EI701 Power plant Instrumentation
UNIT - I
1. Definition cogeneration:
A production of electricity and useful thermal energy simultaneously from a common fuel
source. The rejected heat from industrial processes can be used to power an electric generator.
Surplus heat from an electric generator can be used for industrial processes, or for heating purposes.
2. What is the advantage of Hydro power plant?


No pollution
No need of fuel
3. Advantage of thermal power plant.
a. The fuel used is quite cheap.
b. Less initial cost as compared to other generating plants.
c. It can be installed at any place irrespective of the existence of coal. The coal can be
transported to the site of the plant by rail or road.
d. It require less space as compared to Hydro power
e. Cost of generation is less than that of diesel power plants.
5. Disadvantage of thermal power plant.


It pollutes the atmosphere due to production of large amount of smoke and fumes.
It is costlier in running cost as compared to Hydro electric plants.
6. Why we can’t completely depend on solar and wind power plant?
It is fully depend on the natural.
7. What is the renewable source of energy?
Water, solar, wind
8. What is the non-renewable source of energy?
Petroleum, Coal
9. What are the various method of power generation?
Thermal power plant, Wind power plant, Hydro power plant .
10. What is meant by pulverising of coal?
Crushing of coal and. during carbonization process
11. Give major building block of thermal power plant?
Coal and ash handling ,Steam generation
12. Mention the use of conveyer?
Transport the material from one place to other.
13. What are the pollution occurs due to thermal power plant?
Water pollution, Air pollution
14. Application of co -generation.
Efficiency Gains Moderate Temperature Saturated Steam
15. What are the fuels used in nuclear power plant?
U-238
16. Define fusion.
Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei) often
producing free neutrons and other smaller nuclei, which may eventually produce photons (in the
form of gamma rays). Fission of heavy elements is an exothermic reaction which can release large
amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments
(heating the bulk material where fission takes place). Fission is a form of elemental transmutation
because the resulting fragments are not the same element as the original atom.
17. Define Chain reactions.
Many heavy elements, such as uranium, thorium, and plutonium, undergo both
spontaneous fission, a form of radioactive decay and induced fission, a form of nuclear reaction.
Elemental isotopes that undergo induced fission when struck by a free neutron are called
fissionable; isotopes that undergo fission when struck by a thermal, slow moving neutron are also
called fissile. A few particularly fissile and readily obtainable isotopes (notably 235U and 239Pu) are
called nuclear fuels because they can sustain a chain reaction and can be obtained in large enough
quantities to be useful .
18. Define nuclear reactor
nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and
sustained at a steady rate, as opposed to a nuclear bomb, in which the chain reaction occurs in a
fraction of a second and is uncontrolled causing an explosion
19. Define fission.
The splitting a part of an atom’s nucleus, releasing a large amount of heat energy.
20. What is pulverized coal?
It is a fine powdered form of coal, which is formed by the crushing, grinding or pulverising of
coal. It is blown in to the combustion zone of a furnace and burns very rapidly and efficiently.
21. What is Once-through boiler?
A boiler in which water flows, without recirculation, sequentially through the economizer,
furnace wall, and evaporating and superheating tubes.
22. Define dew point temperature.
The saturation temperature at the partial pressure of water vapour.
23. Define latent heat.
The heat that is added in converting from the liquid to the vapour phase at constant
temperature is called the latent heat.
24. Define dry saturation steam.
Steam that is fully vaporized but not been heated to temperature above the saturation
temperature is called dry saturation steam.
25. Define wet steam.
Steam that is not fully vaporized is called wet steam.
UNIT-II
Measurements in Power Plants.
1. State the effects of Bleeding.
Assume I Kg of steam is expanded in the turbine. Before complete amount of steam
is expanded, some amount of Steam (m Kg) is extracted .Extracting the steam in the turbine
before exhaust is called bleeding. This bled steam is used to heat the feed water.
2. What are the two scales used for the temperature measurement in power plants?
Kelvin scale & Rankine scale.
3. Write the relationship between Celsius scale & Fahrenheit scale
◦c/100 =0F-32/180
4. Write the relationship between Kelvin scale & Rankine scale.
R=0F +459.69
5. How is the correction factor for temperature accounted during measurement of steam flow?
An empirical correction factor is
CF =100.0224(t-Tr)(t-Tr)
Where, CF = Temperature correction factor
T= Mid-depth temperature (◦C)
Tr = Reference temperature (◦C)
6. What are the basic factors to be considered for feed water flow?

Valve pressure drop

System disturbance, Interlocks

Cycling or base load.

Water regulation by pump

Thermal; efficiency

pH value
7. State the need for radiation detector in a power plant.
A lot of instrumentation is needed to measure the amount of radio activity encountered in
nuclear power plant, and for tracking of radiated alpha, beta and gamma particles. The
energy of particles is absorbed by other molecules, producing chemical change ionization or
other reactions that produce visual evidence of the presence of other particles. These
processes are used to detect, count and trace the movement of such highly energized
particles.
8. Why is drum level measurement very important? How is it taken care of?

To control the drum level to a set point

To minimize the interaction with the combustion control system

To make smooth changes in the boiler water inventory as boiler load changes

Properly balance the boiler steam output with the feed water input.

Compensate for feed water pressure variation without process upset or set point
shift.
9. How the following parameters can measure energy, resistance current and power? (Or)
specify the devices used for electrical measurement i n power plant?
Electro dynamometer types of instruments are used as A.C voltmeters and
ammeters both in the range of power frequencies and lower part of the audio frequency
range. They are used as wattmeter and with some modification as power factor meters and
frequency meters.
10. Why float type level measurement is not suitable for boiler drum level measurement?
Float type level sensor cant withstand very high steam temperature so it is not
recommended.
11. What is an ever clean window?
The principle of the ‘’ Ever clean window’’ is that dust will not be deposited at the
end of the tube (ie., on the projector and receiver lenses) at right angles to the duct, if the
ratio of the length to the diameter is an least 4:1 for the coarser particles and 16:1 for the
finer dust particles and fumes.
12. What is the need of connecting thermocouples in series and parallel during temperature
measurement?
To increase the temperature range and efficiency more than two thermocouples are
connected in series to from thermopile for the measurement of high temperature.
13. How feed water flow is is measured in power plant? (or) list the various methods of flow
measurement for feed water flow in power plant.

Pressure different method.

Displacement method

Inferential method

Non-inferential method.
Method (i) is used for all main flows of steam and feed water.
Method (ii) and (iii) are used for ancillary flows of steam and feed water and also for oil flow
to burns of oil-fired boilers.
14. List the elements used for flow measurement.

Orifice plates

Nozzles

Venturi tubes

Dall tubes
15. What are the basic parts of feed water supply system in boiler?

Boiler feed pumps

Control valves, feed water piping and headers

Feed water heaters.
16. Give different types of radiations in nuclear power plant.
Radiation comes in 2 forms namely,

Highly energized particles and

Energy waves.
Different types of radiation include:
Alpha radiation:
Atomic particles containing two neutrons and two protons. Alpha radiation is the
weakest type of radiation, and can be stopped by a piece of paper.
Beta radiation:
A stream of high-energy electrons with a negative charge. This type of radiation can
be stopped by wood or aluminium.
Gamma rays:
Pure electromagnetic waves or photons. These penetrate further, and can onbly be
stopped by a thick shield of water, earth or hardened steel.
Neutrons:
Atomic particles given off during, radioactive decay of an element such as uranium.
As they knock more neutrons off of other atoms, eventually creating a chain reaction that
releases other types of radiation.
17. How can you detect nuclear radiation? What are the detectors used?

Radiation cannot be detected by human senses. A variety of handheld and
laboratory instruments is available for detecting and measuring radiation.

The most common handheld or portable instruments are:

Geiger counter, with Geiger-Muller(GM) tube

MicroR meter, either sodium iodide detector.

Portable multichannel analyzer.

Ionization (ion) chamber

Neutron REM meter, with proportional counter

Radon detectors

Liquid scintillation counters.

Scintillation crystal detectors.
18. What is the application of Geiger counter in power plants?
A Geiger counter, also called a Geiger-Muller counter, is a type of particle detector
that measures ionizing radiation. They are notable for being used to detect if objects emit
nuclear radiation.
Geiger counters are used to detect ionizing radiation (usually been particles and gamma
rays, but certain models can detect alpha particles).
19. What is dall tube?
The dall tube is a shortened version of a venture meter, with a lower pressure drop
than an orifice plate. As with these flow meters the flow rate in a dall tube is determined by
measuring the pressure drop caused by restriction in the conduit. The pressure differential is
typically measured using diaphragm pressure transducers width digital readout. Since these
meters have significantly lower permanent pressure losses than orifice meters, dall tubes
are widely used for measuring the flow rate of large pipe works.
20. What are power frequency?
The power frequency (utility frequency) or line frequency (American English) or
mains frequency (British English) is the frequency at which alternating current (AC) is
transmitted from a power plant to the end user. In most parts of the world this is 50 HZ,
although in the Americas it is typically 60 HZ. Current usage by country or region is given in
the list of countries with mains power plugs, voltages and frequencies.
21. What are power factor?
The power factor of an AC alternating power system is defined as the ratio of the
real power flowing to the load to the apparent p[ower, and is a dimensionless number
between 0 and 1 (frequently expressed as a percentage, eg. 0.5 pf=50%pf) real power is the
capacity of the circuit for performing work in a particular time. Apparent power is the
product of the current and the voltage of the circuit. Due to energy is stored in the load and
returned to the source, or due to a non-linear load that distorts the wave shape of the
current drawn from the source, the apparent power will be greater than the real power.
22. How to find percentage smoke density from ringleimann chart?
To determine average smoke emission over a relatively long period of time, such as
an hour, observations are usually repeated at one-fourth or one-half minute intervals. The
readings are then reduced to the total equivalent of no. 1 smoke as a standarad. No. 1
smoke being considered as 20 percent dense, the percentage “density’’ of the smoke for the
entire period of observation is obtained by the formula:
Equivalent units of no. 1 smoke 0.20 10 =percentage smoke density.
Number of observations
23. What is the thermal efficiency of cant cycle?
The second law of thermodynamics puts a fundamental limit on the thermal
efficiency of all heat engines. Surprisingly, even an ideal, frictionless turbine cant convert
anywhere near 100% of its input, heat into work. The limiting factors are the temperature,
TH are the temperature at which the fuel burns in an internal combustion engine. Tc is
usually the ambient temperature where the engine is located, or the temperature of a lake
or river that waste heat is discharged into are measured in an absolute scale, such as the
Kelvin or ranki9ne scale.
From Carnots theorem, for any engine working between these two temperatures:
This limiting value is called the carnot cycle efficiency because it is the efficiency of an
unattainable, ideal, reversible engine cycle called cantos cycle.
24. What is the thermal efficiency of rankine cycle?
Rankine cycle is a cycle which converts heat into work. The heat is supplied
externally to a closed loop, which usually uses water.this cycles generates about 80% of all
electric power used throughout the world, including virtually all solar thermal, biomass, coal
and nuclear power plants. Common heat sources for power plants using the rankine cycle
are the combustion of coal, natural gas and oil, nuclear fission.
Efficiency of the rankine cycle is given by
ᵑth =Wnet = Wt -Wp
Q
Q
Where, WT is the work transferred from the working fluid,KJ/Kg.
WP is the work transferred in to the working fluid, KJ/Kg.
Q is the heat transferred to the working fluid,KJ/Kg.
25. Mention three materials used for insulation of steam pipes.

Polyethylene

Neoprene foam

Fibreglass

Foil-encased bubble wrap

Spray-on ceramic coatings

Closed-cell rubber insulation sheets.

However, fibreglass insulation is currently the most common product for steam pipe
insulation in residential and commercial settings.

The pipe need to insulate can vary from ½ inch to 6 inches in diameter.
UNIT-III
Analysers in Power Plants
1. Define total suspended particulates?
Total suspended particulates (TSP) are small solid or liquid particles suspended in air.
major sources of TSP are diesel vehicles and coal-burning power plants.
2. Name the different parts of gas chromatography?
 Sample injection system
 Chromatographic column
 Thermostat
 Detector
 Recorder
3. List the selection criteria for carrier gas in chromatography.
The selection criteria for carrier gas are
It should be very cheap
It should have high thermal conductivity.
It should be inert.
The carrier gas should be selected according to the type of detector used.
4. Explain chromatographic column.
The column acts as the heart of a gas chromatography, where the fundamental
process of separation takes place. Its action is based on the fact that when a sample of gas
or vapour is introduced into the column, it spreads by molecular diffusion to give a
concentration profile. As the sample moves through the column, additional spreading takes
place. But, the band maintains the general shape, which is detected and recorded as a
chromatographic peak.
5. List some detectors in gas chromatography.
 Thermal conductivity detector
 Flame ionization detector’
 Thermionic emission detector
 Electron capture detector
 Flame photometer detector
 Photo ionization detector
 Electrolytic conduction type of detection.
 Dual detector.
6. What are the factors to be considered for emission in coal-fired power plants?
Particulate emissions from coal-fired power stations depend on boilers firing
configuration, boiler operation, type of control equipment of coal properties. A boiler firing
coal with a heat percentage of ash has particulate emissions dependent more on the fuel
ash content and the furnace ash collection than on combustion efficiency. In contrast,
particulate emissions from boiler burning a low ash content depend more on the
combustion efficiency.
7. List the particulate matter (PM) collectors in the emission from coal fired power plant.
8.
9.
10.
11.
12.
13.
 Electrostatic precipitator (ESP)
 Fabric filter.
 Compact hybrid particulate technology (COHPAC) and
 Advanced hybrid particulate collector (AHPC).
What are the methods adopted to monitor fine particle emissions?
Direct measurement,
-mass concentration
-volumetric flows
Continuous emission monitoring systems (CEMS)
-opacity measurement
-beta attenuation
-light extinction
-light scattering
-probe electrification
-optical scintillation
Emission factors.
Define emission rate.
Emission rates are determined by multiplying the concentration and the volumetric
source flow rate. Volumetric flow rate is a critical factor in calculating mass flow rates.
What is gas thermometer?
A gas thermometer measures temperature by the variation in volume or pressure of
a gas. One common apparatus is a constant volume thermometer. It consists of a bulb
connected by a capillary tube to a manometer. The bulb is filled with a gas such that the
volume of the gas in the bulb remains constant. The pressure of the gases in the bulb can be
obtained by measuring the level difference in the two arms of the manometer. Gas
thermometers are often used to calibrate other thermometers.
Specify the sensors used for the measurement of oxygen in flue gas.
There are a number of possible methods to measure the concentration of oxygen in
a gas sample. By far the most common is the electrochemical sensor to measure the
concentration directly. The methods regularly used to measure oxygen are:
 Electrochemical – oxygen sensor
 Partial pressure sensor
 Zirconium oxide – oxygen sensor
 Paramagnetic – oxygen sensor
 Ambient temperature- oxygen sensor
 Polarographic-oxygen sensor.
Mention the principle used in oxygen analyzer.
The change in oxygen percentage is proportional to the change in excess air. The
oxygen analyzer employs the paramagnetic property of oxygen and dependence of this
property on temperature.
What is the need for boiler water treatment?
 Inhibit corrosion
 Prevent freezing of the water in the system
 Increase the boiling point of the water in the system
 Inhibit the growth of mould and bacteria
14.
15.
16.
17.
Allow improved leak detection (for example, dyes that fluoresce under ultraviolet light)
Why flue gas analysis is used in power plants?
To remove pollutants like carbon monoxide, sulphur dioxide, nitrogen oxides and to
remove some other toxic pollutants.
Methods to remove pollutants from flue gas?
 Stack gas scrubbers
 It uses a pulverized limestone or other alkaline wet slurry remove sulphur and
nitrogen oxide pollutants from the exits stack gas.
 Catalysts
 Catalysts to remove Nitrous Oxide compounds from the flue gas stream.
What should be the temperature of exist flue gas in to the atmosphere and why?
The gas travelling up the flue gas stack to atmosphere is about 50◦C (120◦F). A
typical flue gas stack may be 150-180 meters (490-590 ft) tall to disperse the remaining flue
gas components in the atmosphere.
List the pollutants in flue gas.
 Ozone (O₃)
 Particular matter
PM10, coarse particles: 2.5 micrometers( µm) to 10 µm in size
(although current implementation includes all particles 10 µm or less in the
standard)
PM2.5, fine particles: 2.5 µm in size or less
 Carbon monoxide (CO)
 Sulphur dioxide (SO₂) Nitrogen oxides (NOx)
 lead (Pb)
18. What are all the parameters to be measured in deaerator control?
Entrained (Or) dissolved Oxygen and dissolved carbon dioxide.
19. Where is pH measurement adopted in power plant and how?
In feed water flow path and in the water treatment plant, pH measurement is adopted.
The pH value is measured by the use of PH meter, output emf voltage produced is directly
proportional to the hydrogen ions in the feed water.
20. What is a the pH value of pure water? it is acidic or base?
The pH value is measure of hydrogen ions in a solution and the letters pH stand for ‘’power
of the hydrogen concentration ‘’ as represented by the negative logarithm of the hydrogen
concentration.
PH = -log10 CH
21. Where CH is the hydrogen ion concentration?
Pure water has 10-7 of ionized hydrogen per litre; the pH value is therefore given as 7
If
pH> 7, Alkaline solution
0<pH< 7, Acidic solution
PH=7, Neutral point (pure water)
22. What is the need to control the pH of feed water?
To reduce feed system corrosion, the products of which become a controlled corrosion
hazard when transported to the boiler.
Boiler water pH is similarly consoled in an alkaline condition to encourage the formation of
the protective magnetic film and also to counteract any impurities which may enter the
boiler and give rise to acid conditions.
23. What does HMPA stand for in a chromatographic analyzer?
Hexamethyl Phosphoramide.
The CO₂ and H₂S can held back by the HMPA column in a flue gas.
24. What is the need of fuel analysis in coal power plant?
Coal is available in a number of grades and classifications vary from bituminous coal (with
almost 15,000 Btu per IB) to a low grade coal called lignite (of less 7,000 Btu per IB)
Two different analysis of coal are,
 Proximate analysis is used for ranking coal.
 Ultimate analysis is the analysis of the chemical constituents by weight percentage
and is used in combustion calculations.
25. List the combustion equipments for burning coal.
 Fuel bed furnaces (coarse particles)
 Pulverized coal furnaces (fine particles)
 Cyclone furnaces (crushed particles)
 Fluidized bed furnaces (crushed small particles)
UNIT-IV
Control Loops in Boilers
1. Define air-fuel ratio.
Air fuel ratio (AFR) is the mass ratio of air to fuel present during combustion. When all the
fuel is combined with all the free oxygen, typically within a vehicle’s combustion chamber,
the is chemically typically balanced and this AFR is called the stoichiometric mixture (often
abbreviated to stoics). AFR is an important measure for anti-pollution and performance
tuning reasons.
AFR = Mair
Mfuel
It is the ratio between the mass of air and the mass of fuel in the fuel air mix at any given
moment.
In industrial fired heaters, power plant steam generators, and large gas-fired turbines, the
more common term is percent excess combustion air. For example, excess combustion air of
15 percent means that 15 percent more than the required stoichiomertic air is being used.
2. State the role of attemperators (or) what is the application of desuperheaters in power
plants?
Attemperator also called as desuperheaters reduce steam termperature by bringing
superheated steam into direct contact with water. The steam is called through the
evaporation of the water.
Attemperators can be mounted either horizontally or vertically and are normally used for
relatively steady load conditions where pressure losses must be minimized. These
desuperheaters are a modification of the venture-type unit, without the venture tail,and
offer increased turndown when mounted vertically up.
3. What is the function of deaerator? (or) what is deaerator?
A deaerator is a device that is widely used for the removal of air and other dissolved gases
from the feedwater to steam-generating boilers. In particular, dissolved oxygen in boiler
feed waters will cause serious corrosion damage in steam systems by attaching to the walls
of metal also combines with any dissolved carbon dioxide to form carbonic acid that causes
further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb
by weight (0.0005 cm³/L) or less.
4. What are the two basic types deaerator?
There are two basic types of deaerators, the tray-type and the spray type:
The tray-type (also called the cascade-type) includes a vertical domed deaeration section
mounted on top of a horizontal cylindrical vessel which serves as the deaerated boiler feed
water storage tank.
The spray-type consists only of a horizontal (or vertical) cylindrical vessel which serves as
both the deaeration section and the boiler feed water storage tank.
5. Define stoichiometric ratio. (or) what is stoichiometric condition of combustion in fuel/
The term stoichiometric ratio describes the chemically correct air-fuel ratio necessary to
achieve complete combustion of the fuel.
In an internal combustion engine the fuel is a mixture of different hydrocarbons, and for
f=gasoline/petrol the average hydrocarbon ratio, is approximately 1.78:1. This corresponds
to a mass Air to Fuel Ratio (AFR) of between 14.6 and 14.7:1. This is known as the ‘’
stoichiometric ratio’’.
6. What is excess air? (or) what is the relation between excess air and stoichiometric air?
One Kg of fuel requires a certain minimum of ambient air to be fully combusted. We call this
minimum amount of air the ‘’stochiometric air’’ or sometimes also ‘’the theoretical air’’ to
combust the fuel. The stochiometric air would completely combust the fuel to carbon
dioxide stochiometric air would completely combust the fuel to carbon dioxide (CO₂), water
(H₂O) , and sulphur dioxide (SO₂) if sulphur is present. If the fuel does not get enough air for
combustion it will generate smoke and a potential unhealthy mixture of stack gas products.
In addition energy is wasted. The sample applies if too much excess air is used for
combustion. A less trivial issue in combustion technology is therefore to ensure the proper
amount of air that minimum environment.
EA = Mass of air (Kg) to combust one Kg of fuel
Stochiometric air (AG)
The AF is a property of fuel that can be calculated from the ultimate chemical composition of
the fuel.
7. What is boiler blow down?
Concentrated solid precipitates at drum bottom (by internal treatment) are removed
through blow down, which may be either intermittent or continuous, the amount of blow
down being governed by the allowed solids concentration and the purity of feed water. It is
usually expressed as a percentage.
%Blowdown = Quantity of water blow down 100
Quantity of feed water
8. What are the methods of measurement of combustion air flow?
Differential pressure measurement.
 With orifice segement in duct.
 With venture section in duct
 With airfoil in duct
 Across a tubular air-preheater
Inferential pressure measurement
Non- inferential pressure measurement
Displacement methods
9. What do you mean by interlocks? Where are interlocks employed in boiler operation?why?
The interlocks function is digital and covers all those’’Yes-No’’ decisions involved in the
equipment operation
This requirement is primarily one of safety and protection for man and machine.
One factor includes the decisions that protect the operators, the equipment and the
ultimate process integrity during the start-up of the process.
10.
11.
12.
13.
14.
15.
16.
Another factor is the safe management of the process during normal operation to assure the
continuity of operation.
 Interlocks in boiler operation:
 Starting and stopping burners.
 Tripping of the main fuel supply
 Tripping of ID and FD fans.
What factors affect the combustion efficiency of boilers?
Sensible heat losses: it is the total head carried away by hot dry flue gases.
Hydrogen losses: It is the heat lost in vaporizing the moisture present in the fuel and the flue
gases.
Combustion losses: it is the heat loss due to incompletely burnt products of combustion.
Which is the predominant factor in setting of automatic controllers for optimum efficiency?
 Time
 Temperature
 Turbulence
 A short period of time, high temperature and very turbulent flame indicates rapid
combustion. Turbulence is a key because the fuel and air must be mixed thoroughly
if the fuel is to completely burned. When fuel and air are well mixed and all the fuel
temperature will be high then the combustion time will be shorter.
What is induced draft?
In a induced draft, the blower is located near the base of the3 chimney and sucks the burned
gases from the furnace and the pressure inside the furnace is reduced below atmosphere
and induces the atmospheric air to flow through the furnace.
What is forced draft?
In a forced draft, blower is installed near the base of the boiler and air is forced to pass
through the furnace, economizer, air-preheater and to the stack.
This draft system is also known as the positive draft system because the pressure of air is
forced to flow through the system.
What is draft (or draught)?
The difference in the pressure of the combustion products within a boiler furnace and the
cold air outside is known as draft.
What is natural draft?
When the draft is generated with the help of chimney only.
What is artificial draft?
The draft produced by the steam jet or mechanical means like fans and blowers.
UNIT-V
Turbine - Monitoring and Control
1. What is DCS in power plant?
A distributed control system (DCS) refers to a control system usually of a
manufacturing system, process or any kind of dynamic system, in which the controller
elements are not central in location (like the brain) but are distributed throughout the
system with each component sub-system controlled by one or more controllers. The
entire system of controllers is connected by networks for communication and
monitoring DCS is a very broad term used in a variety of industries, to monitor and
control distributed equipment.
2. What are accelerometers (or) list the uses of accelerometers.
Accelerometers are the preferred motion sensors for most vibration monitoring
applications. They are useful for measuring low to very high frequencies and are
available in a wide variety of general purpose and application specific designs. The
piezoelectric sensor is versatile, reliable and the most popular vibration sensors for
machinery monitoring.
3. List the types of accelerometer.
 Bricett navigation grade pendulous quartz accelerometers
 Piezo-flim or piezoelectric sensor
 Shear mode accelerometer
 Surface micro machined capacitive (MEMS)
 Thermal (sub micrometre CMOS process)
 Bulk micro machined capacitive
 Bulk micro machined piezo resistive
 Capacitive spring mass base
 Electromechanical servo (servo force balance)
 Null-balance
 Strain gauge’
 Resonance
 Magnetic induction
 Optical
 Surface acoustic wave (SAW)
 Laser accelerometer
 DC response
 High temperature
 Low frequency
 High gravity
 Trixial
 Modally tuned impact hammers
 Seat pad accelerometers
 PIGA accelerometer
4. Define water steam-critical point.
The level where vapour and liquid are indistinguishable.
When dater and steam reach the level of absolute pressure 32036.2 psia (221.2 bar) and
a corresponding saturation temperature 705.40◦F(374.15◦C), the vapour and liquid are
indistinguishable. This level is called the critical point.
5. Define critical temperature.
Gases can be converted to liquids by compressing the gas at a suitable temperature.
The critical temperature of a substance is the temperature at and above which vapour of
the substance cannot be liquefied, no matter how much pressure is applied.
Some examples are shown below.
Substance
critical temperature (C◦)
NH₃
O₂
CO₂
H₂O
132
-119
31.2
374
6. Define critical pressure.
The critical pressure of a substance is the pressure required to liquefy a gas at its
critical temperature. The critical pressure is the vapour pressure at the critical
temperature.
Some examples below.
substance
Critical pressure (atm)
NH₃
111.5
O₂
49.7
CO₂
73.0
H₂O
217.7
7. What are steam and water turbines?
Steam turbine is a mechanical device that extracts thermal energy from pressurized
steam, and converts it into rotary motion.
It has almost completely replaced the reciprocating piston steam engine primary
because of its greater thermal efficiency and higher power to weight ratio. Because the
turbine generates rotary motion, it is particularly suited to be used to drive an
electrical generator – about 80% of all electricity generation in the world is by use of
steam turbines. The steam turbine is a form of heat engine that derivers much of its
improvement in thermodynamic efficiency through the use of multiple stages in the
expansion of the steam, which results in a closer approach to the ideal reversible
process.
Water turbine is a rotary engine that takes energy from moving water. Water turbines
were developed in the nineteenth century and were widely used for industrial power
prior to electrical grids. Now they are mostly used for industrial power generation.
They harness a clean and renewable energy source.
8. Define vibration.
Vibration refers to mechanical oscillations about an equilibrium point. The
oscillations may be periodic such as the motion of a pendulum or random such as the
movement of a tire on a gravel road.
Vibration is occasionally ‘’desirable’’. For example the motion of a tuning fork, the reed
in a woodwind instrument or harmonica, or the cone of a loudspeaker is desirable
vibration, necessary for the correct functioning of the various devices.
More often, vibration is undesirable, wasting energy and creating unwanted soundnoise. For example, the vibration motions of engines, electric motors, or any
mechanical device in operation are typically unwanted such vibrations can be used
imbalances in the rotating parts, uneven friction, the meshing of gear teeth, etc.
9. What is the need for vibration monitoring in turbine?
Vibration monitoring is effective in reducing overall operating costs of industrial
plants.
Monitoring vibration levels over time allows the plant engineer to predict problems
before serious damage occurs.
Machinery damage and costly production delays can be prevented.
When pending problems are discovered early, the plant engineer has the opportunity
to schedule maintenance and reduce downtime in a cost effective manner.
Vibration analysis used as a tool to determine machine condition and the specific cause
and location of machinery problems.
10. What are the factors to be considered for choosing vibration sensors?
 Vibration level
 Frequency range
 Temperature range
 Corrosive chemicals
 Atmosphere combustible
 Acoustic or electromagnetic fields
 Electrostatic discharge (ESD)
 Grounding
 Sensor size and weight constraints.
11. What is the balancing a turbine?
Blanking is the process of attempting to improve the mass distribution of a rotor, so
that it rotates in its bearings without uncompensated centrifugal forces. This is usually
done by adding compensating masses to the rotor at prescribed locations. It can also
done by removing fixed quantities of material for example drilling.
12. List the losses in steam turbines.
 Losses in regulating valves
 Nozzle friction loss
 Blade friction loss
 Disc friction loss
 Partial admission loss
 Gland leakage loss
 Residual velocity loss
13.
14.
15.
16.
17.
18.
19.
 Carry-over loss
 External losses.
What are the possible causes of excessive vibration or noise in a turbine?
 Misalignment
 Worn bearings
 Worn coupling to driven machine
 Unbalanced coupling to driven machine
 Unbalanced wheel
 Piping strain
Bent shaft
What is hydrogen-cooled turbo generator?
This generator is of two-pole type, using radial hydrogen cooling for the rotor winding
and indirect hydrogen cooling of the stator winding.
Mention the various cooling methods for turbo generator.
Open or once through system
Closed system
 Water cooling
air cooling
mixed cooling
Classify instrumentation systems for vibrating monitoring.
Instrumentation systems for vibration monitoring can be broadly classified in to three
levels based upon
 Their speed of operation
 How early they can detect faults
 How accurately the ultimate failure can be predicted.
What are the requirements for a vibration monitoring instruments?
 High-operational reliability
 Long term stability
 Immunity to adverse environmental conditions
 Irregularities which can cause false alarms
 Capable of operating in humid and dust free condition
 Ruggedness
 Work at high temperature
How is turbine casing movement measured?
Eccentricity detectors
During turning gear operation
During run-up to speed and at normal speed.
Differential expansion detectors.
How are steam turbines be classified?
They can be classified with respect to the action of steam:
 Impulse
 Reaction
 Impulse and reaction combined
Number of step reductions involved:
 Single stage
 Multi stage
 Revolving vanes separated by stationary reversing vanes
Direction of steam flow:
 Axial
 radial
 Mixed
 Tangential
 Helical
 Re-entry
Inlet steam pressure
 High pressure
 Medium pressure
 Low pressure
Final pressure


Condensing
Non-condensing
Source of steam


Extraction
Accumulator
20. What are the transducers used for shaft vibration measurement?
Relative displacement transducers


Eddy current transducers
Proximity probes
Seismic transducers
o
o
Velocity pick-up transducers
Piezo-electric accelerometers
While relative displacement transducers are the best for some specific shaft monitoring
applications
seismic transducers which measure absolute vibration.
21. What are the monitoring parameters in vibration measurement?



Acceleration
Velocity
Displacement