1. 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.
2. How many Laws of Thermodynamics are there?
There are three laws of the thermodynamics.
First Law: Energy can be neither created nor destroyed. It can only change forms.In any process in an isolated system, the total energy remains the same.
Second Law: When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, but not in equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems, and they exchange matter or energy, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initial, isolated systems is less than or equal to the entropy of the final exchanging systems. In the process of reaching a new thermodynamic equilibrium, entropy has increased, or at least has not decreased.
Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.
3. State Laws of conservation of energy?
According to the laws of conservation of energy, “energy can neither be created nor be destroyed. It can only be transformed from one form to another.”
4. Is the boiler a closed system?
Yes definitely the boiler is a closed system.
5. 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.
6. Which formula forms a link between the Thermodynamics and Electro chemistry?
Gibbs Helmholtz formula is the formula which forms the link between the thermodynamics and electromagnetism.
∆Hs/R = [∂ lnp /∂ (1/T)]x
where: x – mole fraction of CO2 in the liquid phase
p – CO2 partial pressure (kPa)
T – temperature (K)
R – universal gas constant
α – mole ratio in the liquid phase (mole CO2 per mole of amine)
7. Which is the hardest compound known?
Diamond.
8. 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.
9. Which has more efficiency: Diesel engine or Petrol engines?
Off course Diesel engine has the better efficiency out of two.
10) Difference between Performance and Efficiency?
· The accomplishment of a given task measured against preset known standards of accuracy, completeness, cost, and speed is called as Performance.
· Efficiency is defined as the input given and the work obtained from that input like money, time, labour etc. It’s the main factor of productivity.
11) What is the difference between Impact Force & Sudden Force?
· An impact is a high force or shock applied over a short time period when two or more bodies collide.
· A force which applies on the body (material) suddenly is known as sudden force.
12) Difference between Antifriction Bearing and Journal Bearing
Generally, journal bearings have higher friction force, consume higher energy and release more heat, but they have larger contact surface, so normally used in low speed high load applications. In anti friction bearings friction is less. One object just rolls over each other.
13) What is a Cotter joint?
A cotter joint is used to connect rigidly two co-axial rods or bars which are subjected to axial tensile or compressive forces. Here shaft is locked in place by a smaller pin that passes through the side of the lug and partly or completely through the shaft itself. This locking pin is named as cotter.
14) What is difference between Hardness and Toughness?
· Toughness is the ability of a material to absorb energy.
· Hardness is the ability of a material to withstand wear.
15) What is the difference between Toughness, Hardness and Strength?
· Toughness is the ability of a material to absorb energy.
· Hardness is the ability of a material to withstand wear.
· Strength is generally withstanding stresses, fatigue etc.
16) What is the difference between Strength and Stamina?
· Strength is capability over a short length of time.
· Stamina is the ability to keep going continuously.
17) Different between technology & engineering?
Engineering is application of science. Technology shows various methods of Engineering. A bridge can be made by using beams to bear the load,by an arc or by hanging in a cable; all shows different technology but comes under civil engineering and science applied is laws of force/load distribution.
18)how a diesel engine works in generator?
Diesel engine is a prime mover,for a generator,pump,and for vehicles etc.generator is connected to engine by shaft.mostly in thermal power plat ,there is an engine is used to drive generator to generate power.
19)WHAT IS THE OTHER NAME OF MICROMETER & VERNIER CALLIPER
Micrometer’s other name is Screw Gauze & Vernier caliper’s other name is slide caliper.
20)What is flashpoint?
Flash point: the lowest temperature at which the vapor of a combustible liquid can be ignited in air.
21)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.
22)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.
23)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.
24)What is refrigerant?
Any substance that transfers heat from one place to another,
creating a cooling effect. water is the refrigerant in absorption machines.
25)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.
26)What are the loads considered when designing the Nut and Bolts?
Shear Loads & crushing loads
27)what is the effect of reheat on rankine cycle?
1.efficiency increases 2.work output increases 3. both 4. none of these.
1.Efficiency increases.
this prevents the vapor from condensing during its expansion which can seriously damage the turbine blades, and improves the efficiency of the cycle, as more of the heat flow into the cycle occurs at higher temperature.
28)If you heat a piece of steel with a hole in the center will the diameter of the steel get bigger or smaller?
It gets bigger.
(Example: Always the bearings are heated first for new installation in a shaft.)
29)What is the difference between Blower and Fan?
Fan is an air pushing device. Either Axial or Centrifugal type systems are used to move the air in low pressure. It is rotated by a motor separately.
When the fan is a housing of blades and motor, then it called as Blower. It directs the air in a single path with high pressure.
30)How to find a Ductile-Brittle Transition Temperature in metals?
The point at which the fracture energy passes below a pre-determined point for a standard Impact tests. DBTT is important since, once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming.
31)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.
32. 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.
33. 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.
34. 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.
35. 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
36. 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.
37. 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.
38.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.
39.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.
40.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.
41.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.
42.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.
43.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.
44.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.
45.When does Emergency Seal Oil Pump automatically start?
When its pressure switch senses Main Seal Oil Pump discharge pressure reduced to 78 PSI.
46.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.
47.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.
48.What are four types of turbine seals?
Carbon rings fitted in segments around the shaft and held together by garter or retainer springs.
Labyrinth mated with shaft serration’s or shaft seal strips.
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.
Stuffing box using woven or soft packing rings that are compressed with a gland to prevent leakage along the shaft.
49.What are two types of clearance in a turbine?
Radial – clearance at the tips of the rotor and casing.
Axial – the fore-and-aft clearance, at the sides of the rotor and the casing.
50.What is the function of a thrust bearing?
Thrust bearings keep the rotor in its correct axial position.
51.What are some conditions that may prevent a turbine from developing full power?
The machine is overloaded.
The initial steam pressure and temperature are not up to design conditions.
The exhaust pressure is too high.
The governor is set too low.
The steam strainer is clogged.
Turbine nozzles are clogged with deposits.
Internal wear on nozzles and blades.
52.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.
53.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.
54.What are the two basic types of steam turbines?
Impulse type.
Reaction type.
55.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.
56.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.
57. 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.
58. 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.
59. Difference between Strainer and Filter
Strainer for coarse size, Filter is more accurate than Strainer.
60. What are differences between Welding & Brazing?
In Welding concentrated heat (high temperature) is applied at the joint of metal and fuse together.
In Brazing involves significantly lower temperatures and does not entail the melting of base metals. Instead, a filler metal is melted and forced to flow into the joint through capillary action.
61. What does a pump develops? Flow or Pressure
A pump does not create pressure, it only creates flow. Pressure is a measurement of the resistance to flow.
62. Which is heavier 1kg of Iron or 1kg of Cotton? and why?
Both of them have same weight. The only difference is the volume of Iron is small compared to Cotton.
63. 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.
64.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.
65.How will you detect that misalignment is the probable cause of excessive vibration?
Coupling to the driven machine is to be disconnected.
The turbine is to be run alone.
If the turbine runs smoothly, either misalignment, worn coupling or the driven equipment is the cause of the trouble.
66.In which part of the steam turbine does corrosion fatigue occur?
In the wet stages of the LP cylinder.
67.In which part of the steam turbine does stress corrosion cracking (SCC) occur?
In the wet stages of the low-pressure turbine.
68.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.
69.What are the types of thrust bearings?
Babbitt-faced collar bearings
Tilting pivotal pads
Tapered land bearings
Rolling-contact (roller or ball) bearings
70.What are the types of turbine seals?
Carbon rings fitted in segments around the shaft and held together by garter or retainer springs.
Labyrinths mated with shaft serrations or shaft seal strips.
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.
Stuffing box using woven or soft packing rings that are compressed with a gland to prevent leakage along the shaft.
71.What are the basic causes of the problem of rotor failure?
Normal wear.
Fatigue failure due to high stress.
Design deficiency.
Aggressive operating environment
72.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.
10) Difference between Performance and Efficiency?
· The accomplishment of a given task measured against preset known standards of accuracy, completeness, cost, and speed is called as Performance.
· Efficiency is defined as the input given and the work obtained from that input like money, time, labour etc. It’s the main factor of productivity.
11) What is the difference between Impact Force & Sudden Force?
· An impact is a high force or shock applied over a short time period when two or more bodies collide.
· A force which applies on the body (material) suddenly is known as sudden force.
12) Difference between Antifriction Bearing and Journal Bearing
Generally, journal bearings have higher friction force, consume higher energy and release more heat, but they have larger contact surface, so normally used in low speed high load applications. In anti friction bearings friction is less. One object just rolls over each other.
13) What is a Cotter joint?
A cotter joint is used to connect rigidly two co-axial rods or bars which are subjected to axial tensile or compressive forces. Here shaft is locked in place by a smaller pin that passes through the side of the lug and partly or completely through the shaft itself. This locking pin is named as cotter.
14) What is difference between Hardness and Toughness?
· Toughness is the ability of a material to absorb energy.
· Hardness is the ability of a material to withstand wear.
15) What is the difference between Toughness, Hardness and Strength?
· Toughness is the ability of a material to absorb energy.
· Hardness is the ability of a material to withstand wear.
· Strength is generally withstanding stresses, fatigue etc.
16) What is the difference between Strength and Stamina?
· Strength is capability over a short length of time.
· Stamina is the ability to keep going continuously.
17) Different between technology & engineering?
Engineering is application of science. Technology shows various methods of Engineering. A bridge can be made by using beams to bear the load,by an arc or by hanging in a cable; all shows different technology but comes under civil engineering and science applied is laws of force/load distribution.
18)how a diesel engine works in generator?
Diesel engine is a prime mover,for a generator,pump,and for vehicles etc.generator is connected to engine by shaft.mostly in thermal power plat ,there is an engine is used to drive generator to generate power.
19)WHAT IS THE OTHER NAME OF MICROMETER & VERNIER CALLIPER
Micrometer’s other name is Screw Gauze & Vernier caliper’s other name is slide caliper.
20)What is flashpoint?
Flash point: the lowest temperature at which the vapor of a combustible liquid can be ignited in air.
21)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.
22)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.
23)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.
24)What is refrigerant?
Any substance that transfers heat from one place to another,
creating a cooling effect. water is the refrigerant in absorption machines.
25)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.
26)What are the loads considered when designing the Nut and Bolts?
Shear Loads & crushing loads
27)what is the effect of reheat on rankine cycle?
1.efficiency increases 2.work output increases 3. both 4. none of these.
1.Efficiency increases.
this prevents the vapor from condensing during its expansion which can seriously damage the turbine blades, and improves the efficiency of the cycle, as more of the heat flow into the cycle occurs at higher temperature.
28)If you heat a piece of steel with a hole in the center will the diameter of the steel get bigger or smaller?
It gets bigger.
(Example: Always the bearings are heated first for new installation in a shaft.)
29)What is the difference between Blower and Fan?
Fan is an air pushing device. Either Axial or Centrifugal type systems are used to move the air in low pressure. It is rotated by a motor separately.
When the fan is a housing of blades and motor, then it called as Blower. It directs the air in a single path with high pressure.
30)How to find a Ductile-Brittle Transition Temperature in metals?
The point at which the fracture energy passes below a pre-determined point for a standard Impact tests. DBTT is important since, once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming.
31)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.
32. 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.
33. 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.
34. 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.
35. 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
36. 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.
37. 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.
38.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.
39.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.
40.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.
41.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.
42.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.
43.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.
44.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.
45.When does Emergency Seal Oil Pump automatically start?
When its pressure switch senses Main Seal Oil Pump discharge pressure reduced to 78 PSI.
46.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.
47.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.
48.What are four types of turbine seals?
Carbon rings fitted in segments around the shaft and held together by garter or retainer springs.
Labyrinth mated with shaft serration’s or shaft seal strips.
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.
Stuffing box using woven or soft packing rings that are compressed with a gland to prevent leakage along the shaft.
49.What are two types of clearance in a turbine?
Radial – clearance at the tips of the rotor and casing.
Axial – the fore-and-aft clearance, at the sides of the rotor and the casing.
50.What is the function of a thrust bearing?
Thrust bearings keep the rotor in its correct axial position.
51.What are some conditions that may prevent a turbine from developing full power?
The machine is overloaded.
The initial steam pressure and temperature are not up to design conditions.
The exhaust pressure is too high.
The governor is set too low.
The steam strainer is clogged.
Turbine nozzles are clogged with deposits.
Internal wear on nozzles and blades.
52.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.
53.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.
54.What are the two basic types of steam turbines?
Impulse type.
Reaction type.
55.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.
56.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.
57. 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.
58. 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.
59. Difference between Strainer and Filter
Strainer for coarse size, Filter is more accurate than Strainer.
60. What are differences between Welding & Brazing?
In Welding concentrated heat (high temperature) is applied at the joint of metal and fuse together.
In Brazing involves significantly lower temperatures and does not entail the melting of base metals. Instead, a filler metal is melted and forced to flow into the joint through capillary action.
61. What does a pump develops? Flow or Pressure
A pump does not create pressure, it only creates flow. Pressure is a measurement of the resistance to flow.
62. Which is heavier 1kg of Iron or 1kg of Cotton? and why?
Both of them have same weight. The only difference is the volume of Iron is small compared to Cotton.
63. 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.
64.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.
65.How will you detect that misalignment is the probable cause of excessive vibration?
Coupling to the driven machine is to be disconnected.
The turbine is to be run alone.
If the turbine runs smoothly, either misalignment, worn coupling or the driven equipment is the cause of the trouble.
66.In which part of the steam turbine does corrosion fatigue occur?
In the wet stages of the LP cylinder.
67.In which part of the steam turbine does stress corrosion cracking (SCC) occur?
In the wet stages of the low-pressure turbine.
68.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.
69.What are the types of thrust bearings?
Babbitt-faced collar bearings
Tilting pivotal pads
Tapered land bearings
Rolling-contact (roller or ball) bearings
70.What are the types of turbine seals?
Carbon rings fitted in segments around the shaft and held together by garter or retainer springs.
Labyrinths mated with shaft serrations or shaft seal strips.
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.
Stuffing box using woven or soft packing rings that are compressed with a gland to prevent leakage along the shaft.
71.What are the basic causes of the problem of rotor failure?
Normal wear.
Fatigue failure due to high stress.
Design deficiency.
Aggressive operating environment
72.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.
