Process Equipment and Plant Design Part 1 Flashcards
Fresh water carrying pipelines in chemical industries are coloured with __________ color.
sea green
brown
yellow
red
sea green
Which of the following material is seldom used for pressure vessel construction ?
Rimmed still
Mild steel
Killed steel
Semi-killed steel
Rimmed still
The ratio of shear stress to shear strain is called
bulk modulus
shear modulus
modulus of rigidity
modulus of elasticity
shear modulus
25 per cent cut segmental baffle means that the baffle
height is 75% of the I.D. of the shell.
height is 25% of the I.D. of the shell.
spacing is 75% of its height.
width is 25% of its height.
height is 75% of the I.D. of the shell.
Liquid/petroleum fuel storage tanks are built underground (as in case of petrol pumps), when the storage capacity is less than __________ kilolitres.
20
30
45
85
45
less tahn 45 kL liquid/petroleum fuel storage tanks
Le/D for fully open globe value may be around
10
25
75
300
300
Lug support is
the most suitable for thick vertical vessel.
same as bracket support.
provided usually for vessels of much smaller height than skirt supported vessels.
all (a), (b) and (c).
all (a), (b) and (c).
Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column.
Bubble cap trays though most expensive are the best in situations, where low vapour rates is to be handled and a positive liquid seal is essential at all flow rates.
Murphree efficiency of all the three trays are nearly equal, however the peak efficiency is generally higher for seive and valve trays than the bubble cap.
Maintenance cost for valve and seive trays are comparatively more than bubble cap tray due to their relatively complicated construction features.
Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provides the maximum flexible operating range.
Maintenance cost for valve and seive trays are comparatively more than bubble cap tray due to their relatively complicated construction features.
With increase in the number of shell passes, the value of FT
increases
decreases
remains same
remains same, only if the number of tube passes does not change.
increases
Holes of a sieve tray are arranged in triangular pitch of __________ times the hole diameter.
1.5 to 2
2.5 to 5
5 to 10
10 to 15
2.5 to 5
sieve tray holes 2.5 to 5 triangular pitch
In case of a shell and tube heat exchanger, the minimum shell thickness for carbon steel (inclusive of corrosion allowance) depends on shell diameter and is in the range of __________ mm.
3-5
5-11
8-15
12-18
5~11
keywords: carbon steel, minimum thickness, 5-11
The stress developed in a material without any permanent set is called the
ultimate stress
yield stress
elastic limit
breaking stress
elastic limit
keywords: stress, without, permanent set, elastic limit
In a shell and tube heat exchanger, the ‘tube pitch’ is defined as the
O.D. of the tube for square pitch.
shortest distance between two adj acent tube holes.
shortest centre to centre distance between adjacent tubes.
none of these.
shortest centre to centre distance between adjacent tubes.
keywords:
pitch - shortest centre to centre
clearance - shortest distance
Which of the following is not a valid assumption in continuous binary distillation for calculating the number of equilibrium stages by Mc-Cabe-Thiele’s method ?
Sensible heat changes for vapour & liquid are negligibly small.
Reflux is not a saturated liquid.
Molar latent heat of the two components are equal.
Heat of mixing of normal liquid is assumed to be zero.
Reflux is not a saturated liquid.
keywords: negligible sensible, equal molar, zero heat of mixing
mnemonic: SMH (shaking my head)
sensible, molar, heat of mixing
Overall distillation column efficiency for most of the refinery columns can be given by (for u = 0.07 - 1.4 cp and relative volatility < 4) (where n = overall column efficiency, % u = molal average viscosity of feed at average column temperature and pressure, cp delta(p) = pressure drop per tray, psi)
n = 17 - 61.1 log u
n = 24.6[delta(p)/u]
n = 1.66 - 0.25 log u
n = 0.25 log u - 1.67
n = 17 - 61.1 log u
keywords/keynumbers: 17, 61.1
The value of fouling factor depends upon the
characteristic of process fluid.
velocity of process fluid containing suspended solids.
suspended solids in the fluid.
all (a), (b) and (c).
all (a), (b) and (c).
In case of bubble cap distillation column of diameter greater than 1.2 metres, the cap diameter is roughly about __________ cms.
10
20
30
35
10
bubble cap 1.2m 10cm
Tube side pressure drop in a 1-2 heat exchanger (for turbulent flow of fluids through the tubes) is about __________ times, that in a 1-1 heat exchanger having the same size & number of tubes and operated at the same liquid flow rate.
2
1/2
4
8
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)^3/2
(1.2)^3/5
(1.2)^2/3
(1.2)^5/3
(1.2)^5/3
Where does the maximum tensile strength occur in a thick cylindrical vessel subjected to internal pressure ?
At the inner surface.
At the mid thickness of the cylindrical wall.
At the outer surface.
None of these.
At the inner surface.
It is not desirable to design a heat exchanger for LMTD correction factor, FT, of less than
0.99
0.95
0.80
0.55
0.8
0.8 not desirable LMTD cf
A rivetted joint does not fail by __________ of rivets.
tearing
shearing
tearing of the plate across a row
none of these
none of these
Bracket supports are the most suitable for supporting __________ vessels.
thick walled vertical
horizontal
thin shperical (e.g. Horton sphere)
none of these
thick walled vertical
thick vertical bracket support
In a multipass shell and tube heat exchanger, the shell side cross flow area does not depend upon
baffle spacing
clearance
pitch
none of these
none of these
Two iron pipes of the same nominal diameter but different schedule numbers will have the same
inside diameter
outside diameter
wall thickness
none of these
inside diameter
Steam side heat transfer co-efficient for design consideration under ordinary condition can be assumed to be about __________ kcal/hr.m^2.C.
1250
2500
7500
15000
7500
Lessing ring is formed by the addition of a partition across the centre of a raschig ring, which results in an area increase of about __________%.
5
20
35
55
20
20LRAI Lessing-raschig area increase 20
In chemical process equipments, the conical bottom heads used, usually has an apex angle of
20 degrees
40 degrees
60 degrees
80 degrees
60 degrees
Smaller sized packings are generally dumped to the packed columns, and the large ones of size greater than __________ mm are stacked individually, which provides better control over bed porosity and offers lower gas pressure drop.
25
50
75
150
75
large ones of size… 75 mm… stacked individually
Shell side heat transfer co-efficient in case of square pitch as compared to the triangular pitch under similar condition of fluid flow and tube size is
more
same
less
twice
less
Correct use of ‘factor of safety’ is very important in equipment design. It is defined as the ratio of the
ultimate stress to breaking stress.
ultimate stress to working stress.
working stress to ultimate stress.
none of these.
ultimate stress to working stress.
The operating velocity in the absorption tower is usually 40-50% of the flooding velocity. Packed absorption towers are normally designed for a pressure drop of about __________ mm of water column per metre height of packing.
1-5
20-40
100-150
1000-1500
20-40
keywords: packed column, pressure drop, 20-40 mm
__________ tray arrangement is recommended for distillation column having diameter upto 4 ft.
Radial flow
Cross flow
Split flow
Cascade
Cross flow
keywords: cross flow, distillation, 4 ft
What is the value of ‘q’ for saturated liquid feed to a distillation column ?
0
<1
1
>1
1
In perforated plate towers, the
hole sizes may be around 1/8” or 3/16”.
total hole area may be around 6 to 15% of tower cross-sectional area.
pressure drop is less compared is similar bubble cap towers.
all (a), (b) and (c).
all (a), (b) and (c).
The main purpose of providing stepping on the trays is to
increase the residence time.
decrease the pressure drop.
facilitate handling of large flow rate of liquid.
improve the flow condition.
facilitate handling of large flow rate of liquid.
stepping…facilitate
The operating pressure drop range in a bag filter is about __________ mm water gauge.
50-150
5-10
500-1500
1500-2500
50-150
50-150 mm operating pd bag filter
The ends of a cylinderical vessel can be closed by a head, which can be one of the four shapes. For the same thickness, choose the one which can withstand the highest pressure.
Flat plate
Hemispherical
Torispherical
Ellipsoidal
Ellipsoidal
keywords: elipsoidal, highest pressure
For laminar flow (NRe < 2100) in steel pipe, the optimum inside pipe diameter is given by
Di, opt = 3 Q^0.36 (rho)^0.18
Di, opt = 3.9 Q^0.45 . (rho)^0.23
Di, opt = 7.6 Q^0.36 . (rho)^0.9
Di, opt = 3 Q^0.36 . (rho)^1.86 (mu)^0.08
Di, opt = 3 Q^0.36 (rho)^0.18
keywords/keynumbers: 3, 0.36, 0.18
Pick out the correct statement.
When highly corrosive fluids are to be handled, the plate towers prove to be cheaper and easier to construct than packed tower.
Packed towers are generally preferred over plate towers, if the liquids have a foaming tendency.
The pressure drop through the packed towers is generally more than the pressure drop through plate towers designed for same duty.
none of these.
Packed towers are generally preferred over plate towers, if the liquids have a foaming tendency.
Pick out the wrong statement pertaining to the design of a basket type evaporator.
It is used for high viscosity liquor having large rate of scaling.
The tube bundle is suspended on bracket.
There is no central downtake.
Downtake is formed by the annular space between the bundle and the shell.
It is used for high viscosity liquor having large rate of scaling.
wrong…basket..high viscosity
Pick out the wrong statement pertaining to the design of the bubble cap tray of a distillation column to give stable operation and even vapour distribution.
The pressure drop due to the caps & slots and the static submergence should be as high as practicable for reasonable operation.
Tendency towards stable operation is increased by increasing the skirt clearance of the caps, lowering the rate of liquid flow per unit plate width or increasing the spacing between the caps.
The dimensionless ratio of liquid gradient to pressure drop head caused by the bubble cap assembly should be less than 0.4.
none of these.
none of these.
Speed of the drum of the rotary vacuum filter normally ranges from __________ rpm.
0.1 to 2
5 to 7
3 to 8
8 to 15
0.1 to 2
0.1 to 2 rpm rotary vacuum drum
A stuffing box is used for
absorbing the contraction/expansion of pipeline due to temperature changes.
prevention of fluid leakage around moving parts.
facilitating smooth opening and closing of a valve.
reducing the resistance of fluid flow.
prevention of fluid leakage around moving parts.
stuffing box… prevention…
Pressure drop (delta(p)) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as
delta(p) = G
delta(p) = G0.5
delta(p) = G2
delta(p) = 1/(G^0.6)
delta(p) = G2
Pick out the wrong statement.
In an agitated vertical cylinderical reaction vessel, the
ratio of liquid depth to tank diameter (i.e. the filling ratio) recommended for most purposes is 1.
filling ratio for dispersing gas in a liquid is 2 for sufficiently long contact period.
flat bottom and conical bottom vessels have low agitation efficiency for agitation of heavy solids in liquids.
dished bottom vessel has very high power consumption.
dished bottom vessel has very high power consumption.
wrong…dished…very high power
Needle valves are generally not used for
very large diameter pipes.
high pressure throttling service.
very accurate flow control.
smaller sizes of pipe.
very large diameter pipes.
Height equivalent to a theoretical plate (HETP) is the height of packing that will give the same separation as one theoretical plate in gas-liquid mass transfer operations like distillation, absorption/stripping and humidification/dehumidification. HETP which is experimentally determined, depends upon the
flow rates of each fluid.
type and size of packing.
concentration of each fluid.
all a, b & c.
all a, b & c.
Pick out the wrong statement.
Safety valves are provided in heat exchangers for removal of non-conden-sables.
Liquid metals and dowtherm are used for very high temperature heating.
In a shell and tube heat exchanger, high pressure fluid is generally routed through the tube.
A loop seal or U-seal is provided in a vertical condenser sub-cooler to prevent quick draining of the condensate.
Safety valves are provided in heat exchangers for removal of non-conden-sables.
With increase in gas flow rate to fabric surface area ratio (Nm3/hr/m2 fabric surface area), the size & the cost of a bag filter
increases
decreases
remain unaffected
none of these
decreases
A head comprises of straight flange section, corner torus, section and central dished section. Crown radius and knuckle radius in a head is related respectively to the
central dished section and corner torus section.
corner torus section and central dished section.
central dished section and straight flange section.
straight flange section and corner torus section.
central dished section and corner torus section.
Which of the following is used to set the diameter of the distillation column ?
Number of theorectical plates.
Static submergence.
Allowable vapour velocity.
Length of straight rectangular weir on cross-flow tray.
Allowable vapour velocity.
vapor velocity - set diameter
Ponchon Savarit method is based on the use of enthalpy concentration diagram, which contains the bubble point curve (saturated liquid curve), dew point curve (saturated vapour curve) and equilibrium tie lines. As compared to McCabe-Thiele’s method, this method
is more accurate in finding the number of equilibrium stages.
accounts for the enthalpy changes in the process.
facilitates direct calculation of heat load on reboiler & condenser from, the diagram used in this method.
all ‘a’, ‘b’ & ‘c’.
all ‘a’, ‘b’ & ‘c’.
The optimum size ratio for two mixed reactors in series depends on the kinetics of the reaction and the conversion level. For reaction orders more than one, the
equal sized reactors are the best.
smaller reactor should come first.
larger reactor should come first.
none of these.
smaller reactor should come first.
Which of the following is not a graphical method (but is an analytical method) for the calculation of theoretical number of stages in case of continuous binary distillation?
Sorel-Lewis method.
McCabe-Thiele’s method.
Ponchon-Savarit method.
none of these.
Sorel-Lewis method.
Saddle supports are used for supporting __________ vessels.
horizontal cylinderical
tall vertical
thick walled vertical
thick spherical
horizontal cylinderical
saddle - horizontal cylindrical
bracket - thick walled vertical
The diameter of a propeller agitator used in agitation tank ranges from __________% of the tank diameter and its peripherial speed is normally 300 to 500 metres/minute.
5 to 10
15 to 30
40 to 50
55 to 75
15 to 30
In packed towers provided with saddle packing, liquid redistributors are positioned at every __________ times column diameter or 6 metres whichever is less.
2-3
5-8
10-15
20-25
5~8
Optimum reflux ratio in a continuous distillation column is determined by the
maximum permissible vapour velocity.
flooding limit of the column.
total cost consideration (fixed cost of the column plus the cooling water & steam cost).
none of these.
total cost consideration (fixed cost of the column plus the cooling water & steam cost).
Cooling water fouling factors vary in the range of 0.001 to 0.003
(BTU/hr.ft^2 . F)^-1
(kcal/hr.m^2 .C)^-1
(W/m^2. K)^-1
(kcal/hr. m. C)^-1
(BTU/hr.ft^2 . F)^-1
Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter )
0.2 D
0.5 D
0.66 D
0.80 D
0.2 D
The maximum liquid gradient over a tray must not exceed
0.5” -1.25”.
2”-3.5”.
5”.
half the tray spacing.
0.5” -1.25”.
An underdesigned steam trap will
waste steam.
destroy itself of acceleration wear due to rapid recycling.
back up condensate and cause water hammer in steam line.
none of these.
back up condensate and cause water hammer in steam line.
The slope of the feed line in distillation opeartion is given by (where, q = fraction of the feed stream that is liquid.)
-q
-q/(1-q)
-q/(q-1)
none of these
[-q/(1-q)]
Speed of industrial paddle agitator ranges from __________ rpm.
1 to 5
20 to 100
500 to 750
1000 to 2000
20 to 100
__________ strain is measured using a ‘strain rosetter’.
Volumetric
Shear
Linear
none of these
Linear
LSR Linear Strain Rosetter
With increase in the reflux ratio for a fixed production from a continuous binary distillation column, the __________ decreases.
fixed charges initially
running cost of cooling water for condenser
vapour & liquid load both
running cost of steam for reboiler
fixed charges initially
The slope of operating line in the rectifying section of a distillation column is unity, if the reflux ratio is
0
infinite
1
minimum
infinite
Vertical vessels are not supported by
brackets
skirts
columns
saddles
saddles
With increase in pressure drop (for a given particle size), the dust collection efficiency of a cyclone separator will
increase
decrease
remain unaffected
increase or decrease depending on the nature of the dust.
increase
Spherical shaped pressure vessel is considered to be the most ideal, because it can
withstand higher pressure for a given metallic shell thickness.
be fabricated very easily.
be designed without wind load considerations.
be supported very easily.
withstand higher pressure for a given metallic shell thickness.
An adequate clearance between the tray and the shell wall of a distillation column is provided to
drain the liquid from the tray when the unit is not in operation.
allow for thermal expansion and facilitate installation.
avoid back-trapping.
none of these.
allow for thermal expansion and facilitate installation.
Overall tray efficiency of a distillation column is the ratio of the number of
overall gas transfer units to the number of ideal trays required.
ideal trays required to the number of real trays required.
real trays required to the number of ideal trays required.
none of these.
ideal trays required to the number of real trays required.
ideal/real overall tray eff.
Pick out the wrong statement about the design of a sieve plate column.
An increased weir height improves the tray efficiency at the cost of high plate pressure drop; optimum wear height being 40-90 mm for column pressure above atmospheric and 6-12 mm for vacuum columns.
For segmental downcomers, the chord length is 60-80% of the column diameter. An initial value of downcomer area of 12% is taken in the design.
Width of the calming section provided at the inlet and outlet sides of the plate is 75 mm for column diameter below 1.5 metres and 100 mm for larger diameter columns.
Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds.
Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds.
wrong… Minimum recommended downcomer