Process Equipment and Plant Design Part 1 Flashcards by Chris Wilfred Estrada

Fresh water carrying pipelines in chemical industries are coloured with __________ color.
sea green
brown
yellow
red

sea green

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Which of the following material is seldom used for pressure vessel construction ?
Rimmed still
Mild steel
Killed steel
Semi-killed steel

Rimmed still

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The ratio of shear stress to shear strain is called
bulk modulus
shear modulus
modulus of rigidity
modulus of elasticity

shear modulus

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25 per cent cut segmental baffle means that the baffle
height is 75% of the I.D. of the shell.
height is 25% of the I.D. of the shell.
spacing is 75% of its height.
width is 25% of its height.

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

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Liquid/petroleum fuel storage tanks are built underground (as in case of petrol pumps), when the storage capacity is less than __________ kilolitres.
20
30
45
85

less tahn 45 kL liquid/petroleum fuel storage tanks

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Le/D for fully open globe value may be around
10
25
75
300

300

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

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

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Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column.
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.
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.
Maintenance cost for valve and seive trays are comparatively more than bubble cap tray due to their relatively complicated construction features.
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.

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

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With increase in the number of shell passes, the value of FT
increases
decreases
remains same
remains same, only if the number of tube passes does not change.

increases

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Holes of a sieve tray are arranged in triangular pitch of __________ times the hole diameter.
1.5 to 2
2.5 to 5
5 to 10
10 to 15

2.5 to 5

sieve tray holes 2.5 to 5 triangular pitch

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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.
3-5
5-11
8-15
12-18

5~11

keywords: carbon steel, minimum thickness, 5-11

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The stress developed in a material without any permanent set is called the
ultimate stress
yield stress
elastic limit
breaking stress

elastic limit

keywords: stress, without, permanent set, elastic limit

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In a shell and tube heat exchanger, the ‘tube pitch’ is defined as the
O.D. of the tube for square pitch.
shortest distance between two adj acent tube holes.
shortest centre to centre distance between adjacent tubes.
none of these.

shortest centre to centre distance between adjacent tubes.

keywords:
pitch - shortest centre to centre
clearance - shortest distance

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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 ?
Sensible heat changes for vapour & liquid are negligibly small.
Reflux is not a saturated liquid.
Molar latent heat of the two components are equal.
Heat of mixing of normal liquid is assumed to be zero.

Reflux is not a saturated liquid.

keywords: negligible sensible, equal molar, zero heat of mixing
mnemonic: SMH (shaking my head)
sensible, molar, heat of mixing

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Overall distillation column efficiency for most of the refinery columns can be given by (for u = 0.07 - 1.4 cp and relative volatility < 4) (where n = overall column efficiency, % u = molal average viscosity of feed at average column temperature and pressure, cp delta(p) = pressure drop per tray, psi)
n = 17 - 61.1 log u
n = 24.6[delta(p)/u]
n = 1.66 - 0.25 log u
n = 0.25 log u - 1.67

n = 17 - 61.1 log u

keywords/keynumbers: 17, 61.1

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

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

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In case of bubble cap distillation column of diameter greater than 1.2 metres, the cap diameter is roughly about __________ cms.
10
20
30
35

bubble cap 1.2m 10cm

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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.
2
1/2
4
8

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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
(1.2)^3/2
(1.2)^3/5
(1.2)^2/3
(1.2)^5/3

(1.2)^5/3

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Where does the maximum tensile strength occur in a thick cylindrical vessel subjected to internal pressure ?
At the inner surface.
At the mid thickness of the cylindrical wall.
At the outer surface.
None of these.

At the inner surface.

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It is not desirable to design a heat exchanger for LMTD correction factor, FT, of less than
0.99
0.95
0.80
0.55

0.8

0.8 not desirable LMTD cf

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

none of these

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Bracket supports are the most suitable for supporting __________ vessels.
thick walled vertical
horizontal
thin shperical (e.g. Horton sphere)
none of these

thick walled vertical

thick vertical bracket support

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In a multipass shell and tube heat exchanger, the shell side cross flow area does not depend upon
baffle spacing
clearance
pitch
none of these

none of these

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Two iron pipes of the same nominal diameter but different schedule numbers will have the same inside diameter outside diameter wall thickness none of these

inside diameter

Steam side heat transfer co-efficient for design consideration under ordinary condition can be assumed to be about __________ kcal/hr.m^2.C. 1250 2500 7500 15000

7500

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 __________%. 5 20 35 55

20 ## Footnote 20LRAI Lessing-raschig area increase 20

In chemical process equipments, the conical bottom heads used, usually has an apex angle of 20 degrees 40 degrees 60 degrees 80 degrees

60 degrees

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. 25 50 75 150

75 ## Footnote large ones of size... 75 mm... stacked individually

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 more same less twice

less

Correct use of 'factor of safety' is very important in equipment design. It is defined as the ratio of the ultimate stress to breaking stress. ultimate stress to working stress. working stress to ultimate stress. none of these.

ultimate stress to working stress.

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. 1-5 20-40 100-150 1000-1500

20-40 ## Footnote keywords: packed column, pressure drop, 20-40 mm

__________ tray arrangement is recommended for distillation column having diameter upto 4 ft. Radial flow Cross flow Split flow Cascade

Cross flow ## Footnote keywords: cross flow, distillation, 4 ft

What is the value of 'q' for saturated liquid feed to a distillation column ? 0 <1 1 >1

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

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

The main purpose of providing stepping on the trays is to increase the residence time. decrease the pressure drop. facilitate handling of large flow rate of liquid. improve the flow condition.

facilitate handling of large flow rate of liquid. ## Footnote stepping...facilitate

The operating pressure drop range in a bag filter is about __________ mm water gauge. 50-150 5-10 500-1500 1500-2500

50-150 ## Footnote 50-150 mm operating pd bag filter

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. Flat plate Hemispherical Torispherical Ellipsoidal

Ellipsoidal ## Footnote keywords: elipsoidal, highest pressure

For laminar flow (NRe < 2100) in steel pipe, the optimum inside pipe diameter is given by Di, opt = 3 Q^0.36 (rho)^0.18 Di, opt = 3.9 Q^0.45 . (rho)^0.23 Di, opt = 7.6 Q^0.36 . (rho)^0.9 Di, opt = 3 Q^0.36 . (rho)^1.86 (mu)^0.08

Di, opt = 3 Q^0.36 (rho)^0.18 ## Footnote keywords/keynumbers: 3, 0.36, 0.18

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. Packed towers are generally preferred over plate towers, if the liquids have a foaming tendency. The pressure drop through the packed towers is generally more than the pressure drop through plate towers designed for same duty. none of these.

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

Pick out the wrong statement pertaining to the design of a basket type evaporator. It is used for high viscosity liquor having large rate of scaling. 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. ## Footnote wrong...basket..high viscosity

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. The pressure drop due to the caps & slots and the static submergence should be as high as practicable for reasonable operation. 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. The dimensionless ratio of liquid gradient to pressure drop head caused by the bubble cap assembly should be less than 0.4. none of these.

none of these.

Speed of the drum of the rotary vacuum filter normally ranges from __________ rpm. 0.1 to 2 5 to 7 3 to 8 8 to 15

0.1 to 2 ## Footnote 0.1 to 2 rpm rotary vacuum drum

A stuffing box is used for absorbing the contraction/expansion of pipeline due to temperature changes. prevention of fluid leakage around moving parts. facilitating smooth opening and closing of a valve. reducing the resistance of fluid flow.

prevention of fluid leakage around moving parts. ## Footnote stuffing box... prevention...

Pressure drop (delta(p)) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as delta(p) = G delta(p) = G0.5 delta(p) = G2 delta(p) = 1/(G^0.6)

delta(p) = G2

Pick out the wrong statement. In an agitated vertical cylinderical reaction vessel, the 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. dished bottom vessel has very high power consumption.

dished bottom vessel has very high power consumption. ## Footnote wrong...dished...very high power

Needle valves are generally not used for very large diameter pipes. high pressure throttling service. very accurate flow control. smaller sizes of pipe.

very large diameter pipes.

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

all a, b & c.

Pick out the wrong statement. Safety valves are provided in heat exchangers for removal of non-conden-sables. 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. 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-conden-sables.

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 increases decreases remain unaffected none of these

decreases

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 central dished section and corner torus section. corner torus section and central dished section. central dished section and straight flange section. straight flange section and corner torus section.

central dished section and corner torus section.

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

Allowable vapour velocity. ## Footnote vapor velocity - set diameter

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 is more accurate in finding the number of equilibrium stages. 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'.

all 'a', 'b' & 'c'.

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 equal sized reactors are the best. smaller reactor should come first. larger reactor should come first. none of these.

smaller reactor should come first.

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? Sorel-Lewis method. McCabe-Thiele's method. Ponchon-Savarit method. none of these.

Sorel-Lewis method.

Saddle supports are used for supporting __________ vessels. horizontal cylinderical tall vertical thick walled vertical thick spherical

horizontal cylinderical ## Footnote saddle - horizontal cylindrical bracket - thick walled vertical

The diameter of a propeller agitator used in agitation tank ranges from __________% of the tank diameter and its peripherial speed is normally 300 to 500 metres/minute. 5 to 10 15 to 30 40 to 50 55 to 75

15 to 30

In packed towers provided with saddle packing, liquid redistributors are positioned at every __________ times column diameter or 6 metres whichever is less. 2-3 5-8 10-15 20-25

5~8

Optimum reflux ratio in a continuous distillation column is determined by the maximum permissible vapour velocity. flooding limit of the column. total cost consideration (fixed cost of the column plus the cooling water & steam cost). none of these.

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

Cooling water fouling factors vary in the range of 0.001 to 0.003 (BTU/hr.ft^2 . F)^-1 (kcal/hr.m^2 .C)^-1 (W/m^2. K)^-1 (kcal/hr. m. C)^-1

(BTU/hr.ft^2 . F)^-1

Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter ) 0.2 D 0.5 D 0.66 D 0.80 D

0.2 D

The maximum liquid gradient over a tray must not exceed 0.5" -1.25". 2"-3.5". 5". half the tray spacing.

0.5" -1.25".

An underdesigned steam trap will waste steam. destroy itself of acceleration wear due to rapid recycling. back up condensate and cause water hammer in steam line. none of these.

back up condensate and cause water hammer in steam line.

The slope of the feed line in distillation opeartion is given by (where, q = fraction of the feed stream that is liquid.) -q -q/(1-q) -q/(q-1) none of these

[-q/(1-q)]

Speed of industrial paddle agitator ranges from __________ rpm. 1 to 5 20 to 100 500 to 750 1000 to 2000

20 to 100

__________ strain is measured using a 'strain rosetter'. Volumetric Shear Linear none of these

Linear ## Footnote LSR Linear Strain Rosetter

With increase in the reflux ratio for a fixed production from a continuous binary distillation column, the __________ decreases. fixed charges initially running cost of cooling water for condenser vapour & liquid load both running cost of steam for reboiler

fixed charges initially

The slope of operating line in the rectifying section of a distillation column is unity, if the reflux ratio is 0 infinite 1 minimum

infinite

Vertical vessels are not supported by brackets skirts columns saddles

saddles

With increase in pressure drop (for a given particle size), the dust collection efficiency of a cyclone separator will increase decrease remain unaffected increase or decrease depending on the nature of the dust.

increase

Spherical shaped pressure vessel is considered to be the most ideal, because it can withstand higher pressure for a given metallic shell thickness. be fabricated very easily. be designed without wind load considerations. be supported very easily.

withstand higher pressure for a given metallic shell thickness.

An adequate clearance between the tray and the shell wall of a distillation column is provided to drain the liquid from the tray when the unit is not in operation. allow for thermal expansion and facilitate installation. avoid back-trapping. none of these.

allow for thermal expansion and facilitate installation.

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. ideal trays required to the number of real 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. ## Footnote ideal/real overall tray eff.

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.

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. ## Footnote wrong... Minimum recommended downcomer

Generally, no corrosion allowance in wall thickness of a part is required, if the thickness is more than __________ mm. 10 20 30 5

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. 0.1 to 0.25 0.3 to 0.5 0.5 to 0.6 0.65 to 0.80

0.1 to 0.25

In a __________ rivetted joint, the rivets in the various rows are opposite to each other. zig-zag chain diamond none of these

chain

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

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

Generally, elliptical dished heads 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/m^2 . resist half the pressure rating compared to hemi spherical head provided on the cylindrical shell of the same thickness and diameter. are approximately as strong as seamless cylindrical shell having the corresponding I.D and O.D. all (a), (b) and (c)

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

Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower. Plate tower is perferred, 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. 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.

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

The circumferential (hoop) stress in a thin walled cylinderical vessel under internal pressure is pd/2t pd/4t pd/t pd/3t

pd/2t

LMTD correction factor is used in heat exchanger design for double pipe heat exchanger. multipass shell and tube heat exchanger. fouling fluids. counter flow of hot and cold fluids.

multipass shell and tube heat exchanger. ## Footnote LMTD cf multipass

Floating head heat exchangers are used for the heat transfer between corrosive fluids. cases where temperature difference between the shell and the tubes is more (>50C). co-current heat transfer systems. counter-current heat transfer systems.

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

The most common standard size of bubble caps used in industrial operation is 1" dia cap with 0.5" dia riser. 6" dia cap with 4" dia riser. 8" dia cap with 1" dia riser. 4" dia cap with 8" dia riser.

6" dia cap with 4" dia riser. ## Footnote 6"4" most common standard bubble cap

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. nozzle or rim flared out fluid in ring plate

nozzle or rim

In case of a continuous distillation column, increase in reflux ratio may result in the lower fixed charges for the column. greater cost for the reboiler heat supply. greater cost for the condenser coolant. all (a), (b) and (c).

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

In a distillation column, the minimum residence time for liquid in the downspout is about __________ seconds. 1 8 80 180

8 ## Footnote 8 downspout minimum residence

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

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

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. 0.3 to 0.8 1.25 to 3.125 3.5 to 7.0 8-12

1.25 to 3.125 ## Footnote plate HE grooves & corrugations 1.25 to 3.125

Rivets are generally specified by the head diameter shank diameter overall length none of these

shank diameter

Length to diameter ratio of most rotary driers is in the range of 1 to 2 4 to 10 10 to 20 20 to 30

4 to 10

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. 16 19 28 38

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. 300 600 1000 1500

600

The dust collection efficiency of a cyclone separator decreases with increase in gas flow rate. is inversely proportional to the mass of the dust particle. is directly proportional to the radius of the dust particle path. none of these.

none of these. ## Footnote dust collection eff... none of these

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 infinity 1 20.8 2

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

A vapor phase reactor.

In a bag filter, the pressure drop increases directly as the density of the gas, but is independent of the viscosity of the gas. density of the gas and inversely as viscosity of the gas. viscosity of the gas and inversely as density of the gas. none of these.

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

The LMTD correction factor (FT) is applied in __________ heat exchangers. 1-1 cocurrent double pipe all multipass all (involving liquid/liquid heat transfer)

all multipass

Movement of pipeline caused by thermal expansion is taken care by providing expansion joint. changes in its direction. change in the shape of pipeline. all (a), (b) and (c).

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

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 decreases upwards. increases upwards. remains same throughout. may decrease or increase upwards depending upon whether vacuum or positive pressure would be maintained inside the shell.

decreases upwards.

In the design of a paddle agitator, the ratio paddle dia/tank dia is normally taken as 0.1 0.8 0.25 0.5

0.8 ## Footnote 0.8 paddle/tank

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. working damaging allowable none of these

damaging

Hole diameter of the seive trays in the distillation column ranges from __________ mm. 1 to 3 4 to 8 3 to 12.5 12.5 to 18.5

3 to 12.5

Factor of safety (i.e., overdesign factor) in heat transfer equipments is about __________% more than the actual/theoretical design factor. 5-10 15-20 30-35 35-40

15-20

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 d1/(d1+d2) d2/(d1+d2) (d2+d2)/d1 (d2+d2)/d2

d1/(d1+d2)

In actual operation of distillation column, the vapour is not distributed uniformly among the bubble caps, primarily because of the liquid gradient on the tray. lower skirt clearance. lower static submergence. small downcomer liquid seal.

liquid gradient on the tray. ## Footnote vapor not distributed uniformly... because of...liquid gradient

The minimum shell thickness for tank =< 15 metres diameter is limited to __________ mm, for reasons of elastic stability. 2 5 10 15

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 D/2 or minimum 2" to 5D. D/5 or minimum 2" to 5D. D/5 or minimum 2" to D. none of these.

D/5 or minimum 2" to 5D. ## Footnote keywords: D525D

Brass valves are usually made for pipe sizes __________ inches. =<1 =<2 >2.5 >3.5

=<2

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 increases decreases remains same may increase or decrease depending upon the solubility of the gas in the liquid

remains same

In a shell and tube heat exchanger, triangular pitch arrangement as compared to square pitch arrangement results in higher shell side pressure drop. can accomodate less number of tubes for a given shell diameter. facilitates easier shell side cleaning; hence is more suitable for handling high dirt factor shell side fluid. creates relatively lower turbulence on the shell side resulting in lower shell side heat transfer co-efficient.

results in higher shell side pressure drop. ## Footnote triangular compared to square.... results in higher...

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.

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

The necessary wall thickness for a metallic storage vessel is a function of the ultimate tensile strength (or yield point) of the material and operating temperature. operating pressure and welding/joint efficiency. diameter of the vessel. all (a); (b) and (c).

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

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. 'n'th (1/n)th 0.5 nth 1.5 nth

(1/n)th

Pick out the wrong statement 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. Flat head covers are most suitable for larger vessels operating at very high pressure. 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.

Pick out the wrong statement pertaining to the design of a horizontal tube evaporator. 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. Liquor flows inside the tube, while the steam is outside submerging the tube.

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

Weep holes provided in the plates of a distillation column facilitate draining out liquid from a tray when the unit is not in operation. are normally located near the overflow weir so that any delivery of liquid during operation follows approximately the same path as the overflow fluid. must be large enough (usually 1/4" to 5/8" dia) to prevent plugging but should not deliver excessive amount of fluid during operation. all (a), (b) and (c).

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

Steam is preferred to be used as a heating medium in heat exchangers, because of its low cost. high latent heat. non-corrosive condensate. high film co-efficient.

high latent heat.

__________ shapedroof is the most commonly used roof for cylinderical storage tanks. Conical Flat Dome Umbrella

Conical

Pick out the wrong statement pertaining to 'Horton sphere' used for the storage of liquid ammonia. Diameter of Horton sphere is normally 6 to 25 metres and it is supported by 6 to 12 nos. tubular or rolled section column. 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. Horton sphere is used for the storage of gases and volatile liquid at a moderate pressure of 1 to 10 kg/cm^2 . Horton sphere is used for the storage of liquid at sub-zero temperature at very high pressure upto 200 kg/cm^2 .

Horton sphere is used for the storage of liquid at sub-zero temperature at very high pressure upto 200 kg/cm^2 .

Value of Peclet number Le/D = infinity, is the representative of laminar flow. complete back mixing, plug flow. eddy diffusivity = 0.

plug flow.

In most of the shell and tube heat exchangers, the tube pitch is generally __________ the tube diameter. less than 1.25-1.50 times 2.5 times one-fourth of

1.25-1.50 times

In a distillation column, bubble caps are located on trays with a pitch of __________ times the outside diameter of the caps. 1.3 to 2 1.6 to 2 2.5 1.5 to 3

1.3 to 2

1.2 to 3.8 cms is the value of the downcomer liquid seal in case of a balanced tray design. static submergence in case of a bubble cap tray for column operating under pressure (>= 1 atm.). skirt clearance for bubble caps. all (a), (b) and (c).

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

Accidents in chemical plants are mostly due to inadequate equipment design. faulty operating procedures. improper layout of the equipments. failure of equipments.

faulty operating procedures.

For identical operating conditions, the pressure drop over __________ tray is the highest out of the following. sieve valve counterflow bubble cap

bubble cap

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 (ph - dh)/ph [ph - dh (dt/2) ]/ph (ph - dt)/ph (ph - dh)/dh

(ph - dt)/ph

__________ is the determining factor for the number of bubble caps to be used per tray. Permissible slot velocity Tray diameter Liquid load Vapor load

Permissible slot velocity

Pick out the wrong statement about distillation operation Distillation under vacuum is a substitute for steam distillation. In differential (simple) distillation, the vapour is removed as soon as it is formed without appreciable condensation. 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.

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

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). 250 450 650 750

650 ## Footnote 650 mmHg vacuum evaporators

Which of the following is the best tube material from thermal conductivity point of view alone? Aluminium Stainless steel Copper Carbon steel

Copper

Normal screwed fittings are used for pipes upto a diameter of __________ inches. 1.5 3 5 7

3 ## Footnote normal screwed up to 3

In a shell and tube heat exchanger, the clearance of the tube is generally not less than one-fourth of the tube diameter or 3/16". more than the tube diameter. equal to the tube diameter. more in case of triangular pitch as compared to the square pitch tube layout.

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

Diameter of the seive tray column is determined by the lower limit of vapour velocity. upper limit of the vapour velocity. hole diameter of the seive tray. height of the plate spacing.

upper limit of the vapour velocity.

For a given fluid, as the pipe diameter increases, the pumping cost decreases. increases. remains unaffected. may increase or decreaes depending upon whether the fluid is Newtonian or non-Newtonion.

decreases.

Maximum acceptable total liquid gradient over a tray is about __________ mm. 5.5 12.5 30.5 45.5

12.5 ## Footnote MLG12.5 max liq grad

In case of a 'thin' pressure vessel, the ratio of its diameter to wall thickness is < 10 > 10 > 20 30

> 10

High pressure fluid in a shell and tube heat exchanger should preferably be routed through the tubes to avoid the expansion of high pressure shell construction. shell side for smaller total pressure drop. shell side, if the flow is counter-current and tube side if the flow is co-current. shell side for large overall heat transfer co-efficient.

tubes to avoid the expansion of high pressure shell construction.

Bubble cap tray is the most commonly used tray in large distillation column, because of its flexibility and nearly constant efficiency under varying conditions of operation. it incurs less pressure drop as compared to any other try designed for the same duty. it eliminates the foaming and entrain-ment tendency during operation. none of these.

of its flexibility and nearly constant efficiency under varying conditions of operation. ## Footnote bubble cap most commonly used....flexibility

In common bubble cap distillation column design practice, riser area is approximately equal to (where, Aa = Annular passage area, and Sa = Slot area) Aa = Sa 1.2 Aa = 1.2 Sa Sa = 1.5 Aa Aa = 1.5 Sa

Aa = Sa

Heat transfer co-efficient, hG(Kcal/hr.m^2.C) and mass velocity of air, G(kg/hr.m^2 ) for air flow parallel to the surface in case of constant drying rate in batch drying is related as hG = 0.0176G^0.8. But when the flow of air perpendicular to the surface is encountered, this equation changes to hG = 1.004G^0.37 hG = 1.004G^0.8 hG = 0.0176G^0.37 hG = 0.0176G^1.37

hG = 1.004G^0.37

In the agitators, the power required will be changed with the increase of diameter of agitator (D) as D^2 D^5 D D^9

D^5

Apex angle of conical heads used in the bottom heads of chemical process equipments is usually 30 degrees 45 degrees 60 degrees 75 degrees

60 degrees ## Footnote 60 apex conical

A pressure vessel is said to be made of 'thick' shell, if the ratio of its diameter to wall thickness is 10 10 20 20

Tube side heat transfer co-efficient for turbulent flow of liquid through tubes is proportional to G^0.2 G^0.5 G^0.8 G^1.5

G^0.8

Circumferential (hoop) stress in a thin cylindrical vessel under internal pressure is _________ the longitudinal stress. half equal to twice eight times

twice

For storing hazardous chemicals in large storage tanks, the minimum safe distance between the two tanks should range between __________ times the tank diameter 1 to 1.5 2.5 to 3.5 4 to 5 6 to 8

1 to 1.5 ## Footnote storing hazardous - 1 to 1.5

Which of the following factors determine the amount of entertainment in a distillation column? Plate spacing. Depth of liquid above the bubble cap slots. Vapour velocity in the volumn between the plates. All (a), (b) and (c)

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

The absorption factor is defined as (where, S1 = slope of the equilibrium curve, S2 = slope of the operating line) S1/S2 S1 * S2 S2 / S1 1/S1*S2

S1/S2

In shell and tube heat exchangers, straight tie rods are used to hold baffle in space. fix the tubes in position. account for thermal strain. none of these.

hold baffle in space. ## Footnote straight tie - hold baffle

In a rotary drier, the average retention time of solid is (where Z = length of the drier, metres rho = apparent solid density, kg/m^3 L = flow rate of dry solids, kg/see*m^2 drier cross-section H = hold up of solid.) (Z * H * rho)/L L/(Z * H * rho) (H * rho)/L (Z * H)/(L * rho)

(Z * H * rho)/L

In case of design of a shell and tube heat exchanger, minimum cleaning lane of 6.5 mm is provided, when tubes are on a square pitch. 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. 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. all (a), (b) & (c).

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

In a cylinderical vessel subjected to internal pressure, the longitudinal stress sigma-L and the circumferential stress, sigma-n are related by sigma-h = 2 sigma-L sigma-h = sigma-L sigma-h = sigma-L/2 no relation exists

sigma-h = 2 sigma-L

Nominal size of a pipe is an indication of its __________ diameter. inner outer approximate none of these

approximate

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

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

The ratio of tube length to shell diameter in case of liquid shell and tube heat exchanger ranges from 2 to 3 3 to 5 4 to 8 6 to 12

4 to 8

In a double pipe concentric heat exchanger, the equivalent diameter of annulus for heat transfer would be (where, D1 and D2 are I.D. of inner and outer pipes) [(D2)^2 - (D1)^2]/(D1)^2 D2 - D1 [(D2)^2 - (D1)^2]/(D2)^2 none of these

[(D2)^2 - (D1)^2]/(D1)^2

What is the slope of the operating line in the stripping section of a distillation column ? 0 infinite > 1 < 1

> 1

__________ shaped roof is most commonly used for cylindrical tanks. Cone Dome Umbrella Flat

Cone

In a thin cylindrical shell, the hoop stress is __________ stress. radial circumferential tensile compressive longitudinal

circumferential tensile

Commercial packed scrubbers are normally designed for a pressure drop range of __________ mm water coloumn per metre of packed height. 4-8 17-34 52-68 88-105

17-34 ## Footnote 17-34 commercial packed scrubbers

The retention time of material in a rotary dryer depends upon its rpm slope & length flights arrangement all (a), (b) and (c)

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

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. molal flow rate of vapour vapour molecular weight pressure and temperature all (a), (b) and (c)

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

Rotary driers are most economically designed for the number of heat transfer units (HTU) from 0.01 to 1 1.5 to 2.5 5 to 10 10 to 20

1.5 to 2.5

The difficulty of liquid distribution in packed towers is accentuated, when the ratio of tower diameter to packing diameter is < 30 < 7 > 7 < 15 > 20 < 50

< 7 ## Footnote < 7 difficulty of liq. distribution

An increase in the liquid resistance to interphase mass transfer and a resultant reduction in plate efficiency is caused by an increase in liquid viscosity. an increase in relatived volatility for rectification columns. decrease in gas solubility for absorbers. all (a), (b) and (c).

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

In the design of a bag filter, the gas temperature is an important consideration, as it affects the gas density gas viscosity fibre selection all (a), (b) & (c)

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

With increase in temperature drop (in a shell and tube heat exchanger), the LMTD correction factor, FT decreases very rapidly increases very rapidly remains constant increases linearly

decreases very rapidly

The normal range of velocity of steam in pipes is __________ m/sec. 0.1-0.5 1-5 10-20 80-100

80-100 ## Footnote 80-100 steam pipe velocities

__________ dished head is the strongest of all. Hemispherical Elliptical Torispherical none of these

Hemispherical

Pick out the correct statement. It is preferred to use a vertical condenser for condensation of vapor from a distillation column without sub-cooling Draining of residual liquid on tray during shut down of distillation column is facilitated by weep holes. Random packing a packed tower offers the advantage of lower pressure drop and higher throughput of fluids as compared to regular/stacked packing. Risers are generally not connected to the plate in a distillation coloumn by bolts, rivets or welding.

Risers are generally not connected to the plate in a distillation coloumn by bolts, rivets or welding. ## Footnote correct - risers...welding

"A claming section" before the liquid flows into the downcomer is privided to permit release of entrained vapour in the liquid. reduce the discharge fluctuation. ensure better vapour-liquid contact. cool the liquid before it flows down.

permit release of entrained vapour in the liquid.

The units of Young's modulus of elasticity and __________ are the same. strain stress modular ratio none of these

stress

In the design of a shell and tube heat exchanger, the corrosion allowance need not be provided for non-pressure parts like tie rods, spacers, baffles, supports etc. for carbon steel and cast iron pressure parts is 1.5 mm (except for tubes) and for severe conditions it is 3 mm. for internal cover and tube sheet is provided on both the sides. all (a), (b) & (c).

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

Vertical condenser is advantageous to the horizontal condenser from operation point of view, when hydrostatic head is required for refluxing the condensate. only the function of condensation is to be carried out. sub cooling of condensate is desired. both the functions of condensation & sub cooling are carried out in a single unit.

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

Hazards associated with the relief valve leakage for extremely hazardous material storage can be taken care of by providing rupture diaphragm dikes surge chamber none of these

rupture diaphragm

Minimum baffle spacing recommended in a shell and tube heat exchanger is equal to 5 cms 40% of the I.D. of the shell 25 cms I.D. of the shell

5 cms

__________ liquor is best handled in a long tube vertical evaporator. Foamy Scaling Viscous Salting

Foamy ## Footnote foamy - long tube vertical

Theoretically calculated diameter of the stripping section of the continuous rectification column is __________ that of the enriching section. less than more than same as either more or less (depending upon relative volatility)

more than

Hold up of material in a operating rotary drier is in the range of 0.05 to 0.15 0.25 to 0.50 0.5 to 0.8 0.8 to 0.9

0.05 to 0.15

A binary liquid azeotropic mixture has boiling point higher than either of the components, when it shows __________ deviation from Raoult's Law. positive negative no none of these

negative negative "higher" positive "lower"

The testing pressure of storage tanks and pressure vessels designed as per Indian standard codes should be about __________ times.the design pressure. 1.5 to 2 3 to 4 4 to 5 >5

1.5 to 2

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

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

The ratio of down take area to cross-sectional area of the tube, for calendria type evaporator ranges from 0.5 to 1 1 to 1.5 1.5 to 2 2 to 2.5

0.5 to 1

Shortest distance between two tubes is called tube pitch. called tube clearance. more in case of triangular pitch as compared to square pitch of tube layout. none of these.

called tube clearance. ## Footnote Remember: tube pitch - shortest center to center distance tube clearance - shortest distance

Process Equipment and Plant Design Part 1 Flashcards

(185 cards)