a propeller agitator used in agitation tank ranges from __________ percent of the tank diameter and its peripherial speed is normally 300 to 500 metres/minute.

Answer 59

15 to 30

Question 60

In packed towers provided with saddle packing, liquid redistributors are positioned at every __________ times column diameter or 6 metres whichever is less.

Answer 60

5 - 8

Question 61

Optimum reflux ratio in a continuous distillation column is determined by the

Answer 61

total cost consideration (fixed cost of the column plus the cooling water & steam cost).

Question 62

Cooling water fouling factors vary in the range of 0.001 to 0.003

Answer 62

(BTU/hr.ft2 . °F)-1

Question 63

Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)

Answer 63

0.2 D

Question 64

The maximum liquid gradient over a tray must not exceed

Answer 64

0.5” -1.25”.

Question 65

An underdesigned steam trap will

Answer 65

back up condensate and cause water hammer in steam line.

Question 66

The slope of the feed line in distillation opeartion is given by (where, q = fraction of the feed stream that is liquid.)

Answer 66

-q/(1-q)

Question 67

Speed of industrial paddle agitator ranges from __________ rpm.

Answer 67

20 to 100

Question 68

_________ strain is measured using a ‘strain rosetter’.

Answer 68

Linear

Question 69

Thin spherical shells subjected to internal pressure, develop __________ stresses.

Answer 69

radial

Question 70

With increase in the reflux ratio for a fixed production from a continuous binary distillation column, the __________ decreases.

Answer 70

fixed charges initially

Question 71

The slope of operating line in the rectifying section of a distillation column is unity, if the reflux ratio is

Answer 71

∞

Question 72

Vertical vessels are not supported by

Answer 72

saddles

Question 73

With increase in pressure drop (for a given particle size), the dust collection efficiency of a cyclone separator will

Answer 73

increase

Question 74

Spherical shaped pressure vessel is considered to be the most ideal, because it can

Answer 74

withstand higher pressure for a given metallic shell thickness.

Question 75

An adequate clearance between the tray and the shell wall of a distillation column is provided to

Answer 75

allow for thermal expansion and facilitate installation.

Question 76

Overall tray efficiency of a distillation column is the ratio of the number of

Answer 76

ideal trays required to the number of real trays required.

Question 77

Pick out the wrong statement about the design of a sieve plate column.

a. An increased weir height improves the tray efficiency at the cost of high plate pressure drop; optimum wear height being 40-90 mm for column pressure above atmospheric and 6-12 mm for vacuum columns.
b. For segmental downcomers, the chord length is 60-80% of the column diameter. An initial value of downcomer area of 12% is taken in the design.
c. Width of the calming section provided at the inlet and outlet sides of the plate is 75 mm for column diameter below 1.5 metres and 100 mm for larger diameter columns.
d. Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds.

Answer 77

Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds.

Question 78

Generally, no corrosion allowance in wall thickness of a part is required, if the thickness is more than __________ mm.

Answer 78

30

Question 79

Multiple blade paddle agitator is used for mixing high viscosity liquids/paste in which the paddle diameter is commonly 0.8 times the tank diameter. However, the width of the blade is in the range of __________ times the paddle diameter.

Answer 79

0.1 to 0.25

Question 80

In a __________ rivetted joint, the rivets in the various rows are opposite to each other.

Answer 80

chain

Question 81

Pick out the wrong statement:

a. The tensile strength of a brittle material is less than its compressive strength.
b. The compressive strength of a ductile materia] is less than its tensile strength.
c. In a thick cylindrical shell, the hoop stress is maximum at the inner radius.
d. The value of crushing load is more than that of buckling load for long colmns.

Answer 81

The value of crushing load is more than that of buckling load for long colmns.

Question 82

Generally, elliptical dished heads
a. are manufactured on 2:1 ratio of major to minor axis and is recommended to be used for pressure vessels operating above a pressure of 1.5 MN/m2 .
b. resist half the pressure rating compared to hemi spherical head provided on the cylindrical shell of the same thickness and diameter.
c. are approximately as strong as seamless cylindrical shell having the corresponding I.D and O.D.
d. all (a), (b) and (c)

Answer 82

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

Question 83

Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower.
a. Plate tower is perferred, if interstage cooling is required to remove heats of reaction or solution.
b. Plate tower is preferred over packed tower, if the operation involves liquids containing dispersed solids.
c. The total weight of a dry plate tower is usually much more than that of a dry packed tower designed for the same duty.
d. In operations involving large temperature changes. (e.g. distillation), plate towers are preferred over packed towers as the packing may be crushed due to large temperature changes.

Answer 83

The total weight of a dry plate tower is usually much more than that of a dry packed tower designed for the same duty.

Question 84

The circumferential (hoop) stress in a thin walled cylinderical vessel under internal pressure is

Answer 84

pd/2t

Question 85

LMTD correction factor is used in heat exchanger design for

Answer 85

multipass shell and tube heat exchanger.

Question 86

Floating head heat exchangers are used for the

Answer 86

cases where temperature difference between the shell and the tubes is more (>50°C).

Question 87

The most common standard size of bubble caps used in industrial operation is

Answer 87

6” dia cap with 4” dia riser.

Question 88

Compensation against openings in process vessels for giving inlet and outlet connections, for providing sight glasses and manholes etc. is provided for strength and rigidity. The most efficient type of compensation is of __________ type.

Answer 88

nozzle or rim

Question 89

In case of a continuous distillation column, increase in reflux ratio may result in the

a. lower fixed charges for the column.
b. greater cost for the reboiler heat supply.
c. greater cost for the condenser coolant.
d. all (a), (b) and (c).

Answer 89

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

Question 90

In a distillation column, the minimum residence time for liquid in the downspout is about __________ seconds.

Answer 90

8

Question 91

Thickness of the frame of a plate and frame filter as compared to that of plates is

Answer 91

more

Question 92

Which of the following factors affect the pressure drop in a co-current gas-liquid absorption packed tower?
a. Size, shape, orientation and surface of the packing particles.
b. Density and viscosity of fluids.
c. Fluid flow rates.
d. All (a), (b) and (c).

Answer 92

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

Question 93

The thickness of heat transfer plates used in the plate type heat exchanger ranges from __________ mm, pressed in a single piece provided with grooves & corrugations.

Answer 93

1.25 to 3.125

Question 94

Rivets are generally specified by the

Answer 94

shank diameter

Question 95

Length to diameter ratio of most rotary driers is in the range of

Answer 95

4 to 10

Question 96

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 96

19

Question 97

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 97

600

Question 98

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 98

none of these.

Question 99

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 99

1

Question 100

Which of the following types of reactors is the safest from operation point of view?
a. A vapor phase reactor.
b. Pot type reactor.
c. A liquid phase reactor.
d. A liquid phase catalytic reactor.

Answer 100

A vapor phase reactor.

Question 101

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

Answer 101

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

Question 102

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

Answer 102

all multipass

Question 103

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 103

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

Question 104

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 104

decreases upwards.

Question 105

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

Answer 105

0.8

Question 106

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 106

damaging

Question 107

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

Answer 107

3 to 12.5

Question 108

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

Answer 108

15-20

Question 109

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 109

d1/(d1+d2)

Question 110

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

Answer 110

liquid gradient on the tray.

Question 111

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

Answer 111

5

Question 112

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 112

D/5 or minimum 2” to D.

Question 113

Brass valves are usually made for pipe sizes __________ inches.

Answer 113

≤2

Question 114

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 114

remains same

Question 115

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

Answer 115

results in higher shell side pressure drop.

Question 116

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

Answer 116

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

Question 117

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 117

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

Question 118

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 118

(1/n)th

Question 119

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 119

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

Question 120

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 120

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

Question 121

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 121

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

Question 122

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

Answer 122

high latent heat.

Question 123

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

Answer 123

Conical

Question 124

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 124

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

Question 125

Value of Peclet number = ∞, is the representative of

Answer 125

plug flow.

Question 126

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

Answer 126

1.25-1.50 times

Question 127

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

Answer 127

1.3 to 2

Question 128

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 128

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

Question 129

Accidents in chemical plants are mostly due to

Answer 129

faulty operating procedures.

Question 130

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

Answer 130

bubble cap

Question 131

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 131

(ph - dt)/ph

Question 132

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

Answer 132

Permissible slot velocity

Question 133

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 133

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

Question 134

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 134

650

Question 135

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

a. Aluminium
b. Stainless steel
c. Copper
d. Carbon steel

Answer 135

Copper

Question 136

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

Answer 136

3

Question 137

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

Answer 137

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

Question 138

Diameter of the seive tray column is determined by the

Answer 138

upper limit of the vapour velocity.

Question 139

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

Answer 139

decreases.

Question 140

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

Answer 140

12.5

Question 141

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

Answer 141

> 10

Question 142

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

Answer 142

tubes to avoid the expansion of high pressure shell construction.

Question 143

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

Answer 143

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

Question 144

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

Answer 144

Aa = Sa

Question 145

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 145

hG = 1.004G^0.37

Question 146

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

Answer 146

D^5

Question 147

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

Answer 147

60°

Question 148

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

Answer 148

10

Question 149

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

Answer 149

G^0.8

Question 150

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

Answer 150

twice

Question 151

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

Answer 151

electrode area.

Question 152

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

Answer 152

1 to 1.5

Question 153

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

Answer 153

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

Question 154

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

Answer 154

S1/S2

Question 155

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

Answer 155

hold baffle in space.

Question 156

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 156

Z.H.p/L

Question 157

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

Answer 157

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

Question 158

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

Answer 158

σh = 2 σL

Question 159

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

Answer 159

approximate

Question 160

Excessive liquid gradient on a tray may result in the
a. maldistribution of gas.
b. back trapping.
c. gas blowing beneath cap skit.
d. all (a), (b) and (c).

Answer 160

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

Question 161

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

Answer 161

4 to 8

Question 162

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

Answer 162

> 1

Question 163

__________ shaped roof is most commonly used for cylindrical tanks.

Answer 163

Cone

Question 164

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

Answer 164

circumferential tensile

Question 165

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

Answer 165

17-34

Question 166

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

a. rpm
b. slope & length
c. flights arrangement
d. all (a), (b) and (c)

Answer 166

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

Question 167

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

Answer 167

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

Question 168

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

Answer 168

1.5 to 2.5

Question 169

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

Answer 169

< 7

Question 170

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

Answer 170

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

Question 171

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

Answer 171

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

Question 172

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

Answer 172

decreases very rapidly

Question 173

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

Answer 173

80-100

Question 174

__________ dished head is the strongest of all.

Answer 174

Hemispherical

Question 175

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 175

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

Question 176

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

Answer 176

permit release of entrained vapour in the liquid.

Question 177

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

Answer 177

stress

Question 178

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

Answer 178

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

Question 179

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

Answer 179

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

Question 180

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

Answer 180

rupture diaphragm

Question 181

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

Answer 181

5 cms

Question 182

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

Answer 182

Foamy

Question 183

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

Answer 183

more than

Question 184

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

Answer 184

0.05 to 0.15

Question 185

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

Answer 185

negative

Question 186

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

Answer 186

1.5 to 2

Question 187

Flanges are connected to pipes by
a. screwing
b. welding
c. brazing
d. all (a), (b) and (c)

Answer 187

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

Question 188

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

Answer 188

0.5 to 1

Question 189

Shortest distance between two tubes is

Answer 189

called tube clearance.

Question 190

__________ tower is the most suitable gas-liquid contacting device involving highly corrosive fluids.

Answer 190

Packed

Question 191

At equal mass velocities, the values of film co-efficients for gases as compared to that for liquids are generally.

Answer 191

lower

Question 192

The ratio of the largest load in a test to the original cross-sectional area of the test specimen is called the __________ stress.

Answer 192

ultimate

Question 193

The wall thickness of thin cylindrical shell with hemispherical ends is __________ that of the spherical ends.

Answer 193

more than

Question 194

A ‘rupture disc’ is provided in chemical equipments as an accessory meant for

Answer 194

relieving excess pressure.

Question 195

In a vertical short tube evaporator (Calendria type), the

a. tube dia of 2.5-7.5 cms, tube length of 75-200 cms and cylinderical drum dia of 1-6 metres are normally used.
b. area of central downtake is equal to 40 to 100% of total cross-sectional area of the surrounding tube.
c. liquor is inside the tube while the steam is outside the tube.
d. all (a), (b) & (c)

Answer 195

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

Question 196

In a shell and tube heat exchanger, the shortest centre to centre distance between the adjacent tubes is

Answer 196

called tube pitch.

Question 197

Any shell opening greater than 5 cms for a storage tank must be reinforced for reason of

Answer 197

preventing the local overstressing of the shell around the opening.

Question 198

Minimum tube pitch recommended for shell and tube heat exchangers is about __________ times the outside diameter of the tube.

Answer 198

1.25

Question 199

Liquid redistribution should be done in a packed tower packed with raschig rings every 6 metres or __________ times the column diameter, whichever is lower.

Answer 199

2.5-3.0

Question 200

Slope of countercurrent flow rotary drier is in the range of __________ meter/metre.

Answer 200

0 to 0.08

Question 201

In case of saddle packing (e.g., berl and intralox saddles), the maximum size of the packing should not exceed __________ of the column diameter.

Answer 201

l/15th

Question 202

The thermal stress in a metallic bar does not depend upon the

Answer 202

cross-sectional area.

Question 203

The minimum baffle height should be

Answer 203

twice the impeller diameter.

Question 204

For turbulent flow (NRe > 2100) of low viscosity fluid (μ > 20cp) in steel pipes, the optimum inside pipe diameter is given by(where, Q = fluid flow rate, ft3/sec.ρ = fluid density, lb/ft3 μ = fluid viscosity, centipoise Di = optimum inside pipe diameter, inches)

Answer 204

Di, opt = 3.9 Q0.45 ρ0.13

Question 205

To avoid the tearing off the plate of an edge, the margin (i.e., the minimum distance from the centre of the rivet hole to the nearest edge of the plate) should be equal to

Answer 205

1.5 d

Question 206

The normal range of velocity of water in pipes is __________ m/sec.

Answer 206

1 - 2

Question 207

Baffles are provided in a shell and tube heat exchanger to increase the turbulence and velocity of the shell side fluid. Which of the following shaped baffles does not fall in the category of transverse baffle?

Answer 207

Flat plate extending across the wall

Question 208

A certain pressure vessel manufacturer avoids doing reinforcements calculations for openings by always providing a reinforcing pad extending upto double the diameter of the opening and of the same material and thickness as that of the shell wall. If area compensation is accepted as a code guideline, his approach leads to safe design

Answer 208

irrespective of the shape of the vessel.

Question 209

In a __________ rivetted joint, the number of rivets decreases from the innermost row to the outermost row.

Answer 209

diamond

Question 210

Large process vessels operating under extreme temperature and pressure conditions are normally clad/ lined with materials like stainless steel, aluminium, nickel & its alloys, copper & its alloys and titanium. The cladding thickness is generally about __________ percent of the total thickness.

Answer 210

10 to 20

Question 211

Heat transfer co-efficient for a horizontal condenser as compared to a vertical condenser operating under similar conditions is

Answer 211

about 3 times

Question 212

Pick out the wrong statement pertaining to the design of the distillation column.

a. Generally, a skirt clerance of 0.5” to 1.5’ is recommended to prevent plugging of the slots by residue build up.
b. The purpose of the slot is to disperse the gas into the liquid in the form of small bubbles.
c. If sufficient slot area is not provided, the gas may pass through the skirt clearance.
d. none of these.

Answer 212

none of these.

Question 213

The longitudinal stress induced in a thin walled cylinderical vessel under internal pressure is

Answer 213

pd/4t

Question 214

The buckling tendency of compression members is always in the direction of the

Answer 214

least radius of gyration.

Question 215

In case of plain carbon steel, butt welded joints are used for shell plate thickness ≤ __________ cms.

Answer 215

3.8

Question 216

The average velocity in the tubes of a 1-4 heat exchanger is __________ times that in 1-1 heat exchanger having the same size & number of tubes and operated at same liquid flow rate.

Answer 216

4

Question 217

Hoop (circumferential) stress induced in a thin walled ‘Horton Sphere’ used for the storage of liquid ammonia under pressure is

Answer 217

pD/2t

Question 218

When one of the fluids is highly corrosive and has fouling tendency, it should

Answer 218

preferably flow inside the tube for its easier internal cleaning.

Question 219

The raio, propeller agitator dia/tank dia is normally taken as

Answer 219

0.15-030

Question 220

A/an __________ is used for changing the direction of a pipeline.

Answer 220

elbow

Question 221

Maximum plate efficiency is achieved in case of __________ flow.

Answer 221

cross

Question 222

The LMTD correction factor (FT) is defined as the

Answer 222

ratio of true temperature difference to the LMTD.

Question 223

The clearance between two tubes in a shell and tube heat exchanger is known as ‘ligament’, whose minimum value is __________ the outside diameter of the tube, but in no case it should be less than 4.5 mm.

Answer 223

one fourth

Question 224

The ratio for the rate of washing to the final rate of filtration in a washing type of plate and frame filter is

Answer 224

0.25

Question 225

Normally, the length to diameter ratio of rotary dryers varies form 4 to 10 and for its economic operation, the number of transfer units (NTU) for such dryers varies from

Answer 225

1.5-2.5

Question 226

Value of Peclet number = 0, is the representative of

Answer 226

complete back mixing.

Question 227

Poisson’s ratio of a material is the ratio of unit lateral strain to the unit axial elongation within its elastic limit. The value of Poisson’s ratio for structural and pressure vessel steel may be taken as

Answer 227

0.3

Question 228

Removable connection of tubes to tube sheet is called

Answer 228

ferrule

Question 229

Typical static submergence for bubble cap plate column operating at atmospheric pressure may be around

Answer 229

0.5”

Question 230

The length of straight rectangular weir used on cross-flow trays is generally __________ the column diameter.

Answer 230

0.6-0.8 times

Question 231

Le/D for couplings and unions would be

Answer 231

negligible

Question 232

What is the slope of the operating line in the rectifying section of a distillation coloumn?

Answer 232

<1

Question 233

Stage efficiency for packed tower varies with the

a. type & size of packing.
b. fluid rates and fluid properties.
c. operating pressure and column diameter.
d. all (a), (b) and (c).

Answer 233

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

Question 234

The minimum plate spacing in most of the pertroleum refinery distillation columns (of dia > 3 ft) is normally __________ inches.

Answer 234

18

Question 235

Joint efficiency (J) for a seamless pipe is

Answer 235

1

Question 236

For a given design of bubble cap, the number of bubble caps to be used per tray is set by the

Answer 236

allowable gas velocity through the slots.

Question 237

The shell side pressure drop in a shell and tube heat exchanger is maximum for __________ baffle.

Answer 237

orifice

Question 238

The function of manholes provided in the shell of a distillation column is to

Answer 238

give access to the individual trays for cleaning, maintenance and installation.

Question 239

Back-trapping in a distillation column results due to

Answer 239

excessive liquid gradient over the tray.

Question 240

For a cylinderical vessel of moderate height, the weld joint efficiency for joints parallel to the cylinderical axis is given as 1.0, while for joints along the girth (circumference) it is given as 0.8. In calculating the shell wall thickness using code formula for an internally pressurised cylinderical vessel, what value of weld joint efficiency should be used?

Answer 240

0.8

Question 241

Diameter of bubble caps used in high pressure columns is __________ as compared to that used in identical vacuum columns.

Answer 241

more

Question 242

The ideal size of round bubble caps to be used in industrial distillation column having a diameter of 3-6 metres is __________ cms.

Answer 242

15

Question 243

Lap joints are preferred for plates having thickness __________ mm.

Answer 243

> 3

Question 244

In a distillation column, minimum clearance to be maintained betweeen the overflow weir and the last row of the bubble caps is __________ cms.

Answer 244

7.5

Question 245

Which of the following lengths of heat exchanger tubes are normally not used in practice ?

Answer 245

10 metres

Question 246

In case of a shell and tube heat exchanger, the effect of L/D on inside film heat transfer co-efficient (hi) vanishes after a Reynold number of

Answer 246

10000

Question 247

Equivalent diameter for heat transfer calculation for a duct of square cross-section having each side as ‘d’ will be

Answer 247

d

Question 248

A cylindrical storage tank can have a self supported conical roof,

Answer 248

if its diameter is less than 15-20metres.

Question 249

For high pressure process equipments/vessels, the connected nozzle should be

Answer 249

flanged

Question 250

Smoker’s equation for the calculation of number of equilibrium stages in a continuous binary distillation column is used, when the

Answer 250

relative volatility is close to one (e.g., separation of close boiling isomers).

Question 251

Column support for the roof of cylindrical storage tank must be provided for

Answer 251

large diameter tanks.

Question 252

For a cylinderical internally pressurised vessel, which of the following closure types would withstand highest pressure, if each closure is of the same material and thickness?

Answer 252

ellipsoidal (2 : 1)

Question 253

In inclined long tube vertical evaporators, the tubes are inclined at an angle of

Answer 253

45°

Question 254

In a continuous distillation column, the optimum reflux ratio ranges from __________ times the minimum reflux ratio.

Answer 254

1.1 to 1.5

Question 255

The wall thickness for a large high pressure pipeline is determined by the consideration of the

Answer 255

circumferential pipewall tension.

Question 256

In the case of a shell and tube heat exchanger, the logarithmic mean temperature difference

Answer 256

is always less than arithmetic average value.

Question 257

Skirt support is the most suitable for supporting __________ vessels.

Answer 257

tall vertical

Question 258

Baffles may be eliminated for

Answer 258

high viscosity liquids (> 600 poise).

Question 259

Generally, as the length of the liquid path on a tray is increased beyond 5 ft, the overall column efficiency

Answer 259

increases

Question 260

In packed absorption tower, onset of flooding usually occurs at a pressure drop of about __________ mm of water column per metre height of packing.

Answer 260

50-75

Question 261

For pipe flows, head is proportional to __________ at constant capacity (where D = pipe diameter).

Answer 261

1/D5

Question 262

Friction factor for turbulent flow in a new pipe is given by

Answer 262

f = 0.04/(NRe)^0.16

Question 263

The minimum tray spacing in distillation column of diameter less than 3 ft is normally __________ inches.

Answer 263

6

Question 264

Oxygen carrying pipelines in chemical industries are coloured with __________ colour.

Answer 264

blue

Question 265

Normally, the ratio of the total riser area to the tower cross sectional area (for bubble cap towers of diameter more than 3 ft) is around

Answer 265

0.1-0.2

Question 266

Pick out the wrong statement about the design of seive plate column and the bubble cap column.
a. The downcomer design and the residence time in the downcomer is almost same for seive plate and bubble cap columns.
b. Weir length for a bubble cap plate is the same as that for the seive plate.
c. Weir height for a bubble cap plate column is the same as that for a seive plate column.
d. Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the seive plate.

Answer 266

Weir height for a bubble cap plate column is the same as that for a seive plate column.

Question 267

Maximum size of the raschig rings used in a packed tower is about __________ of the coloumn diameter.

Answer 267

1/30th

Question 268

Longitundinal stress induced in a thin walled cylindrical storage vessel is

Answer 268

pD/4t

Question 269

The type of stress developed in a metallic bar on subjecting it to a change in temperature without allowing it to be deformed is __________ stress.

Answer 269

thermal

Question 270

The safe distance of habitation from a hazardous chemical plant (TLV of its product < 1000 ppm) should be about __________ kms.

Answer 270

25

Question 271

Pick out the wrong statement pertaining to a shell and tube heat exchanger.
a. The minimum value of baffle spacing is 50 mm.
b. The maximum value of baffle spacing is equal to the I.D. of the shell.
c. The maximum unsupported tube span is generally about 75 times tube diameter, but is reduced to about 60 times for aluminium, copper & alloys of these.
d. Disk and doughnut baffle is the most commonly used baffle.

Answer 271

Disk and doughnut baffle is the most commonly used baffle.

Question 272

Maximum allowable vapour velocity in a bubble cap tower is determined by the

Answer 272

entrainment considerations.

Question 273

Normally, the plate thickness of the bottoms and roofs of vertically cylindrical storage vessels as compared to that of the cylindrical shell is

Answer 273

less

Question 274

The practical representative values of HETP for a number of commercial operations lies within a range of __________ metre.

Answer 274

0.4-0.9

Question 275

Of the pressure vessels, with same thickness but different diameters, which one withstands higher pressure?

Answer 275

Smaller dia vessel.

Question 276

Reflux ratio variation in a distillation column is between

Answer 276

minimum and infinity

Question 277

Width and depth of grooves in the tube sheet holes normally are __________ inch respectively.

Answer 277

1/8 and 1/64

Question 278

In condenser, the cooling water is passed in the tube side in a pass arrangement, because

Answer 278

it reduces heat transfer area.

Question 279

In packed towers provided with pall rings liquid redistributors are positioned at heights of every 6 metres or 5-10 times the column diameter, whichever is less. Maximum size of the pall rings should not exceed __________ of the column diameter.

Answer 279

1/10-1/15th

Question 280

Height of the flights in the rotary drier is in the range of

Answer 280

0.08 to 0.12 d

Question 281

Vapor velocity in a distillation column for non-foaming mixture is in the range of __________ times the flooding velocity.

Answer 281

0.6 to 0.7

Question 282

Cylindrical storage tanks used for the storage of volatile liquids (e.g., naphtha) have __________ roofs.

Answer 282

floating

Question 283

Pick out the wrong statement.
a. Plate efficiency increases with increase in superficial vapour velocity till entrainment limit.
b. Increase in depth of the liquid about the slots increases the plate efficiency, particularly if the liquid depth is < 1”.
c. Too small a plate spacing can cause a low efficiency, if the vapour velocity is greater than the allowable value.
d. none of these.

Answer 283

none of these.

Question 284

Pick out the wrong statement.
a. In practical operation, distillation towers having diameter 3-6 metres equipped with bubble cap (round) size of 15 cms are used.
b. Height of packing in a packed tower is about 3 times the column diameter for raschig rings and about 5 to 10 times the column diameter for saddle packing.
c. In a seive tray, the minimum hole diameter is equal to the tray thickness.
d. In a stainless steel seive tray, the minimum hole diameter is equal to 10 times the plate thickness.

Answer 284

In a stainless steel seive tray, the minimum hole diameter is equal to 10 times the plate thickness.

Question 285

In the downcomer of a distillation column, the minimum recommended residence time is about __________ seconds.

Answer 285

5

Question 286

For identical situation, condensing film coefficient in case of a horizontal condenser is almost __________ the value expected in case of vertical condenser.

Answer 286

thrice

Question 287

Diameter of rivet hole (d, mm) and the plate thickness (t, mm) are related by Unwin’s formula as

Answer 287

d = 1.6 sqrt(t)

Question 288

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

Answer 288

positive

Question 289

In which of the following evaporators, steam is fed inside the tube while the liquor is outside the tube?

a. Long tube vertical evaporator
b. Short tube vertical evaporator
c. Horizontal tube evaporator
d. None of these

Answer 289

Horizontal tube evaporator

Question 290

A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of

Answer 290

2^0.8

Question 291

In a multipass shell and tube heat exchanger, the baffles on shell side is primarily provided for

Answer 291

creating turbulence.

Question 292

For turbine agitator, the impeller diameter is about

Answer 292

0.3 to 0.5 d

Question 293

If a single tube pass heat exchanger is converted to two passes; for the same flow rate, the pressure drop per unit length in tube side will __________ times.

Answer 293

increase by 2^1.6

Question 294

Pick out the wrong statement pertaining to the design of a long tube vertical evaporator.
a. Tube dia is 3-6 cms, while tube length in 3-6 metres.
b. Steam is fed to the shell, whereas the liquor is filled inside the tube.
c. Liquor level is maintained at l/3rd to 1/2 of the height of the tube.
d. none of these.

Answer 294

none of these.

Question 295

Which of the following is the most common type of baffle used in industrial shell and tube heat exchanger?
a. 75% cut segmental baffle.
b. 25% cut segmental baffle.
c. Orifice baffle.
d. Disk and doughnut baffle.

Answer 295

25% cut segmental baffle.

Question 296

What is the minimum recommended ligament for square pitch arrangement in case of heat exchangers?

Answer 296

6.5 mm

Question 297

Pick out the correct statement
a. Centre to centre distance between two consecutives rivets in a row is called the pitch.
b. A rivetted joint made in overlapping plates is called butt joint.
c. Hole size drilled in rivetted plates is less than the actual size of the rivet.
d. none of these.

Answer 297

Centre to centre distance between two consecutives rivets in a row is called the pitch.

Question 298

Safety valves are provided in chemical equipments to guard against excessive

Answer 298

pressure/pressure fluctuation

Question 299

The equivalent diameter for pressure drop is __________ that for heat transfer.

Answer 299

smaller than

Question 300

The distance between the top of the slots and the liquid surface when the static liquid is just ready to flow over the overflow weir is called

Answer 300

static submergence

Question 301

Liquid gradient over the tray results due to the

Answer 301

resistance offered to flow of liquids by caps & risers and the flow of gas.

Question 302

The centre to centre distance between two consecutive baffles in a shell and tube heat exchanger is called the baffle pitch or baffle spacing, which is more than 1/5th the I.D. of the shell. Which of the following is not a function of the baffles?

Answer 302

To increase the tube side heat transfer co-efficient by inducing turbulence.

Question 303

A high vapour velocity is required for high plate efficiency in a seive plate coloumn. The satisfactory value of operating vapor velocity for design purpose in seive plate column is about __________ percent of the flooding velocity.

Answer 303

80

Question 304

The approximate liquid depth in an agitation tank is equal to (where, d = tank diameter)

Answer 304

d

Question 305

Baffle width is normally taken as __________ times the tank diameter.

Answer 305

0.1-0.12

Question 306

A cylinderical pressure vessel of volume 6 πm3 has to be designed to withstand a maximum internal pressure of 10 atm. The allowable design stress of the material is 125N/mm2 and corrosion allowance is 2 mm. The thickness of the vessel for a length/diameter ratio of 3 will be close to

Answer 306

10 mm

Question 307

Which of the following packing materials provides for maximum mass transfer?
a. Lessig rings.
b. Raschig rings.
c. Cross-partition rings.
d. All give the same value.

Answer 307

Cross-partition rings.

Question 308

__________ of water makes it a widely used coolant in heat exchangers.

Answer 308

High specific heat

Question 309

The equivalent diameter for fluid flow through a channel of constant non-circular cross section of area ‘A’ is given by (where, P = perimeter of the channel in contact with the fluid)

Answer 309

4 A/P

Question 310

Fouling factor must be included in the calculation of over all design heat transfer coefficient, when the liquid

Answer 310

containing suspended solids flows at low velocity.

Question 311

Lug support is meant for supporting __________ vessels.

Answer 311

small

Question 312

Overall mass transfer co-efficient in case of absorption of __________ in water is based on the gas film co-efficient only, as the mass transfer process is gas film (phase) controlling.

Answer 312

NH3

Question 313

Which tube arrangement in a heat exchanger would facilitate highest heat transfer rate?

Answer 313

Triangular pitch.

Question 314

In case of 1.5” heat exchanger tubes, the inside flow area __________ with decrease in BWG.

Answer 314

decreases

Question 315

Cylindrical pressure vessels in horizontal condition is generally supported on a __________ support.

Answer 315

saddle

Question 316

Pressure drop per tray in the atmospheric distillation column is about __________ psi.

Answer 316

0.07 - 0.12

Question 317

Welded joint efficiency in the design of chemical process equipment is taken as

Answer 317

0.85

Question 318

The thickness of segmental baffles (25 -35% cut truncated plates usually) is generally __________ the tube wall thickness.

Answer 318

twice

Question 319

The safe height (h) to diameter (d) ratio (i.e., h/d) for liquid/petro fuel storage tank of capacity more than 45 kilolitres is less than

Answer 319

1

Question 320

For given number of passes, pitch & tube diameter, the maximum number of tubes that can be accommodated in a shell of tripled inside diameter will be __________ times.

Answer 320

considerably more than 9

Question 321

The ratio of linear stress to linear strain is termed as the

Answer 321

modulus of elasticity

Question 322

__________ head is the most economical for cylindrical vessels designed for operating at high pressure (> 15 atm.).

Answer 322

Ellipsoidal

Question 323

Bubble cap plate column is

Answer 323

a finite stage contactor.

Question 324

In seive plate column, holes are drilled or punched in sizes ranging from 2.5 to 12 mm (5 mm being widely used). The hole pitch is normally __________ times the hole diameter to give the required hole area.

Answer 324

2.5 to 4.0

Question 325

Pick out the wrong statement.
a. Rivetting provides a permanent fastening method.
b. The joint made by overlapping of one plate over the other, and then rivetting the two plates together with two rows of rivets is called ‘double rivetted butt joint’.
c. Shank diameter of the rivets should be less than the size of the hole drilled in the plate for rivetting.
d. The efficiency of a rivetted joint is the ratio of the strength of the rivetted joint to the strength of the solid plate.

Answer 325

The joint made by overlapping of one plate over the other, and then rivetting the two plates together with two rows of rivets is called ‘double rivetted butt joint’.

Question 326

The force due to wind load acting on a tall vessel depends upon its
a. shape.
b. outside diameter.
c. height.
d. all (a), (b) & (c).

Answer 326

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

Question 327

Bubble cap diameter used for the distillation column having diameter ranging from 1.5 to 4.5 metres is about __________ mm.

Answer 327

100

Question 328

Power required for agitation depends upon the
a. height & properties of the liquid.
b. agitator type & speed of agitation.
c.size of agitator & the tank.
d. all (a), (b) and (c).

Answer 328

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

Question 329

Tube height in a calendria type evaporator is normally less than __________ metres.

Answer 329

2

Question 330

Pick out the wrong statement.

a. Lug supports are less expensive than other type of supports.
b. A pipe is differentiated from a tube by the fact that a pipe has a greater wall thickness compared to the tube.
c. A reducer is used to change the direction of a pipe in a straight run.
d. The method of fixing tubes to a tube sheet by expanding is called ‘tube rolling’.

Answer 330

A reducer is used to change the direction of a pipe in a straight run.

Question 331

For a 25 mm hole drilled in plates to be rivetted, the shank diameter of the rivet should be __________ mm.

Answer 331

23

Question 332

Optimum economic pipe diameter for fluid flow is determined by the

Answer 332

total cost considerations (pumping cost plus fixed cost of the pipe).

Question 333

Pressure differential maintained across a continuous rotary vacuum filter is in the range of __________ mm Hg column.

Answer 333

250 to 500

Question 334

Vertical storage vessels are never supported by __________ support.

Answer 334

saddle

Question 335

In a double pipe (concentric) heat exchanger, the hydraulic radius for heat transfer (for a fluid flowing through the annulus) would be

Answer 335

more than that for fluid flow.

Question 336

Elastic failure of a material occurs, when the tensile stress equals yield strength, yield point or the elastic limit. Also, the elastic failure occurs according to maximum strain theory, when the maximum tensile strain equals (where, σ = yield strength and E = modulus of elasticity)

Answer 336

σ/E

Question 337

In a pressure vessel containing multiple openings of various dimensions at different parts, stress concentration at the edges of the opening is maximum which becomes negligibly small beyond the area covered by __________ times the hole diameter.

Answer 337

two

Question 338

What is the slope of the feed line, if the feed to a distillation column is a saturated liquid?

Answer 338

∞

Question 339

Filtration rate is affected by the
a. pressure drop across the cake & filter medium.
b. cake & filter medium resistance.
c. area of filtering surface & the viscosity of filtrate.
d. all (a), (b) and (c).

Answer 339

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

Question 340

Liquid gradient over a tray can be minimised by
a. providing a higher skirt clearance or a higher weir.
b. decreasing the number of rows of caps through which the liquid flows or by decreasing the velocity of liquid flow past the caps or by reducing the distance along the tray through which the liquid must flow.
c. using split flow, radial flow or cascade flow for column diameter large than 4 ft.
d. all (a), (b) and (c).

Answer 340

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

Question 341

In a shell and tube heat exchanger for a given heat transfer surface area, smaller diameter tubes are favoured as compared to larger diameter ones ; because the smaller diameter tubes

Answer 341

can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less.

Question 342

Le/D for 90° elbow (medium radius) and 90°square elbow would be respectively around

Answer 342

25 and 60

Question 343

__________ heat exchanger is also known as ‘hair pin type’ exchanger,

Answer 343

Double pipe

Question 344

In hydrostatic testing of welded pipe (for leakage, strength etc.) the ratio of minimum hydrostatic test pressure to internal design pressure is around

Answer 344

1.5

Question 345

Frame thickness in the plate and frame filter press is normally in the range of __________ inches.

Answer 345

0.25 to 8

Question 346

Cylinderical shell thickness of rotary drier is generally __________ mm.

Answer 346

6 - 8

Question 347

The ratio of lateral strain to linear strain is termed as the

Answer 347

Poisson’s ratio

Question 348

The distance between the centre of a rivet hole to the nearest edge of the plate is called

Answer 348

margin

Question 349

Mc Cable Thiele method used for finding theoretical stages in a distillation column assumes that the
a. sensible heat differences are small, because the temperature changes from tray to tray is small.
b. Trouton’s rule is applicable.
c. liquid/vapor loading across the column remains constant.
d. all (a), (b) and (c).

Answer 349

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

Question 350

A minimum clearance of about __________ mm is maintained between the distillation column wall and the bubble cap.

Answer 350

38

Question 351

Pick out the wrong statement.

a. If sufficient residence time (around 8 seconds) is not proivided to the downcoming liquid in the downcomer, it may entrain some vapour.
b. The liquid head in the downcomer should not be greater than one half the plate spacing to avoid flooding.
c. The dischare end of the downcomer must project far enough into the tray liquid so that no gas bubbles can enter the open end and by pass the bubble caps.
d. none of these.

Answer 351

none of these.

Question 352

Pick out the wrong statement pertaining to shell and tube heat exchanger.
a. Clearance between shell & baffles and between tube & baffles should be minimum to avoid by-passing of the fluid, but it should be enough to permit the removal of tube bundle.
b. Baffles are supported independently of the tubes by tie rods and positioned by spacers.
c. Tie rods are fixed at one end in the tube sheet by making blind holes and the minimum number of tie rods is 4 with at least 10 mm diameter.
d. Bracket supports are used for horizontal shell, while saddle support is used for vertical shell.

Answer 352

Bracket supports are used for horizontal shell, while saddle support is used for vertical shell.

Question 353

Wind load consideration in the design of a support can be neglected, when the vessel is

Answer 353

short (< 2 m) and housed indoor.

Question 354

The ratio of volumes of the mixed reactor to the plug flow reactor (for identical feed composition, flow rate, conversion, and for all positive reaction orders) is always

Answer 354

> 1

Question 355

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

Answer 355

60

Question 356

Log mean temperature difference in case of multi-pass shell and tube heat exchanger is always

Answer 356

less than arithmetic mean value.

Question 357

Tubes are fixed to the tube sheet (a thick circular metallic plate) by the method of tube rolling and brazing (non-removable) or ferrule connection (removable). Thickness of the tube, sheet is normally __________ the outside diameter of the tube but in no case it should be less than 22 mm (7/8”).

Answer 357

equal to

Question 358

A shell may by termed as thin if its thickness to diameter ratio is less than 0.1. The factor which can be neglected in the calculation of membrane stresses is

Answer 358

bending

Question 359

Scale up problem in design based on the similarity concept takes into account __________ similarity.
a. geometrical
b. kinematic
c. dynamic
d. all (a), (b) and (c)

Answer 359

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

Question 360

__________ closure is the weakest enclosure for cylindrical vessels.

Answer 360

Conical or flat plate

Question 361

Which of the following efficiencies can be greater than 100%?
a. Overall plate efficiency.
b. Murphree plate efficiency.
c. Point efficiency.
d. None of these.

Answer 361

Murphree plate efficiency.