Frequently Asked Interview Questions for Mechanical Engineers!!

1.         What is friction?

2.         What is gear ratio? How it can calculate

3.         What is gyroscopic and gyroscopic effect?

4.         What is mean by Resistance welding

5.         What Is Mean By Ss-314(Stainless Steel Pipe Grade)?

6.         What is pulverization?

7.          What is requirement of bottle filling machine

8.          What is Solution Annealing? kindly explain its process in brief.

9.          What is the basic need for designing the bottle filling machines

10.        What is the critical speed. Compare the critical speed of hollow shaft and solid shaft.

11.        What is the definition of mechanical

12.        What Is The Difference Between Rated Speed And Economic Speed?

13.        What Is The Difference In Is2062 And Is1239

14.        What is the difference between construction of reaction turbine and impulse turbine

15.        What is the difference  between Torque and Power ( layman Idea)?

16.        What is the manufacturing process for impellers of closed, semi open and open type?

17.        What is the principle of operation of simple jet propulsion system?

18.        What is the relationship between cop and hp(horse power) of compressor?

19.        What is the thermodynamics?

20.        What is the use of vanadium (non metal) ?

21.        What is thermodynamics?

22.        What is unit Ps ?

23.        What’s the difference between front and rear wheel drive? on what basis we choose the type of drive?

24.        Whats the range of poissons ratio of a stable material??

25.        When a solid shaft is subjected to tension its linear dimension changes equally as its lateral dimension,then what will               be its poissons

26.        Whether ductile material can fail in brittle manner? WHEN?

27.        Which engine is more suitable over all. petrol engine, diesel engine . what are their differences

28.        Who are the leaders among expansion valve manufacturers? what are the recent developments in the expansion                     valve industry, used in refrigeration abd air-conditioning?

29.        Why Air Conditioner capacity measured in Ton. Like 1.5ton

30.        Why as atmospheric pressure increases,boiling point also increases?

31.        Why desuperheater tubes are bend in shape

32.        Why diesel engine does not have spark plug like petrol engine, how ever petrol is better fuel than diesel?

33.        Why does cycle rim don’t bend even in heavy loads?

34.        Why green curtons are used in hospital?

35.        Why petrol engine gives more power than diesel engine even though diesel engine has high compression ratio?

36.        Why petrol engines have more power than diesel engines of same capacity?

37.        Why the back wheel of tractor is bigger than front wheel?

38.        Why the path of a satellite is always elliptical with earth not at the center of the ellipse?

39.        Why tyres are manufactured in black colour?

40.        Why we cant measure absolute entropy directly,but the change we can?

41.        Why we express the unit of torque in Nm.even though it can be expressed as Joule ( J )?

42.        Why we have to know the specific frequency of any equipment? does anybody know about specific frequency ?

43.        Will you tell me about types and numbers of sensors in Toyota Corolla GLI, Honda Civic and Suzuki Cultus VXRI?

44.        Write down the expression for air standard efficiency of diesel cycle?

45.        You have to design a machine component. For what type of failure (ductile or brittle) you will design?

46.        Even though LPG is economical than petrol,why we are not promoting LPG usage?

47.        Explain bearing nomenclature with example.

48.        Explain Why Nozzles are made convergent and Divergent?

49.        Function of clutch?

50.        How a Diesel Engine Works in Generators?Explain with Labeled Diagram.

51.        How can u increase the efficiency of power plant without changing in effort?

52.        How gravity filling machine is designed

53.        How Hydraulic Power Steering & Clutch works please explain ?

54.        How much efficiency loss will took place in a steam turbine due to low vacuum

55.        how to calculate the speed of conveyor in meter per minute

56.        How to convert from HP to BHP or CC to BHP please explain?

57.        How to find rating of Chiller a.c. plant i.e. how to calculate the a.c. load of an area, needed by Chiller ?

58.        How to measure sound level of engine of tractor?

59.        How turbo charger works?

60.        If I want to set a power plant in desert of ‘Rajasthan’ and I have option of steam and gas power plant. Which plant I                 should set up?

61.        If the blade height is increased,then how it increases the specific speed of centrifugal pump?

62.        If u have to give support in 1 km long bridge,where u will give it & how many?

63.        In a Waste heat recovery boiler feed control valve is after the economizer where as in auxiliary boiler feed control                   valve is given before the economizer.why?

64.        In auto mobile industry for any type of vehicle how can we differentiate 2 stroke and 4 stroke engine….

65.        In hydraulic clutch mechanism can i adjust clutch play? if it is possible please explain ?

66.        increase in unit speed increases the discharge of impulse turbine how?

67.        Name fuels used in nuclear power plant?

68.        On what property u can distinguish material as brittle or ductile?

69.        On what thermodynamic cycle nuclear power plant works?

70.        Pipe. Whats The Concept Behind It?

71.        Purpose of centrifugal pump casing wear ring and impeller wear ring what is back plate in centrifugal pumps and its                 purpose?

72.        Suppose a steel bar of cross sectional area A is subjected to load P at one end and 2P at the other end ,what will be                  the induced

73.        What is vaily gap in welding?

74.        What are engines that use carburetor and that use inductor ? difference between them

75.        What are the conditions considered while evaluating MARGIN OF SAFETY for newly designed mechanical                                components….?

76.        What are the types of welding machine?

77.        What are your significant functional achievements in the present company? How did they contribute to the total                       process

78.        What do you mean gy “Clausius inequality”?

79.        What does a pump develops? Flow or Pressure. Give the Answer with Proper Logic.

80.        What for orifice using in liquid flow line

81.        What is bearing? how many types of bearing

82.        What is difference between sand blasting and grit blasting ? What is its purpose and how is it done ?

83.        What is drive speed & what is driven speed

84.        What is Dry Bulb Temperature and Wet Bulb temperature?

85.        what is electronically operated pneumatic valves? give one example

86.        What is FEED?

87.        A bearing is designated as 6205 , what is it’s bore diameter?

88.        Advantages and disadvantages of using LPG in car?

89.        All Rector or Exchanger have spherical/hemispherical end Why?

90.        Compare Bray-ton and Otto cycle.

91.        Current rating of a 3 phase DG set is 20 Amps, but what will be the per phase current for single phase supply.

92.        Define Overall Heat transfer coefficient.

93.        Does Is 2062 Specifies Only Seamless Pipes Or Erw Pipe Is Also Covered Under Is 2062

Vertical screw conveyors

A vertical screw conveyor conveys material upward in a vertical path. It requires less space than some other types of elevating conveyors. Vertical screw conveyor can handle most of the bulk materials provided there is no large lump. The maximum height is usually limited to 30m.

A vertical screw conveyor consists of a screw rotating in a vertical casing. The top bearing for the screw shaft must be designed to stand against radial and thrust loads. A suitable inlet port at the lower end and a discharge port at the upper end of the casing are provided. Feeding a vertical screw conveyor deserves careful consideration. Most materials are fed to the vertical conveyor by a straight or offset horizontal feeder conveyor. The ideal operation of a vertical screw conveyor is to have a controlled and uniform volume of material feeding.

Uneven feeding and start stop operation may adversely affect the performance of the vertical screw conveyor in terms of speed, capacity and horse power.

Average capacities and speeds of vertical conveyor

Nominal diameter of screw in mm	Capacities in m3/hr	Speed of screw
150	10	Up to 400 RPM
250	35	300 RPM
300	75	250 RPM
400	170	200 RPM

Vertical screw conveyors or some special design of vertical screw conveyor finds wide application in ship unloading.

Practical experience with these conveyors has shown that the resistance factor for vertical conveyors is higher than those of the horizontal conveyors. Resistance factor λ may be taken as 5.5 to 7.5 for grains. 6.5 to 8.3 for salt.

The driving power of the loaded screw conveyor is given by:

P = P_H + P_N + P_st

Where,

P_H = Power necessary for the progress of the material

P_N = Driving power of the screw conveyor at no load

P_st = Power requirement for the inclination of the conveyor

Power necessary for the progress of the material P_H:

For a length L of the screw conveyor (feeder), the power PH in kilo watts is the product of the mass flow rate of the material by the length L and an artificial friction coefficient λ, also called the progress resistance coefficient.

P_H = I_m.L. λ.g / 3600 (kilowatt)

= I_m.L. λ / 367 (kilowatt)

Where,

I_m = Mass flow rate in t/hr

λ = Progress resistance coefficient

Each material has its own coefficient λ. It is generally of the order of 2 to 4. For materials like rock salt etc, the mean value of λ is 2.5. For gypsum, lumpy or dry fine clay, foundry sand, cement, ash, lime, large grain ordinary sand, the mean value of λ is 4.0.

In this connection it should be noted that the sliding of the material particles against each other gives rise to internal friction. Other resistance due to grading or shape of the output discharge pattern contributes to the resistance factor. That is why the parameter λ is always higher than that due to pure friction.

Drive power of the screw conveyor at no load, P_N:

This power requirement is very low and is proportional to the nominal diameter and length of the screw.

P_N = D.L / 20 (Kilowatt)

Where,

D = Nominal diameter of screw in meter

L = Length of screw conveyor in meter

Power due to inclination: P_st

This power requirement will be the product of the mass flow rate by the height H and the acceleration due to gravity g.

P_st = I_m.H.g / 3600

= I_m.H / 367

H should be taken positive for ascending screws and will be negative for descending screws.

Total power requirement:

The total power requirement is the sum total of the above items

P = (I_m (λ.L + H) / 367) + (D.L /20) (Kilowatt)

PULLEY

Pulley:

The diameters of standard pulleys are: 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1400 and 1600 mm. pulley may be straight faced or crowned. The crown serves to keep the belt centered. The height of the crown is usually 0.5% of the pulley width, but not less than 4 mm. The pulley diameter D_p depends on the number of plies of belt and may be also be determined from the formula:

D_p > K.i (mm)

Where

K = a factor depending on the number of plies (125 to 150)

i = no of plies

The compound value should be rounded off to the nearest standard size. While selecting the pulley diameter it should be ascertained that the diameter selected is larger than the minimum diameter of pulley for the particular belt selected.

The drive pulley may be lagged by rubber coating whenever necessary, to increase the coefficient of friction. The lagging thickness shall vary between 6 to 12 mm. The hardness of rubber lagging of the pulley shall be less than that of the cover rubber of the running belt.

Pulley types:

Pulleys are manufactured in a wide range of sizes, consisting of a continuous rim and two end discs fitted with hubs. In most of the conveyor pulleys intermediate stiffening discs are welded inside the rim. Other pulleys are self cleaning wing types which are used as the tail, take-up, or snub pulley where material tends to build up on the pulley face. Magnetic types of pulleys are used to remove tramp iron from the material being conveyed.

Typical welded steel pulley-Drum conveyor pulley

Spun end curve crown pulley

Spiral drum conveyor pulley

Welded steel pulley with diamond grooved lagging

Welded steel pulley with grooved Lagging

Spiral Wing Conveyor pulley

 

Power calculation for the drive unit:

The horse power required at the drive of a belt conveyor is derived from the following formula:

H.P = T_e . V

Where

T_e is the effective tension in the belt in N

V = velocity of the belt in m/s

The required effective tension T_e on the driving pulley of a belt conveyor is obtained by adding up all the resistances.