## Multiple Choice Questions and Answers on Process Equipment and Plant Design

**Question 1 : 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.

**Answer : 4**

**Question 2 : 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

**Answer : 1**

**Question 3 : 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.

**Answer : 2**

**Question 4 : Pressure drop (Δ p) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as**

- Δ
*p*=*G* - Δ
*p*=*G*^{0.5} - Δ
*p*=*G*^{2} - Δ
*p*= 1/*G*^{0.6}

**Answer : 3**

**Question 5 : 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.

**Answer : 4**

**Question 6 : 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

**Answer : 4**

**Question 7 : For laminar flow ( N_{Re} < 2100) in steel pipe, the optimum inside pipe diameter is given by**

*D*= 3_{i, opt}*Q*^{0.36}ρ^{0.18}*D*= 3.9_{i, opt}*Q*^{0.45}. ρ^{0.23}*D*= 7.6_{i, opt}*Q*^{0.36}. ρ^{0.9}*D*= 3_{i, opt}*Q*^{0.36}. ρ^{1.86}μ^{0.08}

**Answer : 1**

**Question 8 : 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.

**Answer : 2**

**Question 9 : Wall thickness of schedule 40 pipe as compared to that of schedule 80 pipe is**

- more
- less
- same
- either (1) or (2); depends upon the I.D. of the pipe

**Answer : 2**

**Question 10 : 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.

**Answer : 1**

**Question 11 : ________ tray arrangement is recommended for distillation column having diameter upto 4 ft.**

- Radial flow
- Cross flow
- Split flow
- Cascade

**Answer : 2**

**Question 12 : What is the value of ‘ q‘ for saturated liquid feed to a distillation column ?**

- 0
- <1
- 1
- >1

**Answer : 3**

**Question 13 : 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 (1), (2) and (3).

**Answer : 4**

**Question 14 : 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.

**Answer : 3**

**Question 15 : The operating pressure drop range in a bag filter is about __________ mm water gauge.**

- 50-150
- 5-10
- 500-1500
- 1500-2500

**Answer : 1**

**Question 16 : In chemical process equipments, the conical bottom heads used, usually has an apex angle of**

- 20°
- 40°.
- 60°
- 80°

**Answer : 3**

**Question 17 : 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

**Answer : 3**

**Question 18 : 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.

**Answer : 2**

**Question 19 : 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
- 20-40
- 20-40

**Answer : 2**

**Question 20 : 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

**Answer : 4**

**Question 21 : 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

**Answer : 1**

**Question 22 : 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

**Answer : 3**

**Question 23 : Pick out the wrong statement**

- For all the cylindrical process vessels operating above atmospheric pressure, formed heads are used for closing the vessel.
- Fouling factor of river water is less than that of sea water.
- Risers provided in bubble cap trays in the distillation column facilitate the flow of both liquid and vapor.
- both (2) and (3).

**Answer : 4**

**Question 24 : 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.**

- 50
- 20
- 35
- 55

**Answer : 2**

**Question 25 : 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.

**Answer : 1**

**Question 26 : It is not desirable to design a heat exchanger for LMTD correction factor, F_{T}, of less than**

- 0.99
- 0.95
- 0.80
- 0.55

**Answer : 3**

**Question 27 : A rivetted joint does not fail by __________ of rivets.**

- tearing
- shearing
- tearing of the plate across a row
- none of these

**Answer : 4**

**Question 28 : Triangular pitch tube layout as compared to square pitch in a shell and tube heat exchanger**

- permits the use of less tubes in a given shell diameter.
- facilitates comparatively easier external cleaning because of large clearance.
- permits the use of more tubes in a given shell diameter.
- both (2) and (3).

**Answer : 3**

**Question 29 : Bracket supports are the most suitable for supporting __________ vessels.**

- thick walled vertical
- horizontal
- thin shperical (e.g. Horton sphere)
- none of these

**Answer : 1**

**Question 30 : 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 (1), (2) and (3).

**Answer : 4**

**Question 31 : 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

**Answer : 1**

**Question 32 : 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

**Answer : 4**

**Question 33 : 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}

**Answer : 4**

**Question 34 : In a heat exchanger, shell side fluid velocity can be changed by changing the tube**

- layout
- pitch
- both (1) & (2)
- neither (1) nor (2)

**Answer : 3**

**Question 35 : 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

**Answer : 2**

**Question 36 : The stress developed in a material without any permanent set is called the**

- ultimate stress
- yield stress
- elastic limit
- breaking stress

**Answer : 3**

**Question 37 : 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.

**Answer : 3**

**Question 38 : 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.

**Answer : 2**

**Question 39 : 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 Δ p = pressure drop per tray, psi)**

- η = 17 – 61.1 log μ
- η = 1.66 – 0.25 log μ
- η = 0.25 log μ – 1.67

**Answer : 1**

**Question 40 : for fully open globe value of **

**may be around**

- 10
- 25
- 75
- 300

**Answer : 4**

**Question 41 : 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 (1), (2) and (3).

**Answer : 4**

**Question 42 : 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.

**Answer : 3**

**Question 43 : With increase in the number of shell passes, the value of F_{T}**

- increases
- decreases
- remains same
- remains same, only if the number of tube passes does not change.

**Answer : 1**

**Question 44 : 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

**Answer : 2**

**Question 45 : Fresh water carrying pipelines in chemical industries are coloured with __________ color.**

- sea green
- brown
- yellow
- red

**Answer : 1**

**Question 46 : Which of the following material is seldom used for pressure vessel construction ?**

- Rimmed still
- Mild steel
- Killed steel
- Semi-killed steel

**Answer : 1**

**Question 47 : The ratio of shear stress to shear strain is called**

- bulk modulus
- shear modulus
- modulus of rigidity
- modulus of elasticity

**Answer : 2 **

**Question 48 : 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.

**Answer : 1**

**Question 49 : 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

**Answer : 3**

**Question 50 : Triangular pitch tube layout as compared to square pitch in a shell and tube heat exchanger**

- permits the use of less tubes in a given shell diameter.
- facilitates comparatively easier external cleaning because of large clearance.
- permits the use of more tubes in a given shell diameter.
- both (2) and (3).

**Answer : 3**