oeod Flashcards
Fresh water carrying pipelines in chemical industries are colored with
sea green
Which of the following material is seldom used for pressure vessel
construction ?
Rimmed still
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
Lug support is
all of the above
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 seive 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 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-CabeThiele’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 of the above
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
layout and pitch
Where does the maximum tensile strength occur in a thick cylindrical vessel
subjected to internal pressure ?
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
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.
a
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
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
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
__________ tray arrangement is recommended for distillation column
having diameter upto 4 ft.
cross flow
What is the value of ‘q’ for saturated liquid feed to a distillation column ?
1
In perforated plate towers, the
all of the above
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 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
2.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.
a. When highly corrosive fluids are to be handled, the plate towers
prove to be cheaper and easier to construct than packed tower.
b. Packed towers are generally preferred over plate towers, if the
liquids have a foaming tendency.
c. The pressure drop through the packed towers is generally more than
the pressure drop through plate towers designed for same duty.
d. none of these.
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
a
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.
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
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 = G^2
Pick out the wrong statement. In an agitated vertical cylinderical reaction
vessel, the
dished bottom vessel has very high power consumption.
Needle valves are generally not used for
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
all a, b & c.
Pick out the wrong statement.
a. Safety valves are provided in heat exchangers for removal of nonconden-sables.
b. Liquid metals and dowtherm are used for very high temperature
heating.
c. In a shell and tube heat exchanger, high pressure fluid is generally
routed through the tube.
d. 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 nonconden-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
. 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
all of the above
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
In a shell and tube heat exchanger, tube side __________ of the mass
velocity.
heat transfer co-efficient is proportional to 0.8th power
b. pressure drop is proportional to the square
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.
15-30
In packed towers provided with saddle packing, liquid redistributors are
positioned at every __________ times column diameter or 6 metres 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 )
0.2D
. The maximum liquid gradient over a tray must not exceed
0.5’-1.25’
An underdesigned steam trap will
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/(1-q)
Speed of industrial paddle agitator ranges from __________ rpm.
20-100
__________ strain is measured using a ‘strain rosetter’
LINEAR
Thin spherical shells subjected to internal pressure, develop __________
stresses
RADIAL
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
INFINITY
Vertical vessels are not supported by
SADDLES
With increase in pressure drop (for a given particle size), the dust collection
efficiency of a cyclone separator will
INCREASE
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.
Overall tray efficiency of a distillation column is the ratio of the number of
ideal trays required to the number of real trays required.
Pick out the wrong statement about the design of a sieve plate column.
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.
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
0.1-0.25
In a __________ rivetted joint, the rivets in the various rows are opposite
to each other.
CHAIN
Pick out the wrong statement:
a. The tensile strength of a brittle material is less than its compressive
strength.
b. The compressive strength of a ductile materia] is less than its tensile
strength.
c. In a thick cylindrical shell, the hoop stress is maximum at the inner
radius.
d. 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
ALL OF THE ABOVE
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 case of a continuous distillation column, increase in reflux ratio may
result in the
all of the above
In a distillation column, the minimum residence time for liquid in the
downspout is about __________ seconds.
8
Thickness of the frame of a plate and frame filter as compared to that of
plates is
more
Which of the following factors affect the pressure drop in a co-current gasliquid absorption packed tower ?
all of the above
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.
1.25-3.125
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 viscoisty
above __________ poise
600
- The dust collection efficiency of a cyclone separator
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
1
Which of the following types of reactors is the safest from operation point of
view ?
vapor phase reactor
In a bag filter, the pressure drop increases directly as the
density of the gas and inversely as viscosity of the gas.
The LMTD correction factor (FT) is applied in __________ heat exchangers
all multipass
Movement of pipeline caused by thermal expansion is taken care by
providing
all of the above
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
In the design of a paddle agitator, the ratio of paddle di/tank di 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 seive trays in the distillation column ranges from
__________ mm
3 to 12.5
Factor of safety (i.e., overdesign factor) in heat transfer equipments 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
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 the same
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.
The necessary wall thickness for a metallic storage vessel is a function of
the
all of the above
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
a. In a flanged and standard dished head, the crown radius is ≤ shell
outside diameter.
b. In a flanged and shallow dished head, the crown radius is > shell
outside diameter.
c. Flat head covers are most suitable for larger vessels operating at very
high pressure.
d. 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
Liquor flows inside the tube, while the steam is outside submerging
the tube
Weep holes provided in the plates of a distillation column
all of the above
Steam is preferred to be used as a heating medium in heat exchangers,
because of its
high latent heat
__________ shapedroof is the most commonly used roof for cylinderical
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 upto 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
1.2 to 3.8 cms is the value of the
all of the above
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
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
_________ is the determining factor for the number of bubble caps to be
used per tray
Permissible slot velocity
- Pick out the wrong statement about distillation operation
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).
650
Which of the following is the best tube material from thermal conductivity
point of view alone?
copper
Normal screwed fittings are used for pipes upto a diameter of __________
inches
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”.
Diameter of the seive tray column is determined by the
upper limit of the vapor velocity
For a given fluid, as the pipe diameter increases, the pumping cost
decreases
Maximum acceptable total liquid gradient over a tray is about __________
mm
12.5
.In case of a ‘thin’ pressure vessel, the ratio of its diameter to wall thickness
is
> 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.
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.
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 = 0.0176G
0.8
. But when the flow of air
perpendicular to the surface is encountered, this equation changes to
. hG = 1.004G
0.37
n 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
equipments is usually
60
The value of Le/d (dimensionless) for 45° elbow and 180° close return
bends would be respectively around
45 and 75
A pressure vessel is said to be made of ‘thick’ shell, if the ratio of its diameter
to wall thickness is
10
Tube side heat transfer co-efficient for turbulent flow of liquid through tubes
is proportional to
G^0.5
Circumferential (hoop) stress in a thin cylindrical vessel under internal pressure
is __________ the longitudinal stress
TWICE
The dust collection efficiency of electrostatic precipitator increases with
increase in the
ELECTRODE AREA
For storing hazardous chemicals in large storage tanks, the minimum safe
distance between the two tanks should range between __________ times the
tank diameter
1-1.5
Which of the following factors determine the amount of entrainment in a
distillation column?
ALL OF THE ABOVE
The absorption factor is defined as (where, S1 = slope of the equilibrium
curve, S2 = slope of the operating line)
S1/S2
In shell and tube heat exchangers, straight tie rods are used to
HOLD BAFFLE IN SPACE
In case of design of a shell and tube heat exchanger
ALL OF THE ABOVE
- 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
Excessive liquid gradient on a tray may result in the
ALL OF THE ABOVE
The ratio of tube length to shell diameter in case of liquid shell and tube heat
exchanger ranges from
4 TO 8
What is the slope of the operating line in the stripping section of a
distillation column ?
> 1
. __________ shaped roof is most commonly used for cylindrical tank
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
The retention time of material in a rotary dryer depends upon its
ALL OF THE ABOVE
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
ALL OF THE ABOVE
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
An increase in the liquid resistance to interphase mass transfer and a
resultant reduction in plate efficiency is caused by
ALL OF THE ABOVE
. In the design of a bag filter, the gas temperature is an important
consideration, as it affects the
ALL OF THE ABOVE
. 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
Pick out the correct statement.
a. It is preferred to use a vertical condenser for condensation of vapor
from a distillation column without sub-cooling
b. Draining of residual liquid on tray during shut down of distillation
column is facilitated by weep holes.
c. 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
. “A claming section” before the liquid flows into the downcomer is privided
to
permit release of entrained vapour in the liquid.
The units of Young’s modulus of elasticity and __________ are the same
STRESS
- In the design of a shell and tube heat exchanger, the corrosion allowance
ALL OF THE ABOVE
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
5cms
__________ 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
Hold up of material in a operating rotary drier is in the range of
0.05-0.15
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
Flanges are connected to pipes by
all of the above
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
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-efficients 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
Baffle spacing is generally __________ the I.D. of the shell.
less than
The wall thickness of thin cylindrical shell with hemispherical ends is
__________ that of the spherical ends.
more than
A ‘rupture disc’ is provided in chemical equipments as an accessory meant
for
relieving excess pressure
In a vertical short tube evaporator (Calendria type), the
all of the above
In a multipass shell and tube heat exchanger, the problem of differential
expansion between the shell and tube passes is taken care of by using a
U-bend
floating head tube sheet
n a shell and tube heat exchanger, the shortest centre to centre distance
between the adjacent tubes is
TUBE PITCH
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.
Minimum tube pitch recommended for shell and tube heat exchangers is
about __________ times the outside diameter of the tube
1.25
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
Slope of countercurrent flow rotary drier is in the range of __________
meter/metre
0-0.08
In case of saddle packing (e.g., berl and intralox saddles), the maximum size
of the packing should not exceed __________ of the column diameter.
1/15TH
The thermal stress in a metallic bar does not depend upon the
CROSS SECTIONAL AREA
The minimum baffle height should be
TWICE THE IMPELLER DIAMETER
. 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 Q 0.45 ρ 0.13
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
1.5d
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
innermost row to the outermost row
diamond
Large process vessels operating under extreme temperature and pressure
conditions are normally clad/ lined with materials like stainless steel,
aluminium, nickel & its alloys, copper & its alloys and titanium. The cladding
thickness is generally about __________ percent of the total thickness.
10-20
Heat transfer co-efficient for a horizontal condenser as compared to a
vertical condenser operating under similar conditions is
about 3 times
Pick out the wrong statement pertaining to the design of the distillation
column
none of these
The longitudinal stress induced in a thin walled cylinderical vessel under
internal pressure is
pd/4t
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
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 raio propeller agitator/tank is normally taken as
0.15-0.30
A/an __________ is used for changing the direction of a pipeline
elbow
Maximum plate efficiency is achieved in case of __________ flow.
cross
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.
1/4
The ratio for the rate of washing to the final rate of filtration in a washing
type of plate and frame filter is
0.25
Normally, the length to diameter ratio of rotary dryers varies form 4 to 10
and for its economic operation, the number of transfer units (NTU) for such
dryers varies from
1.5-2.5
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
The point ‘A’ on the Fig. represents the
elastic limit
Typical static submergence for bubble cap plate column operating at
atmospheric pressure may be around
0.5”
The length of straight rectangular weir used on cross-flow trays is generally
__________ the column diameter.
0.6-0.8 times
Le/D for coupling and unions
Negligible
What is the slope of the operating line in the rectifying section of a
distillation coloumn ?
<1
Stage efficiency for packed tower varies with the
all of the above
The minimum plate spacing in most of the pertroleum refinery distillation
columns (of dia > 3 ft) is normally __________ inches.
18
Joint efficiency (J) for a seamless pipe is
1
For a given design of bubble cap, the number of bubble caps to be used per
tray is set by the
allowable gas velocity through the slots.
The shell side pressure drop in a shell and tube heat exchanger is maximum
for __________ baffle.
orifice
The function of manholes provided in the shell of a distillation column is to
give access to the individual trays for cleaning, maintenance and
installation
Back-trapping in a distillation column results due to
excessive liquid gradient over the tray
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
Diameter of bubble caps used in high pressure columns is __________ as
compared to that used in identical vacuum columns.
more
. The ideal size of round bubble caps to be used in industrial distillation column
having a diameter of 3-6 metres is __________ cms.
15
Lap joints are preferred for plates having thickness __________ mm.
> 3
In a distillation column, minimum clearance to be maintained betweeen the
overflow weir and the last row of the bubble caps is __________ cms
7.5
Which of the following lengths of heat exchanger tubes are normally not
used in practice ?
10 meters
In case of a shell and tube heat exchanger, the effect of L/D on inside film
heat transfer co-efficient (hi) vanishes after a Reynold number of
10000
Equivalent diameter for heat transfer calculation for a duct of square crosssection having each side as ‘d’ will be
d
. 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
For a cylinderical internally pressurised vessel, which of the following
closure types would withstand highest pressure, if each closure is of the same
material and thickness ?
ellipsoidal (2:1)
In inclined long tube vertical evaporators, the tubes are inclined at an angle
of
45
In a continuous distillation column, the optimum reflux ratio ranges from
__________ times the minimum reflux ratio
1.1 to 1.5
The wall thickness for a large high pressure pipeline is determined by the
consideration of the
circumferential pipewall tension.
In the case of a shell and tube heat exchanger, the logarithmic mean
temperature difference
is always less than arithmetic average value.
Skirt support is the most suitable for supporting __________ vessels.
tall vertical
Baffles may be eliminated for
high viscosity liquids (>600 poise)
Generally, as the length of the liquid path on a tray is increased beyond 5 ft,
the overall column efficiency
increases
In packed absorption tower, onset of flooding usually occurs at a pressure
drop of about __________ mm of water column per metre height of packing.
50-75
For pipe flows, head is proportional to __________ at constant capacity
(where D = pipe diameter ).
1/D2
The minimum tray spacing in distillation column of diameter less than 3 ft
is normally __________ inches.
6
Oxygen carrying pipelines in chemical industries are coloured with
__________ colour
BLACK
Normally, the ratio of the total riser area to the tower cross sectional area
(for bubble cap towers of diameter more than 3 ft) is around
0.1-0.2
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.
Maximum size of the raschig rings used in a packed tower is about
__________ of the coloumn diameter
1/30th
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
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.
. 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
Of the pressure vessels, with same thickness but different diameters, which
one withstands higher pressure ?
SMALLER DIAMETER VESSEL
Reflux ratio variation in a distillation column is between
minimum and infinity
In condenser, the cooling water is passed in the tube side in a pass
arrangement, because
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 to 1/15th
Height of the flights in the rotary drier is in the range of
0.08 - 0.12 d
Vapor velocity in a distillation column for non-foaming mixture is in the
range of __________ times the flooding velocity.
0.6-0.7
Pick out the wrong statement.
a. Plate efficiency increases with increase in superficial vapour
velocity till entrainment limit.
b. Increase in depth of the liquid about the slots increases the plate
efficiency, particularly if the liquid depth is < 1”.
c. Too small a plate spacing can cause a low efficiency, if the vapour
velocity is greater than the allowable value.
d. none of these
none of these
Pick out the wrong statement.
a. In practical operation, distillation towers having diameter 3-6 metres
equipped with bubble cap (round) size of 15 cms are used.
b. 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.
c. In a seive tray, the minimum hole diameter is equal to the tray
thickness.
d. In a stainless steel seive tray, the minimum hole diameter is equal to
10 times the plate thickness.
In a stainless steel seive tray, the minimum hole diameter is equal to
10 times the plate thickness.
In the downcomer of a distillation column, the minimum recommended
residence time is about __________ seconds.
5
For identical situation, condensing film coefficient in case of a horizontal
condenser is almost __________ the value expected in case of vertical
condenser.
thrice
Diameter of rivet hole (d, mm) and the plate thickness (t, mm) are related by
Unwin’s formula as
1.6 sqrt t
A binary liquid azeotropic mixture has boiling point lower than either of the
components, when it shows __________ deviation from Raoult’s Law
positive
. In which of the following evaporators, steam is fed inside the tube while the
liquor is outside the tube?
horizontal tube evaporator
A single pass air heater is connected to a two pass unit. For the air flow rate
and other conditions remaining the same, the film heat transfer co-efficient for
air will vary in the ratio of
2^0.8
In a multipass shell and tube heat exchanger, the baffles on shell side is
primarily provided for
creating turbulence
For turbine agitator, the impeller diameter is about
0.3 to 0.5d
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 2^1.6
Pick out the wrong statement pertaining to the design of a long tube vertical
evaporator
none of these
Which of the following is the most common type of baffle used in industrial
shell and tube heat exchanger ?
25% cut segmental baffle
What is the minimum recommended ligament for square pitch arrangement
in case of heat exchangers ?
6.5mm
. Pick out the correct statement
a. Centre to centre distance between two consecutives rivets in a row
is called the pitch.
b. A rivetted joint made in overlapping plates is called butt joint.
c. Hole size drilled in rivetted plates is less than the actual size of the
rivet.
d. none of these.
Centre to centre distance between two consecutives rivets in a row
is called the pitch.
Safety valves are provided in chemical equipments to guard against
excessive
pressure/pressure fluctuations
. 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
Liquid gradient over the tray results due to the
resistance offered to flow of liquids by caps & risers and the flow of
gas
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
he approximate liquid depth in an agitation tank is equal to (where, d =
tank diameter)
d
Baffle width is normally taken as __________ times the tank diameter
0.1-0.12
A cylinderical 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
10mm
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
The equivalent diameter for fluid flow through a channel of constant noncircular cross section of area ‘A’ is given by (where, P = perimeter of the channel
in contact with the fluid)
4 A/P
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
Overall mass transfer co-efficient in case of absorption of __________ in
water is based on the gas film co-efficient only, as the mass transfer process is
gas film (phase) controlling.
nh3
Which tube arrangement in a heat exchanger would facilitate highest heat
transfer rate?
triangular pitch
In case of 1.5” heat exchanger tubes, the inside flow area __________ with
decrease in BWG
decreases
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
The thickness of segmental baffles (25 -35% cut truncated plates usually) is
generally __________ the tube wall thickness.
twice
The safe height (h) to diameter (d) ratio (i.e., h/d) for liquid/petro fuel
storage tank of capacity more than 45 kilolitres is less than
1
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 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 plate column is
finite stage contactor
- In seive plate column, holes are drilled or punched in sizes ranging from 2.5
to 12 mm (5 mm being widely used). The hole pitch is normally __________
times the hole diameter to give the required hole area.
2.5-4.0
Pick out the wrong statement.
a. Rivetting provides a permanent fastening method.
b. The joint made by overlapping of one plate over the other, and then
rivetting the two plates together with two rows of rivets is called
‘double rivetted butt joint’.
c. Shank diameter of the rivets should be less than the size of the hole
drilled in the plate for rivetting.
d. The efficiency of a rivetted joint is the ratio of the strength of the
rivetted joint to the strength of the solid plate.
The joint made by overlapping of one plate over the other, and then
rivetting the two plates together with two rows of rivets is called
‘double rivetted butt joint’.
The force due to wind load acting on a tall vessel depends upon its
all of the above
Bubble cap diameter used for the distillation column having diameter
ranging from 1.5 to 4.5 metres is about __________ mm
100
Power required for agitation depends upon th
all of the above
Tube height in a calendria type evaporator is normally less than __________
metres
2
Pick out the wrong statement.
a. Lug supports are less expensive than other type of supports.
b. A pipe is differentiated from a tube by the fact that a pipe has a
greater wall thickness compared to the tube.
c. A reducer is used to change the direction of a pipe in a straight run.
d. 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
For a 25 mm hole drilled in plates to be rivetted, the shank diameter of the
rivet should be __________ mm
23
Optimum economic pipe diameter for fluid flow is determined by the
total cost considerations (pumping cost plus fixed cost of the pipe).
Pressure differential maintained across a continuous rotary vacuum filter is
in the range of __________ mm Hg column
250-500
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.
Elastic failure of a material occurs, when the tensile stress equals yield
strength, yield point or the elastic limit. Also, the elastic failure occurs
according to maximum strain theory, when the maximum tensile strain equals
(where, σ = yield strength and E = modulus of elasticity)
σ/E
In a pressure vessel containing multiple openings of various dimensions at
different parts, stress concentration at the edges of the opening is maximum
which becomes negligibly small beyond the area covered by __________ times
the hole diameter
2
What is the slope of the feed line, if the feed to a distillation column is a
saturated liquid ?
∞
. Filtration rate is affected by the
all of the above
Liquid gradient over a tray can be minimised by
all of the above
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
Le/D for 90° elbow (medium radius) and 90°square elbow would be
respectively around
25 and 60
__________ heat exchanger is also known as ‘hair pin type’ exchanger,
double pipe
What is the value of ‘q’ for saturated vapor feed to a distillation column
?(where q = fraction of the feed stream that is liquid.)
0
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
Frame thickness in the plate and frame filter press is normally in the range
of __________ inches
0.25 to 8
Cylinderical shell thickness of rotary drier is generally __________ mm.
6-8
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
Mc Cable Thiele method used for finding theoretical stages in a distillation
column assumes that the
all of thea bove
A minimum clearance of about __________ mm is maintained between the
distillation column wall and the bubble cap.
38
. Pick out the wrong statement.
a. If sufficient residence time (around 8 seconds) is not proivided to
the downcoming liquid in the downcomer, it may entrain some
vapour.
b. The liquid head in the downcomer should not be greater than one
half the plate spacing to avoid flooding.
c. The dischare 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.
d. none of these.
none of these
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.
Souders Brown equation given by, , is used for the
calculation of the __________ in a continuous distillation column.
diameter of the bubble cap column
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
Le/D for a tee would be around
60
Log mean temperature difference in case of multi-pass shell and tube heat
exchanger is always
less than arithmetic mean value.
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 thicknes (whatever’s larger)
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
. 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
Scale up problem in design based on the similarity concept takes into
account __________ similarity.
all of the above
- __________ 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.
