Mechanical Interview Questions contains questions about
1. Define maintenance?
Maintenance is the routine and recurring process of keeping a particular machine or asset in its normal operating conditions So that it can deliver the expected performance or service without any loss or damage.
2. 1 hp how much watt?
746.2Watt
3. Define reliability?
Reliability is defined as the probability that a component /system, when operating under given condition, will perform its intended functions adequately for a specified period of time. It refers to the like hood that equipment will not fail during its operation.
4. State the benefits of reliability analysis in industries?
The main advantages of imposing reliability requirements are increased productivity and reductions in forced outage equipment due to planned maintenance activity.
5. What is the need for drafting?
Drafting is the allowance give to casting process.it also used to remove the casting from mould without damage of corners.
6. What is the difference between BSP thread and BSW thread?
The British Standard Pipe thread (BSP thread) is a family of standard screw thread types that has been adopted internationally for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread.
British Standard Whitworth (BSW) is one of a number of imperial unit based screw thread standards which use the same bolt heads and nut hexagonal sizes.
7. What is basic difference between impulse turbine and reaction turbine?
In impulse turbine, jet is used to create impulse on blades which rotates the turbine and in reaction turbine, no jet is used pressure energy is converted into kinetic energy.
In impulse turbine fluid enter& leave with same energy ,but in reaction turbine fluid enter with pressure energy & leaves with kinetic energy
In impulse turbine all the pressure drops in nozzle only & in reaction turbine pressure drops both fixed & moving blades.the difference is due to blade profiles.
8. What is refrigerant?
Any substance that transfers heat from one place to another, creating a cooling effect. water is the refrigerant in absorption machines.
9. The amount of carbon present in Cast Iron
Carbon is basically present in the form of cementite in cast iron.Its percentage lies in the range of 2.03-6.67(% by weight of cementite for Cast Iron.If the amount is less than the above range than it is stainless steel.
10. What are the loads considered when designing the Nut and Bolts?
Shear Loads & crushing loads
11. What is the Difference between a Generator and Inverter?
An inverter is only effective if there is already a source of electrical energy. It cannot generate its own. It can simply convert electrical energy that is already there.
On the other hand, a traditional generator cannot make AC current into DC current.
12. What is the Difference between Quantitative and Qualitative Research?
Quantitative research involves gathering data that is absolute, such as numerical data, so that it can be examined in as unbiased a manner as possible.
Qualitative research may yield stories, or pictures, or descriptions of feelings and emotions. The interpretations given by research subjects are given weight in qualitative research, so there is no seeking to limit their bias. At the same time, researchers tend to become more emotionally attached to qualitative research, and so their own bias may also play heavily into the results.
13. What is the importance of the Thermodynamics in the field of Mechanical Engineering?
All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very important for the mechanical engineers.
[ads id="ads1"]
14. Is the boiler a closed system?
Yes definitely the boiler is a closed system.
15. What is Carnot engine?
It was being designed by Carnot and let me tell you that Carnot engine is an imaginary engine which follows the Carnot cycle and provides 100% efficiency.
16. Which is the hardest compound known?
Diamond.
17. What is Hess Law?
According to the Hess law the energy transfer is simply independent of the path being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.
[ads id="ads1"]
18. Which has more efficiency: Diesel engine or Petrol engines?
Off course Diesel engine has the better efficiency out of two.
19. What is Bending moment?
When a moment is applied to bend an element, a bending moment exists in the element
20. What are the points in the Stress Strain curve for Steel?
Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.
21. How many Joules is 1 BTU?
1 BTU is equal to 1055.056 joules.
22. What is PS?
PS is Pferdestarke, the German unit for Horsepower.
23.Explain Otto cycle.
Otto cycle can be explained by a pressure volume relationship diagram. It shows the functioning cycle of a four stroke engine.
The cycle starts with an intake stroke, closing the intake and moving to the compression stroke, starting of combustion, power stroke, heat exchange stroke where heat is rejected and the exhaust stroke.
It was designed by Nicolas Otto, a German engineer.
24. Explain the nomenclature of a 6203-ZZ bearing.
6 is the type code, which shows it is a single-row ball bearing,
2 is the series, means light,
03 is the bore, which is 17 mm and
ZZ is the suffix meaning double shielded bearing.
25. What is Gear ratio?
It is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.
26. What is Annealing?
It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.
27. Define Torque.
Torque is defined as a force applied to an object that results in rotational motion.
28. What is Ductile-Brittle Transition Temperature?
It is the temperature below which the tendency of a material to fracture increases rather than forming. Below
this temperature the material loses its ductility. It is also called Nil Ductility Temperature.
29. What is Auto Dosing?
Auto dosing is an automated system of feeding the equipment with liquid products.
It is the ideal way to ensure the correct calibrated dose at the right time every time in auto.
30. Difference between Codes, Standards and Specifications?
- Code is procedure of acceptance and rejection criteria.
- Standard is accepted values and compare other with it.
- Specification is describing properties of any type of materials.
31. What will be the position of Piston Ring?
In 180 degree angle the Top ring, Second ring and Oil ring are fixed. Position the ring approximately 1 inch gap below the neck.
32. What is Heat rate of a Power plant?
Heat rate is a measure of the turbine efficiency. It is determined from the total energy input supplied to the Turbine divided by the electrical energy output.
33. What is a Hydrostatic system?
Hydrostatics is the study of fluid bodies that are
- At rest
- Moving sufficiently slowly so there is no relative motion between adjacent parts of the body
For hydrostatic situations
- There are no shear stresses
- There are only pressure forces that act perpendicular to any surface.
35. What is Hydrodynamic Cavitation?
Hydrodynamic cavitation describes the process of vaporization in a constrained channel at a specific velocity.
Bubble generation and Bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in pressure.
36. Explain about Powder Technology?
Powder technology is one of the ways of making bearing material. In this method metals like bronze, Al, Fe are mixed and compressed to make an alloy.
[ads id="ads1"]
37. What are the points in the Stress Strain curve for Steel?
Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.
38. What is the difference between Pipe and Tube?
Ex. Iron Pipe, Carbon Tube, Steel Tube etc.
Tube is defined by Outer diameter and Wall thickness (OD and WT). While Pipe is defined by Inner diameter (ID).
Example:
2 inch pipe have 2.375 inch outer diameter, where 2 inch tube have same 2 inch outer diameter.
· Tube is easily shaped by bending, where Pipe needs some mechanical work to shape it.
· Tube is tight then Pipe.
· Tube is applicable to non cylindrical sections like Square and Rectangular.
[ads id="ads1"]
39. How does Welding damage Eye sight?
An Electric welding arc produces Ultraviolet light and the UV light (Sun burn) will damage the retina. Welding shields or Goggles with the proper shade (Automatic shading) of lens is the best protection for welders.
Light filtering curtains and reduced reflective surfaces help protect both welders and observers in the area.
40. Explain why BCC, FCC and CPH lattice packing and features of grain structure affect the Ductility and Brittleness of parent metallic materials?
Ductility is the mechanical property of a material. (It is the material’s ability to deform under the tensile stress without fracture).
So it is depends on the atoms how they arranged in a lattice and its grain size.
The ability to absorb the energy of the impact and fracture resistance depends on the arrangement of the atoms in a lattice and features of grain structure.
41. Why do you have Truss Bridges?
Truss bridges carry load in tension and compression rather than bending (Self weight + The weight of vehicles crossing it + Wind loads).
A truss has the ability to dissipate a load through the truss work. The beams are usually arranged in a repeated triangular pattern, since a triangle cannot be distorted by stress.
42. Why I-section beam is preferred for heavy loading?
Cross sectional shape I, giving many benefits.
It is very good for giving stiffness (less deformation on loading) and to withstand higher bending moments (as a result of heavy loading) on comparison with other cross- sectional shapes of same area.
Also, it is very easy to manufacture. It will have more moment of inertia.
43. What is difference between Center of Mass and Center of Gravity?
Both terms are same when gravity is uniform. When gravity is non-uniform following are the terms:
The center of mass is a point that acts as if all the mass was centered there (the mass on one side of the point is equal to the mass on the opposite side). If supported at the center of mass, an object will be balanced under the influence of gravity.
The center of gravity is the point at which where the sum (vector) of the gravitational forces act on an object which will be balanced on that point.
44. What is the difference between Center of Mass and Centroid?
If the material composing a body is uniform or homogeneous, the density or specific weight will be constant throughout the body, and then the centroid is the same as the center of gravity or center of mass.
Centroid: Centroid is the point, where the whole area of plane is going to be act. It is valid only for 2D problems like plane figures, square plate etc.
The center of mass is a point that acts as if all the mass was centered there (the mass on one side of the point is equal to the mass on the OPPOSITE side).
If supported at the center of mass, an object will be balanced under the influence of gravity.
45. What are the differences between Weight and Mass?
Mass is a measure of how much matter an object has. Mass is specified in Gram or Kilograms.
Weight is a measure of how strongly gravity pulls on that matter. Force is measured in Newton’s.
F=m.g
Thus if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter.
46. What is the difference between Projectile motion and a Rocket motion?
A projectile has no motor/rocket on it, so all of its momentum is given to it as it is launched. An example of a projectile would be pen that you throw across a room.
A rocket or missile does have a motor/rocket on it so it can accelerate itself while moving and so resist other forces such as gravity.
In mechanics point of view projectile don’t have any particular shape it is a point mass.
Whereas rocket has a particular shape and hence it has center of gravity situated at particular point on its body. Therefore rocket motion comes under kinetics and projectile comes under kinematics.
47. What type of cooling used in High Voltage Transformer?
The big transformers you find on power poles usually use oil as a dielectric insulator, in smaller HV transformers, like the ones in TV’s are usually filled with resin.
48. What is honing of Cylinder Liners?
The honing equipment used has been manufactured by "Chris Marine". The head of the honing device consists of four synchronized stones.
For the initial honing diamond stones are used to break up the hardened surface in the scuffed areas. For the main honing very coarse and hard stones are used to produce a very desirable rough surface all over the liner.
The advantage, especially for the 2-stroke engines, is possibility to save the liner after a seizure, scuffing or blow-by or even to eliminate the ovality of the liner.
Another advantage is that it is possible to machine a rough liner wall to obtain a well oiled surface.
49.What is the difference between Speed and Velocity?
Speed is scalar quantity and Velocity is a vector
– velocity has both speed and direction.
Speed is expressed as distance moved (d) per unit of time(t).
Speed is measured in the same physical units of measurement as velocity, but does not contain an element of direction. Speed is thus the magnitude component of velocity.
50. Difference between Yield Stress and Yield Strength?
Stress is a measure of the load applied to a sample relative to a cross sectional area of the sample. Strength is a quantification of the samples ability to carry a load.
The terms "yield strength" and "yield stress" of a material are usually used interchangeably (correct or not). It is the stress which will just cause the material to plastically deform.
If a material yields at 30,000 psi, the yield stress is 30,000 psi. If the part in question has a cross sectional area of 2 square inches, the strength at yield would be 60,000 pounds, but usually we just say the yield strength is 30,000 psi.
51. What is the difference between Yield and Ultimate tensile strength?
The yield strength is reached when the material becomes Non – linear (that is non elastic) and takes a permanent set when load is released.
Material stretches but does not break. Ultimate strength is when it breaks and is higher than yield strength.
52. What is the difference between Flexural strength and Tensile strength?
Flexural strength is resistance offered against bending. Tensile strength is resistance offered against tensile force.
53. What is the difference between Shear and Tensile strength?
Tensile Strength for a Bolt is determined by applying a Force along it long axis.
Shear Strength for a Bolt is determined by applying a Force across its diameter, as it would be loaded in a lug joint.
Tensile strength is strength in tension when pulling force is applied. And shear strength is strength against cutting force which is known as shear force.
54. What is the difference between Tensile strength and Tensile modulus?
Tensile strength is the ultimate capacity of the material to resist a tensile load regardless of deflection.
Tensile modulus also known as Young’s modulus is a measure of the stiffness of an isotropic elastic material.
It is defined as the ratio of the uni-axial stress over the uni-axial strain. It is determined from the slope of a stress-strain curve traced during tensile tests conducted on a sample of the material.
55. What is OEE?
OEE means Overall Equipment Effectiveness. This terminology widely used in Total productive maintenance, which is used to calculate the effectiveness of machines in manufacturing. Basically it captures the losses of machines in production and try to improve defects on machines. Higher the OEE, more capable is the machine.
56. Why Involutes Curve used in Gear?
Involute curve is the path traced by a point on a line as the line rolls without slipping on the circumference of a circle.
Involute curve has a contact angle between two gears when the tangents of two gears pass through the contact point without friction.
57. What is Bearing stress?
The stress which acts on the contact surface area between two members is known as Bearing stress. An example for this is the stress between nut and the washer.
58. Which is hard material Cast Iron or Mild Steel?
Cast iron. Due to the excess carbon content than mild steel it is harder. The more carbon content, the more hardness will be.
But it reduces the weldability due to this hardness. It is brittle too.
59. What are the materials used for Sliding Wear pad?
1. Urethane-Coated Base Material Provides Optimum Sliding Surfaces for Maximum Wear Ability
2. Galvanized Steel for Backing on Head and Side Pads
3. For crane services, We use Velcro Nylon wearing pad
60. What is the difference between a Shaper machine and a Planner machine?
In Shaper machine tool is having reciprocating motion and work piece is clamped on table which is stationary.
It is mostly suitable for light duty operation. In Shaping large cutting force is transferred to tool.
In Planer machine tool is having stationary and work piece is clamped on table which is reciprocating motion. It is mostly suitable for Heavy duty operation. In planner large cutting force is transferred to table.
61. How will you calculate the tonnage of Mechanical Press?
F = S x L x T / 1000
F = Force in kilo Newton’s
S = shear stress of material in MPa
L = the total length of peripheries being cut/ sheared in mm
T = thickness of material in mm
62. What is the composition of Grey cast iron Grade 20?
Carbon : 3.10 – 3.25%
Silicon : 1.75-
1.95% Manganese : 0.50 – 0.7%
Sulphur : 0.05
– 0.07%
Phosporous : 0.04 – 0.07%
[ads id="ads1"]
63. What is the composition of Cast iron Grade 35?
Carbon=2.90-3.10%
Manganese=0.60- 1.00%
Silicon=1.50-1.90%
Sulphur=0.10%
Phosphorus=0.15%
Chromium=0.30%
Molybdenum=0.30%
Cupper=0.25%
64. What are the super alloys?
Super alloys is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, having good surface finish.
65. Why the Super alloys used for land- based turbines?
Super alloys are the top most alloys used for their excellent strength and corrosion
resistance as well as oxidation resistance. No other alloys can compete with these grade.
[ads id="ads1"]
66. What kinds of NDT methods are available?
1.Visual Inspection
2.Microscopy inspection
3.Radiography Test
4.Dye Penetrate technique
5.Ultrasonic testing
6.Magnetic Particle inspection
7.Eddy Current technology
8.Acoustic Emission
9. Thermograph
10.Replica Metallographic
67. What is Stress Corrosion cracking?
Stress corrosion cracking (SCC) is a process involving the initiation of cracks and their propagation, possibly up to complete failure of a component, due to the combined action of tensile mechanical loading and a corrosive medium.
[ads id="ads1"]
68. What is meant by D2 Material used for Die tooling?
D2 – High Carbon Cold Work Tool Steel
D2 is a high Carbon, high Chromium, Molybdenum, Vanadium, Air hardening alloy tool steel which offers good wear resistance, high surface hardness, through hardening properties, dimensional stability and high resistance to tempering effect. D2 tool steel is also suitable for vacuum hardening.
Typical Composition
C.-1.50%
Si.-0.30% Cr. -12.00%
Mo. -0.80%
V. -0.90%
69. What is Vacuum Induction Melting?
As the name suggests, the process involves melting of a metal under vacuum conditions.
Electromagnetic induction is used as the energy source for melting the metal. Induction melting works by inducing electrical eddy currents in the metal.
The source is the induction coil which carries an alternating current. The eddy currents heat and eventually melt the charge.
70. What is Bending moment?
When a moment is applied to bend an element, a bending moment exists in the element
71. Where Multi-stage pump used?
Pressure washing of Aircraft, Trains, Boats and Road vehicles as well as Spray washing of industrial parts and Electronic components.
72. What is the function of Scoop in BFP (Boiler Feed Water Pump) in Thermal Power Station?
The Function of Scoop tube is regulating the varying amount of oil level in the coupling during operation of infinite variable speed.
73. In the Thermal Power Plant why Deaerator (D/A) placed on height?
To build a Very high pressure and the temperature for a boiler feed water pump and it discharge high pressure water to the boiler.
And to provide the required Net Positive Suction Head (NPSH) for the BFW pump and to serve as a storage tank to ensure a continuous supply of feed water during rapid changes in BFP.
74. How to determine the capacity of Refrigeration system? How we use Condenser coils, Compressor, Capillarity?
To determine the Refrigeration system by test of C.O.P and use the Condenser coils, Compressor, Capillarity, based on the properties
75. In orifice why the Pressure and Temperature are decreases?
Orifice is a small hole like a nozzle. When a high pressure fluid passes through the orifice,
Pressure gets reduced suddenly and the velocity of the fluid gets increased. Also the heat transfer rate increases.
We know that Heat transfer rate is directly proportional to the difference in temperature, Area and the Heat transfer coefficient.
Heat transfer Coefficient remains constant for a fluid at a particular temperature.
Q= KA (T1-T2)
If the heat transfer rate increases, it seems the difference in temperature gets increased.
There is no way in reduction of inlet temperature of the orifice. As a result, the outlet temperature of the orifice gets reduced. Hence the pressure and temperature gets reduced when it passes through orifice.
76 What is a radial-flow turbine?
In a radial-flow turbine, steam flows outward from the shaft to the casing. The unit is usually a reaction unit, having both fixed and moving blades.
77 What are four types of turbine seals?
o Carbon rings fitted in segments around the shaft and held together by garter or retainer springs.
o Labyrinth mated with shaft serration’s or shaft seal strips.
o Water seals where a shaft runner acts as a pump to create a ring of water around the shaft. Use only treated water to avoid shaft pitting.
o Stuffing box using woven or soft packing rings that are compressed with a gland to prevent leakage along the shaft.
78. What are two types of clearance in a turbine?
o Radial – clearance at the tips of the rotor and casing.
o Axial – the fore-and-aft clearance, at the sides of the rotor and the casing.
79. What is the function of a thrust bearing?
Thrust bearings keep the rotor in its correct axial position.
80 What are some conditions that may prevent a turbine from developing full power?
o The machine is overloaded.
o The initial steam pressure and temperature are not up to design conditions.
o The exhaust pressure is too high.
o The governor is set too low.
o The steam strainer is clogged.
o Turbine nozzles are clogged with deposits.
o Internal wear on nozzles and blades.
81. What is the difference between Bolt and Screw?
The main difference was based on the load acting on it, and the size. For smaller loads, screws are enough but in case of greater-loads, bolts are to be used.
In bolt we give centrifugal force or tangential force and screw we give axial force for driving.
82. What is the differences between gas turbine and a steam turbine?
Gas turbine works on Bryton cycle where as steam turbine works Rankine cycle.
Construction, operation of a gas turbine are entirely different to steam turbine.
Gas turbine has a compressor to compress the combustion air, a combustion chamber to burn the fuel and a turbine section to extract the work for burning fuel.
Steam turbine is just has a turbine section to extract the work from steam.
83. What is operating pressure?
The amount of pressure nearest the point of performing work at the output end of a pneumatic system. The system operating pressure is used to specify the capability of valves and actuators.
[ads id="ads1"]
84. What are the safety valves? How many on each boiler?
A valve opening automatically to relieve excessive pressure, especially in a boiler.
There are normally two to six safety valves provided in the drum depending upon the capacity.
The super heater outlet will have one to three safety valves on either side of the boiler. There will be an electromatic relief valve on the super heater pipe in addition.
This valve will be set at lower pressure than the lowest set safety valve on the super heater.
The reheater pipes both at the inlet and outlet side will also have safety valves which can range from two to eight both in the inlet and outlet of the reheater put together.
85. What is a sentinel valve?
Sentinel valves are simply small relief valves installed in some systems to warn of impending over pressurization.
Sentinel valves do not relieve the pressure of the system. If the situation causing the sentinel valve to lift is not corrected, a relief valve (if installed) will lift to protect the system or component.
If a relief valve is not installed, action must be taken quickly to secure the piece of equipment or system to reduce the pressure.
86. What is the function of Hydrogen seals work on a generator?
Provide a seal between the generator housings and rotor shaft to maintain the pressurized hydrogen gas inside the generator.
Also, provides a trap-vent system to prevent the release of hydrogen into the turbine generator lube oil system and building atmosphere.
[ads id="ads1"]
87. How is the excess discharge pressure prevented?
Pressure relief valves on the discharge side of each seal oil pump relieves back to seal oil system.
88. Which two seal oil pumps are driven from the same motor?
Main seal oil pump and re-circular seal oil pump; both are driven by Main seal oil pump motor.
89. When does Emergency Seal Oil Pump automatically start?
When its pressure switch senses Main Seal Oil Pump discharge pressure reduced to 78 PSI.
90. What is the consequence of not maintaining hydrogen (or air) pressure in generator casing at a value above atmospheric pressure when seal oil system is in service?
Failure to do so will cause excessive seal oil to be drawn into the generator.
91. What is a stage in a steam turbine?
In an impulse turbine, the stage is a set of moving blades behind the nozzle.
In a reaction turbine, each row of blades is called a "stage."
A single Curtis stage may consist of two or more rows of moving blades.
92. What is a diaphragm?
Partitions between pressure stages in a turbine’s casing are called diaphragms. They hold the vane-shaped nozzles and seals between the stages.
Usually labyrinth-type seals are used. One-half of the diaphragm is fitted into the top of the casing, the other half into the bottom.
93. What are the two basic types of steam turbines?
o Impulse type.
o Reaction type.
94. What are topping and superposed turbines?
Topping and superposed turbines arc high- pressure, non-condensing units that can be added to an older, moderate-pressure plant.
Topping turbines receive high-pressure steam from new high-pressure boilers.
The exhaust steam of the new turbine has the same pressure as the old boilers and is used to supply the old turbines.
95. What is a combination thrust and radial bearing?
This unit has the ends of the Babbitt bearing extended radically over the end of the shell.
Collars on the rotor face these thrust pads, and the journal is supported in the bearing between the thrust collars.
96. What is important to remember about radial bearings?
A turbine rotor is supported by two radial bearings, one on each end of the steam cylinder.
These bearings must be accurately aligned to maintain the close clearance between the shaft and the shaft seals, and between the rotor and the casing.
If excessive bearing wear lowers the he rotor, great harm can be done to the turbine.
97. How many governors are needed for safe turbine operation? Why?
Two independent governors are needed for safe turbine operation. One is an over speed or emergency trip that shuts off the steam at 10 percent above running speed (maximum speed).
The second, or main governor, usually controls speed at a constant rate; however, many applications have variable speed control.
98. How is a fly ball governor used with a hydraulic control?
As the turbine speeds up, the weights are moved outward by centrifugal force, causing linkage to open a pilot valve that admits and releases oil on either side of a piston or on one side of a spring-loaded piston.
The movement of the piston controls the steam valves.
99. What is meant by critical speed?
It is the speed at which the machine vibrates most violently.
It is due to many causes, such as imbalance or harmonic vibrations set up by the entire machine.
To minimize damage, the turbine should be hurried through the known critical speed as rapidly as possible.
(Caution, be sure the vibration is caused by critical speed and not by some other trouble).
100. How is oil pressure maintained when starting or stopping a medium-sized turbine?
An auxiliary pump is provided to maintain oil pressure. Some auxiliary pumps are turned by a hand crank; others are motor-driven.
This pump is used when the integral pump is running too slowly to provide pressure, as when starting or securing a medium-sized turbine.
101. Besides lubrication, what are two functions of lubricating oil in some turbines?
In larger units, lube oil cools the bearings by carrying off heat to the oil coolers. Lube oil in some turbines also acts as a hydraulic fluid to operate the governor speed-control system.
102. Do you stop cooling-water flow through a steam condenser as soon as the turbine is slopped?
You should keep the cooling water circulating for about 15 mill or more so that the condenser has a chance to cool down gradually and evenly.
Be sure to have cooling water flowing through the condenser before starting up in order to prevent live steam from entering the condenser unless it is cooled. Overheating can cause severe leaks and other headaches.
103. How can the deposits be removed?
o Water soluble deposits may be washed off with condensate or wet steam.
o Water insoluble deposits are removed mechanically after dismantling the turbine.
o Experience shows that water soluble deposits are embedded in layers of water-insoluble deposits. And when the washing process is carried out, water soluble parts of the deposit dissolve away leaving a loose, friable skeleton of water- insoluble deposits which then break loose and wash away.
104. How can the fatigue damage on high- pressure blades be corrected?
Fatigue-damage on high-pressure blades arises due to vibration induced by partial-arc admission. This can be corrected by switching over to full arc admission technique.
105. How will you detect that misalignment is the probable cause of excessive vibration?
o Coupling to the driven machine is to be disconnected.
o The turbine is to be run alone.
o If the turbine runs smoothly, either misalignment, worn coupling or the driven equipment is the cause of the trouble.
106. In which part of the steam turbine does corrosion fatigue occur?
In the wet stages of the LP cylinder.
107 In which part of the steam turbine does stress corrosion cracking (SCC) occur?
In the wet stages of the low-pressure turbine.
108. In which zone of steam turbines has temperature-creep rupture been observed?
Damage due to creep is encountered in high temperature (exceeding 455°C) zones. That is, it has been found to occur in the control stages of the high-pressure and intermediate-pressure turbines where steam temperature sometimes exceed 540°C.
In the reheat stage, it has been observed that creep has caused complete lifting of the blade shroud bands.
109. What are the types of thrust bearings?
o Babbitt-faced collar bearings
o Tilting pivotal pads
o Tapered land bearings
o Rolling-contact (roller or ball) bearings
110. What are the types of turbine seals?
o Carbon rings fitted in segments around the shaft and held together by garter or retainer springs.
o Labyrinths mated with shaft serrations or shaft seal strips.
o Water seals where a shaft runner acts as a pump to create a ring of water around the shaft. Use only treated water to avoid shaft pitting.
o Stuffing box using woven or soft packing rings that are compressed with a gland to prevent leakage along the shaft.
111. What are the basic causes of the problem of rotor failure?
Normal wear.
Fatigue failure due to high stress.
Design deficiency.
Aggressive operating environment
112. What are the differences between impulse and reaction turbines?
The impulse turbine is characterized by the fact that it requires nozzles and that the pressure drop of steam takes place in the nozzles.
The reaction turbine, unlike the impulse turbines has no nozzles, as such. It consists of a row of blades mounted on a drum.
The drum blades are separated by rows of fixed blades mounted in the turbine casing. These fixed blades serve as nozzles as well as the means of correcting the direction of steam onto the moving blades.
In the case of reaction turbines, the pressure drop of steam takes place over the blades. This pressure drop produces a reaction and hence cause the motion of the rotor.
[ads id="ads1"]
113. What is the difference between Critical speed & Whirling speed?
In Solid mechanics, in the field of rotor dynamics, the critical speed is the theoretical angular velocity which excites the natural frequency of a rotating object, such as a shaft, propeller or gear.
As the speed of rotation approaches the objects natural frequency, the object begins to resonate which dramatically increases system vibration.
The resulting resonance occurs regardless of orientation.
Whirling Speed is due to the unbalanced forces acting on a rotating shaft.
114. What is the significance of Torque(in N-m) given in the engine specification ?
It give the moment about any point or simple rotation.
115. What is the abbreviation of Welding rod 7018?
7018=
70=tensile strength 70000psi
1= welding position
8=current flux
116. What are the uses of Graphite electrode in various field.
Graphite electrode is used in EDM.. and in Battery cells..
It is also used in electric arc furnaces to melt the steel .
117. Difference between TIG & MIG welding
Tungsten inert gas welding-non consumable electrode
MIG-Metal inert gas welding-uses consumable electrode
118. What is Specific speed of turbine?
The specific speed is defined as the the speed of the geometric turbine which can produce unit power at unit head
119. Material of Aircraft turbine blade?
Ni, Cr, Al, Traces of C
120. Do you know epicyclic gear box? What are the practical application of epicyclic gear box?
Epicyclic gear box consists of sun gear planetary gears and an annular called ring gear.
Different speed ratios are obtained by locking any one gear.
If you lock any two gear , direct gear will be obtained.
Mostly used in overdrives.
Wrist watch is a practical application of epicyclic gear box
121. What is the function of EGR valve?
EGR means Exhaust Gas Recirculation.
The main function of EGR is to control NOx emission from the engine. At elevated temperature (during long run & full condition) if due to some reasons engine gets heated up beyond certain level… it produces NOx emission.
In order to avoid this pollution , we have to control the temperature rise inside the cylinder.
This can be achieved by mixing some amount of exhaust gas with intake air. By doing this the temperature inside the combustion chamber is reduced. And NOx is controlled.
122. What do you mean by super critical above 500MW in Thermal power plant?
In super critical boiler means all the steam to converted in to superheated steam at outlet of boiler no need to sent to super heater once again.
123. What is the purpose of scrapper ring?
Scrap the excess lube oil from the cylinder walls. There by preventing oil from entering combustion zone.
[ads id="ads1"]
124. How catalyst converter works?
In Fuel Cell, a catalyst is a substance that causes or accelerates a chemical reaction without itself being affected.
Catalysts participate in the reactions, but are neither reactants nor products of the reaction they catalyze.
125. What will happen if relief valve in Hydraulic system fails?
The main function of pressure relief valve is to maintain the pressure in hydraulic system.
It is one mounting which is used for safety. W
hen pressure increases then safety valve comes into action & if the valve get fail the system get damage due to excessive pressure.
126. What does CC Stand for?
CC is the abbreviated form of cubic centimeter.
It is the unit by which the capacity of an engine is designated.
It is the volume between TDC and BDC.
It represents the quantity of fuel-air mix or exhaust gas that is pumped out in a single piston stroke.
Alternatively it can represent the volume of the cylinder itself.
We have read that when the piston goes up and down then the engine works i.e. the suction,compression etc etc. then what happens in the case
of big vehicles, which start at stable condition, i.e. how does their piston moves when they are at rest. how suction,compression etc
Smaller vehicles like bikes, cars are started with the help of motors. initially, motors turn the crank shaft till sufficient suction pressure is reached.
when sufficient suction pressure is reached, the engine starts to suck the fuel in and then the cycle begins when the fuel is taken in and ignited. similarly, for huge engines, instead of motors, we use starting air. air at a pressure of 10-30 bar is fed to the engine which is at rest. this air rotates the engine till it attains sufficient suction pressure. once the pressure is reached, the cycle starts and it starts firing.
[ads id="ads1"]
127. What is the difference between S.S to EN8
SS- Stainless steel
En- Medium carbon steel
SS is Non Magnetic material & EN8 is Magnetic material
SS is Corrosion resistant & EN8 is Magnetic material
128. The Compression ratio of Petrol engine is always less than Compression Ratio of Diesel engine why?
Petrol is not self igniting , it needs spark to flame up in chamber.
Where as diesel is self igniting in dieselengine , to attain that state it requires high temp &pressure.
This temperature & pressure is more than what’s required in Petrol Engines by property of that fluid.
[ads id="ads1"]
129. What is the temperature of space ?
The short answer is that the temperature in space is approximately 2.725 Kelvin.
That means the universe is generally just shy of three degrees above absolute zero – the temperature at which molecules themselves stop moving.
That’s almost -270 degrees Celsius, or -455 Fahrenheit.
130. How to calculate the speed of conveyer in Meter Per Minute
Measure the diameter of the rollers around which the conveyor belt is wrapped.
Multiply the diameter of the roller by pi (3.14159).
This calculation will yield the circumference of the rollers.
Every time the roller spins one revolution, the conveyor will be moved a linear distance equivalent to the circumference of the roller.
Pi is a dimensionless factor, meaning it does not matter whether inches, centimeters or any other units of measurement are used.
Measure the revolutions per minute (RPM) of the rollers. Count how many full revolutions (rotations) are made by the roller in one minute.
Multiply the RPM by the circumference of the roller.
This calculation will give the linear distance traversed by a point on the conveyor belt in one minute.
131. How can problems of "excessive vibration or noise" due to piping strain be avoided on steam turbines?
The inlet as well as exhaust steam lines should be firmly supported to avoid strains from being imposed on the turbine.
Adequate allowance should be made for expansion of steam pipes due to heat.
132. How the deposits in turbine be removed?
Water soluble deposits may be washed off with condensate or wet steam.
Water insoluble deposits are removed mechanically after dismantling the turbine.
o Experience shows that water soluble deposits are embedded in layers of water- insoluble deposits. And when the washing process is carried out, water soluble parts of the deposit dissolve away leaving a loose, friable skeleton of water-insoluble deposits which then break loose and wash away.
133. How the fatigue damage on high-pressure blades be corrected?
Fatigue-damage on high-pressure blades arises due to vibration induced by partial- arc admission.
This can be corrected by switching over to full arc admission technique.
134. How the misalignment of Flanges be rectified?
The bolts holding the flanges together are to be tightened.
The coupling is to be checked for squareness between the bore and the face. At the same time axial clearance is to be checked.
135. How the problem of excessive speed variation due to throttle assembly friction be overcome?
The throttle should be dismantled.
Moving parts should be checked for free and smooth movement.
Using very fine-grained emery paper, the throttle valve seats and valve steam should be polished.
136. How the problems of vibration and fatigue arise in steam turbine blades?
o These arise due to flow irregularities introduced because of manufacturing defects, e.g. lack of control over tolerances.
o System operating parameter,
e.g. low flow may excite various modes of vibration in the blades.
137. How does solid-particle erosion occur?
Solid-particle erosion, i.e. SPE occurs in the high-pressure blades. And it takes place when hard particles of iron exfoliated by steam from super heater tubes, reheater tubes, steam headers and steam leads strike on the surface of turbine blades.
138. How does the internal efficiency monitoring lead to the detection of turbine deposits?
o Process heat drop.
o Adiabatic heat drop.
o The process heat drop and adiabatic heat drop are obtained from a Mollier- Chart for the corresponding values of steam parameters – pressure and temperature – at initial and final conditions.
139. How is a flyball governor used with a hydraulic control?
As the turbine speeds up, the weights are moved outward by centrifugal force, causing linkage to open a pilot valve that admits
and releases oil on either side of a piston or on one side of a spring-loaded piston. The movement of the piston controls the steam valves.
140. What is the difference between rated speed and economic speed?
The rated speed tells us about the maximum speed which can be achieved by a vehicle or some other machine but the economical speed means the speed limit at which the machine works efficiently with least consumption of fuel.
Example- In normal bikes(not racing),the max.speed limit shown on speedometer is upto 120 kmph but companies always advice their customers to drive such bikes at around 60 kmph to have maximum mileage.
141. What is the purpose of scrapper ring?
scrap the excess lube oil from the cylinder walls.there by preventing oil from entering combustion zone.
142. What are the causes of main engine black smoke?
There is many cause of black smoke.
1.It is improper mixture of fuel supply by carburetor like very rich mixture so the fuel improper burn.
2. It is when piston or piston ring is fail so back side cooling oil release in combustion chamber it cause black smoke.
3. Improper ignition system like not sufficient time of pressure rise delay period .
143. How cooling tower height selected?
The Function of a cooling tower is to cool the water coming from condenser.
The water coming from condenser is hot and it is sprayed in a cooling tower and a air coming out from bottom cool the water which is coming down.
Outside air is cool and air in inside the cooling tower is hot due to humidity.So there is a density difference between outside and inside air which caused pressure difference.
Pr Difference = g x H x ( density difference)
Where,
H = Height of chimney
Pr Difference = Pr Difference so that air can flow to cooling tower from outside
144. How does axial thrust balance in multistage pump?
A balancing line from discharge end is connected to suctionside to balance axial thrust.
145. How to calculate the boiler efficiency? Any formula is there?
Boiler efficiency= (heat transferred to feed water in converting it to steam)/(heat released by complete combustion of fuel)
n(eta)= Mass of steam * (h- H(water))/(mass of fuel *calorific value fuel)
What is the significance of torque(in N-
m) given in the engine specification it give the moment about any point or simple rotation.
146. What is the exact requirement of priming?
Priming is done in pumps to remove the entrapped air from the suction pipe thus aiding in smooth operation and avoiding in excess load on the pump.
147. What is the use of a PULLEY?
transmission of power(force) in rotary form
148. Why does cycle rim don’t bend even in heavy loads?
Because of rubber tires. The load is distributed and its effect reduces i.e. tires absorbs heavy load and shocks with the support of steel rim.
The rim has many spokes. The spokes distribute the load equally and the rubber tires absorb more than half of the load.
149. How tonnage can be controlled in PLC base hydraulic press?
Custom integration of press interlocks to inter facing with other parts of the hydraulic press line such as the feeder or transfer systems.
150. What is BHP?
Brake horsepower is the amount of work generated by a motor under ideal conditions.
This work is calculated without the consideration of effects of any auxiliary component, that may slow down the actual speed of the motor.
Brake horsepower is measured within the engines output shaft and was originally designed to calculate and compare the output of steam engines.
As per the conventions, 1 BHP equals to:
745.5 watts
1.01389 ps
33,000 ft lbf/min
42.2 BTU/min
151. What are different between MIG & MAG ?
MIG stands for Metal Inert Gas welding, while MAG stands for Metal Active Gas welding. The main difference lies in the type of shielding gas used.
MIG welding uses inert gases like argon or helium to shield the weld pool from atmospheric contamination, while MAG welding uses active gases like carbon dioxide or a mixture of gases.
MIG welding is typically used for non-ferrous metals like aluminum, while MAG welding is more suitable for ferrous metals like steel.
MIG welding produces cleaner welds with less spatter, while MAG welding can penetrate thicker materials more effectively.
Both processes use a wire electrode that is fed through a welding gun, but the choice of shielding gas determines whether it is MIG or MAG welding.
152. What is PQR Process ?
PQR stands for Procedure Qualification Record.
PQR Process is a procedure used in welding to qualify the welding procedure specification.
It involves testing and documenting the variables used during the welding process.
The purpose is to ensure that the welding procedure will produce the desired quality of welds.
PQR Process is essential for ensuring the integrity and strength of welded joints.
Examples of variables tested include welding parameters, material thickness, and joint design
153. What Is GMAW ?
GMAW stands for Gas Metal Arc Welding, a welding process that uses a continuous solid wire electrode and shielding gas to create a weld.
Uses a continuous solid wire electrode
Requires a shielding gas to protect the weld from atmospheric contamination
Commonly used in industries like automotive, construction, and manufacturing
154. What is WPS Procee ?
WPS Procee is a welding procedure specification that outlines the details of a specific welding process.
WPS Procee includes information such as welding materials, welding parameters, preheat and post-weld heat treatment requirements.
It is essential for ensuring consistency and quality in welding operations.
WPS Procee is often required in industries such as construction, manufacturing, and oil & gas.
Example: A WPS Procee document may specify the type of welding machine to be used, the welding technique, and the required inspection procedures.
155. What is VAR refrigeration system and where it is used? Differentiate VAR & VCR.
Ans. VAR refrigeration system is a type of refrigeration system that uses variable speed compressors to adjust cooling capacity.
VAR stands for Variable Refrigerant Volume or Variable Refrigerant Flow.
It is used in buildings with varying cooling loads, such as hotels, hospitals, and offices.
VAR systems use multiple indoor units connected to a single outdoor unit.
VCR stands for Variable Capacity Refrigeration and uses a variable capacity compressor to adjust cooling capacity.
VCR systems are used in commercial refrigeration applications, such as supermarkets and cold storage warehouses.
156. What is all boiler parameters values for startup and runing condition?
Boiler parameters values vary depending on the type of boiler and fuel used.
- Boiler pressure
- Boiler water level
- Fuel flow rate
- Air flow rate
- Steam temperature
- Steam pressure
- Feedwater temperature
- Blowdown rate
157. How to calculate bearing number to diameter of the inner and outer
Divide the shaft diameter size by 5, it will give last two digit of the bearing no. and according to type of load we have to chose the type of bearing and that will give prior no. of the bearing.
158.Definition of Octane number & Cetane number
Octane No.-
Octane number is defined as the percentage, by volume, of iso octane in the mixture of iso octane and h-heptane. It is the measure of rating of SI engine.
Cetane No.-
Cetane number is defined as the percentage, by volume, of n-cetane in the mixture of n-cetane and alpha methyl naphthalene. It is the measure of rating of CI engine.
159. What is the other name of Micro meter & Vernier Caliper?
Micrometer’s other name is Screw Gauze.
Vernier caliper’s other name is slide caliper.
160. Define failure rate?
Failure rate is the ratio of the number of failures during particular unit interval to the average population during that interval. This failure rate is also known as hazard rate and instantaneous failure rate.
161. What is Mean Failure Rate?
The mean failure rate h is obtained by finding the mean of the failures rates for specified period of time.
162. Define Mean Time to Failure.
Let t1 is the time to failure for the first specimen, t2 is the time to failure for the second specimen and t n is the time to failure for the Nth specimen. Hence the mean time to failure for N specimens are
MTTR = (t1+t2+......+t N) /N
163. What is Mean Time between Failures (MTBF)?
Mean Time between Failures (MTBF) is the mean or average time between successive failures of a product. Mean time between failures refers tom the average time of breakdown until the device is beyond repair.
164. Define Mean Time to Repair (MTTR)?
Mean Time to Repair is the arithmetic mean of the time required to perform maintenance action. MTTR is defined as the Ratio of total maintenance time and number of maintenance action.
MTTR = Total maintenance time/ Number of maintenance action.
165. Define Maintenance Action Rate?
Maintenance action rate is the number of maintenance action that can be carried out on equipment per hour.
166. Define Failure Density?
Failure Density is the ratio of the number of failures during a given unit interval of time to the total number of items at the very beginning of the test.
167. State the types of reliability?
Reliability can be generally of two types:
(i) Inherent Reliability: It is associated with the quality of the material and design of machine parts.
(ii) Achievable Reliability: It depends upon other factors such as maintenance and operation of the equipment.
168. Draw the equipment life cycle and name the various phases ln it?
Phase I - Failure pattern inherent in a new product because of manufacturing or design defects.
Phase II - Life period of an equipment
Phase III - Failures due to wear out conditions because to aging of the equipment.
169. Define maintainability?
Maintainability is defined as the probability that a unit or system will be restored to specified working conditions within a given period when maintenance action is taken in accordance with the prescribed procedures and resources.
170. Define availability?
Availability is the ratio of the time at which equipment is available for the designated operation/service to the total time of operation and maintenance of the equipment. It is also defined as the ratio of equipment uptime to the equipment uptime and downtime over a specified period of time.
171. State the advantages of life cycle cost analysis.
(i) Integration of engineering, economics and financial aspects lead to the way of robust metric for the selection and purchase equipment required for the industry.
(ii) Reduced operating and maintenance cost of equipment due to cost analysis over span of time.
(iii) It leads to the selection of proper and economically viable equipment.
172. Draw the curve to determine the economic life of equipment?
The economic life of equipment depends on the maintenance and repair costs, availability and operational efficiency. A plot of cumulative efficiency and maintenance and repair cost per cumulative hours Vs operating hours of the equipment to find the economic life of the equipment is shown in the figure.
173. State the components of maintenance cost?
The maintenance cost is comprised of two factors:
(i) Fixed cost: This includes the cost of support facilities including the maintenance staff.
(ii) Variable cost: This includes the consumption of spare parts, replacement of components and cost other facilities requirements of maintenance.
174. State the role of maintenance budget
The maintenance budget is used to set aside certain amount of money to meet the expenditures incurred in achieving the objectives of maintenance.
175. State the types of maintenance budget?
(i) Appropriation Budget : Budget used to allocate money for each activity independently.
(ii) Fixed Budget: Fixed used to allocate money for a specified period of time.
(iii) Variable Budget: Dynamic allocation of expenditure based on maintenance requirements and activities.
176. List the main factors of maintenance cost?
The maintenance cost is comprised of two factors:
(i) Fixed cost: This includes the cost of support facilities including the maintenance staff.
(ii) Variable cost : This includes the consumption of spare parts, replacement of components and cost other facilities requirements of maintenance.
Preventive Maintenance
177. Define the term Preventive Maintenance?
It is a maintenance program which is committed to the elimination or prevention of corrective and breakdown maintenance. It is designed for day to day maintenance like cleaning, inspection, lubricating, retightening etc. to retain the healthy condition of equipments.
178. Define predictive maintenance?
Predictive maintenance is a management technique that uses regular evaluation of the actual operating conditions of plant equipment, production systems and plant management function to optimize total plant operation.
179. What is meant by Breakdown maintenance approach?
It is a type of maintenance approach in which equipment is allowed to function / operate till no failure occurs that no maintenance work is carried out ion advance to prevent failure.
180. Classify various planned maintenance approach.
1. Preventive maintenance
2. Corrective maintenance
3. Predictive maintenance
4. Condition based maintenance
181. Define corrective maintenance approach.
Corrective maintenance is the program focused on regular planed tasks that will maintain all critical machinery and system in optimum operation conditions
182. What is meant by preventive maintenance approach?
A comprehensive preventive maintenance program involves periodical evaluation of critical equipment, machinery to detect problem and schedule maintenance task to avoid degradation in operating conditions. It is designed for day to day maintenance like cleaning inspection, lubricating, retightening etc. to retain the healthy condition of equipments.
183. List the objectives of corrective maintenance?
1. Elimination break downs
2. Elimination deviations from optimum operating condition.
3. Elimination unnecessary repairs
184. What is meant by predictive Maintenance?
Predictive maintenance is a management technique that uses regular evaluation of the actual operating conditions of plant equipment production systems and plant management functions to optimize total plant operation.
185. List out some condition based monitoring techniques and briefly discuss on them.
1. Vibration monitoring
2. Thermograph
3. Tribology
4. Electrical motor analysis
186. What is meant by Reliability Centered Maintenance (RCM)?
Reliability centered maintenance is one of the well-established systematic and a step by step instructional tool for selecting applicable and appropriate maintenance operation types. It helps in how to analyze all failure modes in a system and define how to prevent or find those failures early.
187. What is Total Productive Maintenance (TPM) and discuss its similarities with TQM?
Total productive maintenance is a maintenance program which involves a newly defined concept of maintaining plants and equipments.
The goal of TPM program is to significantly increase the production, at the same time increasing employee morale and job satisfaction.
188. What does safety, health and environment pillar of TPM aims at?
This pillar aims at achieving Zero accident, Zero health damage and Zero fires.
189. What is limitation of breakdown maintenance?
1. Most repairs are poorly planned due to time constraint caused by production and plant management.1 This will cost three to four times than the same repair when it is well planned.
2. This approach focus only on repair or the symptoms of failure and not on the root cause of failure. This results only in increase in the frequency of repair and correspondingly the maintenance costs.
190. List the benefits of implementing preventive maintenance.
1. It maintains the equipment in good condition to prevent them from bigger problems.
2. Prolongs the effective life of the equipments.
3. Detects the problem at earlier stages.
4. minimizes/eliminates the rework/scrap and helps in reducing the process variability
5. Significantly reduces unplanned downtime.
191. List the various pillars of TPM?
1. 5,S Principle
2. Jishu Hozen (JH)
3. Kaizen
4. planned maintenance
5. Quality maintenance.
6. Training
7. Office TPM
8. Safety, Health and Environment
192. What are the objectives of TPM?
The main objectives of TPM are
1. To achieve zero defects
2. Achieve zero accidents and zero break downs in all functional areas of an organization
3. To create different team of people to have active participation.
4. To aim at minimization of defects and
5. To inculcate autonomous policy.
193. Name the various stakeholders of maintenance scheduling.
1. Operators
2. Planners
3. Schedulers
4. Maintenance supervisors
5. Craftsman
6. Store’s in charge
7. Operation superintendent
194. Define Maintenance Scheduling.
Maintenance scheduling is a joint maintenance operations activity in which maintenance agrees to make the recourses available at a specific time when the unit can also be made available by operations.
Condition Monitoring
195. What is equipment health monitoring?
Conditions monitoring is one of the maintenance methods which are used to assess the health and condition of equipments machines, systems or process by absorbing checking, measuring and monitoring several parameters. This technique is also called as equipment health monitoring.
196. List down the factors for increasing the demand condition monitoring
1. Increased quality expectations reflected in produces liability legislation
2. Increased automation to improve profitability and maintain competitiveness
3. Increased safety and reliability expectations
4. Increased cost of maintenance due to labour and material cost.
197. List down the key features of condition monitoring.
1. Links between cause and effect
2. Systems with sufficient response
3. Mechanisms for objective data assessment
4. Benefits outweighing cost
5. Data storage and review facilities.
198. Write down the basic steps in condition monitoring.
1. Identifying critical systems
2. Selecting suitable techniques for condition monitoring
3. Setting baselines
4. Data collection
5. Data assessment
6. Fault diagnosis and repair
7. System review
199. What are three types of condition monitoring?
a. Subjective condition monitoring
b. Minimized breakdown costs
c. Improved morality of the operating personnel and safety.
200. State the advantages and disadvantages and disadvantages of condition monitoring.
Advantages
1. Improved availability of equipment
2. Minimized breakdown cost
3. Improved reliability
Disadvantages
1. Gives only marginal benefits
2. Increased running cost
3. Sometimes difficult to organize
201. Mention the various costs involved in costing of condition monitoring mainly
I. Installation cost
II. Operating cost
202. State the methods of measuring vibration
a. Amplitude
b. Frequency
c. Phase
203. Name the types of pyrometers.
1. Total radiation pyrometers
2. Infra red pyrometers
3. Optical radiation pyrometers
204. Mention the application of bimetallic strip.
1. Bimetallic strips are frequently used in simple ON – OFF switches.
2. The bimetal strips are also used in control switches.
205. List down the features of RTD.
1. High degree of accuracy
2. Resistance thermometer is interchangeable in a process without compensation or recalibration.
206. State the application and limitation of Thermisters.
Applications:
1. It is used for varying temperatures
2. it is used in time delay circuits
3. Thermistors are used for temperature compensation.
207. What are two main types of infrared Themography?
1. Passive thermography
2. Active thermography
208. What are the principles very important for the study of eddy current test.
i. Permeability
ii. Conductivity
iii. Material thickness
iv. Edge effect and end effect
v. Lift off
vi. Fill factor
209. Describe the limitation of eddy current test.
The main limitation is the low penetration of parts being examined, using limited to thin walls or near surface flaws. It is difficult to use on ferromagnetic materials.
False indications are possible because of mixed variables, edge effects and lift-off effects. Extensive technical knowledge is required for the development of inspection procedures, specific probes and to interpret the inspection data.
210. Mention th effect of X-rays to human body?
I. Injuries to superficial tissue
II. General effects on the body, particularly the blood forming organs; eg. Producers of anema and leukerma
III. Induction of mahgnant tumors.
IV. Genetic effects.
211. What are the limitations of Ultrasonic test?
a. Unfavorable geometries and coarse anisotropic grain structures are difficult to inspect.
b. extensive technical knowledge is required for the development of inspection procedure.
c. Parts that are rough, irregular in shape, very small or thin or not homogenous are difficult to examine, specific probes and to interpret the inspection data.
212. Name some of the methods of leakage monitoring.
1. Interstitial monitoring
2. level monitoring
3. Vapor monitoring
4. Liquid Monitoring
213. Define see back effect?
The basic principle of thermocouple is ‘when two dissimilar metals are joined together and emf will exist between the two points A and B, which is primarily a function of the junction temperature. The above said to be principle of see back effect.
214. State the various methods of corrosion monitoring?
a. Weight loss method
b. Electrical resistance method
c. linear polarization method
d. corrosion potential measurement
e. Ultrasonic testing
f. Sentinel hole method.
Repair Methods for Basic Machine Element
215. Define the term failure.
The term failure may be defined as
1. Any loss that interrupts the continuity of production
2. A loss of assets availability
3. The unavailability of equipment
4. A deviation from the status quo
5. Not meeting target expectations
6. Any secondary defect.
216. What are the various possible causes for a failure ?
- Unexpected and unintentional damage
- Workmanship
- Improper design
- Manufacturing defects
- Incorrect usage of equipment
217. Define failure analysis?
Failure analysis is the process by which information/data about failure occurring in equipments/ systems are collected and analyzed to find the root cause of failures, and the causes are addressed to prevent recurrence of failures.
218. Name the three types of failure models?
- Predictable failure model
- Unpredictable failure model
- Running-In-Failure model
219. What are called age-dependent failures?
Time dependent failures are called age dependent failures
220. What are predictable failures?
In spite of all the working conditions maintained at same level, the cause of failure will be random in nature and cannot be assigned to any particular mechanism of failure. This type of failures is called Unpredictable Failures.
221. What are Running In Failures?
Suppose if some components/ equipments are installed with unnoticed defects, may fail in a short duration after installation than during its useful life. This type of failures is Running In Failures.
222. Define Fault tree diagrams
Fault tree diagrams are logic block diagrams that display the state of a system in terms of the states of its components.
223. Write down the capabilities of Fault Tree Diagram.
1. Fault tree analysis and failure modes and effects analysis,
2. Design for reliability
3. Design for safety
224. Define Event tree Analysis
An event tree is a visual representation of all the events which can occur in a system. As the number of events increases, the pictures fans out like the branches of a tree
225. What is the aim of event tree analysis?
The aim of event tree is to determine the probability of an event based on the outcomes of each event in the chronological sequence of events leading up to it. By analyzing all possible outcomes, we can determine the percentage of outcomes which lead to the desired result.
226. Define Root cause analysis?
RCA is a step by step method that leads to the discovery of faults first or root cause. Every equipment failure happens for a number of reasons. There is a definite progression of actions and consequences that lead to a failure. An RCA investigation from the end failure is back to the root cause.
227. Define FMEA?
FMEA is methodology for analyzing potential reliability problems early in the development cycle where it is easier to take actions to overcome the issues, thereby enhancing reliability through design.
228. Define Risk Priority Number(RPN)
Risk priority numbers is the product of the numerical severity, occurrence and detection ratings.
RPN = (S) X (O)X(D)
229. Name the factors based on the satisfactory performance of gears/drives.
I. Proper design and manufacture of drive
II. Selection of proper type and size
III. Proper installation
IV. Proper use of service
V. Proper maintenance of unit in it entire life.
230. Name the factors that contribute to tooth breakage.
The common reasons for gear tooth breakage may be due to any of the following reasons
a. Fatigue
b. Heavy wear
c. Overload
d. Cracking
231. List some of the inspection performed on gears
1. Pitch error
2. Axial and
3. Radial run out
4. Tooth profile
232. Name some of the geometric properties that are checked for guide ways.
1. Straightness
2. Flatness
3. Parallel both on horizontal and vertical surfaces.
232. What are the factors influence the performance of sleeve bearings.
The following are the factors that affect the bearing performance:
1. Dirt
2. Fatigue
3. Hot Shot phenomenon and
4. Crush problem
234. Define Crush
Normally, the bearings are manufactured so that they are slightly longer circumferentially than the mating housing. The bearing will be elastically deformed during assembly. If the amount of crush is insufficient, relative motion occurs between the bearing and its bore, which causes fretting and makes the bearing back a highly polished or pitted.
Repair Methods for Material Handling Equipment
235. State few examples of material handling equipments.
Material handling equipments include carts, hand trucks, fork lifts, conveyors, shelf pickers and other specialized industrial trucks powered by electric motors or internal combustion engines.
236. State the benefits of proper maintenance of material handling equipments.
The benefits of a maintenance program for material handling equipments are to maintain the high efficiency, keep them in running condition, reduce the cost of repairs, safer operation and enhanced productivity.
237. State the major stages in preventive maintenance of material handling equipments.
There are three stages of preventive maintenance are:
1. Inspection
2. Repair and
3. Over haul
238. State the various phases present in a good maintenance management system.
1. Work identification
2. Planning
3. Scheduling
4. Execution
5. Recording and
6. Analysis
239. Define the term Computerized Maintenance Management System (CMMS)
Computerized maintenance management system is the application of computers in planning, scheduling, monitoring and control of maintenance activities.
240. State the objectives of CMMS.
1. Maintenance of existing equipments
2. Inspection and service of the equipment
3. Installation or revamping of the equipment
4. Maintenance storekeeping
5. Craft administration
241. State the advantages of CMMS.
1. Improve maintenance efficiency
2. Reduce maintenance costs
3. Reduce the equipment downtime by proper scheduling preventative maintenance.
4. Provide maintenance reports in specific formats depending on the requirements.
5. Quicker access to plant maintenance statistics
242. Define work order system.
Work order system is the information system used by the industry to keep track of its maintenance works.
243. Mention the use of work order backlog.
Work order back log is used to find out all active maintenance works order in an industry.
244. What is job card?
Job cards contain necessary details for performing individual job in maintenance organizations. Job card may be in the form of a card, sheet or printout.
245. State the benefits of job card system.
1. Information about maintenance history
2. Knowledge of frequency of frequency of maintenance for equipments
3. Details of equipments which require maximum resources
4. Helps in job auditing
5. Evaluation of cost of maintenance.
246. State the role equipment records in maintenance.
Equipment records are information containing the details of installation, service, repair, maintenance activities, schedules and plans for future implementation. Equipment records are to be used to maintain control on maintenance cost, reliability and availability.
247. State the benefits of keeping equipments records.
1. Clear picture about the details of maintenance programmes is obtained.
2. Information about completed, pending and regular jobs carried out to the equipment are available
3. Records disseminated to various units of the industry.
4. Helps in standardization of procedures.
5. Evaluation of performance of maintenance tasks.
248. List some of the inspection performed on gears
- Pitch error
- Axial and
- Radial run out
- Tooth profile
249. List the main factors of maintenance cost?
The maintenance cost is comprised of two factors:
(i) Fixed cost: This includes the cost of support facilities including the maintenance staff.
(ii) Variable cost : This includes the consumption of spare parts, replacement of components and cost other facilities requirements of maintenance.
250. Name the three types of failure models?
- Predictable failure model
- Unpredictable failure model
- Running-In-Failure model
251. What are two main types of infrared themography?
1. Passive thermography
2. Active thermography
Principles and Practices of Maintenance Planning
252. What are the principles of maintenance?
a) Plant management in maintenance work:
The main role of a maintenance function is to provide safe and effective operation of the equipment to achieve the desired targets on time with economics usage of resources.
b) Production and maintenance objectives:
The plant operation is driven by the production targets. The objective of maintenance function is to support these target. The achievement of desired goals of Athe production system is to be supported by both the production and maintenance department to ensure smooth and successful operation of the industry.
c) Establishment of work order and recording system:
The maintenance system should have proper work and recording system. The work order for the maintenance function indicates the nature of work to be performed and the series of operations to be followed to execute a particular job. It is necessary to maintain proper records and entries to monitor the maintenance function.
d) Information based decision making:
The maintenance objectives are successfully achieved by the use of reliable information system. This information is used to meet the manpower and spare parts re4quirements of the industry.
e) Adherence to planned maintenance strategy:
A sound maintenance management should adhere to the planned maintenance strategy. This also includes the use of manufacturer information on the life and maintenance schedules of the equipment and other material resources available.
f) Planning of maintenance function:
All the maintenance function are to be carefully executed by a way of proper planning to ensure the effective utilization of manpower and materials.
g) Manpower for maintenance:
The manpower requirement of the maintenance system must be carefully evaluated based on the time and motion study. The requirements should also satisfies the need arising in case of overhauls, component replacement, emergency and unscheduled repair.
h) Work force control:
Determination of exact work force required to meet the maintenance objectives of the system is difficulty task due to the element of uncertainty. Hence the proper control and monitoring of workforce are needs to be ensured.
i) Role of spare parts :
A good maintenance management system requires appropriate tools. So the system should have good quality tools and that too available in required quantities to ensure the proper function of the maintenance work.
j) Training of maintenance work force:
Training of the workforce must be integral part of any good maintenance management system. Training helps the workforce to learn about the modern techniques, recent trends in maintenance and to chalk out a strategy to meet the growing demands of the industry.
253. What are important factors considered in maintenance planning?
a) Job distribution:
The first and foremost task in maintenance planning is the distribution of the jobs to the personnel for preventive and emergency maintenance works. It is the practice to form two separate task groups to tackle the both. If not possible a same group can also be used to tackle both the situations in such way that during scheduling, time must be devoted for unforeseen breakdowns or situations in maintenance.
b) Program :
The development of maintenance programs involves o Selection of activities for maintenance
- Determination of the frequency of preventive maintenance
- Decision on the cost effective methodology
Selection of activities
This selection is based on cost involved between preventive and breakdown maintenance.
c) Manpower allocation:
The manpower allocation is the most important task of the maintenance management group. It provides adequate manpower to execute various jobs in the system. This should also take into consideration the skill level of personal deputed for the maintenance tasks. The central idea of manpower allocation can be drafted using the information available from maintenance records and planning the task to meet the objectives of the organization.
d) Staffing:
Staffing is the task of providing the required manpower for the maintenance function. This has to be achieved at optimum cost. Staffing is depend upon the ability of the organization to tackle the regular as well as attending the unforeseen situations.
Staffing should be sufficient to handle preventive and emergency maintenance task.
e) Planning technique :
The planning methods are Gantt charts, Milestone method, Critical path method and program evaluation review. Evolutionary computation based techniques are recently used for maintenance planning and scheduling.
f) Planning procedure:
Planning procedure involves four step processes. Organizing maintenance resources to ensure their effective use in future
· Scheduling the resources for the planned period
· Execution of plans according to the schedules
· Establishing a feedback system for all the above processes to know the deficiencies of each of the processes.
g) Estimation of maintenance work:
Estimation is used to find out the quantity and quality of the maintenance work. This will help in allocation of the required manpower. The following methods are used for the estimation of maintenance wok. Measurement by estimates, historical data and by conventional standard time data.
h) Maintenance control:
Maintenance control is the auditing techniques to ensure the effective utilization of the maintenance budget. This involves the integration of accountability with in the system. Proper accounting of maintenance work should be carried out at every level of the maintenance organization.