Process Equipment and Plant Design Quiz 5

1 / 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

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

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

2 / 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

3 / 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 standard dished head, the crown radius is ? shell outside diameter

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

4 / 50

Pick out the wrong statement ?

Both B. and C.

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

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

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

5 / 50

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

None of these

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

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

6 / 50

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

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

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

7 / 50

Pick out the wrong statement?

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

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

None of these

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

8 / 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?

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

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

9 / 50

Rate of filtrate delivery is inversely proportional to the_____?

Both A. and B.

Filtering area & the pressure difference driving force

Cake & filter medium resistance

Viscosity of filtrate

10 / 50

Pick out the wrong statement?

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

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

11 / 50

Pick out the wrong statement?

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

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

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

12 / 50

Removable connection of tubes to tube sheet is called_____?

Ferrule

Saddle

Socket

Nipple

13 / 50

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

1.5 to 2.5

5 to 10

0.01 to 1

10 to 20

14 / 50

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

< 4 : 1 for gas-gas exchangers

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

Both B. & C.

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

15 / 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

All A, B. & C.

is more accurate in finding the number of equilibrium stages

16 / 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

17 / 50

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

Higher pressure fluid stream should be routed through the shell side

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

Lower flow rate fluid should be routed through the shell side

The viscous fluid should be routed through the shell side

18 / 50

Saddle supports are used for supporting ______ vessels?

Horizontal cylindrical

Tall vertical

Thick walled vertical

Thick spherical

19 / 50

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

Kinematic

Dynamic

Geometrical

All A., B. and C.

20 / 50

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

The tube bundle is suspended on bracket

There is no central downtake

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

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

21 / 50

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

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

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

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

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

22 / 50

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

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

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

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

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

23 / 50

Reflux ratio variation in a distillation column is between_____?

None of these

Zero and one

Minimum and infinity

Zero and infinity

24 / 50

Shortest distance between two tubes is_____?

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

None of these

Called tube clearance

Called tube pitch

25 / 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 = G

?p = G2

?p = G0.5

?p = 1/G0.6

26 / 50

Pick out the wrong statement?

Liquid metals and Dowtherm are used for very high temperature heating

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

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

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

27 / 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 ______?

0.95

0.3

0.75

0.01

28 / 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

29 / 50

Pick out the wrong statement about distillation operation___________?

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

Distillation under vacuum is a substitute for steam distillation

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

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

30 / 50

Rivets are generally specified by the______?

Head diameter

Overall length

None of these

Shank diameter

31 / 50

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

600 to 700

100 to 150

250 to 500

50 to 100

32 / 50

Pick out the correct statement_____?

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

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

33 / 50

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

Pressure/pressure fluctuation

Turbulence

Noise

Temperature

34 / 50

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

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

Disk and doughnut baffle is the most commonly used baffle

The minimum value of baffle spacing is 50 mm

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

35 / 50

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

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

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

36 / 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________?

180 and 300

300 and 500

45 and 75

5 and 10

37 / 50

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

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

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

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

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

38 / 50

Pick out the wrong statement ?

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

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

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

39 / 50

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

1 ? 3

0.5 ? 1.0

0.01 ? 0.5

0.07 ? 0.12

40 / 50

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

Dished bottom vessel has very high power consumption

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

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

41 / 50

Power required for agitation depends upon the________?

All A., B. and C.

Agitator type & speed of agitation

Size of agitator & the tank

Height & properties of the liquid

42 / 50

Pick out the correct statement?

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

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

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

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

43 / 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 in only stripping section is to be calculated

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

Number of equilibrium stages required is likely to be very small

Feed is not at its bubble point

44 / 50

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

Overall gas transfer units to the number of ideal trays required

Real trays required to the number of ideal trays required

None of these

Ideal trays required to the number of real trays required

45 / 50

Seamless pipe is made_________?

From rolled strips formed into cylinders and seam-welded

Both B. and C.

By extrusion & casting into static and centrifugal molds

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

46 / 50

Pick out the wrong statement ?

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

None of these

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

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

47 / 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

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

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

48 / 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

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

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

49 / 50

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

0 to 0.08

0 to 1.5

0 to 0.8

0 to 2.2

50 / 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?

6% of I.D.

3 times the thickness

Either A. or B., whichever is smaller

Either A. or B., whichever is larger

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