Process Equipment and Plant Design (Set 3)

Question 1

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

Answer 1

Packed

Question 2

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

Answer 2

lower

Question 3

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

Answer 3

ultimate

Question 4

Baffle spacing is generally ____ the I.D. of the shell.
a. more than
b. not greater than
c. not less than one fifth of
d. both (b) and (c)

Answer 4

both (b) and (c)

Question 5

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

Answer 5

more than

Question 6

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

Answer 6

relieving excess pressure.

Question 7

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 7

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

Question 8

In a multipass shell and tube heat exchanger, the problem of differential expansion between the shell and tube passes is taken care of by using a
a. U-bend
b. floating head tube sheet

Answer 8

either (a) or (b)

Question 9

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

Answer 9

called tube pitch.

Question 10

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

Answer 10

preventing the local overstressing of the shell around the opening.

Question 11

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

Answer 11

1.25

Question 12

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 12

2.5-3.0

Question 13

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

Answer 13

0 to 0.08

Question 14

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 14

l/15th

Question 15

Seamless pipe is made

a. from rolled strips formed into cylinders and seam-welded.
b. by extrusion & casting into static and centrifugal molds.
c. by forging a solid round, piercing it by simultaneously rotating & forcing it over a piercer point and further reducing it by rolling gas drawing.

Answer 15

both (b) and (c).

Question 16

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

Answer 16

cross-sectional area.

Question 17

The minimum baffle height should be

Answer 17

twice the impeller diameter.

Question 18

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 18

Di, opt = 3.9 Q0.45 ρ0.13

Question 19

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 19

1.5 d

Question 20

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

Answer 20

1-2

Question 21

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 21

Flat plate extending across the wall

Question 22

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 22

irrespective of the shape of the vessel.

Question 23

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

Answer 23

diamond

Question 24

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 24

10 to 20

Question 25

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

Answer 25

about 3 times

Question 26

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.

Answer 26

none of these.

Question 27

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

Answer 27

pd/4t

Question 28

In distillation columns, bubble caps are held in place over trays by

Answer 28

both (b) and (c)

“a hold down bar” and “bolts”

Question 29

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

Answer 29

least radius of gyration.

Question 30

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

Answer 30

3.8

Question 31

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 31

4

Question 32

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

Answer 32

pD/2t

Question 33

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

Answer 33

preferably flow inside the tube for its easier internal cleaning.

Question 34

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

Answer 34

0.15-030

Question 35

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

Answer 35

elbow

Question 36

Maximum plate efficiency is achieved in case of ____ flow.

Answer 36

cross

Question 37

The LMTD correction factor (FT) is defined as the

Answer 37

ratio of true temperature difference to the LMTD.

Question 38

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 38

one fourth

Question 39

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

Answer 39

0.25

Question 40

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 40

1.5-2.5

Question 41

Value of Peclet number = 0, is the representative of

Answer 41

complete back mixing.

Question 42

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 42

0.3

Question 43

Removable connection of tubes to tube sheet is called

Answer 43

ferrule

Question 44

Stress-strain diagram for low carbon steel/mild steel is shown below in the Fig.
https://www.indiabix.com/_files/images/chemical-engineering/process-equipment-and-plant-design/572-178-1.png The point ‘A’ on the Fig. represents the

Answer 44

elastic limit

Question 45

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

Answer 45

0.5”

Question 46

In the allocated cap area, bubble caps are generally arranged on equilateral triangular pitch. Number of caps fixed on a plate is with a

a. clearance of 25-75 mm.
b. cap pitch of 1.3-2 times the cap diameter.

Answer 46

either ‘a’ or ‘b’.

Question 47

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

Answer 47

0.6-0.8 times

Question 48

Le/D for couplings and unions would be

Answer 48

negligible

Question 49

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

Answer 49

<1

Question 50

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.

Answer 50

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

Question 51

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

Answer 51

18

Question 52

Joint efficiency (J) for a seamless pipe is

Answer 52

1

Question 53

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

Answer 53

allowable gas velocity through the slots.

Question 54

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

Answer 54

orifice

Question 55

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

Answer 55

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

Question 56

Back-trapping in a distillation column results due to

Answer 56

excessive liquid gradient over the tray.

Question 57

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 57

0.8

Question 58

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

Answer 58

more

Question 59

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

Answer 59

15

Question 60

Lap joints are preferred for plates having thickness ____ mm.

Answer 60

> 3

Question 61

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

Answer 61

7.5

Question 62

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

Answer 62

10 metres

Question 63

A pipe is generally made of circular cross-section, because a circular cross-section has the

a. higher structural strength.
b. lowest surface area requirement for a given volume.

Answer 63

both (a) & (b).

Question 64

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 64

10000

Question 65

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

Answer 65

d

Question 66

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

Answer 66

if its diameter is less than 15-20metres.

Question 67

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

Answer 67

flanged

Question 68

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

Answer 68

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

Question 69

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

Answer 69

large diameter tanks.

Question 70

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 70

ellipsoidal (2 : 1)

Question 71

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

Answer 71

45°

Question 72

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

Answer 72

1.1 to 1.5

Question 73

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

Answer 73

circumferential pipewall tension.

Question 74

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

Answer 74

is always less than arithmetic average value.

Question 75

Skirt support is the most suitable for supporting ____ vessels.

Answer 75

tall vertical

Question 76

Baffles may be eliminated for

Answer 76

high viscosity liquids (> 600 poise).

Question 77

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

Answer 77

increases

Question 78

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 78

50-75

Question 79

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

Answer 79

1/D5

Question 80

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

Answer 80

f = 0.04/(NRe)^0.16

Question 81

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

Answer 81

6

Question 82

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

Answer 82

blue

Question 83

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 83

0.1-0.2

Question 84

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 84

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

Question 85

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

Answer 85

1/30th

Question 86

Longitundinal stress induced in a thin walled cylindrical storage vessel is

Answer 86

pD/4t

Question 87

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 87

thermal

Question 88

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

Answer 88

25

Question 89

Pick out the wrong statement pertaining to a shell and tube heat exchanger.

Answer 89

Disk and doughnut baffle is the most commonly used baffle.

Question 90

Corrosion allowance in the design of pressure vessel/chemical equipment is not necessary, if

a. plain carbon steel and cast iron parts are used.
b. wall thickness is > 30 mm.
c. material of construction is high alloy steel.

Answer 90

both (b) & (c).

Question 91

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

Answer 91

entrainment considerations.

Question 92

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

Answer 92

less

Question 93

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

Answer 93

0.4-0.9

Question 94

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

Answer 94

Smaller dia vessel.

Question 95

Reflux ratio variation in a distillation column is between

Answer 95

minimum and infinity

Question 96

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

Answer 96

1/8 and 1/64

Question 97

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

Answer 97

it reduces heat transfer area.

Question 98

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 98

1/10-1/15th

Question 99

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

Answer 99

0.08 to 0.12 d

Question 100

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

Answer 100

0.6 to 0.7