Process Equipment and Plant Design Flashcards
Fresh water carrying pipelines in chemical industries are coloured with __________ color.
sea green
Which of the following material is seldom used for pressure vessel construction ?
Rimmed steel
The ratio of shear stress to shear strain is called
shear modulus
25 per cent cut segmental baffle means that the baffle
height is 75% of the I.D. of the shell.
Liquid/petroleum fuel storage tanks are built underground (as in case of petrol pumps), when the storage capacity is less than __________ kilolitres.
45
Le/D for fully open globe value may be around
300
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.
With increase in the number of shell passes, the value of FT
increases
Holes of a sieve tray are arranged in triangular pitch of __________ times the hole diameter.
2.5 to 5
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.
5-11
The stress developed in a material without any permanent set is called the
elastic limit
In a shell and tube heat exchanger, the ‘tube pitch’ is defined as the
shortest center to center distance between adjacent tubes.
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 ?
Reflux is not a saturated liquid.
Overall distillation column efficiency for most of the refinery columns can be given by (for μ = 0.07 - 1.4 cp and relative volatility < 4) (where η = overall column efficiency, % μ = molal average viscosity of feed at average column temperature and pressure, cp Δp = pressure drop per tray, psi)
η = 17 - 61.1 log μ
In case of bubble cap distillation column of diameter greater than 1.2 metres, the cap diameter is roughly about __________ cms.
10
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.
8
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)^5/3
Where does the maximum tensile strength occur in a thick cylindrical vessel subjected to internal pressure ?
At the inner surface.
It is not desirable to design a heat exchanger for LMTD correction factor, FT, of less than
0.80
Triangular pitch tube layout as compared to square pitch in a shell and tube heat exchanger
permits the use of more tubes in a given shell diameter.
Bracket supports are the most suitable for supporting __________ vessels.
thick walled vertical
Two iron pipes of the same nominal diameter but different schedule numbers will have the same
inside diameter
Steam side heat transfer co-efficient for design consideration under ordinary condition can be assumed to be about __________ kcal/hr.m2.°C.
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 __________ percent.
20
In chemical process equipments, the conical bottom heads used, usually has an apex angle of
60°
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.
75
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
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.
20-40
Correct use of ‘factor of safety’ is very important in equipment design. It is defined as the ratio of the
ultimate stress to working stress.
What is the value of ‘q’ for saturated liquid feed to a distillation column ?
1
__________ tray arrangement is recommended for distillation column having diameter up to 4 ft.
Cross flow
The main purpose of providing stepping on the trays is to
facilitate handling of large flow rate of liquid.
The operating pressure drop range in a bag filter is about __________ mm water gauge.
50-150
The ends of a cylindrical 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.
Ellipsoidal
For laminar flow (NRe < 2100) in steel pipe, the optimum inside pipe diameter is given by
Di, opt = 3 Q^0.36 ρ^0.18
Pick out the correct statement.
Packed towers are generally preferred over plate towers, if the liquids have a foaming tendency.
Wall thickness of schedule 40 pipe as compared to that of schedule 80 pipe is
LESS
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.
Speed of the drum of the rotary vacuum filter normally ranges from __________ rpm.
0.1 to 2
A stuffing box is used for
prevention of fluid leakage around moving parts.
Pressure drop (Δp) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as
Δp = G2
Pick out the wrong statement.
dished bottom vessel has very high power consumption.
Pick out the wrong statement.
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
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.
Which of the following is used to set the diameter of the distillation column ?
Allowable vapor velocity.
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
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.
Saddle supports are used for supporting __________ vessels.
horizontal cylindrical
The diameter of a propeller agitator used in agitation tank ranges from __________ percent of the tank diameter and its peripherial speed is normally 300 to 500 metres/minute.
15 to 30
In packed towers provided with saddle packing, liquid redistributors are positioned at every __________ times column diameter or 6 meters whichever is less.
5-8
Optimum reflux ratio in a continuous distillation column is determined by the
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.ft2 . °F)-1
Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter )
0.2 D
The maximum liquid gradient over a tray must not exceed
0.5” -1.25”.
An under designed steam trap will
back up condensate and cause water hammer in steam line.
Speed of industrial paddle agitator ranges from __________ rpm.
20-100
__________ strain is measured using a ‘strain rosetter’.
Linear
With increase in the reflux ratio for a fixed production from a continuous binary distillation column, the __________ decreases.
fixed charges initially
The slope of operating line in the rectifying section of a distillation column is unity, if the reflux ratio is
∞
Vertical vessels are not supported by
saddles
Spherical shaped pressure vessel is considered to be the most ideal, because it can
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
allow for thermal expansion and facilitate installation.
Pick out the wrong statement about the design of a sieve plate column.
Minimum recommended down comer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds.
Generally, no corrosion allowance in wall thickness of a part is required, if the thickness is more than __________ mm.
30
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
In a __________ rivetted joint, the rivets in the various rows are opposite to each other.
chain
Pick out the wrong statement:
The value of crushing load is more than that of buckling load for long colmns.
Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower.
The total weight of a dry plate tower is usually much more than that of a dry packed tower designed for the same duty.
The circumferential (hoop) stress in a thin walled cylinderical vessel under internal pressure is
pd/2t
LMTD correction factor is used in heat exchanger design for
multipass shell and tube heat exchanger.
Floating head heat exchangers are used for the
cases where temperature difference between the shell and the tubes is more (>50°C).
The most common standard size of bubble caps used in industrial operation is
6” dia cap with 4” dia riser.
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
In a distillation column, the minimum residence time for liquid in the downspout is about __________ seconds.
8
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.
1.25 to 3.125
Rivets are generally specified by the
shank diameter
Length to diameter ratio of most rotary driers is in the range of
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
19
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 viscosity above __________ poise
600
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
1
Which of the following types of reactors is the safest from operation point of view ?
A vapor phase reactor.
The LMTD correction factor (FT) is applied in __________ heat exchangers.
all multipass
For a cylindrical shell, (subject to the thickness of uppermost course being more than the minimum for diameter of the tank in question), the thickness of the courses of shell
decreases upwards.
In the design of a paddle agitator, the ratio paddle dia / tank dia is normally taken as
0.8
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.
Damaging
Hole diameter of the sieve trays in the distillation column ranges from __________ mm.
3 to 12.5
Factor of safety (i.e., overdesign factor) in heat transfer equipment is about __________ percent more than the actual/theoretical design factor.
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
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
The minimum shell thickness for tank ≤ 15 metres diameter is limited to __________ mm, for reasons of elastic stability.
5
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/5 or minimum 2” to 5D.
Brass valves are usually made for pipe sizes __________ inches.
≤ 2
In a shell and tube heat exchanger, triangular pitch arrangement as compared to square pitch arrangement
results in higher shell side pressure drop.
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.
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.
(1/n)th
Pick out the wrong statement
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.
Liquor flows inside the tube, while the steam is outside submerging the tube.
Steam is preferred to be used as a heating medium in heat exchangers, because of its
high latent heat.
__________ shaped roof is the most commonly used roof for cylindrical storage tanks.
Conical
Pick out the wrong statement pertaining to ‘Horton sphere’ used for the storage of liquid ammonia.
Horton sphere is used for the storage of liquid at sub-zero temperature at very high pressure up to 200 kg/cm2 .
Value of Peclet number = ∞, is the representative of
plug flow.
In most of the shell and tube heat exchangers, the tube pitch is generally __________ the tube diameter.
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
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 - dt)/ph
Accidents in chemical plants are mostly due to
faulty operating procedures.
For identical operating conditions, the pressure drop over __________ tray is the highest out of the following.
bubble cap
Pick out the wrong statement about distillation operation
Flash distillation, differential distillation & steam distillation are all continuous distillation processes.
Normal screwed fittings are used for pipes upto a diameter of __________ inches.
3
Which of the following is the best tube material from thermal conductivity point of view alone?
Copper
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).
650
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”.
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.
In case of a ‘thin’ pressure vessel, the ratio of its diameter to wall thickness is
> 10
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.
Diameter of the sieve tray column is determined by the
upper limit of the vapour velocity.
Maximum acceptable total liquid gradient over a tray is about __________ mm.
12.5
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
Heat transfer co-efficient, hG(Kcal/hr.m2 .°C) and mass velocity of air, G (kg/hr.m2 ) for air flow parallel to the surface in case of constant drying rate in batch drying is related as hG = 0.0176G0.8. But when the flow of air perpendicular to the surface is encountered, this equation changes to
hG = 1.004G0.37
In the agitators, the power required will be changed with the increase of diameter of agitator (D) as
D^5
Apex angle of conical heads used in the bottom heads of chemical process equipment’s is usually
60
Circumferential (hoop) stress in a thin cylindrical vessel under internal pressure is __________ the longitudinal stress.
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
The absorption factor is defined as (where, S1 = slope of the equilibrium curve, S2 = slope of the operating line)
S1/S2
In a cylinderical vessel subjected to internal pressure, the longitudinal stress σL and the circumferential stress, σn are related by
σh = 2 σL
Nominal size of a pipe is an indication of its __________ diameter.
approximate
__________ shaped roof is most commonly used for cylindrical tanks.
cone
In a thin cylindrical shell, the hoop stress is __________ stress.
circumferential tensile
Commercial packed scrubbers are normally designed for a pressure drop range of __________ mm water coloumn per metre of packed height.
17-34
Rotary driers are most economically designed for the number of heat transfer units (HTU) from
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
< 7
With increase in temperature drop (in a shell and tube heat exchanger), the LMTD correction factor, FT
decreases very rapidly
The normal range of velocity of steam in pipes is __________ m/sec.
80-100
__________ dished head is the strongest of all.
Hemispherical
“A claming section” before the liquid flows into the down comer is provided to
permit release of entrained vapour in the liquid
The units of Young’s modulus of elasticity and __________ are the same.
stress
Vertical condenser is advantageous to the horizontal condenser from operation point of view, when
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
Minimum baffle spacing recommended in a shell and tube heat exchanger is equal to
5 cms
__________ liquor is best handled in a long tube vertical evaporator.
Foamy
Theoretically calculated diameter of the stripping section of the continuous rectification column is __________ that of the enriching section.
more than
A binary liquid azeotropic mixture has boiling point higher than either of the components, when it shows __________ deviation from Raoult’s Law.
negative
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
The ratio of down take area to cross-sectional area of the tube, for calendria type evaporator ranges from
0.5 to 1
Shortest distance between two tubes is
called tube clearance.
__________ tower is the most suitable gas-liquid contacting device involving highly corrosive fluids.
Packed
At equal mass velocities, the values of film co-efficient for gases as compared to that for liquids are generally.
lower
The ratio of the largest load in a test to the original cross-sectional area of the test specimen is called the __________ stress.
ultimate
A ‘rupture disc’ is provided in chemical equipment as an accessory meant for
relieving excess pressure
In a shell and tube heat exchanger, the shortest centre to centre distance between the adjacent tubes is
called tube pitch.
Minimum tube pitch recommended for shell and tube heat exchangers is about __________ times the outside diameter of the tube.
1.25
Any shell opening greater than 5 cms for a storage tank must be reinforced for reason of
preventing the local overstressing of the shell around the opening.
Slope of countercurrent flow rotary drier is in the range of __________ meter/metre.
0 to 0.08
Liquid redistribution should be done in a packed tower packed with raschig rings every 6 metres or __________ times the column diameter, whichever is lower.
2.5-3.0
In case of saddle packing (e.g., berl and intralox saddles), the maximum size of the packing should not exceed __________ of the column diameter.
l/15th
The thermal stress in a metallic bar does not depend upon the
cross-sectional area.
For turbulent flow (NRe > 2100) of low viscosity fluid (μ > 20cp) in steel pipes, the optimum inside pipe diameter is given by(where, Q = fluid flow rate, ft3/sec.ρ = fluid density, lb/ft3 μ = fluid viscosity, centipoise Di = optimum inside pipe diameter, inches)
Di, opt = 3.9 Q0.45 ρ0.13
To avoid the tearing off the plate of an edge, the margin (i.e., the minimum distance from the centre of the rivet hole to the nearest edge of the plate) should be equal to
1.5 d
The normal range of velocity of water in pipes is __________ m/sec.
1-2
Baffles are provided in a shell and tube heat exchanger to increase the turbulence and velocity of the shell side fluid. Which of the following shaped baffles does not fall in the category of transverse baffle ?
Flat plate extending across the wall
A certain pressure vessel manufacturer avoids doing reinforcements calculations for openings by always providing a reinforcing pad extending upto double the diameter of the opening and of the same material and thickness as that of the shell wall. If area compensation is accepted as a code guideline, his approach leads to safe design
irrespective of the shape of the vessel.
In a __________ rivetted joint, the number of rivets decreases from the inner most row to the outer most row.
diamond
Large process vessels operating under extreme temperature and pressure conditions are normally clad/ lined with materials like stainless steel, aluminum, nickel & its alloys, copper & its alloys and titanium. The cladding thickness is generally about __________ percent of the total thickness.
10 to 20
The buckling tendency of compression members is always in the direction of the
least radius of gyration.
In case of plain carbon steel, butt welded joints are used for shell plate thickness ≤ __________ cms.
3.8
The average velocity in the tubes of a 1-4 heat exchanger is __________ times that in 1-1 heat exchanger having the same size & number of tubes and operated at same liquid flow rate.
4
Hoop (circumferential) stress induced in a thin walled ‘Horton Sphere’ used for the storage of liquid ammonia under pressure is
pD / 2t
When one of the fluids is highly corrosive and has fouling tendency, it should
preferably flow inside the tube for its easier internal cleaning.
The LMTD correction factor (FT) is defined as the
ratio of true temperature difference to the LMTD.
The clearance between two tubes in a shell and tube heat exchanger is known as ‘ligament’, whose minimum value is __________ the outside diameter of the tube, but in no case it should be less than 4.5 mm.
one fourth
Value of Peclet number = 0, is the representative of
complete back mixing.
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
0.3
Removable connection of tubes to tube sheet is called
ferrule
Typical static submergence for bubble cap plate column operating at atmospheric pressure may be around
0.5”
What is the slope of the operating line in the rectifying section of a distillation coloumn ?
<1
Back-trapping in a distillation column results due to
excessive liquid gradient over the tray.
The minimum plate spacing in most of the pertroleum refinery distillation columns (of dia > 3 ft) is normally __________ inches.
18
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 ?
0.8
The ideal size of round bubble caps to be used in industrial distillation column having a diameter of 3-6 metres is __________ cms.
15
A/an __________ is used for changing the direction of a pipeline.
elbow
Maximum plate efficiency is achieved in case of __________ flow.
cross
A cylindrical storage tank can have a self supported conical roof,
if its diameter is less than 15-20metres.
For high pressure process equipments/vessels, the connected nozzle should be
flanged
Smoker’s equation for the calculation of number of equilibrium stages in a continuous binary distillation column is used, when the
relative volatility is close to one (e.g., separation of close boiling isomers).
Column support for the roof of cylindrical storage tank must be provided for
large diameter tanks
large diameter tanks
ellipsoidal (2 : 1)
In condenser, the cooling water is passed in the tube side in a pass arrangement, because
it reduces heat transfer area.
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.
1/10-1/15th
Maximum allowable vapour velocity in a bubble cap tower is determined by the
entrainment considerations.
Normally, the plate thickness of the bottoms and roofs of vertically cylindrical storage vessels as compared to that of the cylindrical shell is
less
The practical representative values of HETP for a number of commercial operations lies within a range of __________ metre.
0.4-0.9
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.
thermal
Of the pressure vessels, with same thickness but different diameters, which one withstands higher pressure ?
Smaller dia vessel.
Reflux ratio variation in a distillation column is between
minimum and infinity
The safe distance of habitation from a hazardous chemical plant (TLV of its product < 1000 ppm) should be about __________ kms.
25
Pick out the wrong statement pertaining to a shell and tube heat exchanger.
Disk and doughnut baffle is the most commonly used baffle.
Oxygen carrying pipelines in chemical industries are coloured with __________ colour.
blue
Pick out the wrong statement about the design of seive plate column and the bubble cap column.
Weir height for a bubble cap plate column is the same as that for a seive plate column.
Cylindrical storage tanks used for the storage of volatile liquids (e.g., naphtha) have __________ roofs.
floating
Pick out the wrong statement.
In a stainless steel seive tray, the minimum hole diameter is equal to 10 times the plate thickness.
For identical situation, condensing film coefficient in case of a horizontal condenser is almost __________ the value expected in case of vertical condenser.
thrice
A binary liquid azeotropic mixture has boiling point lower than either of the components, when it shows __________ deviation from Raoult’s Law.
positive
If a single tube pass heat exchanger is converted to two passes; for the same flow rate, the pressure drop per unit length in tube side will __________ times.
increase by 21.
In a multipass shell and tube heat exchanger, the baffles on shell side is primarily provided for
creating turbulence.
Which of the following is the most common type of baffle used in industrial shell and tube heat exchanger ?
25% cut segmental baffle.
Safety valves are provided in chemical equipment to guard against excessive
pressure/pressure fluctuation
The equivalent diameter for pressure drop is __________ that for heat transfer.
not related with
The distance between the top of the slots and the liquid surface when the static liquid is just ready to flow over the overflow weir is called
static submergence
The centre to centre distance between two consecutive baffles in a shell and tube heat exchanger is called the baffle pitch or baffle spacing, which is more than 1/5th the I.D. of the shell. Which of the following is not a function of the baffles ?
To increase the tube side heat transfer co-efficient by inducing turbulence.
A high vapour velocity is required for high plate efficiency in a seive plate coloumn. The satisfactory value of operating vapor velocity for design purpose in seive plate column is about __________ percent of the flooding velocity.
80
A cylindrical pressure vessel of volume 6 πm3 has to be designed to withstand a maximum internal pressure of 10 atm. The allowable design stress of the material is 125N/mm2 and corrosion allowance is 2 mm. The thickness of the vessel for a length/diameter ratio of 3 will be close to
10 mm
Which of the following packing materials provides for maximum mass transfer ?
Cross-partition rings.
__________ of water makes it a widely used coolant in heat exchangers.
High specific heat
Fouling factor must be included in the calculation of over all design heat transfer coefficient, when the liquid
containing suspended solids flows at low velocity.
Lug support is meant for supporting __________ vessels.
small
Which tube arrangement in a heat exchanger would facilitate highest heat transfer rate ?
Triangular pitch.
Cylindrical pressure vessels in horizontal condition is generally supported on a __________ support.
saddle
Pressure drop per tray in the atmospheric distillation column is about __________ psi.
0.07 - 0.12
Welded joint efficiency in the design of chemical process equipment is taken as
0.85
For given number of passes, pitch & tube diameter, the maximum number of tubes that can be accommodated in a shell of tripled inside diameter will be __________ times.
considerably more than 9
The thickness of segmental baffles (25 -35% cut truncated plates usually) is generally __________ the tube wall thickness.
twice
The ratio of linear stress to linear strain is termed as the
modulus of elasticity
__________ head is the most economical for cylindrical vessels designed for operating at high pressure (> 15 atm.).
Ellipsoidal
Bubble cap diameter used for the distillation column having diameter ranging from 1.5 to 4.5 metres is about __________ mm.
100
Optimum economic pipe diameter for fluid flow is determined by the
total cost considerations (pumping cost plus fixed cost of the pipe).
Vertical storage vessels are never supported by __________ support.
saddle
In a double pipe (concentric) heat exchanger, the hydraulic radius for heat transfer (for a fluid flowing through the annulus) would be
more than that for fluid flow.
In a shell and tube heat exchanger for a given heat transfer surface area, smaller diameter tubes are favoured as compared to larger diameter ones ; because the smaller diameter tubes
can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less.
__________ heat exchanger is also known as ‘hair pin type’ exchanger,
Double pipe
In hydrostatic testing of welded pipe (for leakage, strength etc.) the ratio of minimum hydrostatic test pressure to internal design pressure is around
1.5
The ratio of lateral strain to linear strain is termed as the
Poisson’s ratio
The distance between the centre of a rivet hole to the nearest edge of the plate is called
margin
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.
Wind load consideration in the design of a support can be neglected, when the vessel is
short (< 2 m) and housed indoor.
The ratio of volumes of the mixed reactor to the plug flow reactor (for identical feed composition, flow rate, conversion, and for all positive reaction orders) is always
> 1
Tubes are fixed to the tube sheet (a thick circular metallic plate) by the method of tube rolling and brazing (non-removable) or ferrule connection (removable). Thickness of the tube, sheet is normally __________ the outside diameter of the tube but in no case it should be less than 22 mm (7/8”).
equal to
A shell may by termed as thin if its thickness to diameter ratio is less than 0.1. The factor which can be neglected in the calculation of membrane stresses is
bending
__________ closure is the weakest enclosure for cylindrical vessels.
Conical or flat plate
Which of the following efficiencies can be greater than 100% ?
Murphree plate efficiency.
Scale up problem in design based on the similarity concept takes into account __________ similarity.
dynamic, geometrical, kinematic
le/D for fully open globe value may be around
300
Lug support is
all (a), (b) and (c).
With increase in the number of shell passes, the value of FT
increases
Holes of a sieve tray are arranged in triangular pitch of __________ times the hole diameter
2.5 to 5.
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.
5-11
The stress developed in a material without any permanent set is called the
elastic limit
In a shell and tube heat exchanger, the ‘tube pitch’ is defined as the
shortest centre to centre distance between adjacent tubes
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 ?
Reflux is not a saturated liquid.
Overall distillation column efficiency for most of the refinery columns can be given by (for μ = 0.07 - 1.4 cp and relative volatility < 4) (where η = overall column efficiency, % μ = molal average viscosity of feed at average column temperature and pressure, cp Δp = pressure drop per tray, psi)
η = 17 - 61.1 log μ
The value of fouling factor depends upon the
all (a), (b) and (c).
In case of bubble cap distillation column of diameter greater than 1.2 metres, the cap diameter is roughly about __________ cms.
10
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.
8
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)^5/3
In a heat exchanger, shell side fluid velocity can be changed by changing the tube
both (a) & (b)
Where does the maximum tensile strength occur in a thick cylindrical vessel subjected to internal pressure ?
At the inner surface.
It is not desirable to design a heat exchanger for LMTD correction factor, FT, of less than
0.80
A rivetted joint does not fail by __________ of rivets.
none of these
Triangular pitch tube layout as compared to square pitch in a shell and tube heat exchanger
permits the use of more tubes in a given shell diameter.
Bracket supports are the most suitable for supporting __________ vessels.
thick walled vertical
In a multipass shell and tube heat exchanger, the shell side cross flow area does not depend upon
none of these
Two iron pipes of the same nominal diameter but different schedule numbers will have the same
inside diameter
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 __________ percent.
20
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.
none of these.
Pick out the wrong statement.
In an agitated vertical cylinderical reaction vessel, the
dished bottom vessel has very high power consumption.
Speed of the drum of the rotary vacuum filter normally ranges from __________ rpm
0.1 to 2
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
all a, b & c.
Needle valves are generally not used for
very large diameter pipes.
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
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.
Which of the following is used to set the diameter of the distillation column ?
Allowable vapour velocity.
In case of a continuous distillation column, increase in reflux ratio may result in the
all (a), (b) and (c).
The slope of the feed line in distillation operation is given by (where, q = fraction of the feed stream that is liquid.)
-q/(1-q)
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
smaller reactor should come first.
Pick out the wrong statement:
The value of crushing load is more than that of buckling load for long columns.
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
remains same
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.
Pick out the wrong statement
Flat head covers are most suitable for larger vessels operating at very high pressure.
In a shell and tube heat exchanger, triangular pitch arrangement as compared to square pitch arrangement
results in higher shell side pressure drop.
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.
In shell and tube heat exchangers, straight tie rods are used to
hold baffle in space.
Tube side heat transfer co-efficient for turbulent flow of liquid through tubes is proportional to
G0.8
An increase in the liquid resistance to interphase mass transfer and a resultant reduction in plate efficiency is caused by
all (a), (b) and (c).
What is the slope of the operating line in the stripping section of a distillation column ?
> 1
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
What is the slope of the operating line in the rectifying section of a distillation column ?
<1
Joint efficiency (J) for a seamless pipe is
1
Heat transfer co-efficient for a horizontal condenser as compared to a vertical condenser operating under similar conditions is
about 3 times
Back-trapping in a distillation column results due to
excessive liquid gradient over the tray.
Liquid gradient over a tray can be minimized by
all (a), (b) and (c).
In perforated plate towers, the
all (a), (b) and (c).
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.
Ellipsoidal
For laminar flow (NRe < 2100) in steel pipe, the optimum inside pipe diameter is given by
Di, opt = 3 Q0.36 ρ0.18
Pick out the correct statement.
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.
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.
none of these.
Speed of the drum of the rotary vacuum filter normally ranges from __________ rpm.
0.1 to 2
Pressure drop (Δp) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as
Δp = G2
