Benha university

Faculty of engineering
Mechanical department

Steam Power Plants

Page (1)
Abstract:
In this report, we study steam power plants, their components and their
modifications
We divided the study to 3 steps:
- The first step study of steam power plant, its working theory and different
methods to add heat to the system.
- The second step study modifications which improve the efficiency of the
plant.
- The third step study of components, their working theory and types.

Page (2)
Contents:
Chapter 1 INTRODUCTION: ......................................................... 12
1.1 HISTORY: ......................................................................................................12
1.1.1 STEAM POWER PLANT: .......................................................................12
1.1.2 STEAM POWER PLANT ANALYSIS: ..................................................17
1.1.2.1 Introduction: ....................................................................................................................... 17
1.1.2.2 Theory: ................................................................................................................................ 17

1.1.3 BASIC STEAM PLANT COMPONENTS: .............................................20

1.2 MODIFICATIONS: ........................................................................................26
1.2.1 PRESSURE DIFFERENCE: ....................................................................26
1.2.1.1 Rising Boiler Pressure:......................................................................................................... 26
1.2.1.2 Lowering Boiler Pressure: ................................................................................................... 26
1.2.2 SUPER HEAT: .........................................................................................28
1.2.3 REHEAT: .................................................................................................28
1.2.4 SUPER CRITICAL: .................................................................................30
1.2.5 REGENERATIVE: ...................................................................................30
1.2.5.1 Open Feed Water Heater: ................................................................................................... 31
1.2.5.2 Closed Feed Water Heater: ................................................................................................. 33
1.2.5.3 Multi Feedwater Heaters: ................................................................................................... 35

Chapter 2 BOILER: .......................................................................... 38

2.1 INTRODUCTION: .........................................................................................38
2.2 WORKING PRINCIPLE: ...............................................................................38
2.3 CLASSIFICATION OF BOILERS: ...............................................................39
2.3.1 Fire Tube Boiler:.......................................................................................40
2.3.1.1 Types of Fire Tube Boiler: ................................................................................................... 40
2.3.1.2 Advantages of Fire Tube Boiler: .......................................................................................... 41
2.3.1.3 Disadvantages of Fire Tube Boiler: ..................................................................................... 41
2.3.2 WATER TUBE BOILER: ........................................................................42
2.3.2.1 Types of Water Tube Boiler: ............................................................................................... 42

Page (3)
 2.3.2.2 Advantages of Water Tube Boiler: ...................................................................................... 43
2.3.2.3 Disadvantages of Water Tube Boiler: ................................................................................. 43

2.4 RANGE AND DIVERSITY OF BOILERS: ..................................................45

2.5 BREAKUP LOSSES: .....................................................................................46
2.6 FUEL TYPE: ..................................................................................................46
2.7 DRAUGHT METHODS: ...............................................................................47
2.8 STEAM BOILER EFFICIENCY: ..................................................................48
2.9 BOILER FITTINGS AND ACCESSORIES:.................................................48
2.9.1 STEAM SUPER HEATER: .....................................................................49
2.9.2 ECONOMIZER: .......................................................................................50
2.9.3 AIR PREHEATER: ..................................................................................51
2.9.4 STEAM SEPARATOR: ...........................................................................52
2.9.5 FEED PUMP: ...........................................................................................53
2.9.6 INJECTOR: ..............................................................................................54
2.10 BOILER DRUMS: ........................................................................................55
2.10.1 Steam Drum: ...........................................................................................55
2.10.2 Mud Drum: .............................................................................................57
2.11 MATERIALS: ..............................................................................................57
2.12 SAFETY: ......................................................................................................58
Chapter 3 STEAM TURBINE: ........................................................ 61
3.1 INTRODUCTION: .........................................................................................61
3.2 TYPES: ...........................................................................................................61
3.3 MERITS and DEMERITS OF STEAM TURBINE:......................................61
3.3.1 MERITS:...................................................................................................61
3.3.2 DEMERITS: .............................................................................................62
3.4 PRINCIPLE OF OPERATION AND DESIGN: ............................................62
3.5 STEAM TURBINE STAGE: .........................................................................62
3.6 TURBINE EFFICIENCY: ..............................................................................63
Page (4)
3.7 LOSSES IN STEAM TURBINE: ...................................................................64
3.8 STEAM TURBINE CLASSIFICATION: ......................................................65
3.8.1 DETAILS OF STAGE: ............................................................................65
3.8.1.1 Impulse:............................................................................................................................... 66
3.8.1.2 Reaction: ............................................................................................................................. 68
3.8.1.3 Impulse-Reaction Turbine: .................................................................................................. 71

3.8.2 STEAM SUPPLY AND EXHAUST CONDITIONS: .........................74

3.8.2.1 Condensing: ........................................................................................................................ 74
3.8.2.2 Back Pressure (Non-Condensing):....................................................................................... 74
3.8.2.3 Mixed Pressure: .................................................................................................................. 75
3.8.2.4 Reheat: ................................................................................................................................ 75
3.8.2.5 Extraction Type (Auto Or Controlled): ................................................................................ 75
3.8.2 CASING OR SHAFT ARRANGEMENTS: ........................................75
3.8.2.1 Single Casing: ...................................................................................................................... 75
3.8.2.2 Tandem Compound: ........................................................................................................... 75
3.8.2.3 Cross Compound: ................................................................................................................ 75

3.8.3 NUMBER OF EXHAUST STAGES IN PARALLEL ............................76

3.8.4 DIRECTION OF STEAM FLOW. ...........................................................77
3.8.5 STEAM SUPPLY. ....................................................................................77
3.9 COMPONENTS: ............................................................................................78
3.9.1 STEAM TURBINE START UP: .............................................................78
3.9.2 PRECAUTIONS DURING RUNNING: .................................................79
3.9.3 FOUNDATIONS: .....................................................................................80
3.9.4 CASINGS: ................................................................................................80
3.9.5 NOZZELS: ...............................................................................................81
3.9.6 ROTORS: .................................................................................................81
3.9.7 BEARINGS: .............................................................................................82
3.9.8 SHAFT PACKING GLANDS: ................................................................83
3.10 BLADE FASTENING: .................................................................................85

Page (5)
 3.10.1 Blade Root Geometry and Load Transfer: .............................................86
Chapter 4 PUMP: .............................................................................. 89
4.1 PARTS OF PUMP: .........................................................................................89
4.2 PARTS OF PUMP SYSTEM: ........................................................................90
4.3 TYPES OF PUMPS: .......................................................................................91
4.3.1 Centrifugal: ...........................................................................................91
4.3.2 Positive Displacement: .............................................................................91
4.4 PUMP OPERATION: .....................................................................................92
4.5 PUMP SYSTEM: ............................................................................................96
4.5.1 PRIMARY PUMP SYSTEMS: ................................................................96
4.5.2 SECONDARY PUMPS SYSTEMS: .......................................................96
4.6 PUMP PARAMETERS: .................................................................................97
CHAPTER 5 CONDENSER: ......................................................... 101
5.1 HEAT EXCHANGER:..............................................................................101
5.1.1 TYPES OF HEAT EXCHANGERS: .....................................................101
5.1.1.1 Concentric Heat Exchanger: .............................................................................................. 101
5.1.1.2Cross Flow Heat Exchanger: ............................................................................................... 102
5.1.1.3 Shell and Tube Heat Exchanger: ....................................................................................... 102

5.1.2 FLOW IN HEAT EXCHANGERS: .......................................................103

5.1.2.1 Parallel Flow: ..................................................................................................................... 103
5.1.2.2 Counter Flow: .................................................................................................................... 103
5.1.3 CALCULATIONS OF HEAT TRANSFER: .........................................104
5.2 CONDENSER: .............................................................................................105
5.2.1 OBJECTIVES OF STEAM CONDENSERS: .......................................105
5.2.2 LOW PRESSURE (VACCUM): ............................................................105
5.2.3 CAPACITY OF CONDENSER: ............................................................106
5.2.4 ADVANTAGES OF USING CONDENSERS IN STEAM PLANTS: .106
2.5.5 TYPES OF STEAM CONDENSERS: ...................................................107

Page (6)
 5.2.5.1 Surface Condenser: ........................................................................................................... 107
5.2.5.2 Jet Condenser: .................................................................................................................. 110

5.2.3 CONDENSER CLEANING: ..................................................................112

References ............................................................................................ 115

Page (7)
List of Figures:
Chapter 1 Introduction:
1. 1 Steam Power Plant -------------------------------------------------------------------- 13
1. 2 Fossil Fueled Plant -------------------------------------------------------------------- 14
1. 3 Nuclear Power Station ---------------------------------------------------------------- 15
1. 4 Solar Power Plant --------------------------------------------------------------------- 16
1. 5 Geothermal power plant -------------------------------------------------------------- 17
1. 6 Rankine cycle -------------------------------------------------------------------------- 18
1. 7 simple Rankine cycle T-S diagram ------------------------------------------------- 19
1. 8 Steam Power Plant Components ---------------------------------------------------- 20
1. 9 -h diagram ------------------------------------------------------------------------------ 21
1. 10 Turbine Calculations ---------------------------------------------------------------- 22
1. 11 h-S diagram --------------------------------------------------------------------------- 22
1. 12 Condenser Calculations ------------------------------------------------------------- 23
1. 13 feed pump ----------------------------------------------------------------------------- 23
1. 14 ideal vs actual Rankine cycle------------------------------------------------------- 25
1. 15 actual Rankine cycle ---------------------------------------------------------------- 25
1. 16 Rising Boiler Pressure and Lowering Condenser Pressure --------------------- 26
1. 17 Rankine with super-heat ------------------------------------------------------------ 28
1. 18 Reheat process ----------------------------------------------------------------------- 29
1. 19 super critical process ---------------------------------------------------------------- 30
1. 20 Regenerative -------------------------------------------------------------------------- 31
1. 21 open feed water heater -------------------------------------------------------------- 32
1. 22 Types of closed feed water heater ------------------------------------------------- 33
1. 23 Closed feed water heater ------------------------------------------------------------ 34
1. 24 Multi feed water heater ------------------------------------------------------------- 35
Chapter 2 Boiler:
2. 1 Classification of boilers ....................................................................................39
2. 2 fire tube boiler ...................................................................................................40
2. 3 water tube boiler................................................................................................42
2. 4 Range and diversity of boilers ..........................................................................45
2. 5 steam super-heater.............................................................................................49

Page (8)
2. 6 Economizer .......................................................................................................50
2. 7 air preheater.......................................................................................................51
2. 8 steam separator ..................................................................................................52
2. 9 Feed pumps .......................................................................................................53
2. 10 injector ............................................................................................................54
2. 11 Anti-priming arrangements .............................................................................56
Chapter 3 Steam Turbines:
3. 1 Turbine Stage -------------------------------------------------------------------------- 63
3. 2 Insulation ------------------------------------------------------------------------------- 64
3. 3 Impulse Turbine ----------------------------------------------------------------------- 66
3. 4 Pressure & Velocity Change In RATEAU ----------------------------------------- 67
3. 5 Pressure & Velocity Change In CRUTIS ------------------------------------------ 69
3. 6 Pressure & Velocity Change in Compound ---------------------------------------- 68
3. 7 Reaction Turbine ---------------------------------------------------------------------- 68
3. 8 Pressure & Velocity Change In Reaction turbine --------------------------------- 69
3. 9 Impulse Vs Reaction ------------------------------------------------------------------ 70
3. 10 Comparison between Pressure & Velocity Change in R&I -------------------- 71
3. 11 Compound Turbine ------------------------------------------------------------------ 72
3. 12 Specific Volume Change ----------------------------------------------------------- 73
3. 13 Turbine Shape Relative To Specific Volume ------------------------------------ 74
3. 14 Two Parallel Flow ------------------------------------------------------------------- 76
3. 15 Four Parallel Flow ------------------------------------------------------------------- 77
3. 16 Turbine Components ---------------------------------------------------------------- 78
3. 17 Start Up Using Slow Motor -------------------------------------------------------- 78
3. 18 Precautions --------------------------------------------------------------------------- 79
3. 19 Elastic Foundation For Expansion ------------------------------------------------- 80
3. 20 Casing --------------------------------------------------------------------------------- 81
3. 21 Nozzle Types ------------------------------------------------------------------------- 81
3. 22 Rotor----------------------------------------------------------------------------------- 82
3. 23 Bearings ------------------------------------------------------------------------------- 82
3. 24 Gland Seals --------------------------------------------------------------------------- 83
3. 25 Losses Due To Clearances---------------------------------------------------------- 84
3. 26 Glands Work ------------------------------------------------------------------------- 84
3. 27 Gland Seals --------------------------------------------------------------------------- 85
Page (9)
3. 28 Blade Fastening ---------------------------------------------------------------------- 86
3. 29 Blade Root Geometry --------------------------------------------------------------- 87
Chapter 4 Pump:
4. 1 Centrifugal Pump---------------------------------------------------------------------- 93
4. 2 Flow Direction ------------------------------------------------------------------------- 94
4. 3 Pumps In Series ----------------------------------------------------------------------- 94
4. 4 Pumps In Parallel ---------------------------------------------------------------------- 95
Chapter 5 Condenser:
5. 1 Concentric Heat Exchanger -------------------------------------------------------- 101
5. 2 Cross Flow Heat Exchanger ------------------------------------------------------- 102
5. 3 Shell and Tube Heat Exchanger --------------------------------------------------- 103
5. 4 Parallel Flow ------------------------------------------------------------------------- 103
5. 5 Counter Flow ------------------------------------------------------------------------ 104
5. 6 Surface Condenser ------------------------------------------------------------------ 107
5. 7 Down Flow Condenser ------------------------------------------------------------- 108
5. 8 Central Flow Condenser ------------------------------------------------------------ 109
5. 9 Evaporation Condenser ------------------------------------------------------------- 109
5. 10 Jet Condenser----------------------------------------------------------------------- 111
5. 11 Barometric Condenser ------------------------------------------------------------ 111
5. 12 Ejector Condenser ----------------------------------------------------------------- 112
5. 13 Condenser Cleaning --------------------------------------------------------------- 113

Page (10)
Chapter 1

Introduction

Page (11)
 Chapter 1
INTRODUCTION

1.1 HISTORY:
The harnessing of steam power ushered in the industrial revolution. It began
with Thomas Newcomen (Dartmouth) in the early 1700's. Early developments were
very slow and Newcomen's design was used in England for nearly 100 years.
Newcomen's engine could be better described as a 'vacuum' engine. The vacuum was
created by condensing steam. The engine however, was extremely inefficient, and
where coal had to be brought from a distance it was expensive to run.
James Watt (1769) brought about a major increase in power and efficiency
with his developments. Watt re-designed the engine so that condensation occurred
outside of the cylinder. This meant that the cylinder did not lose heat during each
stroke. It also allowed the use of pressurized boilers thus obtaining power on the up-
stroke as well as the down-stroke. The beam engine gave way to the reciprocating
steam engine which was refined to a high degree. Double and triple expansion steam
engines were common and there was scarcely a demand for mechanical energy
which steam could not meet. However, reciprocating steam engines were
complicated, and hence not always reliable.
In 1884 Charles Parsons produced the first steam turbine. With Michael
Faraday's earlier discovery of electromagnetic induction (1831) the widespread
use of electricity had begun. The two technologies came together and with the
National grid, progressively eliminated the need for factories to have their own
steam plant.
Today, mechanical power production using steam is almost wholly confined
to electricity generation.
1.1.1 STEAM POWER PLANT:
Steam power plants are the most conventional source of electric power. These
power plants are variations of a thermodynamic cycle in which water is the working
fluid. In this kind of cycle, the water is in liquid phase in a part of the cycle and it is
in vapor phase in another one.

Page (12)
 On the other hand, steam turbine is the responsible of more than 70% of power
electricity generated in the world. They are present in many types of power plants,
such as nuclear plants, conventional thermal plants, combined cycles, biomass plants
and solar power plants. Thermal (coal, gas, nuclear) and hydro-generations are the
main conventional methods of generation of Electrical Energy. These enjoy the

1. 1 Steam Power Plant

advantages of reaching perfections in technologies for these processes. Further, single

units rated at large power-outputs can be manufactured along with main components,
auxiliaries and switch- gear due to vast experiences during the past century. These
are efficient and economical. These suffer from the disadvantages listed below:
The fuels are likely to be depleted in near future, forcing us to conserve them
and find alternative resources.
Toxic, hazardous fumes and residues pollute the environment.
Overall conversion efficiency is poor.
Generally, these are located at remote places with respect to main load centers,
increasing the transmission costs and reducing the system efficiency.
Maintenance costs are high.
Page (13)
Types of steam power plant according to the heating method:
1. fossil-fueled plants:
Vaporization is accomplished in fossil-fueled plants by heat transfer to
water passing through the boiler tubes from hot gases produced in the
combustion of the fuel This is also seen in plants fueled by biomass, municipal
waste (trash), and mixtures of coal and biomass.

1. 2 Fossil Fueled Plant

Advantages of Thermal Power Plants:

I. Fuel used i.e coal is quite cheaper.
II. Initial cost is less as compared to other generating stations.
III. It requires less space as compared to hydro-electric power stations.
Disadvantages of Thermal Power Plants:
I. It pollutes atmosphere due to production of smoke & fumes.
II. Running cost of the power plant is more than hydroelectric plant.

2. Nuclear Power Station:

The nuclear power generating stations are similar to the thermal stations
in more ways than one. However, the exception here is that, radioactive

Page (14)
elements like uranium and thorium are used as the primary fuel in place of
coal. Also in a Nuclear station, the furnace and the boiler are replaced by the
nuclear reactor and the heat exchanger tubes. For the process of nuclear power
generation, the radioactive fuels are made to undergo fission reaction within
the nuclear reactors. The fission reaction, propagates like a controlled chain
reaction and is accompanied by unprecedented amount of energy produced,
which is manifested in the form of heat. This heat is then transferred to the
water present in the heat exchanger tubes. As a result, super-heated steam at
very high temperature is produced. Once the process of steam formation is
accomplished, the remaining process is exactly similar to a thermal power
plant, as this steam will further drive the turbine blades to generate electricity.

1. 3 Nuclear Power Station

Advantages of Nuclear Generation:

a. Quantity of fuel required is small for generating a given amount of
electrical energy, compared to that with other fuels.
b. It is more reliable, cheaper for running cost, and is efficient when
operated at rated capacity.
Disadvantages:
1. Fuel is expensive and not abundantly available everywhere.
2. It has high capital cost.
3. Maintenance charges are high.
4. Nuclear waste disposal is a problem.

Page (15)
3. solar power plants:
Solar power plants have receivers for collecting and concentrating solar
radiation a suitable substance, molten salt or oil, flows through the receiver,
where it is heated, directed to an interconnecting heat exchanger that replaces
the boiler of the fossil- and nuclear-fueled plants, and finally returned to the
receiver. The heated molten salt or oil provides energy required to vaporize
water flowing in the other stream of the heat exchanger. This steam is
provided to the turbine.

1. 4 Solar Power Plant

4. Geothermal power plant:

The geothermal power plant also uses an interconnecting heat exchanger.
In this case, hot water and steam from deep below Earths surface flows on
one side of the heat exchanger. A secondary working fluid having a lower
boiling point than the water, such as isobutane or another organic substance,
vaporizes on the other side of the heat exchanger. The secondary working
fluid vapor is provided to the turbine.

Page (16)
 1. 5 Geothermal power plant

1.1.2 STEAM POWER PLANT ANALYSIS:

1.1.2.1 Introduction:
A steam power station is a power plant in which the prime mover is steam driven.
Water is heated, turns into steam and spins a steam turbine which either drives an
electrical generator or does some other work, like ship propulsion. After it passes
through the turbine, the steam is condensed in a condenser and recycled to where it
was heated; this is known as a Rankine cycle. The greatest variation in the design of
steam power stations is due to the different fuel sources. Some prefer to use the term
energy center because such facilities convert forms of heat energy into electrical
energy.
1.1.2.2 Theory:
Steam cycles used in electrical power plants and in the production of shaft
power in industry are based on the familiar Rankine cycle, studied briefly in most
courses in thermodynamics.
Page (17)
Rankine Cycle: The Ideal Cycle for Vapor Power Cycle:

1. 6 Rankine cycle

(a) The impracticalities associated with Carnot cycle can be eliminated by

superheating the steam in the boiler and condensing it completely in the
condenser. This cycle that results is the Rankine cycle, which is the
ideal cycle for vapor power plants. The construct of power plant and T-
s diagram is shown in Figures (a) and (b).
(b) The ideal Rankine cycle does not involve any internal irreversibility
(c) The Rankine cycle consists of the following four processes:
1-2: Isentropic compression in pump (compressors)
2-3: Constant pressure heat addition in boiler
3-4: Isentropic expansion in turbine
4-1: Constant pressure heat rejection in a condenser

Page (18)
 1. 7 simple Rankine cycle T-S diagram

Process 1-2
The superheated vapor at state 1 enters the turbine, where it
expands isentropically and produces work by rotating the shaft
connected to an electric generator. The pressure and the temperature of
the steam drops during this process to the values at state 2, where steam
enters the condenser.

Process 2-3
At this state, the steam is usually a saturated liquid-vapor mixture
with a high quality. Steam is condensed at constant pressure in the
condenser which is basically a large heat exchanger, by rejecting heat
to a cooling medium from a lake, or a river. Steam leaves the condenser
as saturated liquid and enters the pump, completing the cycle.

Process 3-4
Water enters the pump at state 3 as saturated liquid and is
compressed isentropically to the operating pressure of the boiler. The
water temperature increases somewhat during this isentropic
compression process due to slight decrease in the specific volume of
the water. The vertical distance between state 3 and 4 on the T-s
diagram is greatly exaggerated for clarity.

Process 4-1
Water enters the boiler as a compressed liquid at state 4 and leaves
as a superheated vapor at state 1. The boiler is basically a large heat
Page (19)
 exchanger where the heat originating from combustion gases, is
transferred to the water essentially at constant pressure. The boiler
together with the section where the steam is superheated (the super
heater), is often called the steam generator.

The ideal Rankine cycle also includes the possibility of superheating the vapor,
as in cycle 12341. Since the ideal Rankine cycle consists of internally
reversible processes, areas under the process lines of Fig. 8.3 can be interpreted as
heat transfers per unit of mass flowing. Applying Eq. 6.51, area 1bc4a1
represents the heat transfer to the working fluid passing through the boiler and area
2bc32, is the heat transfer from the working fluid passing through the
condenser, each per unit of mass flowing. The enclosed area 1234a1 can be
interpreted as the net heat input or, equivalently, the network output, each per unit
of mass flowing.

1.1.3 BASIC STEAM PLANT COMPONENTS:

Basic Steam Plant consists of a:

1-2: Steam generator (or Boiler)

2-3: Steam Turbine
3-4: Condenser
4-1: Feed pump.

1. 8 Steam Power Plant Components

Page (20)
1- Steam Generator or Boiler:
The purpose of the boiler is to convert water (pumped into it under
pressure) to steam. The steam may emerge wet, dry saturated, or superheated
depending on the boiler design. We may analyze the boiler as a steady state
open system using

h1 is the specific enthalpy of sub-cooled water. (ie at a temperature

below its saturation temperature). It can be found from 'sub-cooled' tables, but
saturated values (at the same temperature) are usually sufficiently accurate.

1. 9 -h diagram

The heat transfer rate to the water/steam is normally less than the rate at
which energy is released inside the boiler (typically by combustion). We may
therefore define a boiler efficiency as:

2- Turbine:
A steam turbine operates in a similar way to a gas turbine. The same
basic performance and efficiency equations are used except that steam
cannot be treated as a perfect gas.

Page (21)
 1. 10 Turbine Calculations

As with a gas turbine the thermodynamic process may be shown on a

T-s chart, or more usefully on an h-s chart

1. 11 h-S diagram

3- Condenser
The condenser brings the exhaust steam into contact with a cool
medium (usually cold water) in order to remove heat and condense it back
to water known as condensate.
Thermodynamically it behaves in the same way as the boiler, but in
reverse.

Page (22)
 1. 12 Condenser Calculations

Notes:
a) The cooling water temperature would be typically in the range 10C
to 30C depending on the source. Condensing temperatures are
therefore in the range 25C to 45C. This means condensing
pressures in the range 3 to 8 kPa, ie well below atmospheric
pressure. This gives rise to problems with air leakage into
condensers, which has to be counteracted by the use of vacuum
pumps.
b) The condensate will normally leave the condenser as a saturated
liquid at the saturation temperature

4- Feed pump:
The feed pump is needed to pump water back into the boiler. In order
to do this, it has to raise the pressure to at least boiler pressure.
It requires mechanical energy to achieve this, but in comparison to the
energy produced by the turbine the amount required is very small, and can
normally be ignored in plant efficiency calculations.

1. 13 feed pump

Page (23)
 To find the actual power requirements of the feed pump we use

Since the water temperature will not change significantly, and also
since water is virtually incompressible:

Deviation of Actual Vapor Power Cycle from Idealized Ones:

The actual vapor power cycle differs from the ideal Rankine cycle, as a result
of irreversibilites in various components. Fluid friction and heat loss to the
surroundings are the two common sources of irreversibilites.
Fluid friction causes pressure drop in the boiler, the condenser and the piping
between various components. Also, the pressure at the turbine inlet is somewhat
lower than that at the boiler exit due to the pressure drop in the connecting pipes.

Page (24)
 To compensate for these pressure drops, the water must be pumped to a
sufficiently higher pressure than the ideal cycle. This requires a large pump and
larger work input to the pump, are shown in Figures (a) and (b).

1. 14 ideal vs actual Rankine cycle 1. 15 actual Rankine cycle

The other major source of irreversibility is the heat loss from the steam to the
surrounding as the steam flows through various components.
Particular importance is the irreversibilites occurring within the pump and the
turbine. A pump requires a greater work input, and a turbine produces a smaller work
output as a result of irreversibilties. Under the ideal condition the flow
through these devices is isentropic.
The deviation of actual pumps and turbine from the isentropic ones can be
accurately accounted by isentropic efficiencies, define as:

Page (25)
1.2 MODIFICATIONS:

1.2.1 PRESSURE DIFFERENCE:

Thermal efficiency of power cycles tends to increase as the average temperature
at which energy is added by heat transfer increases and/or the average temperature
at which energy is rejected by heat transfer decreases. Let us apply this idea to study
the effects on performance of the ideal Rankine cycle of changes in the boiler and
condenser pressures. Although these findings are obtained with reference to the ideal
Rankine cycle, they also hold qualitatively for actual vapor power plants.
1.2.1.1 Rising Boiler Pressure:
Figure. a shows two ideal cycles having the same condenser pressure but
different boiler pressures. By inspection, the average temperature of heat addition is
seen to be greater for the higher-pressure cycle 12341 than for cycle 12
341. It follows that increasing the boiler pressure of the ideal Rankine cycle tends
to increase the thermal efficiency.

1. 16 Rising Boiler Pressure and Lowering Condenser Pressure

1.2.1.2 Lowering Boiler Pressure:

Figure. b shows two cycles with the same boiler pressure but two different
condenser pressures. One condenser operates at atmospheric pressure and the other
at less than atmospheric pressure. The temperature of heat rejection for cycle 12

Page (26)
341 condensing at atmospheric pressure is 100 C (212F). The temperature of heat
rejection for the lower-pressure cycle 12341 is correspondingly lower, so
this cycle has the greater thermal efficiency. It follows that decreasing the condenser
pressure tends to increase the thermal efficiency. The lowest feasible condenser
pressure is the saturation pressure corresponding to the ambient temperature, for this
is the lowest possible temperature for heat rejection to the surroundings. The goal of
maintaining the lowest practical turbine exhaust (condenser) pressure is a primary
reason for including the condenser in a power plant. Liquid water at atmospheric
pressure could be drawn into the boiler by a pump, and steam could be discharged
directly to the atmosphere at the turbine exit. However, by including a condenser in
which the steam side is operated at a pressure below atmospheric, the turbine has a
lower-pressure region in which to discharge, resulting in a significant increase in net
work and thermal efficiency. The addition of a condenser also allows the working
fluid to flow in a closed loop. This arrangement permits continual circulation of the
working fluid, so purified water that is less corrosive than tap water can be used
economically.
Noting that an increase in the boiler pressure or a decrease in the condenser
pressure may result in a reduction of the steam quality at the exit of the turbine. This
can be seen by comparing states 2 and 2 of Figures a and b to the corresponding
state 2 of each diagram. If the quality of the mixture passing through the turbine
becomes too low, the impact of liquid droplets in the flowing liquidvapor mixture
can erode the turbine blades, causing a decrease in the turbine efficiency and an
increased need for maintenance. Accordingly, common practice is to maintain at
least 90% quality (x > 0.9) at the turbine exit. The cycle modifications known as
superheat and reheat permit advantageous operating pressures in the boiler and
condenser and yet avoid the problem of low quality of the turbine exhaust.
First method depends on rising the pressure of the boiler as (3-4-1-2).
Second method depends on lowering the pressure of condenser(3-4-1-2) . Using
This method offer
Advantages:

Increase work net output.

Increase thermal efficiency.
Increase back work ratio.
Increase the temperature.
Page (27)
 Disadvantages:

Decrease the quality of the steam passing through turbine.

Lower the life time of the turbine.
Maintenance for turbine.
1.2.2 SUPER HEAT:
As we are not limited to having saturated vapor at the turbine inlet, further
energy can be added by heat transfer to the steam, bringing it to a superheated vapor
condition at the turbine inlet. This is accomplished in a separate heat exchanger
called a superheater. The combination of boiler and superheater is referred to as a
steam generator. Figure 8.3 shows an ideal Rankine cycle with superheated vapor at
the turbine inlet: cycle 12341. The cycle with superheat has a higher average
temperature of heat addition than the cycle without superheating (cycle 1234
1), so the thermal efficiency is higher. Moreover, the quality at turbine exhaust state
29 is greater than at state 2, which would be the turbine exhaust state without
superheating. Accordingly, superheating also tends to alleviate the problem of low
steam quality at the turbine exhaust. With sufficient superheating, the turbine
exhaust state may even fall in the superheated vapor region.
Advantages:

Higher thermal efficiency.

Higher work net.
Increasing the steam temperature.
Increase the steam quality.
Increase the back-work ratio.

1. 17 Rankine with super-heat

1.2.3 REHEAT:
A common modification of the Rankine cycle in large power plants involves
interrupting the steam expansion in the turbine to add more heat to the steam before
completing the turbine expansion. Reheating process of extracted steam from a high-
pressure (HP) turbine through the "cold reheat" line restores steam to a temperature
comparable to the throttle temperature of the high-pressure turbine. The reenergized

Page (28)
steam is routed through the "hot reheat" line to the low-pressure turbine for
completion of the expansion to the condenser pressure. Furthermore, reheating tends
to increase the average temperature at which heat is added. If the low-pressure
turbine exhaust state is superheated, the use of reheat may also increase the average
temperature at which heat is rejected. The thermal efficiency may therefore increase
or decrease, depending on specific cycle conditions. Thus, reheating process yields
an increase in net work, a dryer turbine exhaust, and possible improved cycle
efficiency.

1. 18 Reheat process

Note that the network of the reheat cycle is the algebraic sum of the work of the
two turbines and the pump work. In addition, that the total added heat is the sum of
the heat added in the feedwater and reheat passes through the steam generator. Thus,
the overall efficiency of the reheat cycle increases.
Figure above shows that reheat shifts the turbine expansion process away from
the two-phase region towards the superheat region of the T-S diagram, thus drying
the turbine exhaust.
Advantages:

Higher thermal efficiency.

Higher work net.
Higher back ratio.

Page (29)
 Higher steam quality.

1.2.4 SUPER CRITICAL:

The temperature of the steam entering the turbine is restricted by the
metallurgical limitations imposed by materials used to fabricate the super heater, re
heater and turbine. high pressure in the steam generator also requires piping that can
withstand great stresses at elevated temperature.
Improved materials and fabrications
methods have gradually permitted
significant increase in maximum allowed
cycle temperature and steam generator
pressure. This progress now allows vapor
power plants to operate with steam
generator pressure exceeding the critical-
pressure of water (21MPa)
Advantage:
1. 19 super critical process
Higher thermal efficiency.
Higher work net.
Higher back ratio.
Higher steam quality.
Disadvantages:

Metallurgical limitation.
High stress due high steam pressure.
1.2.5 REGENERATIVE:
Rankine cycle efficiency may be improved by increasing the average water
temperature at which heat is received. This could be accomplished by an internal
transfer of heat from higher-temperature steam to low-temperature feedwater. An
internal transfer of heat that reduces or eliminates low-temperature additions of
external heat to the working fluid is known as regeneration.

Page (30)
 In figure below in cycle 1-2-3-4-a-1, the working fluid enters the boiler as a
compressed liquid at state 4 and is heated while in the liquid phase to state a. with
regenerative feed water heating, the working fluid enters the boiler at a state between
4 and a.
As a result, the average temperature of heat addition is increased, thereby
tending to increase the thermal efficiency .

1. 20 Regenerative

Advantages:

Higher thermal efficiency.

Higher work net.
Higher back ratio.
Higher steam quality.
Low heat additions.
Lower heat losses.
1.2.5.1 Open Feed Water Heater:
Open feed water heater is a type of direct-contact heat exchanger in which
streams at different temperature mix to form a stream at an intermediate temperature
as shown in figure below.

Page (31)
 1. 21 open feed water heater

For this cycle, the working fluid passes isentropically through the turbine
stages and pumps, and flow through the steam generator, condenser, and feed water
heater takes place with no pressure drop in any of these components. Still, there is a
source of irreversibility owing to mixing within the feed water heater.
Steam enters the first-stage turbine at state 1 and expands to state 2, where a
fraction of the total flow is extracted, or bled, into an open feed water heater
operating at the extraction pressure, p2. The rest of the steam expands through the
second-stage turbine to state 3. This portion of the total flow is condensed to
saturated liquid, state 4, and then pumped to the extraction pressure and introduced
into the feed water heater at state 5. A single mixed stream exits the feed water heater
at state 6. For the case shown in Fig. 8.9, the mass flow rates of the streams entering
the feed water heater are such that state 6 is saturated liquid at the extraction
pressure. The liquid at state 6 is then pumped to the steam generator pressure and
enters the steam generator at state 7. Finally, the working fluid is heated from state
7 to state 1 in the steam generator.
Referring to the Ts diagram of the cycle, note that the heat addition would take
place from state 7 to state 1, rather than from state a to state 1, as would be the case
without regeneration. Accordingly, the amount of energy that must be supplied from

Page (32)
the combustion of a fossil fuel, or another source, to vaporize and superheat the
steam would be reduced. This is the desired outcome. Only a portion of the total
flow expands through the second-stage turbine (Process 23), however, so less work
would be developed as well. In practice, operating conditions are such that the
reduction in heat added more than offsets the decrease in net work developed,
resulting in an increased thermal efficiency in regenerative power plants.
1.2.5.2 Closed Feed Water Heater:
Closed heaters are shell-and-tube-type recuperators in which the feedwater
temperature increases as the extracted steam condenses on the outside of the tubes
carrying the feedwater. Since the two streams do not mix, they can be at different
pressures. The diagrams of Fig below show two different schemes for removing the
condensate from closed feedwater heaters.

1. 22 Types of closed feed water heater

In Fig. a, this is accomplished by means of a pump whose function is to pump

the condensate forward to a higher-pressure point in the cycle. In Fig. b, the
condensate is allowed to expand through a trap into a feedwater heater operating at
a lower pressure or into the condenser. A trap is a type of valve that permits only
liquid to pass through to a region of lower pressure.

Page (33)
 A regenerative vapor power cycle having one closed feedwater heater with the
condensate trapped into the condenser is shown schematically in Fig. below. For this
cycle, the working fluid passes isentropically through the turbine stages and pumps.
Except for expansion through the trap, there are no pressure drops accompanying
flow through other components. The Ts diagram shows the principal states of the
cycle.
The total steam flow expands through the first-stage turbine from state 1 to
state 2. At this location, a fraction of the flow is bled into the closed feedwater heater,
where it condenses. Saturated liquid at the extraction pressure exits the feedwater
heater at state 7. The condensate is then trapped into the condenser, where it is
reunited with the portion of the total flow passing through the second-stage turbine.
The expansion from state 7 to state 8 through the trap is irreversible, so it is shown
by a dashed line on the Ts diagram. The total flow exiting the condenser as
saturated liquid at state 4 is pumped to the steam generator pressure and enters the
feedwater heater at state 5. The temperature of the feedwater is increased in passing
through the feedwater heater. The feedwater then exits at state 6. The cycle is
completed as the working fluid is heated in the steam generator at constant pressure
from state 6 to state 1. Although the closed heater shown on the figure operates with
no pressure drop in either stream, there is a source of irreversibility due to the stream-
to-stream temperature difference.

1. 23 Closed feed water heater

Page (34)
1.2.5.3 Multi Feedwater Heaters:
The thermal efficiency of the regenerative cycle can be increased by
incorporating several feedwater heaters at suitably chosen pressures. The number of
feedwater heaters used is based on economic considerations, since incremental
increases in thermal efficiency achieved with each additional heater must justify the
added capital costs (heater, piping, pumps, etc.). Power plant designers use computer
programs to simulate the thermodynamic and economic performance of different
designs to help them decide on the number of heaters to use, the types of heaters,
and the pressures at which they should operate.
Figure below shows the layout of a power plant with three closed feedwater
heaters and one open heater. Power plants with multiple feedwater heaters ordinarily
have at least one open feedwater heater operating at a pressure greater than
atmospheric pressure so that oxygen and other dissolved gases can be vented from
the cycle. This procedure, known as deaeration, is needed to maintain the purity of
the working fluid in order to minimize corrosion. Actual power plants have many of
the same basic features as the one shown in the figure below.

1. 24 Multi feed water heater

Page (35)
 In analyzing regenerative vapor power cycles with multiple feedwater heaters,
it is good practice to base the analysis on a unit of mass entering the first-stage
turbine.
To clarify the quantities of matter flowing through the various plant
components, the fractions of the total flow removed at each extraction point and the
fraction of the total flow remaining at each state point in the cycle should be labeled
on a schematic diagram of the cycle. The fractions extracted are determined from
mass and energy rate balances for control volumes around each of the feedwater
heaters, starting with the highest-pressure heater and proceeding to each lower-
pressure heater in turn.

Page (36)
Chapter 2

Boiler

Page (37)
 Chapter 2
BOILER
2.1 INTRODUCTION:
The steam generator or boiler is an integral component of a steam engine when
considered as a prime mover. However, it needs be treated separately, as to some
extent a variety of generator types can be combined with a variety of engine units.
A boiler incorporates a firebox or furnace in order to burn the fuel and generate heat.
The generated heat is transferred to water to make steam, the process of boiling. This
produces saturated steam at a rate which can vary according to the pressure above
the boiling water. The higher the furnace temperature, the faster the steam
production. The saturated steam thus produced can then either be used immediately
to produce power via a turbine and alternator, or else may be further superheated to
a higher temperature; this notably reduces suspended water content making a given
volume of steam produce more work and creates a greater temperature gradient,
which helps reduce the potential to form condensation. Any remaining heat in the
combustion gases can then either be evacuated or made to pass through an
economizer, the role of which is to warm the feed water before it reaches the boiler.
Boilers have several strengths that have made them a common feature of
buildings. They have a long life, can achieve efficiencies up to 95% or greater,
provide an effective method of heating a building, and in the case of steam systems,
require little or no pumping energy. However, fuel costs can be considerable, regular
maintenance is required, and if maintenance is delayed, repair can be costly.
Guidance for the construction, operation, and maintenance of boilers is provided
primarily by the ASME (American Society of Mechanical Engineers

2.2 WORKING PRINCIPLE:

Both gas and oil-fired boilers use controlled combustion of the fuel to heat
water. The key boiler components involved in this process are the burner,
combustion chamber, heat exchanger, and controls.
The burner mixes the fuel and oxygen together and, with the assistance of an
ignition device, provides a platform for combustion. This combustion takes place in
the combustion chamber, and the heat that it generates is transferred to the water
through the heat exchanger. Controls regulate the ignition, burner firing rate, fuel

Page (38)
supply, air supply, exhaust draft, water temperature, steam pressure, and boiler
pressure.
Hot water produced by a boiler is pumped through pipes and delivered to
equipment throughout the building, which can include hot water coils in air handling
units, service hot water heating equipment, and terminal units. Steam boilers produce
steam that flows through pipes from areas of high pressure to areas of low pressure,
unaided by an external energy source such as a pump. Steam utilized for heating can
be directly utilized by steam using equipment or can provide heat through a heat
exchanger that supplies hot water to the equipment.
The discussion of different types of boilers, below, provides more detail on the
designs of specific boiler systems.

2.3 CLASSIFICATION OF BOILERS:

Boilers are classified according certain condition. Following figure shows
classification of boiler.

2. 1 Classification of boilers

There are mainly two types of boiler water tube boiler and fire tube boiler. In
fire tube boiler, there are numbers of tubes through which hot gases are passed and
Page (39)
water surrounds these tubes. Water tube boiler is reverse of the fire tube boiler. In
water tube boiler, the water is heated inside tubes and hot gasses surround these
tubes.
2.3.1 Fire Tube Boiler:
As it indicated from the name, the fire tube boiler consists of numbers of tubes
through which hot gasses are passed. These hot gas tubes are immersed into water,
in a closed vessel. Actually, in fire tube boiler one closed vessel or shell contains
water, through which hot tubes are passed. These fire tubes or hot gas tubes heated
up the water and convert the water into steam and the steam remains in same vessel.
As the water and steam both are in same vessel a fire tube boiler cannot produce
steam at very high pressure. Generally, it can produce maximum 17.5 kg/cm2 and
with a capacity of 9 Metric Ton of steam per hour.

2. 2 fire tube boiler

2.3.1.1 Types of Fire Tube Boiler:

There are different types of fire tube boiler likewise, external furnace and
internal furnace fire tube boiler. External furnace boiler can be again categorized
into three different types-

1. Horizontal Return Tubular Boiler.

2. Short Fire Box Boiler.
3. Compact Boiler.

Page (40)
 A gain, internal furnace fire tube boiler has also two main categories such as
horizontal tubular and vertical tubular fire tube boiler. Normally horizontal return
fire tube boiler is used in thermal power plant of low capacity. It consists of a
horizontal drum into which there are numbers of horizontal tubes. These tubes are
submerged in water. The fuel (normally coal) burnt below these horizontal drum and
the combustible gasses move to the rear from where they enter into fire tubes and
travel towards the front into the smoke box. During this travel of gasses in tubes,
they transfer their heat into the water and steam bubbles come up. As steam is
produced, the pressure of the boiler developed, in that closed vessel.

2.3.1.2 Advantages of Fire Tube Boiler:

1. It is quite compact in construction.

2. Fluctuation of steam demand can be met easily.
3. It is also quite cheap.

2.3.1.3 Disadvantages of Fire Tube Boiler:

1. As the water required for operation of the boiler is quite large, it requires long
time for rising steam at desired pressure.
2. As the water and steam are in same vessel the very high pressure of steam is
not possible.
3. The steam received from fire tube boiler is not very dry.

Page (41)
2.3.2 WATER TUBE BOILER:
A water tube boiler is such kind of boiler where the water is heated inside tubes
and the hot gasses surround them. This is the basic definition of water tube boiler.
Actually, this boiler is just opposite of fire tube boiler where hot gasses are passed
through tubes which are surrounded by water.

2. 3 water tube boiler

2.3.2.1 Types of Water Tube Boiler:

There are many types of water tube boilers, such as

Horizontal Straight Tube Boiler.

Bent Tube Boiler.
Cyclone Fired Boiler.

Horizontal Straight Tube Boiler again can be sub - divided into two different
types,

Longitudinal Drum Water Tube Boiler.

Cross Drum Water Tube Boiler.

Page (42)
 Bent Tube Boiler also can be sub divided into four different types,

Two Drum Bent Tube Boiler.

Three Drum Bent Tube Boiler.
Low Head Three Drum Bent Tube Boiler.
Four Drum Bent Tube Boiler.

2.3.2.2 Advantages of Water Tube Boiler:

There are many advantages of water tube boiler due to which these types of
boiler are essentially used in large thermal power plant.

1. Larger heating surface can be achieved by using more numbers of water tubes.
2. Due to convectional flow, movement of water is much faster than that of fire
tube boiler, hence rate of heat transfer is high which results into higher
efficiency.
3. Very high pressure in order of 140 kg/cm2 can be obtained smoothly.

2.3.2.3 Disadvantages of Water Tube Boiler:

1. The main disadvantage of water tube boiler is that it is not compact in

construction.
2. Its cost is not cheap.
3. Size is a difficulty for transportation and construction.
4. These are the main two types of boiler but each of the types can be sub divided
into many:

No Fire tube boiler Water tube boiler

In Fire-tube boilers hot flue In Water-tube boilers water passes

1 gases pass through tubes and through tubes and hot flue gasses
water surrounds them. surround them.

These are operated at low The working pressure is high enough,

2
pressures up to 20 bars. up to 250 bars in super critical boilers.

The rate of steam generation and

3 The rate of steam generation and quality of steam are better and suitable
quality of steam are very low, for power generation.

Page (43)
 therefore, not suitable for power
generation.

Load fluctuations cannot be Load fluctuations can be easily

4
handled. handled.

It requires more floor area for a It requires less floor area for a given
5
given output. output

These are bulky and difficult to These are light in weight, hence
6
transport. transportation is not a problem.

Overall efficiency with an economizer

7 Overall efficiency is up to 75%.
is up to 90%.

Water doesnt circulate in a Direction of water circulated is well

8
definite direction. defined.

The drum size is large and

If any water tube is damaged, it can be
9 damage caused by bursting is
easily replaced or repaired.
large.

It requires more floor area for a It requires less floor area for a given
10
given output. output

Simple in design, easy to erect Complex, design, difficult to erect and

11
and low maintenance cost. high maintenance cost.

Even less skill operators are Skilled operators are required for
12
sufficient for efficient operation. operation.

The treatment of feed water is not

Treatment of feed water is very essential
very essential, as overheating due
13 as small scale deposits inside the tubes
to scale formation cannot burst
can cause overheating and bursting.
thick shell.

Page (44)
 14 Used in process industry. Used in large power plants.

2.4 RANGE AND DIVERSITY OF BOILERS:

Boilers are made in various shapes and sizes to burn a variety of fuels with the
end purpose of producing varying amounts of steam for either process or power or
both. An attempt is made here to capture practically the whole range of fired boilers,
from the humble smoke/ue tube boilers for modest steam to the ultra-supercritical
(USC) for mega power plants in a single graph to let the reader get acquainted with
the magnitude and variety. Figure helps to provide an insight into the diversity. It is
to be noted that the boiler capacity is on a log graph, which helps at once to
accommodate the entire range, but also renders a visual distortion.

2. 4 Range and diversity of boilers

Page (45)
2.5 BREAKUP LOSSES:
1- Stack Losses:
These are measures of:
How well the ue gases are cooled
How low the ue gas quantities are kept

2- Unburnt Loss:
Unburnt loss is a measure of how well the fuel is burnt in the firing
equipment for the excess air chosen. Efficiency of heat release of the firing
equipment is measured by the amount of carbon burnup, which is

3- Radiation Loss:
Radiation losses are below 1%, and become smaller as the boiler size and
water cooling increase.

4- Unaccountable Losses (Lu):

Unaccountable losses cannot be exactly quantified and are small enough
to be combined and assigned a reasonable value. They comprise, usually,
Heat loss in ash
Effects of sulfation and calcination reactions in FBC boilers
Unstated instrument tolerances and errors
Any other immeasurable losses

2.6 FUEL TYPE:

In commercial buildings, natural gas is the most common boiler fuel, because
it is usually readily available, burns cleanly, and is typically less expensive than oil
or electricity. Some boilers are designed to burn more than one fuel (typically natural
gas and fuel oil). Dual fuel boilers provide the operator with fuel redundancy in the
event of a fuel supply interruption. They also allow the customer to utilize the fuel
oil during peak time rates for natural gas. In times when the rates for natural gas

Page (46)
are greater than the alternate fuel, this can reduce fuel costs by using the cheaper
alternate fuel and limiting natural gas use to occur only during off peak times.

2.7 DRAUGHT METHODS:

The pressure difference between the boiler combustion chamber and the flue
(also called the exhaust stack) produces a draft which carries the combustion
products through the boiler and up the flue. Natural draft boilers rely on the natural
buoyancy of hot gasses to exhaust combustion products up the boiler flue and draw
fresh air into the combustion chamber.
Most boilers now depend on mechanical draught equipment rather than natural
draught. This is because natural draught is subject to outside air conditions and
temperature of flue gases leaving the furnace, as well as the chimney height. All
these factors make proper draught hard to attain and therefore make mechanical
draught equipment much more economical. There are three types of mechanical
draught:

Induced draught:
This is obtained one of three ways, the first being the "stack effect" of a
heated chimney, in which the flue gas is less dense than the ambient air
surrounding the boiler. The denser column of ambient air forces combustion
air into and through the boiler. The second method is through use of a steam
jet. The steam jet oriented in the direction of flue gas flow induces flue gasses
into the stack and allows for a greater flue gas velocity increasing the overall
draught in the furnace. This method was common on steam driven
locomotives which could not have tall chimneys. The third method is by
simply using an induced draught fan (ID fan) which removes flue gases from
the furnace and forces the exhaust gas up the stack. Almost all induced draught
furnaces operate with a slightly negative pressure.

Forced draught:
Draught is obtained by forcing air into the furnace by means of a fan (FD
fan) and ductwork. Air is often passed through an air heater; which, as the
name suggests, heats the air going into the furnace in order to increase the
overall efficiency of the boiler. Dampers are used to control the quantity of

Page (47)
 air admitted to the furnace. Forced draught furnaces usually have a positive
pressure

Balanced draught:
Balanced draught is obtained through use of both induced and forced
draught. This is more common with larger boilers where the flue gases have
to travel a long distance through many boiler passes. The induced draught fan
works in conjunction with the forced draught fan allowing the furnace
pressure to be maintained slightly below atmospheric.

2.8 STEAM BOILER EFFICIENCY:

The percentage of total heat exported by outlet steam in the total heat supplied
by the fuel (coal) is called steam boiler efficiency. It includes with thermal
efficiency, combustion efficiency & fuel to steam efficiency. Steam boiler efficiency
depends upon the size of boiler used. A typical efficiency of steam boiler is 80% to
88%. Actually, there are some losses occur like incomplete combustion, radiating
loss occurs from steam boiler surrounding wall, defective combustion gas etc.
Hence, efficiency of steam boiler gives this result.

2.9 BOILER FITTINGS AND ACCESSORIES:

Accessories are the devices being used to increase the efficiency of the boiler.
A large amount of heat is being carried out by the flue gases, this is wastage of useful
energy, which can be recovered. Accessories are that equipment which recovers the
wastage along with smoothing the operation to increase the utilization of energy as
well as reducing the cost of operation. The waste recovery takes place by the help of
flue gases, which has a large amount of heat.
Accessories are not the mandatory parts or devices but being used for efficient
operation.

Page (48)
2.9.1 STEAM SUPER HEATER:
The function of a super heater is to increase the temperature of steam above its
saturation point. That means it gives assurance of the quality of steam. During
superheating pressure of steam remains same but the volume increases with its
temperature, increasing the internal energy which in turns prove to increase in
kinetic energy, resulting in

Reduction of steam consumption of turbine.

Reduction in losses due to condensation in steam pipes.
Elimination of erosion of turbine blades
Increase in efficiency.
There are two types of super heaters:

Convective Super heater

Radiant Super heater

2. 5 steam super-heater

Page (49)
2.9.2 ECONOMIZER:
In best way, it is known as feed water heater, that refers heating of feed
water, which is supplied to the boiler shell to get vaporized. It utilizes heat
carried out but the waste furnace gases to heat the water before it enters boiler.
By increasing the temperature of water, chilling of the boiler surface is
prevented and then a less amount of sensible heat is required to achieve
saturation temperature, it reduces then the input heat to the boiler and
increasing efficiency. There are two types of economizer
Independent type (not a part of boiler)
Integrated type (a part of boiler)

2. 6 Economizer

Page (50)
2.9.3 AIR PREHEATER:
The function of an air preheater is to heat the inlet air before it is sent to
the furnace. It is placed after economizer, flue gases coming from economizer
is being utilized to heat air. Preheated air accelerate combustion and
increasing the amount of heat produced.
Degree of preheating depends upon
Type of fuel
Type of fuel burning equipment
Rating of the boiler and furnace
Two types of preheaters commonly used,

Recuperative type (Both the fluids pass simultaneously)

Regenerative type (Fluids pass alternatively)

2. 7 air preheater

Page (51)
2.9.4 STEAM SEPARATOR:
The basic work of steam separator is to ensure the quality of steam, steam
from the boiler may be in the form of wet steam, or in case of regenerative
cycle, where condensate from turbine is supplied back or being used by
smaller capacity turbines to recover heat, steam must be in the wet format.
Steam separator removes water particles. There are three types of steam
separator
Impact or baffle type
Reverse current type
Centrifugal type

2. 8 steam separator

Page (52)
2.9.5 FEED PUMP:
Feed pumps is the device required to supply water to the boiler. The quantity
of feed water should be at least equal to the amount of steam delivered to the turbine
or required space. For open cycle boiler in case of large plants, where there is no
condenser or the amount of feedback water is less, pumps are inevitable.
There are two types of feed pumps,

Reciprocating feed pump (Piston cylinder arrangement) (Single acting

& )Double acting
Rotary or centrifugal feed pump

2. 9 Feed pumps

Page (53)
2.9.6 INJECTOR:
The basic work of an injector is to feed water to the boiler on high pressure, it
finds its application in such places where there is no space to install feed pumps. It
works by the help of steam pressure in a way that the pressure of steam is being
utilized to increase the kinetic energy of feed water.
Advantages:

Low initial cost

Simplicity
Compactness
No dynamic parts
High thermal efficiency
Disadvantages:

Low pumping efficiency

Cant work for very hot steam
Irregularity in the operation when steam pressure varies considerably

2. 10 injector

Page (54)
2.10 BOILER DRUMS:
Two types of boiler drums used in all types of boilers are steam drum and
mud drum. Both the drums have specific functions.
2.10.1 Steam Drum:
The functions of steam drum in feed water steam circuit are:

To store water and steam sufficiently to meet varying load demands.

To provide a head and thereby aiding the natural circulation of water
through water tubes.
To separate vapor or steam from water- steam mixture, discharged by
the risers.
To aid in chemical treatments to remove dissolved O2 and to maintain
required ph.

Separating steam from two-phase mixtures in the steam drum:

o Steam must be separated from the mixture before it leaves the drum,
because:
o Any moisture carried with steam contains dissolved salts. In the super
heater, water evaporates and the salt remain deposited on the inside
surface of the tubes to form a scale. This scale reduces the life of the
super-heaters.
o Some of the impurities in the moisture (like vaporized silica) may cause
turbine blade deposits.
o One of the important functions of steam-drum is to separate steam from
steam water mixture. At low pressure (below 20 bar; 1 bar = 1.0197
kg/cm2) simple gravity separation is used. In the method of gravity
separation, the water particles disengaged from steam due to higher
density.
o As the pressure inside the boiler drum increases the density of steam
increases, as steam is very compressible. Hence difference between the
densities of steam and water decreases. Hence gravity separation
becomes in efficient.
o Hence in the steam drum of the high-pressure boilers, there are some
mechanical arrangements (known as drum internals or anti-priming
arrangements) for separating steams from water.

Page (55)
o Following picture illustrates different Anti-priming arrangements used
in thermal power plants:

2. 11 Anti-priming arrangements

o Baffles are separators which separate the hot steam-water mixture

from dry steam and provide a guided path for the dry steam.
o In the cyclone separator steam water two-phase mixture is allowed to
move in a helical path and due to centrifugal forces, the water particles
separate out from the two-phase mixture. The small vanes inside the
cyclone separator collect the deposited water particles.
o In the scrubber the two-phase mixture is allowed to move in a zigzag
path and it provides the ultimate stage of drying the steam.
o After scrubber steam is allowed to move to super-heated through a
perforated screen.

Page (56)
2.10.2 Mud Drum:
Mud drum is another header which is situated at the bottom of the boiler and
usually helps in natural circulation of water through the steam tubes. Mud drum
usually contains water at saturation temperature, and also the precipitated salts and
impurities known as slurries. It is periodically washed to remove the slurry by
opening the discharge valve.

2.11 MATERIALS:
The pressure vessel of a boiler is usually made of steel (or alloy steel), or
historically of wrought iron. Stainless steel, especially of the austenitic types, is
virtually prohibited by the ASME Boiler Code for use in wetted parts of modern
boilers, but ferritic stainless steel is used often in super-heater sections that will not
be exposed to liquid boiler water. However, electrically-heated stainless-steel shell
boilers are allowed under the European "Pressure Equipment Directive" for
production of steam for sterilizers and disinfectors.
In live steam models, copper or brass is often used because it is more easily
fabricated in smaller size boilers. Historically, copper was often used for fireboxes
(particularly for steam locomotives), because of its better formability and higher
thermal conductivity; however, in more recent times, the high price of copper often
makes this an uneconomic choice and cheaper substitutes (such as steel) are used
instead.
For much of the Victorian "age of steam", the only material used for boiler
making was the highest grade of wrought iron, with assembly by riveting. This iron
was often obtained from specialist ironworks, such as at Cleator Moor (UK), noted
for the high quality of their rolled plate and its suitability for high-reliability use in
critical applications, such as high-pressure boilers. In the 20th century, design
practice instead moved towards the use of steel, which is stronger and cheaper, with
welded construction, which is quicker and requires less labor.
Cast iron may be used for the heating vessel of domestic water heaters.
Although such heaters are usually termed "boilers" in some countries, their purpose
is usually to produce hot water, not steam, and so they run at low pressure and try to
avoid actual boiling. The brittleness of cast iron makes it impractical for high
pressure steam boilers.
Page (57)
2.12 SAFETY:
To define and secure boilers safety, some professional specialized
organizations such as the American Society of Mechanical Engineers (ASME)
develop standards and regulation codes. For instance, the ASME Boiler and Pressure
Vessel Code is a standard providing a wide range of rules and directives to ensure
compliance of the boilers and other pressure vessels with safety, security and design
standards.
Historically, boilers were a source of many serious injuries and property
destruction due to poorly understood engineering principles. Thin and brittle metal
shells can rupture, while poorly welded or riveted seams could open up, leading to a
violent eruption of the pressurized steam. When water is converted to steam, it
expands to over 1,000 times its original volume and travels down steam pipes at over
100 kilometers per hour. Because of this steam is great way of moving energy and
heat around a site from a central boiler house to where it is needed, but without the
right boiler feed water treatment, a steam-raising plant will suffer from scale
formation and corrosion. At best, this increases energy costs and can lead to poor-
quality steam, reduced efficiency, shorter plant life and unreliable operation. At
worst, it can lead to catastrophic failure and loss of life. Collapsed or dislodged boiler
tubes can also spray scalding-hot steam and smoke out of the air intake and firing
chute, injuring the firemen who load the coal into the fire chamber. Extremely large
boilers providing hundreds of horsepower to operate factories can potentially
demolish entire buildings.
A boiler that has a loss of feed water and is permitted to boil dry can be
extremely dangerous. If feed water is then sent into the empty boiler, the small
cascade of incoming water instantly boils on contact with the superheated metal shell
and leads to a violent explosion that cannot be controlled even by safety steam
valves. Draining of the boiler can also happen if a leak occurs in the steam supply
lines that is larger than the make-up water supply could replace.
All combustion equipment must be operated properly to prevent dangerous
conditions or disasters from occurring, causing personal injury and property loss.
The basic cause of boiler explosions is ignition of a combustible gas that has
accumulated within the boiler. This situation could arise in a number of ways, for
example fuel, air, or ignition is interrupted for some reason, the flame extinguishes,
and combustible gas accumulates and is reignited. Another example is when a

Page (58)
number of unsuccessful attempts at ignition occur without the appropriate purging
of accumulated combustible gas. There is a tremendous amount of stored energy
within a boiler.
Boiler safety is a key objective of the National Board of Boiler and Pressure
Vessel Inspectors. This organization reports and tracks boiler safety and the number
of incidents related to boilers and pressure vessels each year. Their work has found
that the number one incident category resulting in injury was poor maintenance and
operator error. These stresses the importance of proper maintenance and operator
training.
Boilers must be inspected regularly based on manufacturers recommendations.
Pressure vessel integrity, checking of safety relief valves, water cutoff devices and
proper float operation, gauges and water level indicators should all be inspected. The
boilers fuel and burner system requires proper inspection and maintenance to ensure
efficient operation, heat transfer and correct flame detection. The Federal Energy
Management Project (FEMP) O&M Best Practices Guide to Achieving Operation
Efficiency is a good resource describing a preventive maintenance plan and also
explaining the importance of such a plan.

Page (59)
Chapter 3

Steam Turbines

Page (60)
 Chapter 3
STEAM TURBINE
3.1 INTRODUCTION:
A steam turbine is a mechanical device that extracts thermal energy and
kinetic energy from pressurized steam, and converts it into rotary motion. It has
almost completely replaced the reciprocating piston steam engine primarily 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 derives 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.

3.2 TYPES:
Steam turbines are made in a variety of sizes ranging from small 0.75 kW units
(rare) used as mechanical drives for pumps, compressors and other shaft driven
equipment, to 1,500,000 kW turbines used to generate electricity. There are several
classifications for modern steam turbines.

3.3 MERITS and DEMERITS OF STEAM TURBINE:

3.3.1 MERITS:
Ability to utilize high pressure and high temperature steam.
High component efficiency.
High rotational speed.
High capacity/weight ratio.
Smooth, nearly vibration-free operation.
No internal lubrication.
Oil free exhaust steam.
Can be built in small or very large units (up to 1200 MW).

Page (61)
3.3.2 DEMERITS:
For slow speed application reduction gears are required.
The steam turbine cannot be made reversible.
The efficiency of small simple steam turbines is poor.

3.4 PRINCIPLE OF OPERATION AND DESIGN:

An ideal steam turbine is considered to be an isentropic process, or constant
entropy process, in which the entropy of the steam entering the turbine is equal to
the entropy of the steam leaving the turbine. No steam turbine is truly isentropic,
however, with typical isentropic efficiencies ranging from 20%-90% based on the
application of the turbine. The interior of a turbine comprises several sets of blades,
or buckets as they are more commonly referred to. One set of stationary blades is
connected to the casing and one set of rotating blades is connected to the shaft. The
sets intermesh with certain minimum clearances, with the size and configuration of
sets varying to efficiently exploit the expansion of steam at each stage.

3.5 STEAM TURBINE STAGE:

A turbine stage consists of stationary stator row (guide vanes or nozzle ring)
and rotating rotor row.
In the guide vanes high pressure, high temperature steam is expanded
resulting in high velocity.
The guide vanes direct the flow to the rotor blades at an appropriate angle.
In the rotor, the flow direction is changed and kinetic energy of the working
fluid is absorbed by the rotor shaft producing mechanical energy.

Page (62)
 3. 1 Turbine Stage

3.6 TURBINE EFFICIENCY:

To maximize turbine efficiency the steam is expanded, generating work, in a
number of stages. These stages are characterized by how the energy is extracted from
them and are known as either impulse or reaction turbines. Most steam turbines use
a mixture of the reaction and impulse designs: each stage behaves as either one or
the other, but the overall turbine uses both. Typically, higher pressure sections are
impulse type and lower pressure stages are reaction type.

Page (63)
 3. 2 Insulation

Here we take care of heat losses so turbine outer casing must be well insulated.

3.7 LOSSES IN STEAM TURBINE:

Profile loss:
Due to formation of boundary layer on blade surfaces. Profile loss is a
boundary layer phenomenon and therefore subject to factors that influence
boundary layer development. These factors are Reynolds number, surface
roughness, exit Mach number and trailing edge thickness.
Secondary loss:
Due to friction on the casing wall and on the blade root and tip. It is a
boundary layer effect and dependent upon the same considerations as those of
profile loss.
Tip leakage loss:
Due to steam passing through the small clearances required between the
moving tip and casing or between the moving blade tip and rotating shaft.

Page (64)
 The extend of leakage depends on the whether the turbine is impulse or
reaction. Due to pressure drop in moving blades of reaction turbine they are
more prone to leakages.
Disc wind age loss:
Due to surface friction created on the discs of an impulse turbine as the
disc rotates in steam atmosphere. The result is the forfeiture of shaft power
for an increase in kinetic energy and heat energy of steam.
Lacing wire loss:
Due to passage blockage created by the presence of lacing wires in long
blade of LP Stages.
Wetness loss:
Due to moisture entrained in the low-pressure steam at the exit of LP
turbine. The loss is a combination of two effects; firstly, reduction in
efficiency due to absorption of energy by the water droplets and secondly,
erosion of final moving blades leading edges.
Annulus loss:
Due to significant amount of diffusion between adjacent stages or where
wall cavities occur between the fixed and moving blades. The extent of loss
is greatly reduced at high annulus area ratios (inlet/outlet) if the expansion of
the steam is controlled by a flared casing wall.
Leaving loss:
Due to kinetic energy, available at the steam leaving from the last stage
of LP turbine. In practice steam does slow down after leaving the last blade,
but through the conversion of its kinetic energy to flow friction losses.
Partial admission loss:
Due to partial filling of steam, flow between the blades is considerably
accelerated causing a loss in power.

3.8 STEAM TURBINE CLASSIFICATION:

Steam Turbines have been classified by:
3.8.1 DETAILS OF STAGE:

Page (65)
3.8.1.1 Impulse:
An impulse turbine has fixed nozzles that orient the steam flow into high speed
jets. These jets contain significant kinetic energy, which the rotor blades, shaped like
buckets, convert into shaft rotation as the steam jet changes direction. A pressure
drop occurs across only the stationary blades, with a net increase in steam velocity
across the stage. Single stage impulse turbine is called DE LAVAL turbine

3. 3 Impulse Turbine

As the steam flows through the nozzle its pressure falls from inlet pressure to
the exit pressure (atmospheric pressure, or more usually, the condenser vacuum).
Due to this higher ratio of expansion of steam in the nozzle the steam leaves the
nozzle with a very high velocity. The steam leaving the moving blades is a large
portion of the maximum velocity of the steam when leaving the nozzle. The loss of
energy due to this higher exit velocity is commonly called the carry over velocity
or leaving loss.
Compounding of impulse turbine:

This is done to reduce the rotational speed of the impulse turbine to practical
limits.

Page (66)
 Compounding is achieved by using more than one set of nozzles, blades rotors
in a series keyed to a common shaft; so that either the blades, rotors, series,
steam pressure or the jet velocity is absorbed by the turbine in stages.

Three main types of compounded impulse turbines are:

Pressure compounded (RATEAU).

Involves splitting up of the whole pressure drop into a series of
smaller pressure drops across several stages of impulse turbine. The
nozzles are fitted into a diaphragm locked in separates one wheel chamber
from the casing that another. All rotors are mounted on the same shaft.

3. 4 Pressure & Velocity Change In RATEAU

Velocity compounded (CURTIS).

Velocity drop is achieved through many moving rows of blades
instead of a single row of moving blades. It consists of a nozzle or a set of
nozzle rows of moving blades attached to the rotor or the wheel and rows
of fixed blades attached to the casing.
Pressure and velocity compounded impulse turbines:
Pressure velocity compounding gives the advantage of producing a
shortened rotor compared to pure velocity compounding. In this design
steam velocity at exit to the nozzles is kept reasonable and thus the blade
speed (hence rotor rpm) reduced.

Page (67)
 3. 5 Pressure & Velocity Change in Compound

3.8.1.2 Reaction:
In the reaction turbine, the rotor blades themselves are arranged to form
convergent nozzles. This type of turbine makes use of the reaction force produced
as the steam accelerates through the nozzles formed by the rotor.

3. 6 Reaction Turbine

Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the
stator as a jet that fills the entire circumference of the rotor. The steam then changes
direction and increases its speed relative to the speed of the blades. The steam then
changes direction and increases its speed relative to the speed of the blades.

Page (68)
 3. 7 Pressure & Velocity Change In Reaction turbine

A pressure drop occurs across both the stator and the rotor, with steam
accelerating through the stator and decelerating through the rotor, with no net change
in steam velocity across the stage but with a decrease in both pressure and
temperature, reflecting the work performed in the driving of the rotor.

Page (69)
IMPULSE Vs REACTION

3. 8 Impulse Vs Reaction

Impulse turbines Reaction turbines

An impulse turbine has fixed Reaction turbine makes use of

nozzles that orient the steam the
flow into high speed jets. reaction force produced as the
steam accelerates through the
nozzles formed by the rotor.

Blade profile is symmetric as Blades have aerofoil profile

no pressure drop takes place (convergent passage)since
in the blade. pressure drop occurs partly in
the rotor.
Suitable for efficiently Efficient at the low pressure
absorbing the high velocity stages.
and high pressure.
Steam pressure is constant Fine blade tip clearances are
across blades and therefore necessary due to the pressure
leakage.

Page (70)
 fine tip clearances are not
necessary.
Efficiency is not maintained in Inefficient at the high pressure
the lower pressure stages. stages due to the pressure
leakage around the blade tips .
High velocity cannot be Fine tip clearances can cause
achieved in steam for the damage to the tips of the
lower pressure stages. blades.

3. 9 Comparison between Pressure & Velocity Change in R&I

3.8.1.3 Impulse-Reaction Turbine:

Modern turbines are neither purely impulse or reaction but a combination of
both.
Pressure drop is effected partly in nozzles and partly in moving blades which
are so designed that expansion of steam takes place in them.
High velocity jet from nozzles produce an impulse on the moving blade and
jet coming out from still higher velocity from moving blades produces a
reaction.

Page (71)
 Impulse turbine began employing reaction of up to 20% at the root of the
moving blades in order to counteract the poor efficiency incurred from zero
or even negative reaction.
Reaction at the root of reaction turbines has come down to as little as 30% to
40% resulting in the reduction of the number of stages required and the
sustaining of 50% reaction at mid-point.

3. 10 Compound Turbine

Page (72)
Pressure turbine size:
It depends on specific volume of the steam .So at high pressure turbine specific
volume of the steam is small unlike at low pressure turbine where specific volume
is large .

3. 11 Specific Volume Change

Page (73)
 3. 12 Turbine Shape Relative To Specific Volume

So, turbine at high pressure stage is smaller than turbine at low pressure stage.

3.8.2 STEAM SUPPLY AND EXHAUST CONDITIONS:

3.8.2.1 Condensing:
Condensing turbines are most commonly found in electrical power plants.
These turbines exhaust steam in a partially condensed state, typically of a quality
near 90%, at a pressure well below atmospheric to a condenser.
3.8.2.2 Back Pressure (Non-Condensing):
Non-condensing or backpressure turbines are most widely used for process
steam applications. The exhaust pressure is controlled by a regulating valve to suit
the needs of the process steam pressure. These are commonly found at refineries,

Page (74)
district heating units, pulp and paper plants, and desalination facilities where large
amounts of low pressure process steam are available.
3.8.2.3 Mixed Pressure:
A steam turbine operated from two or more sources of steam at different
pressures.
3.8.2.4 Reheat:
Reheat turbines are also used almost exclusively in electrical power plants. In
a reheat turbine, steam flow exits from a high-pressure section of the turbine and is
returned to the boiler where additional superheat is added. The steam then goes back
into an intermediate pressure section of the turbine and continues its expansion.
3.8.2.5 Extraction Type (Auto Or Controlled):
Extracting type turbines are common in all applications. In an extracting type
turbine, steam is released from various stages of the turbine, and used for industrial
process needs or sent to boiler feedwater heaters to improve overall cycle efficiency.
Extraction flows may be controlled with a valve, or left uncontrolled.

3.8.2 CASING OR SHAFT ARRANGEMENTS:

3.8.2.1 Single Casing:

Single casing units are the most basic style where a single casing and shaft are
coupled to a generator.
3.8.2.2 Tandem Compound:
Tandem compound is used where two or more casings are directly coupled
together to drive a single generator
3.8.2.3 Cross Compound:
A cross compound turbine arrangement features two or more shafts not in line
driving two or more generators that often operate at different speeds. A cross
compound turbine is typically used for many large applications.

Page (75)
3.8.3 NUMBER OF EXHAUST STAGES IN PARALLEL

Two flows, Four flow or Six flow.

3. 13 Two Parallel Flow

Page (76)
 3. 14 Four Parallel Flow

3.8.4 DIRECTION OF STEAM FLOW.

Axial flow, Radial flow or Tangential flow.

Steam turbines are axial flow machines (radial steam turbines are rarely used).
3.8.5 STEAM SUPPLY.

Superheated or saturated.

Page (77)
3.9 COMPONENTS:

3. 15 Turbine Components

3.9.1 STEAM TURBINE START UP:

When warming up a steam turbine for use, the main steam stop valves (after
the boiler) have a bypass line to allow superheated steam to slowly bypass the valve
and proceed to heat up the lines in the system along with the steam turbine.

3. 16 Start Up Using Slow Motor

Page (78)
 Also a turning gear is engaged when there is no steam to the turbine to slowly
rotate the turbine to ensure even heating to prevent uneven expansion. After first
rotating the turbine by the turning gear, allowing time for the rotor to assume a
straight plane (no bowing), then the turning gear is disengaged and steam is admitted
to the turbine, first to the astern blades then to the ahead blades slowly rotating the
turbine at 10 to 15 RPM to slowly warm the turbine.
3.9.2 PRECAUTIONS DURING RUNNING:

Problems with turbines are now rare and maintenance requirements are
relatively small. Any imbalance of the rotor can lead to vibration, which in extreme
cases can lead to a blade letting go and punching straight through the casing.

3. 17 Precautions

It is, however, essential that the turbine be turned with dry steam. If water gets
into the steam and is blasted onto the blades (moisture carryover) rapid impingement
and erosion of the blades can occur, possibly leading to imbalance and catastrophic
failure.
Also, water entering the blades will likely result in the destruction of the thrust
bearing for the turbine shaft. To prevent this, along with controls and baffles in the
boilers to ensure high quality steam, condensate drains are installed in the steam
piping leading to the turbine.

Page (79)
3.9.3 FOUNDATIONS:

Turbine foundations are built up from a structural foundation in the hull to

provide a rigid supporting base. All turbines are subjected to varying degrees of
temperature-from that existing during a secured condition to that existing during
full-power operation. Therefore, means are provided to allow for expansion and
contraction.
At the forward end of the turbine, there are various ways to give freedom of
movement. Elongated bolt holes or grooved sliding seats are used so that the forward
end of the turbine can move fore and aft as either expansion or contraction takes
place.

3. 18 Elastic Foundation For Expansion

The forward end of the turbine may also be mounted with a flexible I-beam
that will flex either for or aft.
3.9.4 CASINGS:

The materials used to construct turbines will vary somewhat depending on the
steam and power conditions for which the turbine is designed. Turbine casings are
made of cast carbon steel for non-superheated steam applications. Superheated
applications use casings made of carbon molybdenum steel. For turbine casings used
on submarines, a percentage of chrome stainless steel is used, which is more resistant
to steam erosion than carbon steel.

Page (80)
 3. 19 Casing

Each casing has a steam chest to receive the incoming high-pressure steam.
This steam chest delivers the steam to the first set of nozzles or blades.
3.9.5 NOZZELS:

3. 20 Nozzle Types

The primary function of the nozzles is to convert the thermal energy of steam
into kinetic energy. The secondary function of the nozzles is to direct the steam
against the blades.
3.9.6 ROTORS:

Rotors (forged wheels and shaft) are manufactured from steel alloys.

Page (81)
 3. 21 Rotor

The primary purpose of a turbine rotor is to carry the moving blades that convert
the steam's kinetic energy to rotating mechanical energy.
3.9.7 BEARINGS:

The rotor of every turbine must be positioned radially and axially by bearings.
Radial (Journal) bearings carry and support the weight of the rotor and maintain the
correct radial clearance between the rotor and casing.

3. 22 Bearings

Axial (thrust) bearings limit the fore-and-aft travel of the rotor. Thrust bearings
take care of any axial thrust, which may develop on a turbine rotor and hold the
turbine rotor within definite axial positions.

Page (82)
 All main turbines and most auxiliary units have a bearing at each end of the
rotor. Bearings are generally classified as sliding surface (sleeve and thrust) or as
rolling contact (antifriction ball or roller bearings).
3.9.8 SHAFT PACKING GLANDS:

3. 23 Gland Seals

Shaft packing glands prevent the leaking of steam out of or air into the turbine
casing where the turbine rotor shaft extends through the turbine casing.

Page (83)
3. 24 Losses Due To Clearances

3. 25 Glands Work

Page (84)
 Labyrinth and carbon rings are two types of packing. They are used either
separately or in combination. Labyrinth packing consists of rows of metallic strips
or fins. The strips fasten to the gland liner so there is a small space between the strips
and the shaft. As the steam from the turbine casing leaks through the small space
between the packing strips and the shaft, steam pressure gradually reduces.

3. 26 Gland Seals

Carbon packing rings restrict the passage of steam along the shaft in much the
same manner as labyrinth packing strips. Carbon packing rings mount around the
shaft and are held in place by springs. Three or four carbon rings are usually used in
each gland. Each ring fits into a separate compartment of the gland housing and
consists of two, three, or four segments that are butt-jointed to each other. A garter
spring is used to hold these segments together. The use of keepers (lugs or stop pins)
prevents the rotation of the carbon rings when the shaft rotates. The outer carbon
ring compartment connects to a drain line.

3.10 BLADE FASTENING:

The majority of today' s steam and gas turbines contain rotor blades, which are
held in place by some type of root lands or serrations. Only in isolated cases and for
some series of small units do we find blading which is an integral part of the rotor
through either welding, hard soldering, electrochemical machining (ECM) or by
casting. Blades, which are integral with the rotor, have considerable strength
advantages in comparison with blades held by root serrations, Figure below a, b, c,
and d. A major disadvantage, however, is the difficulty and unreliability of replacing
one or several blades, if damaged. Usually the whole blade row requires

Page (85)
replacement. For electrochemically machined blades a replacement might be
achieved with later introduced axial entry roots.

3. 27 Blade Fastening

Some of the basic shape s of blade fastenings are shown in Figure below. The
three columns A, B, and C represent circumferential type roots, the internal groove
A, the straddled root B and the slotted and pinned root C. Column D shows axial
entry roots and some of the integral designs.
3.10.1 Blade Root Geometry and Load Transfer:

The most common types of blade fastenings in steam turbines were shown in
Figure below under columns A and B. Blades, fastened in this manner, have t o
conform in their root design with the cylindrical geometry of the rotor.

Page (86)
3. 28 Blade Root Geometry

Page (87)
Chapter 4

Pump

Page (88)
 Chapter 4
PUMP
A pump is a device that moves fluids (liquids or gases), by mechanical action.

4.1 PARTS OF PUMP:

When a pump breaks down, sometimes buying replacement parts or
components is an alternative to buying a new pump. Most centrifugal pumps consist
of a few basic components:
Housing/casing:

The outer shell of the pump which protects most of the components from
the outside elements. The casing of the pump should be of materials suitable
to withstand the environmental conditions of the application (e.g. submersible
pumps should be water and rust corrosion resistant

Impeller:
A rotating disk with a set of vanes coupled to a shaft. When the impeller
rotates, it imparts energy to the fluid to induce flow. Flow characteristics of
the pump vary widely based on the impeller design.

Motor:

The power source of the pump which drives the shaft. AC motors and
DC motors are the most common power sources for pumps, but internal
combustion engines (ICEs), hydraulic power, and steam power are other
possibilities.

Shaft:

The shaft connects the impeller to the motor/engine that provides power
for the pump.

Volute:

Page (89)
 The inner casing that contains the impeller and collects, discharges, and
(sometimes) recirculates the fluid being pumped. The materials used to
construct the lining of the pump volute must be compatible with the handled
media.

Bearing assembly:

The mechanical support that allows continuous rotation of the impeller

and is continuously lubricated.

Hub:

Device attached to the bearing assembly which is the connecting point

for the motor or engine.

Seal:

Protects the bearing assembly from being contaminated by the pumped

media. Some pump designs are sealless, meaning the pumping mechanism is
completely contained within a pressurized volute chamber with static seals
(e.g. gaskets or O-rings).

4.2 PARTS OF PUMP SYSTEM:

Outside of the pump itself are a number of additional components which are
part of a complete pumping system.

Controllers:

Used in conjunction with probes and sensors to provide operational

information as well as automatic or manual control of different pumping
functions.

Fittings and adapters:

Parts which connect different system components (pumps, motors,

pipe, hose, etc.) to one-another.

Mounting devices:

Page (90)
 Used to allow pumps to be mounted in different ways, such as on walls,
on the ground, or on/near associated stationary equipment.

Pump motor adapters:

Mounting devices used to connect dissimilar motor and pump bolt

configurations.

Probes and sensors:

Used to measure liquid level, pressure, temperature, and other important

system factors during system operation. Data from probes and sensors are sent
to controllers or computers for system analysis or response.

Valves:

Used to control flow within different parts of the system, including the
pump inlet and outlet.

4.3 TYPES OF PUMPS:

4.3.1 Centrifugal:
Centrifugal pumps can be classified further as

End suction pumps

In-line pumps
Double suction pumps
Vertical multistage pumps
Horizontal multistage pumps
Submersible pumps
Self-priming pumps
Axial-flow pumps

4.3.2 Positive Displacement:

The positive displacement pump can be classified as:
Reciprocating pumps - piston, plunger and diaphragm

Page (91)
 Power pumps

Steam pumps

Rotary pumps - gear, lobe, screw, vane, regenerative (peripheral) and

progressive cavity

4.4 PUMP OPERATION:

In terms of operation, all pumps are ultimately classified as either positive
displacement or dynamic (kinetic). However, since most dynamic pumps in industry
are centrifugal pumps, the distinction is often between positive displacement and
centrifugal.
Dynamic (Kinetic):

Dynamic pumps, also called kinetic pumps, include all pumps which use
fluid velocity to build momentum and produce pressure to move the fluid
through the system. These pumps are classified as either centrifugal or
specialized based on the method used to induce this velocity.

Centrifugal:

Centrifugal pumps, which are the most common, use an impeller

attached to a shaft which rotates to provide the energy to generate fluid
velocity. The impeller is mounted in a casing which provides a pressure
boundary and channels the fluid through a volute (funnel). The image below
shows a simplified centrifugal pump layout:

Page (92)
 4. 1 Centrifugal Pump

Centrifugal pumps can be further differentiated based on how they direct flow:
Axial flow pumps lift liquid in a direction parallel to the pump
shaft. They operate essentially the same as a boat propeller.
Radial flow pumps accelerate liquid through the center of the
impeller and out along the impeller blades at right angles
(radially) to the pump shaft.
Mixed flow pumps incorporate characteristics from both axial
and radial flow pumps. They push liquid out away from the pump
shaft at an angle greater than 90.

Page (93)
 4. 2 Flow Direction

Pumps in Parallel or Serial:

Pumps can be arranged and connected in serial or parallel to provide

additional head or flow rate capacity.

Pumps in Serial - Head Added:

When two (or more) pumps are arranged in serial their resulting pump
performance curve is obtained by adding their heads at the same flow rate as
indicated in the figure below.

4. 3 Pumps In Series

Centrifugal pumps in series are used to overcome larger system head

loss than one pump can handle alone.

Page (94)
 For two identical pumps in series the head will be twice the head of a
single pump at the same flow rate - as indicated with point 2.

With a constant flow rate the combined head moves from 1 to 2

- BUT in practice the combined head and flow rate moves along the system
curve to point 3.

point 3 is where the system operates with both pumps running

point 1 is where the system operates with one pump running

Note that for two pumps with equal performance curves running in series

the head for each pump equals half the head at point 3

the flow for each pump equals the flow at point 3

Operation of single stage pumps in series are seldom encountered - more

often multistage centrifugal pumps are used.

Pumps in Parallel - Flow Rate Added:

When two or more pumps are arranged in parallel their
resulting performance curve is obtained by adding the pumps flow rates at the
same head as indicated in the figure below.

4. 4 Pumps In Parallel

Centrifugal pumps in parallel are used to overcome larger volume flows

than one pump can handle alone.

Page (95)
 for two identical pumps in parallel and the head kept constant -
the flow rate doubles compared to a single pump as indicated
with point 2

Note! In practice the combined head and volume flow moves along
the system curve as indicated from 1 to 3.

point 3 is where the system operates with both pumps running

point 1 is where the system operates with one pump running

In practice, if one of the pumps in parallel or series stops, the operation

point moves along the system resistance curve from point 3 to point 1 - the
head and flow rate are decreased.

Note that for two pumps with equal performance curves running in
parallel

the head for each pump equals the head at point 3

the flow for each pump equals half the flow at point 3

4.5 PUMP SYSTEM:

4.5.1 PRIMARY PUMP SYSTEMS:
include:

Boiler feed pumps (primary and startup)

Condensate pump

Cooling water circulation pump

Cooling water make-up pump

Heater drain pumps

4.5.2 SECONDARY PUMPS SYSTEMS:

include:

Chemical feed pumps

Chemical transfer pumps

Page (96)
 Fuel transfer pumps

Fuel injection pumps

Slurry pumps and de-watering pumps

Lubrication pumps

Service water pumps, fire service pumps

4.6 PUMP PARAMETERS:

Pump operation and performance can best be described by a few fundamental
parameters; flow rate, pressure, head, power, and efficiency.
Flow Rate:

Volume flow rate (Q), also referred to as capacity, is the volume of liquid
that travels through the pump in a given time (measured in gallons per minute
or gpm). It defines the rate at which a pump can push fluid through the
system. In some cases, the mass flow rate ( ) is also used, which describes
the mass through the pump over time. The volume flow rate is related to mass
flow rate by the fluid density () via the equation:

When selecting pumps, the flow rate or rated capacity of the pump must
be matched to the flow rate required by the application or system.

Pressure:

Pressure is a measure of resistance: the force per unit area of resistance in

the system. A pressure rating in a pump defines how much resistance it can
handle or overcome. It is usually given in bar or psi (pounds per square inch).

Pressure, in conjunction with flow rate and power, is used to

describe pump performance. Centrifugal pumps, however, typically use head
(described below) instead of pressure to define the energy or resistance of the
pump, since pressure in a centrifugal pump varies with the pumped fluid's
specific gravity.

Page (97)
 When selecting pumps, the rated operating or discharge pressure of the
pump must be equal to or more than the required pressure for the system at
the desired flow rate.

Head:

Head is the height above the suction inlet that a pump can lift a fluid. It
is a shortcut measurement of system resistance (pressure) which is
independent of the fluid's specific gravity. It is defined as the mechanical
energy of the flow per unit weight. It is expressed as a column height of water
given in feet (ft) or meters (m). In other words, if water was pumped straight
up, the pump head is equivalent to the height it reaches.

Pump head (H) can be converted to pressure (P) using the specific
gravity (SG) of the fluid by the equation:

P = 0.434 H (SG)

or by the density of the fluid () and the acceleration due to gravity (g):

P=Hg

When selecting centrifugal pumps, the rated pump head must be equal
to or greater than the total head of the system (total dynamic head or TDH)
at the desired flow rate.

Power:

Net head is proportional to the power actually delivered to the

fluid, called output power (Pout) or the water horsepower (measured in
horsepower or hp). This is the horsepower rating which describes the useful
work the pump will do to the fluid. It can be calculated by the equation:

Pout = gH = .g.Q.H

where:

is fluid density

g is the acceleration due to gravity

Page (98)
 Q is the volumetric flow rate

H is the pump head

is the mass flow rate

In all pumps there are losses due to friction, internal leakage, flow
separation, etc. Because of these losses, the external power supplied to the
pump, called the input power (Pin) or brake horsepower, is always larger than
the water horsepower. This specification is typically provided by the pump
manufacturer as a rating or in the pump's performance curve and is used to
select the proper motor or power source for the pump.

Efficiency:

The ratio between the water horsepower and brake horsepower (useful
power vs. required power) describes the pump efficiency (pump):

pump = Pout/Pin

Keep in mind that any efficiency rating of the pump given by the
manufacturer assumes certain system conditions such as the type of fluid
transported: water is a typical standard. The efficiency may not be accurate if
these assumptions differ from the consumer's intended application.

Page (99)
Chapter 5

Condenser

Page (100)
 CHAPTER 5
CONDENSER
5.1 HEAT EXCHANGER:
It is a device that transfer heat between solid object and a fluid or between two
fluids. The fluids may be separated by solid wall to prevent mixing between them or
they may be in direct contact.
5.1.1 TYPES OF HEAT EXCHANGERS:
Heat exchangers are classified according to flow arrangement and type of
construction.
5.1.1.1 Concentric Heat Exchanger:
It is the simplest heat exchanger where hot and cold fluids move in same
or opposite direction in a concentric tube (or double pipe) construction.
In the parallel flow arrangement the hot and cold fluids enter the same
end, flow in the same direction and leave at same end .
In the counter flow arrangement fluids enter at opposite ends , flow in
opposite direction and leave at opposite ends .

5. 1 Concentric Heat Exchanger

Page (101)
5.1.1.2Cross Flow Heat Exchanger:
In this type fluids move in cross flow (perpendicular to each other) by
finned and unfinned heat exchangers. the two configurations differ according
to whether the fluid moving over the tube is mixed or unmixed.

5. 2 Cross Flow Heat Exchanger

5.1.1.3 Shell and Tube Heat Exchanger:

In shell and tube heat exchanger specific forms differ according to
number of shell and tube passes. baffles are usually installed to increase the
convection coefficient of the shell side fluid by inducing turbulence and cross-
flow velocity component.

Page (102)
 5. 3 Shell and Tube Heat Exchanger

5.1.2 FLOW IN HEAT EXCHANGERS:

5.1.2.1 Parallel Flow:

The hot and cold fluids flow in the same direction .

5. 4 Parallel Flow

5.1.2.2 Counter Flow:

The hot and cold fluids move in opposite directions .

Page (103)
 5. 5 Counter Flow

5.1.3 CALCULATIONS OF HEAT TRANSFER:

q = U A Tlm

where:
Tlm: is a log mean temperature difference
U: overall heat transfer coefficient

A : is the surface area

T2 T1
Tlm = T2
ln( )
1

For parallel flow exchangers:

T1 = Th,i Tc,i
T2 = Th,o Tc,o
For counter flow exchangers:

T1 = Th,i Tc,o
T2 = Th,o Tc,i

Page (104)

1 1 1 1 ln 1
= = = + +
2

5.2 CONDENSER:
Condensers are heat exchangers that convert steam into water.
5.2.1 OBJECTIVES OF STEAM CONDENSERS:

The first objective is to create low back pressure at the turbine exhaust to
obtain maximum energy conversion from the high pressure and high
temperature steam and this increases the efficiency of the power plant.
The second objective is to condense the exhaust steam coming from the
turbine and therefore recover the high-quality feed water for the reuse in the
cycle of operation.
When a condenser is introduced in a plant with steam turbine the work
obtained per kg of steam is increased in comparison to the non-condensing
turbine.
Heat transfer rate of condenser depends on the flow of cooling water and the
temperature difference between the steam and cooling water.

5.2.2 LOW PRESSURE (VACCUM):

The maximum possible thermal efficiency of the power system is given by

(T1-T2)/T1
Where:

T1 is the supply temperature

T2 is the exhaust temperature
The expression of the efficiency shows that the efficiency of the system
increases with increase in supply temperature (T1) and decrease in exhaust
temperature (T2). The maximum value of the supply temperature T1 of the steam
supplied to the prime-mover is limited by the material consideration. The
temperature T2 (temperature at which heat is rejected) can be reduced if the exhaust

Page (105)
of the steam prime-mover takes place below atmospheric pressure. This is because
there is a definite relation between the steam temperature and pressure. Low exhaust
pressure means low exhaust temperature.

5.2.3 CAPACITY OF CONDENSER:

Q = m0Cpw T
Where:
M = mass flow rate of condensed water
C = specific constant of water
T = temperature difference between outlet and inlet of condenser
Qout
Thermal efficiency of plant = 1

Where
Q in = boiler's capacity

5.2.4 ADVANTAGES OF USING CONDENSERS IN STEAM PLANTS:

It increases the work done per kg of steam due to increase in expansion ratio
of steam. Increase in expansion ratio means total enthalpy drop in a steam
turbine from inlet of turbine to the exit (last stage of turbine) of the turbine
which indicates the conversion of heat energy of steam into the useful work.

It increases the thermal efficiency of the plant, means with less fuel
consumption it gives more power output. Hence size of power plant reduces
for the given output.

Once the exhaust steam is condensed in a condenser, it provides a good source

of pure and high-quality feed water to the boiler and thus it reduces the water
treatment plant capacity to considerable extant.

Page (106)
 The condensed steam temperature is always higher than the fresh water which
is added as a make-up water in a boiler, so the amount of the total heat supplied
per kg of steam generation in a boiler is reduced to a great extent.

It minimizes the rate of corrosion in boiler tubes with the reuse of pure water.

The deposition of the salt in the boiler is prevented with the use of condensate
instead of using feed water from outer source which may contain salt. The
deposition of the salt in boiler shell also reduces the boiler efficiency. Thus is
particularly important in marine steam power plant

2.5.5 TYPES OF STEAM CONDENSERS:

The steam condenser is one of the essential components of all modern steam
power plants.
5.2.5.1 Surface Condenser:

5. 6 Surface Condenser

Surface condenser is a commonly used term for a water-cooled shell and tube
heat exchangers used in steam power plants.
These condensers convert the exhaust steam from the turbine into liquid water
at pressure below atmospheric pressure.
Page (107)
 Surface condensers are also used in applications and industries other than the
condensing of steam turbine exhaust in power plants.
In surface condensers, there is no direct contact between the steam and cooling
water and the condensate can be re-used in the boiler: In such condenser, even
impure water can be used for cooling purpose whereas the cooling water must be
pure in jet condensers.
Although the capital cost and the space needed is more in surface condensers
but it is justified by the saving in running cost and increase in efficiency of plant
achieved by using this condenser.
Depending upon the position of condensate extraction pump, flow of
condensate and arrangement of tubes the surface condensers may be classified as
follows:

Down Flow Type:

The figure in the left shows a sectional view of down flow condenser,
the other figure shows a longitudinal section of a two pass down-flow
condenser.

5. 7 Down Flow Condenser

Central Flow Condenser:

The figure above shows a central flow condenser. In this condenser, the
steam passages are all around the periphery of the shell. Air is pumped away
from the center of the condenser. The condensate moves radially towards the
center of tube nest. Some of the exhaust steams while moving towards the
center meets the undercooled condensate and pre-heats it thus reducing
undercooling.

Page (108)
 5. 8 Central Flow Condenser

Evaporation Condenser:
In this condenser steam to be condensed is passed through a series of
tubes and the cooling waterfalls over these tubes in the form of spray. A steam
of air flows over the tubes to increase evaporation of cooling water, which
further increases the condensation of steam.

5. 9 Evaporation Condenser

Requirements of Surface Condenser:

The steam entering the condenser should be evenly distributed over the
whole cooling surface of the condenser vessel with minimum pressure
loss.
The amount of cooling water being circulated in the condenser should
be so regulated that the temperature of cooling water leaving the

Page (109)
 condenser is equivalent to saturation temperature of steam
corresponding to steam pressure in the condenser. This will help in
preventing under cooling of condensate.
The deposition of dirt on the outer surface of tubes should be prevented.
Passing the cooling water through the tubes and allowing the steam to
flow over the tubes achieve this.
There should be no air leakage into the condenser because presence of
air destroys the vacuum in the condenser and thus reduces the work
obtained per kg of steam. If there is leakage of air into the condenser
air extraction pump should be used to remove air as rapidly as possible

5.2.5.2 Jet Condenser:

In jet condensers, the exhaust steam and cooling water come in direct contact
with each other.
The temperature of cooling water and the condensate is same when leaving the
condensers.
Elements of the jet condenser are as follows:

Nozzles or distributors for the condensing water.

Steam inlet.
Mixing chambers: They may be (a) parallel flow type (b) counter flow
type depending on whether the steam and water move in the same
direction before condensation or whether the flows are opposite.
Hot well.

Types of jet condensers:

Low level jet condensers (Parallel flow type):

In this condenser water is sprayed through jets and it mixes with
steam. The air is removed at the top by an air pump. In counter flow
type of condenser, the cooling water flows in the downward direction
and the steam to be condensed moves upward.

Page (110)
 5. 10 Jet Condenser

High level or Barometric condenser:

The figure below shows a high-level jet condenser. The condenser
shell is placed at a height of 10.33 m (barometric height) above the hot
well. As compared to low level jet condenser. This condenser does not
flood the engine if the water extraction pump fails. Separate air pump
is used to remove the air .

5. 11 Barometric Condenser

Ejector Condenser:
The figure below shows an ejector condenser. In this condenser,
cold water is discharged under a head of about 5 to 6 m through a series
Page (111)
 of convergent nozzles. The steam and air enter the condenser through a
non-return valve. Mixing with water condenses steam. Pressure energy
is partly convert into kinetic energy at the converging cones. In the
diverging come the kinetic energy is partly converted into pressure
energy and a pressure higher than atmospheric pressure is achieved so
as to discharge the condensate to the hot well.

5. 12 Ejector Condenser

5.2.3 CONDENSER CLEANING:

The quality of the cooling water intake and the amount of debris in that water
affects the operation and performance of the condenser and therefore the thermal
performance of the typical steam plant.
Material such as slime, calcium carbonate, calcium sulfate, magnesium dioxide,
silt, petroleum products, corrosion products, and the like adhere to the inside of the
heat exchanger and condenser tubes cause reduction of the overall heat transfer
coefficient and this leads to an adverse effect on the operation of process equipment,
plant availability, production, and maintenance cost.
Traditionally, plant maintenance teams isolate and open each heat exchanger or
condenser unit periodically in order to clean the tubes manually using high-pressure
water jets or mechanical scrapers. This process is labor-intensive, costly, and may
require process shutdown, condensers also could be cleaned chemically.

Page (112)
 There is an alternative. Two excellent online cleaning systems can keep the
condensers clean and the unit heat rate down: a debris filter and an automatic tube-
cleaning system. Both automate the process of continuously keeping heat
exchangers surfaces clean.
Debris filters are typically installed downstream from the circulating water
pump before the inlet of the heat exchanger or condenser. The debris filter consists
of a rotating screen installed inside of a spool piece in the cooling water piping. As
debris collects on the screen and differential pressure across the screen rises, it
begins to rotate removing debris through backwashing. The collected debris is then
bypassed downstream from the heat exchangers or condensers and discharged into
the outflow

5. 13 Condenser Cleaning

Condenser Tube Cleaning System Benefits:

Page (113)
 Increased Power Generation: Increase power output. Power is
generated at maximum efficiency at all times. Extend plant availability,
as there is no need to shut down the condenser for tube cleaning.
Improved Reliability: Less moving parts = higher reliability.
Reduced Maintenance Expense: Drastically reduce or eliminate costly
and time-consuming offline condenser cleaning costs.
Sustainability: Reduce energy consumption and greenhouse gas
emissions. Eliminate chemical cleaning of condensers so there are no
hazardous chemical handling or disposal.

Page (114)
References
Steam power plant engineering 1917 by George F. Gebhardt.
Steam power plant operation 8th edition by Everett B. Woodruff.
fundamentals-of-engineering thermodynamics Moran & shapiro 5th edition
2006 wiley1.
Fundamentals of engineering thermodynamics 8th edition by Moran &
shapiro.
Boilers for power and process by Kumar Rayaprolu.

Page (115)