answers - ies master

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ESE-2017 PRELIMS TEST SERIESDate: 20th November, 2016

24. (c)

25. (b)

26. (d)

27. (c)

28. (a)

29. (b)

30. (c)

31. (c)

32. (a)

33. (c)

34. (a)

35. (b)

36. (a)

37. (a)

38. (d)

39. (d)

40. (a)

41. (a)

42. (a)

43. (b)

44. (b)

45. (b)

46. (c)

47. (d)

48. (b)

49. (d)

50. (d)

51. (c)

52. (a)

53. (b)

54. (b)

55. (d)

56. (d)

57. (d)

58. (d)

59. (c)

60. (a)

61. (d)

62. (a)

63. (a)

64. (b)

65. (c)

66. (d)

67. (a)

68. (b)

69. (c)

70. (d)

71. (d)

72. (b)

73. (a)

74. (c)

75. (a)

76. (a)

77. (a)

78. (a)

79. (c)

80. (d)

81. (d)

82. (a)

83. (d)

84. (d)

85. (b)

86. (c)

87. (a)

88. (a)

89. (a)

90. (b)

91. (c)

92. (b)

93. (c)

94. (b)

95. (a)

96. (a)

97. (c)

98. (b)

99. (c)

100. (b)

101. (a)

102. (b)

103. (c)

104. (d)

105. (b)

106. (a)

107. (c)

108. (d)

109. (a)

110. (c)

111. (d)

112. (d)

113. (c)

114. (b)

115. (b)

116. (d)

117. (d)

118. (c)

119. (b)

120. (c)

121. (c)

122. (d)

123. (b)

124. (c)

125. (d)

126. (b)

127. (c)

128. (b)

129. (c)

130. (c)

131. (c)

132. (d)

133. (d)

134. (c)

135. (d)

136. (b)

137. (a)

138. (c)

ANSWERS

1. (c)

2. (a)

3. (c)

4. (a)

5. (a)

6. (a)

7. (c)

8. (c)

9. (a)

10. (a)

11. (d)

12. (b)

13. (c)

14. (d)

15. (d)

16. (a)

17. (b)

18. (b)

19. (a)

20. (b)

21. (a)

22. (a)

23. (a)

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(2) ME (Test-10), Objective Solutions, 20th November 2016

139. (a)

140. (b)

141. (a)

142. (a)

143. (a)

144. (b)

145. (a)

146. (a)

147. (a)

148. (b)

149. (b)

150. (a)

151. (a)

152. (c)

153. (a)

154. (a)

155. (b)

156. (a)

157. (c)

158. (b)

159. (d)

160. (a)

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Sol–1: (c)The function of injector is same as feedpump. The injector is used in lowpressure vertical or locomotive boilers.It is replaced by feed pump in highcapacity boiler.

Sol–2: (a)The temperature in the fluidized bedboiler is lower than conventional becauseof inert material present in the bed.For more detail, in fluidized bedcombustion, the fuel packed with inertmaterial and su lphur absorbent(dolomite etc) is burnt in fluidizedconditions which results in,

Low temperature in the range of900°C.

Low temperature result in low NOxformation

Sulphur is removed by absorbent(dolomite) and SO2 formation is neg-ligible.

Poor quality fuel can be burnt. The amount of fuel in the packed

bed is very small i.e. 1-2% only.Sol–3: (c)

(1) The fusible plug protects boilers fromoverheating when water level dropsbelow safe limit in drum.

(2) Blow-off cock is used for blow downthe mud and sediments to ensuredesired PPM in drum. This is alsoused for emptying drum duringmaintenance.

(3) Steam Trap- It removes the conden-sate and non-condensible gases fromsteam pipe before the steam goes toturbine.

(4) Feed check value:- It checks the feedof water into drum at high pressureand stops the backflow from boilerdrum.

Sol–4: (a)• Due to very high pressure in high pres-

sure boilers, the natural circulation isnot so effective. So forced circulation isprovided for effective steam genertionand heat utilization.

• The tubes are also cleaned by highpressure steam in addition to sootblower.

Sol–5: (a)A. Lancashire boiler is horizontal water

drum and two gas tube.B. Cornish is similar to Lancashire but

it has one flue gas tube in place oftwo.

C. La-mont boiler is high pressure wa-ter tube with recirculation or sub-critical boiler.

D. Cochran-It is vertical water drum andhorizontal gas tube boiler. The gastubes are inside boiler drum.

Sol–6: (a)Water walls are provided in furnace forhigh pressure steam generation. Theytake heat from convection, radiation andprotect refractory walls from high tem-perature. They have nothing to do withwater circulation rate. Since water wallshas no direct contact with fire or fluegases, so evaporation is mainly byradiation.

Sol–7: (c)Soot Blower – It is a fan inside thefurnace to remove the flyash from heattransfer surfaces of tubes to increasethe heat transfer coefficient.Electrostatic precipitator – Itremoves the solid carbon particles fromflue gases at the exit of furnace.Blow Down – It is a process duringwhich impurites dissolved in water indrum of boiler are removed to maintainthe purity level i.e. removal of solidsfrom boiler drum.Zeolite – It is a chemical compoundwhich purify water before entering toboiler drum.

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Sol–8: (c)Fusible Plug : Safety precautionagainst low water level in steam boilers.Safety valve : To prevent excessiveinternal pressure.Blow off cock : To remove sludge andother impurites from inside the boiler.

Sol–9: (a)Boilers are provided with economizer andair preheaters to recover heat from fluegas. An increase of about 20% in boilerefficiency is achieved by providing botheconomizers and air-preheaters. Thefeedwater from high pressure heatersenters the economizer and picks up heatfrom the flue gases after the lowtemperature superheater. Similarly, airpreheaters are provided in boilers topreheat the combustion air.

Sol–10: (a)I D fans are used to exhaust the productsof combustion from the boiler.Maintaining balanced draft conditions inthe furnace improves boiler operation andprovides energy to move the flue gases atthe velocities needed for good heat transfer.I D fans are subjected to more serviceconditions than forced draft fans, becausethey must handle larger volumes of gasat high temperatures and containing ashparticles. Backward inclined fans areacceptable for non-abrasive gas service,while radial or radial fans arerecommended for abrasive service. Thehigher temperature of gases handled bythe I D fans sometimes makes itnecessary to use water-cooled bearings toprevent overheating. Inlet damper controlsor variable speed drives are used to controlI D fan capacity.

Sol–11: (d)In high pressure boilers, pumps are usedto maintain forced circulation of waterthrough the tubes of the boiler. Thisensures positive circulation of water andincreases evaporative capacity of the boilerand less number of steam drums will berequired. Pressurised combustion is usedwhich increases rate of firing of fuel thus

increasing the rate of heat release.The tendency of scale formation iseliminated due to high velocity of waterthrough the tubes.The steam can be raised quickly to meetthe variable load requirements withoutthe use of complicated control devices.

Sol–12: (b)The primary purpose of blow down is tomaintain the solid concentration of boilerwater within certain limits. This may berequired for specific reasons such ascontamination of the boiler water. In thiscase, a high blowdown rate is required toeliminate the contaminants as rapidly aspossible.

Sol–13: (c)Steam drum stores the steam generatedin water tubes and acts as separator forsteam/water mixture. In benson boiler,the boiler pressure is raised to criticalpressure and hence there is no formationof bubbles, hence steam drum is notrequired.

Sol–14: (d)Steam trap: Boiler accessoryWater-level indicator: BoilermountingCornish boiler: Fire tube typeBenson boiler: Drumless type

Sol–15: (d)Boiler mountings are fittings for the safetyof the boiler, and for complete control ofthe process of steam generation. Themountings form an integral part of theboiler and are mounted on the body of theboiler itself.Ex- Safety valve, water level indicators,pressure gauge, fusible plug, steam stopvalve, feed check valve, blowoff cock.Boiler accessories are installed to increasethe efficiency of the steam power plants.Ex-Air preheater, Economiser,superheater, feed pump, Injector.

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Sol–16: (a)Soot blower is a device for removing thesoot that is deposited on the furnace tubesof a boiler during combustion.LP Steam is normally used as a mediumfor blowing away the soot since capitalcost of steam pressure reducingequipment and drain is less than the costof compressor, motor and control of airsystem.

Sol–17: (b)Fly ash is captured and removed fromthe flue gas by electrostatic precipitatorlocated at the outlet of the furnace andbefore the induced draft fan.

Sol–18: (b)The safety valves are designed to go fullopen within an over pressure leveltypically of 3% of the rated valve. Thesafety valve will close once the systempressure reduces to what is called reseatpressure. The valve will have to be set insuch a way that the reseat pressure is95% of the set pressure and is limited toa maximum of 5% to avoid wastage ofsteam produced.The superheater outlet will have one tothree safety valves on either side of theboiler. Safety valves are provided in thedrum, superheater and reheater.

Sol–19: (a)

Rate of air consumption am = 80kg/s ×11kg/kg of coal = 880 kg/s

Density of air a = 1.2 kg/m3

Pressure developed = 1.2 × 103 × 9.81 Power of FD fan

= 3880 1.2 10 9.81

1.2 0.8

= 10.97 MW

Sol–20: (b)Flue gases flow at supersonic velocity tofacilitate very high rate of heat transfer

Sol–21: (a)Blow off cock is a boiler mounting whichremoves water from the shell at regular

intervals to remove the various impuritiesthat may be settled at the bottom of theshell.

Sol–22: (a)Path of flue gasSuperheater Economiser Airpreheater Precipitator.

Sol–23: (a)According to Dalton’s law, the totalpressure exerted by the mixture of non-reactive gases is the sum of partialpressure of individual gases. Condenser pressure = partialpressure of steam + partial pressure ofair = 0.06 + 0.007 = 0.067 bar.

Sol–24: (c)A supercritical steam generator operatesabove the critical pressure i.e. 22 MPa or217.7 atm. These days, it has become apractice to use supercritical boilers above300 MW capacity plants.Once through boilers are always used insupercritical cycles. Once through boilersare better suited to frequent loadvariations than drum type boilers. Alsothese don’t need to have a boiler blowdown.

Sol–25: (b)Cooling towers are used to cool water tolower temperature by evaporative coolingin which air takes away water along withit.

Sol–26: (d)WBT decides the capacity to which aircan carry the water along with it, henceit decides the maximum cooling towerefficiency.

Sol–27: (c)Economiser is used to heat the waterbefore it enters the boiler, by utilisingthe energy flue gases from the furnace.

Sol–28: (a)The cyclone collection efficiency increaseswith increasing (a) particle size, (b)particle density, (c) inlet gas velocity (d)cyclone body length (e) number of gasrevolutions, and (f) smoothness of cyclone

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walls. The cyclone collection efficiencydecreases with increasing (a) cyclonediameter, (b) gas outlet duct diameter,and (c) gas inlet area.

Sol–29: (b)

0

mass of all particle retained bycollector ESP

mass of all particle entering collector

0m

0AV

1 expQ

Sol–30: (c)Manufacturing equipment machinesused in batch production is generalproduction machines, which are de-signed for higher production rate. Forexample, turret lathes capable of hold-ing several cutting tools are used ratherthan engine lathes. The machine tools usedin batch production are usually com-bined with specially designed jigs andfixtures, which increase the productionrate.Batch production plants includemachine shops, foundries, plastic moul-ding units and press shops. This alsoincludes some kinds of chemical andpharmaceutical units. Batch quantitiesmay vary from very few units to manythousands of units.

Sol–31: (c)Sol–32: (a)

A closely packed grain structure, smallgrains, high cutting speed, low feed rateand small depth of cut will all tend toresult in a low value of undeformed chipthickness. Further, because of the rela-tively inefficient cutting conditions ingrinding, the specific cutting energy isconsiderably higher in grinding than inmetal-cutting process.

Sol–33: (c)Sol–34: (a)

Because all materials have a finitemodulus of elasticity, plastic deformationis followed by elastic recovery uponremoval of the load; in bending this

recovery is known as spring back.Sol–35: (b)

Since the axial feed of tool is200 mm/min and the tool is 150 mmlong, hence the time taken

= 150mm min200mm = 3 60s 45s=

4

Sol–36: (a)

Tailstock offset = 2 1d d 50 38=2 2 = 6 mm

Sol–37: (a)Turret head is mounted directly on thesaddle, which moves on the lathe bedways. Turret cathe is capable of handlingheavier jobs in comparison to capstanlathe.

Sol–38: (d)The centre of the workpiece is slightlyabove the centre of the grinding wheel.The directions of rotation of workpieceand grinding wheel are opposite.

Sol–39: (d)In down-milling the chip starts as maxi-mum thickness and goes to zerothickness gradually and reverse will bethe case for a chip formed by up-mill-ing.

Sol–40: (a)Sol–41: (a)

High speed steel < Tungsten carbide <Cermet < cemented titanium carbide.

Sol–42: (a)51 (Manufacturer’s option of nature of

abrasive)A (Type of abrasive) – Al2O3

36 (Grain size) – MediumL (Grade) – MediumT (Structure) – CloseR (Type of bond) – Rubber23 (Manufacturer’s reference)

Sol–43: (b)• EDM is used for shaping alloying steel

and tungsten carbide dies, used for

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moulding, forging, extrusion, wire drawingor suitable mould cavities, press tools andto given any intricate shape or profile.

• ECM is used for machinery difficult tomachine materials and complex shapedparts.

• Laser beam machining can make holes ina wide variety of materials such asplastics, ceramics and many metals andalloys.

• USM can be used for drilling circular ornon-circular holes in very hard materials.

Sol–44: (b)Right-hand spiral reamers have betterchip-removal capabilities and for thisreason, these are used for reaming deepblind holes. Straight-fluted chuckingreamers are usually designed withstaggered flutes. The flutes are irregularlyspaced around the circumference of thereamer body to prevent setting upvibrations that will result in chattering.Left hand spiral reamers tend to pushback against the feeding mechanism ofthe machine and are well-suited to looselinkage. In other words, they keep anyslack or backlash in the feedingmechanism in one direction.

Sol–45: (b)UCON: Consists of 50% columbium,30% titanium, and 20% tungsten.Cubic Boron Nitride: It consists ofatom of boron and nitrogen.Stellite: It contains 40-45% cobalt, 30%chromium, 14-25% tungsten and 2%Carbon.Tungsten Carbide: It contains 85–95%tungsten carbide and 5-15% cobalt.

Sol–46: (c)Sol–47: (d)

When friction between the tool and chipis high while machining ductile mate-rials, some particles of chip adhere tothe tool rake face near the tool tip. Whensuch sizeable material piles up on therake face, it acts as a cutting edge inplace of the actual cutting edge. This is

termed as built-up edge (BUE). Byvirtue of work hardening, BUE isharder than the parent work material.As the size of BUE grows larger, itbecomes unstable and parts of it getremoved while cutting. The removedportions of BUE partly adhere to thechip underside and partly to the ma-chined surface. This causes finishedsurface to be rough. However, since thecutting is being carried by the BUEand not the actual toop tip, the life ofthe cutting tool increases while cuttingwith BUE. That way BUE is not harm-ful while rough machining.The conditions that normally induce theformation of BUE are low cutting speed,high feed and low rake angle. One ofthe prerequisites for the formation ofBUE is the work hardenability of theworkpiece material. Higher the workhardenability, rougher is the machinedsurface produed.

Sol–48: (b)Sol–49: (d)

The resultant roughness producedduring turning operation is due to thecombined effect of two independentquantities such as ideal roughness andnatural roughness. Ideal roughness isdue to the tool geometry and its feed.It is a geometrical phenomenon and isthe minimum possible magnitude of theunevenness, which results from amachining operation.Movement of a cutting tool across thesurface of the turning componentproduces the diamond turnedroughness, therefore, it always hassome periodic surface roughness. Thesurface texture is directly related to thecombination of the tool shape and radius,and the tool’s path over the surface.The machines operating conditionsaffect this surface figure and finish inthe direct quantitative manner indicatedin the theoretical surface finish equationgiven as:

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Maximum height of unevenness

=

2feed/rev8 tool nose radius

Sol–50: (d)UCON: It is a combination ofcolumbium, titanium and tungsten. Itcontains 50% columbium, 30% titaniumand 20% tungsten.Ceramic: These are also calledcemented oxide. It is major constituentis aluminium oxide.Stellite: These are non-ferrous castalloys. Stellite contains 40-45% cobalt,30% chromium, 14-25% tungsten and2% carbon.HSS: It is usually carbon steelcontaining 1.5 to 2% carbon, 18%tungsten, 4% chromium, 1% vanadiumand the rest is iron.

Sol–51: (c)Gear shaping with pinion cutter cancut internal gears. If a rack cutter isused in place of pinion cutter, the rackwill move tangential to the gear blankwhile reciprocating. Since the length ofrack is limited, it needs to beperiodically indexed to bring the rackback to its original position. This has afacility for the vertical axis to beswivelled in the vertical plane such thatsingle helical gears can be producedwithout any additional mechanisms.Gear hobbing is a continuous processeliminating the unproductive returnmotion of the gear-shaping operation.

Sol–52: (a)In ultrasonic machining, the materialis removed from a surface bymicrochipping and erosion with fineabrasive grains in a slurry. The tip ofthe tool vibrates which imparts a highvelocity to abrasive grains between thetool and the workpiece. Thus high stressis produced by the impact of abrasiveparticles on the workpiece surface,which causes microchipping and erosionof the workpiece surface.

Sol–53: (b)In a turret lathe, a hexagonal turretreplaces the tailstock. The turret hassix cutting tools which can be usedseparately by bringing each of them inthe operating position. Important partsof a turret lathe include saddle, workholding device, cross-slide and tool post(rear and front).

Sol–54: (b)

Chip thickness ratio = depth of cutchip thickness

If depth of cut is halved, then for chipthickness ratio to be same, the chipthickness should also be halved.

Sol–55: (d)Taylor’s equation VTn = constant

V10.25

1T = V20.252T

2

1

VV =

0.251

2

TT

12 =

0.251

2

TT

1

16 = 1

2

TT

Tool life increases by sixteen times.Sol–56: (d)

Orthogonal cuttingCutting edge remains perpendicular tothe cutting velocity. Direction of chipflow velocity is normal to the cuttingedge. Angle of inclination and chip flowvelocity are zero. Cutting edge is largerthan the width of cut. Only twomutually perpendicular components ofcutting forces are acting on the toolcutting edge. The maximum chipthickness occurs in the middle. The toolprepares a surface which is parallel tothe work surface.Oblique CuttingCutting edge is inclined at an acuteangle to the cutting velocity. Threemutually perpendicular components of

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cutting forces act at the cutting edge ofthe tool. Cutting edge may or may notbe longer than the width of cut. Themaximum chip thickness may notoccur at its middle. Frequently, morethan one cutting edges are in action.The tool prepare a surface which mayor may not be parallel to the worksurface. Direction of chip flow velocityis at an angle.

Sol–57: (d)Stroke length = 250 mm = 250 ×10–3 m = 0.25 mThe shaping machine makes 30 doublestrokes per min.Hence, the length travelled per minuteis 0.25 × (30 × 2) = 15m/min.

Sol–58: (d)The multi-spindle performs fouroperations simultaneously so its cycletime is simply whichever is the largestsingle operation performed.So, have the longest time = 75 secondshence, cycle time = 75 seconds

Sol–59: (c)Method study results in reducedproduction time. It is used to reduceexcessive materials handling ormovement and thereby reducing thefatigue of workman. It forms the basisfor determining time standards. It helpsin efficient planning of production, processand also in manpower planning.

Sol–60: (a)• The string diagram is one of the most

useful techniques for recording andexamining activities in method study. Itis a scaled plan or model or which thepath of workers, materials or equipmentsis traced by winding a string along thepath of movement. The length of pathtraced by man, material or equipment ismeasured by the length of the string usedduring a specified sequence of events. Instring diagram, movement is shown bywinding a string around the pins insertedat each work station.

• Flow diagram simply shows the path ofmovement of workers, materials orequipments.

• Travel chart in a two-way matrix tablefor presenting quantitative data about themovements of workers, materials orequipments between any number of workstations over any given period of time.The main purpose of travel chart is tomake an efficient layout of plant and shopsso that the distance travelled by manand materials during the manufacture ofa product is minimum.

• Man and Machine process chartIt is a special type of multiple activitychart in which the activities of differentoperative and machines are recorded interms of working time and idle time.

Sol–61: (d)

Total cost

Fixed cost

Production quantity

Sales r

evenu

e Co

st

Break even point

We can see from the figure that atbreak even point, profit/loss is zero andsales revenue is equal to the total cost.

Sol–62: (a)Sol–63: (a)

In-process inventory is high in processlayout because material moves fromwork-center to work-center waiting tobe processed. Finished goods inventory,however, is low because goods are beingmade for particular layouts.

Sol–64: (b)Scheduling can be defined prescribingof when and where each operationnecessary to produce a product is toperformed. It can also be defined asfixing up starting and finishing timesof each operation comprising a

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procedure.Sol–65: (c)

Standard time = Observed time ×(Rating factor) × (1+ Allowance)2 × 1.2 × (1 + 0.1) = 2.64 minutes

Sol–66: (d)sx = F + v x + P

x = F P ;sv

At BEP, P = 0

x = Fsv

Higher the value of s, lesser will be x.Sol–67: (a)

A good plant layout can achieve theobjective of economy in handling ofmaterials, work-in-progress and finishedgoods, and efficient utilization of availablespace. However, there will be need of anew plant layout in the following cases: Change in product design Introduction of new product Obsolescence of facilities Change in demand Market changes Competitive cost reduction Frequent accidents Adoption of new safety standards Decision to build a new plant

Sol–68: (b)A route sheet or route card listsmanufacturing operations in propersequence and associated machine tools foreach parts. It also indicates thedepartments in which a particularoperation is to be done on a part and towhich department the parts must go tofor the next operation. A route sheettravels with the parts which moves inbatches between the process from onepoint in the plant to another.

The operation sheet lists the variousoperations in sequence, required forproducing a part. Operation sheets varygreatly as to details. In common types ofoperation sheets, complete details aregiven regarding manufacturingoperations e.g. cutting speeds, feeds,depths of cut and tools. Often, the timeanalysis for each operation is alsoincluded in the operation sheet.

Sol–69: (c)Break-even analysis can be used for bothprofit analysis and comparison of twodifferent methods of production.Thus, we can analyse that at whatquantity of production, we can recoverboth fixed as well as variable cost.After break-even quantity, there will beprofits depending upon the volume ofproduction.

Totalsales/revenue

Break evenQuantity

Quantity

Fixe

d Co

stCo

st

Quantity

FC2

FC1

1 2

Thus, two different production methodscan also be compared and it can be foundout that for a given volume of production,which method would be beneficial.

Sol–70: (d)Work measurement techniquesTime study : Short cycle repetitivejobs.Work sampling: long cycle jobs/heterogeneous operations.

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Synthetic data: Short cycle repetitivejobs.MTM: Manual operations confined toone work centre.Analytical estimating: Short cyclenon-repetitive jobs.

Sol–71: (d)Fixed position – Ship buildingProduct Layout – helps in reducingtotal production time, also duplicateequipment is employed to avoidbacktracking.Process Layout or FunctionalLayout – machines performing similaroperations are grouped together. Herebacktracking is common.

Sol–72: (b)For vertical equilibrium,

TA

TB

60°30°

80 NTB cos 60° = 80

BT2 = 80

TB = 160 NSol–73: (a)

Static Friction: Angle between thenormal reaction and the resultant of forceof friction and normal reaction.Dynamic Friction: The force of frictiondeveloped between two bodies at rest.Solid Friction: The force of frictionbetween two bodies in motion.Angle of Friction: Friction between drysurfaces which are not lubricated.

Sol–74: (c)

13 m

A P

12 mT

Q

O

40 kN

5 mThe weight 120 kN would be equallyshared by the three legs.Since, the vertical height OP = 12 mand length of leg OA = 13 mhence, AP = 2 2OA OP 5m=

If the force on the tripod leg is T, thenT cos = 40

where, cos = 1213

T = 40 40 13 43.3kN= =cos 12

Sol–75: (a)

Work done = 21 kx2

= 3 21 10 10 (1 0.6)2

= 800 JSol–76: (a)

R = 2 2P Q 2PQ cos

R will be maximum, when cos 1=

maxR = 2 2P Q 2PQ = (P + Q)

R will be minimum, when cos 1=

Rmin = 2 2P Q 2PQ = (P – Q)Rmax = 40 = P + Q andRmin = 10 = P – Q

P = 25 kN and Q = 15 kNSol–77: (a)

Energy, work = scalarsForce, momentum, velocity = vectors

Sol–78: (a)Let the box have a mass m and the personhave a mass of M.

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m

M

Then, mg = WLet N be the normal reactionThen, mg – N = ma

mg

N

But, the acceleration ‘a’, while jumpingwould be ‘g’.Hence mg – N = mg N = 0 Hence, the man would feel a load ofthe magnitude of the normal reactionwhich is zero

Sol–79: (c)The acceleration will be directed towardsthe mean position due to the restoringforce. The acceleration will be maximumat the end points whereas velocity will bemaximum at the mean position.

Sol–80: (d)

Range =2u sin 2

g

where = angle with the horizontalu = initial velocity

So, range will be maximum when sin 2 1=

2 = 2

= 4

Sol–81: (d)

Kinetic energy of flywheel = 21 I2

Sol–82: (a)m1g – T = m1 a

m2

m1

m1g

T

and T = m2a

m1g – m2a = m1a

m1g = (m1 + m2)a

a = 1

1 2

m gm m

Sol–83: (d)

LT

T

T

W

45°

W1

LFor the equilibrium of mass W1

T = W1

For the equilibrium of the rod

(T sin 45°) × L = LW2

T2 = W

2

T = W 22 =

W2

W1 = W2

Sol–84: (d)Let AB = l and its weight = WMoment about A will be zero.

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AW

BT cos 30°30°

T cos 60°

Hence, (T cos 60°) × l cos 30°

+ (T cos 30° × l cos 60°) = W cos 302l

llT 3 T 32 2 2 2 =

3W2 2l

T

30°60°

T = W2

W = 2T = 2 × 200 = 400 kgfLet the reaction be R at A, at angle of Q.Then, considering the equilibrium ofvertical forces,

R

A

T cos 60° + R sin = W

Rsin = TW T cos 60 W=2

400= 200 300=2

...(i)

Again, considering the equilibrium ofhorizontal forces,

R cos = T cos 30°

= 3200 100 3=2...(ii)

From (i) & (ii), we have,

R2 = 22300 100 3

R = 200 3 kgf

Again R sinR cos

= 300

100 3

tan = 3

= 60°

Sol–85: (b)Automatic expansion valve maintains aconstant pressure and hence a constanttemperature in the evaporator. The floatvalve is a type of expansion valve whichmaintains the level of liquid refrigerantconstant in a vessel or an evaporator.Hence, the mass flow rate of therefrigerant through the expansion valveis proportional to the evaporation rateof the refrigerant in the evaporator,which in turn is proportional to the load.

Sol–86: (c)For dehumidification to take place, theevaporator temperature should be lowerthan the apparatus dew pointtemperature.

Sol–87: (a)Sol–88: (a)

For comfort condition DBT = 25°C andRH = 50-60%. So for low energy conditionwe will keep DBT = 25°C and relativehumidity as low as possible.

Sol–89: (a)The conditioned air supplied to the roommust have the capacity to take upsimultaneously both the room sensibleheat and room latent heat loads. Thepoint S on psychrometric chartrepresents the supply air condition andpoint R represents the room designcondition. The line SR is called roomsensible heat factor line (RSHF line).The slope of the line gives the ratio ofthe room sensible heat (RSH) to the roomlatent heat (RLH). Thus, the supply airhaving its conditions given by any pointon this line will satisfy the requirementsof the room with adequate supply of suchair.

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Dry bulb temperature

Roomdesigncondition

Sp. h

umid

ity

ADPS

Supply aircondition

R

RSHFline

RTH

RSH

RLH

td1 td2

Sol–90: (b)

BPF = 2 c

1 c

t tt t

= 30 2540 25

= 0.33

Coolingcoil t = 25°CC

t =

30°C

2t =

40°C

1

Sol–91: (c) wm = 0.003 kg/s,

am = 1 kg/s, T = ?

Cp = 1 kJ/kgK,LH = 2500 kJ/kg

wm LH = a pm C T

T =

w

a p

m LHm C

= 0.003 2500 7.5 C1 1

Sol–92: (b)All points located on a given effectivetemperature line in the comfort chart don’tindicate conditions of equal comfort ordiscomfort. The extremely high or lowrelative humidities may produce conditionsof discomfort regardless of the existenteffective temperature. The most desirablerelative humidity range is between 30 and70 percent. Further, it does not take intoaccount the variations in comfortconditions when there are wide variationsin the mean radiant temperature. Theeffect of mean radiant temperature on

comfort is less pronounced at hightemperature than at low temperatures.Effective temperature takes intoconsideration the air velocity and isapplicable to reasonably still air with airvelocity 5 to 8m/min.

Sol–93: (c)• When there is a direct addition of heat

to the enclosed space, a gain in thesensible heat is said to occur.

• The heat gain through the walls ofducts carrying conditioned air throughunconditioned space in the building isan example of sensible heat.

• Sensible heat gain is due to temperaturedifference. Latent heat gain is due todifference in moisture content.

• When there is an addition of watervapour to the air of enclosed space, again in latent heat is said to occur. Thislatent heat is to be removed during theprocess of summer air-conditioning.

Sol–94: (b)Sol–95: (a)

The numerical value of effectivetemperature is equal to the temperatureof still saturated air, which producesthe same sensation of warmth or coolnessas produced under the given conditions.

Sol–96: (a)Low value of BPF for an air conditioningequipment signifies higher performance.Cooling coil efficiency = 1–BPFBPF signifies hypothetically the fractionof air that passes through the coolingcoil unaffected i.e. the fraction of airthat remains at the inlet temperatureof the cooling coil.

Sol–97: (c)In hot and dry condition, the humidityis very low, so wet bulb depression isvery large. In this condition, evaporativecooling by desert coolers is suitable.

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Sol–98: (b)

HPCOP = R 1COP = 4.5 + 1 = 5.5

Sol–99: (c)

4

3

2

1

P = c

P = cT

sSol–100: (b)

DBT

2 SC

HumidityRatio(

DPT t1t2

1

WBT LineDPT

The psychrometric chart clearly indicatesthat during sensible cooling its wet bulbtemperature decreases and the dew pointtemperature remains constant.

Sol–101:(a)Q2 = 1 kW

For Carnot refrigerator

1

1

QT = 2

2

QT

Q1 = 21

2

Q TT

=1 300 1.5kW=

200

Work inputW = 1 2Q Q 1.5 1 0.5kW= =

Sol–102:(b)

The name of refrigerant m n p qC H Cl F

would be 1 1R m n q where

2 2n p q m

Inorganic refrigerants are designated byadding 700 to the molecular mass of the

compound.Dichloro-difluoromethane: R 12

Sol–103: (c)The main components of steam jetrefrigeration system are flash chamber orevaporator, steam nozzle, ejector andcondenser.Expansion valve is not used in a steamjet refrigeration system. In the steamejector, the high pressure steam from theboiler expands while flowing through theconvergent-divergent nozzle. Theexpansion causes a very low pressure andincreases steam velocity. The watervapours from the flash chamber areentrained by the high velocity steam andboth are mixed in the mixing section atconstant pressure. The mean velocity ofthe mixture will be supersonic, after themixing is complete. This supersonic steamgets a normal shock, in the constant areathroat of the diffuser. This results in therise of pressure and subsonic flow. Thefunction of the diverging section of thediffuser is to recover the velocity head aspressure head by gradually reducing thevelocity.

Sol–104:(d)In vapour absorption system, thecompressor of the vapour compressioncycle is replaced by absorber, pump,generator, and a pressure reducingvalve.

Sol–105:(b)Sol–106:(a)

The pressure in capillary tube decreasesdue to two factors:(i) The refrigerant has to overcome

frictional resistance offered by tubewalls

(ii) The liquid refrigerant flashes intomixture of liquid and vapour as itspressure reduces. The density ofvapour is less than that of the liquid.Hence, the average density ofrefrigerant decreases as it flows inthe tube. The mass flow rate and

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the tube diameter and hence areabeing constant, the velocity ofrefrigerant increases as m VA .The increase in velocity oracceleration of the refrigerant alsorequires pressure drop.

Sol–107:(c)In reciprocating compressors, wetcompression is avoided due to followingreasons:(i) Liquid droplets present in the wet

vapour wash away the lubricating oilfrom the cylinder walls of thecompressor. Then there will not beany sealing agent between the pistonand the cylinder bore. It results intoa large friction between the piston andthe cylinder. Subsequently, the drivingmotor will be overloaded and may leadto burning of the same. Since there isno proper sealing between the pistonand the cylinder bore, the compressorefficiency will be very poor. The blowbyloss will increase loading to poorvolumetric efficiency.

(ii) Liquid droplets in the refrigerantwould enter the compressor anddamage the valves and other movingparts.Dry compression is preferred over wetcompression since it gives highvolumetric efficiency and themechanical efficiency of the compressoris increased with less chance ofdamage to it.

Sol–108:(d)

The name of refrigerant m n p qC H Cl F

would be 1 1R m n q where

2 2n p q m

Inorganic refrigerants are designated byadding 700 to the molecular mass of thecompound.Dichloro-difluoromethane: R 12Water: R 718

Methyl Chloride: R 40Monochlorodi-fluoromethane: R 22

Sol–109:(a)Copper and copper-bearing materials areattached by ammonia, so they are notused in ammonia refrigeration pipingsystem.

Sol–110:(c)1 2 : Isentropic compression2 3 : Constant pressure heat rejection3 4 : Isenthalpic expansion4 1 : Constant pressure heat extraction

Sol–111.(d)A programmable logic controller (PLU) orprogrammable controller is a digitalcomputer used for automation of electro-mechanical processes.

Sol–112.(d)All above applications of Hall effect sensorsare correct.

Sol–113: (c)Sol–114: (b)Sol–115: (b)

TON =1

5 500= 0.4 × 10–3 sec

Sol–116: (d)Sol–117: (d)

ALU - (a) consists of accumulator,temporary registers, arithmetic and logiccircuits and five flags register.(b) Performs all arithmetic and logicaloperation of a given program.

Sol–118: (c)Memory = 216 = 26 × 210 = 64 K

Sol–119: (b)Sol–120: (c)

• Applicable for linear system• Does not provide exact location of closed

loop poles.

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Sol–121: (c)DAD H : Add the contents of register pair HLto contents of HL pair and store the result inHL pair.• Register addressing mode• 1 byte instruction• Three machine cycles• Only carry (CY) flag is set if result is

more than 16 bits. Other flags will notbe affected.

Addition of number with same number willshift the number one bit position left.

Sol–122: (d)From the given system,

A =0 1 0, B1 2 1

, C = 1, 1

AB =0 1 0 11 2 1 2

Qc = B AB

=0 11 2

cQ = 1,Hence, system is controllableFor output controllability

Q0c = [CB CAB CA2B ...]if Q0c 0 output controllable

Q0c = 0 Output non controllable

CB = 0[1 1] 11

CAB =0 1 0[1 1]1 2 1

=0[ 1 3] [3]1

Qc0 = [1 3] 0,Hence, output is controllable.

Sol–123: (b)

From block diagram (1),

C sR s

= 1

1 2

G1 G G


C sR s = 1

1 2

G1 G G


C sR s

= 2 1

2 12

G G11 G GG

C sR s

= 1

1 2

G1 G G


C sR s

= 2 1

2 12

G G11 G GG

C sR s =

1

1 2

G1 G G

so option (b) is correct.Sol–124: (c)

Mean time between failure (MTBF) = TR

where T = total timeR = number of failures

MTBF = 10 5002

= 2500 hours/failure

Mean Time To failure (MTTF) = TN

where T = total timeN = number of units under test

MTTF = T 10 500N 10

= 500 hours/failureSol–125: (d)

All above statements regarding acceleratedtesting are correct.

Sol–126: (b)System reliability, Rs = R1 × R2 × R3 × R4× R5

Rs = (Ri)5

Ri = (0.999)1/5

= 0.9998Component unreliability, Ui = 1 – Ri= 1 – 0.9998 = 0.0002

Sol–127: (c)Both statements regarding series systemsare correct.

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Sol–128: (b)Processor Bus Memory

Input Output0.99 0.990.95

The probability that computer will work,(Re)s = 0.99 × 0.95 × 0.99

= 0.931095Sol–129: (c)

The system operates if one of thesubsystem operates,

R = P(atleast one sub-systemworks)

= 1 – P (both subsystemsfails)

P(subsystem A fails) = 1 – (0.9)2

P(subsystem B fails) = 1 – (0.9)2

R = 1 – [1 – (0.9)2]2

= 0.9639Sol–130: (c)

Plant fault is one when there is leakageor some hindrance, resulting in productionstoppage.

Sol–131: (c)Fault isolation is determining where thefault is.

Sol–132: (d)There are either model-free methods ormodel-based methods. Among model- freemethods, fault tree analysis (i.e. causeeffect analysed backwards) spectrumanalysis (fault specific freequency in sound,vibration etc), limit checking (checkingmeasurements against preset limits) aresome mthoes are methods used for faultdiagnosis.

Sol–133.(d)In FMEA proceduree, RPN = Severity ×Occurrence × Detection, is computed andthen implementation of corrective actionsis done for highest RPN’s.

Sol–134.(c)When all possible failure modes are ofconcern, FMEA is preferred over FTAbecause of limitations of FTA.

Sol–135.(d)All these tests are used to verify resonancein a machine.

Sol–136.(b)Vibration monitoring cannot reduce thecost of the machine. However, it can helpto minimize damage, reduce downtime andincrease productivity of pumps.

Sol–137:(a)The total weight of a benson boiler is20% less than other boilers becausethere are no drums.

Sol–138:(c)An economiser is a heat exchangerwhich raises the temperature of thefeedwater leaving the highest pressurefeedwater heater to about the satura-tion temperature corresponding to theboiler pressure. This is done by the hotflue gases exiting the last superheateror reheater at a temperature varyingfrom 370°C to 540°C. The termeconomiser is used because the throw-ing away of such high temperature gasesinvolved a great deal of energy loss. Byutilizing these gases in heatingfeedwater, higher efficiency and bettereconomy are achieved.

Sol–139:(a)Fire-tube boilers have large water stor-age capacity and can thus meet rela-tively large and sudden load demandswith only small pressure changes. Re-duction in pressure leaves the storedwater superheated and causes a part ofit to flash into steam. However, thelarge water storage increases the ex-plosion hazard of the unit, and also be-cause of it, a longer period of time isrequired to bring the unit to steamingfrom a cold condition.

Sol–140: (b)As load increases, the demand for steamincreases, hence the fuel and air flow ratesincrease. Thus, the combustion productsmass rate of flow increases, whichincreases the convective heat transfercoefficient.

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Alternatively, as demand for steamincreases with increase in load, fuel andair flow and hence, combustion gas floware increased. The convective heat transfercoefficients (hi and ho) increase both insideand outside the tubes, increasing theoverall heat transfer coefficient (Uo)between gas and steam faster than theincrease in mass flow rate of steam alone.The combustion temperature do notmaterially change with load. Thus, thesteam receives greater heat transfer perunit mass flow rate, and its temperatureincreases with load.

Radiant Superheater

Convective SuperheaterCombined Superheater

Steam flow, percent

Stea

m-o

utle

t tem

pera

ture

Sol–141:(a)The major shortcoming of a fire-tubeboiler is that definite size and pressurelimitations are inherent in its basic de-sign i.e. the maximum size of the unitand the maximum operating pressureare limited. The tensile stress on thedrum wall is a function of the drumdiameter and the internal pressuregiven by

= pd2t

where = tensile stressp = gauge pressured = internal diameter of shellt = thickness of wall

Creep mechanism is elongation understress over a period of time, usually atelevated temperatures.

Sol–142: (a)In naturally circulation boiler, the re-sponse to load variation on turbine andboiler is not good. So in steam power

plant, forced circulation boilers are used.Another reason is to have high effi-ciency, high pressure is requirement.At high pressure natural natural circu-lation is not effective.

Sol–143: (a)The distinguishing feature of diamondtools is their hardness, which is greaterthan that of any other material. It is alsochemically inert and has high thermalconductivity. However, oxidation ofdiamond starts at about 450°C andthereafter, it can even crack. For thisreason, the diamond tool is kept floodedby the coolant during cutting, and lightfeeds are used.

Sol–144: (b)It is also called the hardness of thewheel. This designates the force holdingthe grains. The grade of a wheeldepends on the kind of bond, structureof wheel, and amount of abrasive grains.Greater bond content and strong bondresults in harder grinding wheel.Harder wheels’ hold the abrasive grainstill the grinding force increase to a greatextent. The grade is denoted by lettergrades as indicated in Fig.

51 A 36 L 5 v 23

Manufacturer'soptionNature ofabrsive

Types ofabrasive

Grainsize

Grade Structure Type ofbond

Manufacturer'sreference

A– –Al O2 3

C–SiC

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

V VitrifiedS–SilicateR–RubberB–ResinoidE–Shellac

–Open

89

1011121314

01234567 Hard

CloseVeryfine220240280320400500600

80100120150180

3036465460

1012141620

Coarse Medium Fine

MediumSoft

Very soft Medium Very hardABCDEFGHKLMNOPQRSTUVWXYX

Sol–145: (a)Hobbing cannot be used for machininginternal gears because of the clearanceneeded for the hob. Gear shaping cancut internal gears, spl ines andcontinuous hearringbone gears thatcannot be cut by other processes.

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Sol–146: (a)High carbon tool steels are usually plaincarbon steels containing 0.6 to 1.5%carbon. Carbon steel tools are easy tomanufacture and their cutting edge canbe easily sharpened. However, theirchief drawback is their low wearresistance and low hot hardness. Theylose their hardness rapidly attemperatures greater than 200°C. Highcarbon steel can therefore be used foronly those applications where cuttingtemperatures remain well below 200°C,e.g. in making cutters, twist drills,turning and form tools for machiningsoft or free cutting materials like wood,magnesium, brass and aluminium.

Sol–147: (a)In isostatic pressing, because of theuniormity of pressure from alldirections and the absence of die-wallfriction, it produces ful ly-densecompacts of practically uniform grainstructure and density, irrespective ofshape. However, it achieves widerdimensional tolerances than are causedby other compacting processes.

Sol–148: (b)If the depth of cut is increased, the areaof the chip-tool contact increasesroughtly in equal proportion to thechange in depth of cut. Consequently,the rise in tool temperature is relativelysmall. That is not the case when feedis changed. In that case, theproportionate change in temperature islarger. This is on account of the factthat area of chip-tool contact changesby a smaller proportion than the changein feed rate. Thus, an increase in depthof cut shortens tool life to some extentby accelerating the abrasive adhesiveand diffusional types of tool wear.

Sol–149: (b)In vapour compression refrigerationsystem throttle valve is used insteady ofexpansion cylinder because the fluidentering the device is liquid and the

positive work recovery in isentropicexpansion of liquid is very small. Ifisentropic expansion device is used thenthe net work input may decrease but itdoes not justify with respect to the cost.Expander cost is high.

Sol–150: (a)A heat pump is superior to an electricresistance heater because a heat pumprejects more heat (Q1 = Q2 + W) ascompare to electric resistance heater (W).

Sol–151: (a)We know that,

PV = mR RM

n T T

PV = m RM

T

Since, P,V,T and R are constant.Therefore mass flow rate is proportionalto the molecular weights.

m MSol–152: (c)

Effective temperature or an index ofcomfort is a function of DBT, velocity andhumidity.

Sol–153:(a)Since reliability is the probability ofproper functioning of an item, so it is ameasure of uncertainty and to estimateit, statistics and probability theory areused. Hence, reason correctly explainsthe assertion.

Sol–154:(a)Diminishing returns is the decrease inthe marginal (incremental) output of aproduction process as the amount of asingle factor of production is incremen-tally increased, while the amounts ofall other factors of production stay con-stant. Hence reason correctly explainsthe assertion.

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Sol–155: (b)The set-up time is high in job orderproduction and low in mass production.The main difference between massproduction and job shop production is thesize of batch used.

Sol–156: (a)Direct costs are those for activities orservices that benefit specific projects e.g.salaries for project staff and materialsrequired for a particular project. Becausethese activities are easily traced toprojects and their costs are usuallycharged to projects on an item-by-itembasis.Indirect cost is more difficult to assessthan the direct cost. Indirect costs arethose for activities or services that benefitmore than one project. Their precisebenefits to a specific project are oftendifficult or impossible to trace. Forexample, it may be difficult to determineprecisely how the activities of the director

of an organization benefit a specificproject. The actual practice of dividingup or allocating the indirect costs is anapproximate and time-consumingactivity.

Sol–157: (c)Micro controller has inbuilt memory.Although, microprocessor has no inbuiltmemory, it needs memory, which isprovided externally.

Sol–158: (b)To make null voltage equal to zero, weneed core made of infinite permeability.

Sol–159:(d)Density of an object does not depend ongravitational acceleration and hencedensity will remain same, whether theobject is on moon or on earth.

Sol–160:(a)

D Alembert showed that one cantransform an accelerating rigid bodyinto an equivalent static system byadding the inertia force. The system canthen be analyzed exactly as a staticsystem subjected to this inertia forceand the external forces.

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