Process Equipment and Plant Design Quiz 5

1 / 50

Shortest distance between two tubes is_____?

More in case of triangular pitch as compared to square pitch of tube layout

Called tube clearance

None of these

Called tube pitch

2 / 50

Pick out the wrong statement pertaining to the design of a basket type evaporator ?

There is no central downtake

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

The tube bundle is suspended on bracket

Downtake is formed by the annular space between the bundle and the shell

3 / 50

Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column ?

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

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

Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provide the maximum flexible operating range

Murphree efficiency of all the three trays are nearly equal, however the peak efficiency is generally higher for sieve and valve trays than the bubble cap

4 / 50

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

Number of equilibrium stages required is likely to be very small

Number of equilibrium stages in only stripping section is to be calculated

Feed is not at its bubble point

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

5 / 50

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__________?

accounts for the enthalpy changes in the process

Facilitates direct calculation of heat load on reboiler & condenser from, the diagram used in this method

is more accurate in finding the number of equilibrium stages

All A, B. & C.

6 / 50

Pick out the wrong statement pertaining to the design of a long tube vertical evaporator ?

Steam is fed to the shell, whereas the liquor is filled inside the tube

None of these

Liquor level is maintained at 1/3rd to 1/2 of the height of the tube

Tube dia is 3-6 cms, while tube length in 3-6 metres

7 / 50

Pressure drop per tray in the atmospheric distillation column is about _________ psi?

0.07 ? 0.12

0.5 ? 1.0

0.01 ? 0.5

1 ? 3

8 / 50

Reflux ratio variation in a distillation column is between_____?

Zero and infinity

Minimum and infinity

Zero and one

None of these

9 / 50

Pressure drop due to pipe fittings can be estimated by the equation, ?P/? = 4f, (Le/D) (V2/2gc) where, Le = equivalent length of straight pipeline which will incur the same frictional loss as the fitting and D = diameter of the fitting. The value of (Le/D) (dimensionless) for 45? elbow and 180? close return bends would be respectively around________?

300 and 500

180 and 300

45 and 75

5 and 10

10 / 50

Pick out the wrong statement about distillation operation___________?

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

Distillation under vacuum is a substitute for steam distillation

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

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

11 / 50

Power required for agitation depends upon the________?

Height & properties of the liquid

Size of agitator & the tank

Agitator type & speed of agitation

All A., B. and C.

12 / 50

Pick out the wrong statement ?

Too small a plate spacing can cause a low efficiency, if the vapour velocity is greater than the allowable value

Increase in depth of the liquid about the slots increases the plate efficiency, particularly if the liquid depth is < 1"

Plate efficiency increases with increase in superficial vapour velocity till entrainment limit

None of these

13 / 50

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______?

Less

Twice

Same

14 / 50

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

100 to 150

50 to 100

250 to 500

600 to 700

15 / 50

Pick out the wrong statement?

Liquid metals and Dowtherm are used for very high temperature heating

A loop seal or U-seal is provided in a vertical condenser sub-cooler to prevent quick draining of the condensate

Safety valves are provided in heat exchangers for removal of non-condensable

In a shell and tube heat exchanger, high pressure fluid is generally routed through the tube

16 / 50

Pick out the wrong statement?

The liquid head in the downcomer should not be greater than one half the plate spacing to avoid flooding

None of these

If sufficient residence time (around 8 seconds) is not provided to the downcoming liquid in the downcomer, it may entrain some vapour

The discharge 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

17 / 50

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

10 to 20

5 to 10

1.5 to 2.5

0.01 to 1

18 / 50

Saddle supports are used for supporting ______ vessels?

Thick spherical

Thick walled vertical

Horizontal cylindrical

Tall vertical

19 / 50

Safety valves are provided in chemical equipments to guard against excessive__________?

Pressure/pressure fluctuation

Turbulence

Temperature

Noise

20 / 50

Pick out the correct statement_____?

A riveted joint made in overlapping plates is called butt joint

Hole size drilled in riveted plates is less than the actual size of the rivet

None of these

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

21 / 50

Pick out the wrong statement ?

The method of fixing tubes to a tube sheet by expanding is called ?tube rolling?

A pipe is differentiated from a tube by the fact that a pipe has a greater wall thickness compared to the tube

Lug supports are less expensive than other type of supports

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

22 / 50

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 ______?

0.75

0.95

0.01

0.3

23 / 50

Pick out the wrong statement ?

Fouling factor of river water is less than that of sea water

Risers provided in bubble cap trays in the distillation column facilitate the flow of both liquid and vapor

For all the cylindrical process vessels operating above atmospheric pressure, formed heads are used for closing the vessel

Both B. and C.

24 / 50

Pick out the wrong statement?

The joint made by overlapping of one plate over the other, and then riveting the two plates together with two rows of rivets is called ?double riveted butt joint?

Shank diameter of the rivets should be less than the size of the hole drilled in the plate for riveting

Riveting provides a permanent fastening method

The efficiency of a riveted joint is the ratio of the strength of the riveted joint to the strength of the solid plate

25 / 50

Seamless pipe is made_________?

By forging a solid round, piercing it by simultaneously rotating & forcing it over a piercer point and further reducing it by rolling gas drawing

Both B. and C.

By extrusion & casting into static and centrifugal molds

From rolled strips formed into cylinders and seam-welded

26 / 50

Pick out the wrong statement. In an agitated vertical cylindrical reaction vessel, the_____?

Dished bottom vessel has very high power consumption

Filling ratio for dispersing gas in a liquid is 2 for sufficiently long contact period

Flat bottom and conical bottom vessels have low agitation efficiency for agitation of heavy solids in liquids

Ratio of liquid depth to tank diameter (i.e. the filling ratio) recommended for most purposes is 1

27 / 50

Practical dividing line between a ductile and brittle materials is suggested, when the ultimate elongation is about 5%. Generally, larger the knuckle radius, stronger is the corner torus section of a head. The knuckle radius provided should be less than _______ of the head?

3 times the thickness

6% of I.D.

Either A. or B., whichever is larger

Either A. or B., whichever is smaller

28 / 50

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

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

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

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

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

29 / 50

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

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

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

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

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

30 / 50

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

?p = G2

?p = G0.5

?p = 1/G0.6

?p = G

31 / 50

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

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

The viscous fluid should be routed through the shell side

Lower flow rate fluid should be routed through the shell side

Higher pressure fluid stream should be routed through the shell side

32 / 50

Scale up problem in design based on the similarity concept takes into account ________ similarity?

Dynamic

Kinematic

All A., B. and C.

Geometrical

33 / 50

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

None of these

Generally, a skirt clearance of 0.5? to 1.5? is recommended to prevent plugging of the slots by residue build up

If sufficient slot area is not provided, the gas may pass through the skirt clearance

The purpose of the slot is to disperse the gas into the liquid in the form of small bubbles

34 / 50

Rivets are generally specified by the______?

Shank diameter

Head diameter

None of these

Overall length

35 / 50

Pick out the wrong statement ?

Flanged only head is a type of flat head in which gradual change in the shape at the centre results in reduced local stresses

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

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

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

36 / 50

Pick out the wrong statement?

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

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

In a sieve tray, the minimum hole diameter is equal to the tray thickness

In practical operation, distillation towers having diameter 3-6 metres equipped with bubble cap (round) size of 15 cms are used

37 / 50

Pick out the correct statement?

Draining of residual liquid on tray during shut down of distillation column is facilitated by weep holes

It is preferred to use a vertical condenser for condensation of vapor from a distillation column without sub-cooling

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

Random packing a packed tower offers the advantage of lower pressure drop and higher throughput of fluids as compared to regular/stacked packing

38 / 50

Pick out the wrong statement about the design of sieve plate column and the bubble cap column ?

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

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

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

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

39 / 50

Pick out the wrong statement?

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

The tensile strength of a brittle material is less than its compressive strength

The compressive strength of a ductile material is less than its tensile strength

In a thick cylindrical shell, the hoop stress is maximum at the inner radius

40 / 50

Pick out the wrong statement pertaining to shell and tube heat exchanger________?

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

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

Baffles are supported independently of the tubes by tie rods and positioned by spacers

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

41 / 50

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

Ideal trays required to the number of real trays required

None of these

Real trays required to the number of ideal trays required

Overall gas transfer units to the number of ideal trays required

42 / 50

Removable connection of tubes to tube sheet is called_____?

Saddle

Socket

Nipple

Ferrule

43 / 50

Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower ?

Plate tower is preferred over packed tower, if the operation involves liquids containing dispersed solids

Plate tower is preferred, if interstage cooling is required to remove heats of reaction or solution

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

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

44 / 50

Slope of counter-current flow rotary drier is in the range of _____ meter/metre?

0 to 0.08

0 to 2.2

0 to 1.5

0 to 0.8

45 / 50

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

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

The minimum value of baffle spacing is 50 mm

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

46 / 50

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

4 : 1 to 8 : 1 for liquid-liquid exchanger

8 : 1 to 12 : 1 for both liquid-liquid and gas-gas heat exchangers

< 4 : 1 for gas-gas exchangers

Both B. & C.

47 / 50

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?

150

48 / 50

Pick out the correct statement ?

When highly corrosive fluids are to be handled, the plate towers prove to be cheaper and easier to construct than packed tower

The pressure drop through the packed towers is generally more than the pressure drop through plate towers designed for same duty

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

None of these

49 / 50

Pick out the wrong statement pertaining to ?Horton sphere? used for the storage of liquid ammonia ?

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

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

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

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

50 / 50

Rate of filtrate delivery is inversely proportional to the_____?

Viscosity of filtrate

Filtering area & the pressure difference driving force

Cake & filter medium resistance

Both A. and B.

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