Section 6

Question 1

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

Answer 1

18

Question 2

Joint efficiency (J) for a seamless pipe is

Answer 2

1

Question 3

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

Answer 3

allowable gas velocity through the slots.

Question 4

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

Answer 4

orifice

Question 5

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

Answer 5

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

Question 6

Back-trapping in a distillation column results due to

Answer 6

excessive liquid gradient over the tray.

Question 7

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 7

0.8

Question 8

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

Answer 8

15

Question 9

Lap joints are preferred for plates having thickness __________ mm.

Answer 9

> 3

Question 10

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

Answer 10

7.5

Question 11

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

Answer 11

10 meters

Question 12

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 12

10000

Question 13

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

Answer 13

d

Question 14

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

Answer 14

if its diameter is less than 15-20metres.

Question 15

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

Answer 15

flanged

Question 16

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

Answer 16

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

Question 17

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

Answer 17

large diameter tanks.

Question 18

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 18

ellipsoidal (2 : 1)

Question 19

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

Answer 19

45°

Question 20

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

Answer 20

1.1 to 1.5

Question 21

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

Answer 21

circumferential pipewall tension.

Question 22

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

Answer 22

is always less than arithmetic average value.

Question 23

Skirt support is the most suitable for supporting __________ vessels.

Answer 23

tall vertical

Question 24

Baffles may be eliminated for

Answer 24

high viscosity liquids (> 600 poise).

Question 25

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

Answer 25

increases

Question 26

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 26

50-75

Question 27

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

Answer 27

1/D^5

Question 28

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

Answer 28

6

Question 29

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

Answer 29

blue

Question 30

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 30

0.1-0.2

Question 31

Pick out the wrong statement about the design of seive plate column and the bubble cap column.

The downcomer design and the residence time in the downcomer is almost same for seive plate and bubble cap columns.

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

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

Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the seive plate.

Answer 31

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

Question 32

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

Answer 32

1/30 th

Question 33

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 33

thermal

Question 34

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

Answer 34

25

Question 35

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

The minimum value of baffle spacing is 50 mm.

The maximum value of baffle spacing is equal to the I.D. of the shell.

Disk and doughnut baffle is the most commonly used baffle.

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.

Answer 35

Disk and doughnut baffle is the most commonly used baffle.

Question 36

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

Answer 36

entrainment considerations.

Question 37

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

Answer 37

less

Question 38

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

Answer 38

0.4-0.9

Question 39

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

Answer 39

Smaller dia vessel.

Question 40

Reflux ratio variation in a distillation column is between

Answer 40

minimum and infinity

Question 41

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

Answer 41

1/8 and 1/64

Question 42

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

Answer 42

it reduces heat transfer area.

Question 43

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 43

1/10-1/15th

Question 44

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

Answer 44

0.08 to 0.12d

Question 45

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

Answer 45

0.6 to 0.7