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Konthawardana K.A.M.K

110304V

Department of Mechanical Engineering

Faculty of Engineering

University of Moratuwa

PREFACE

I have a great satisfaction in introducing this report which includes the information of

experience I gathered during my industrial training session from 20th

October 2014 to 13th

March 2015 at Kelanitissa Power Station, Kelanitissa Combined Cycle Power Station and

Sapugaskanda Power Station under the Ceylon Electricity Board. Industrial Training has

provided Undergraduates of B.Sc. Engineering (Honours) Degree and it is a valuable

opportunity to gain practical training and experience in industry. This training helped to

improve the additional knowledge as well as to upgrade our skills and modify our attitudes

and also it supported to relate the theoretical concepts learnt at the University to the industrial

applications in practice. This report contained with my experiences and knowledge I gathered

during my training period of 21 weeks.

The training report contains the training experiences of me with special attention focused on

the areas of exposure during my industrial training at Ceylon Electricity Board. There are

three main chapters in my report such as “Introduction to the Training Establishment”,

“Training Experiences” and the final chapter is Conclusion. Finally the report is included

separately all annexes such as assignments and projects were carried out during our industrial

training.

Brief introductions of the training establishment and the three thermal power stations are

included in first chapter which focused to the company structure, functions and hierarchical

levels. It also consists of the importance and usefulness of the establishment to the country

and SWOT analysis of CEB as well as the thermal power plants which was mentioned above.

The second chapter describes the training experiences, projects worked out, observations,

equipment and machinery encountered during the training and works carried out at three

thermal power stations. This chapter includes the details of work place along with names and

designations of key training personnel involved with. In addition, it expresses the details of

problems encountered and how solved during the training. The final chapter includes the

conclusion which summarizes the all training experiences gathered during my training.

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ACKNOWLEDGEMENT

One of my life’s top most achievements is having this wonderful opportunity to be trained at

Kelanitissa Power Station (KPS), Kelanitissa Combined Cycle Power Station (KCCPS) and

Sapugaskanda Power Station (SPS) under Ceylon Electricity Board. The industrial training

helped us to involve in a professional environment as well as to gain the knowledge of

electricity power generation, transmission and electricity distribution. It is my responsibility

to present sincere gratitude to each and every person involved in making a true success of my

training period. Further this won’t be succeed and useful without the clear guidance and

advise of following personals and I would like to deliver my sincere thanks to them for the

enthusiasm given for make this a immense success.

I would like to express my deepest appreciation to Eng. N.A.Wijeyewickrama (Director,

Training Division, Faculty of Engineering, University of Moratuwa), Eng. Roy

Sankaranarayana (Senior Lecturer, Industrial Training Division) and other officials in the

Training Division of University of Moratuwa for arranging and assigning training places and

giving some instructions to complete the training successfully for undergraduate trainees. I

would like to declare my sincere gratitude and thanks to Dr.W.K.Wimalsiri

Head of the Department of Mechanical Engineering, University of Moratuwa and

Dr.R.A.C.P.Ranashinghe the Training Coordinator, the Department of Mechanical

Engineering, University of Moratuwa for their contribution to successfully complete my

industrial training.

Then, I would like to thank the officials of the National Apprentice & Industrial Training

Authority (NAITA), for giving all the necessary arrangements to successfully complete our

in-plant training in CEB.

Finally it is my responsible to deliver special thanks and appreciation to Mr. A.P.Sampath

(Mechanical Engineer- Fr 5 gas turbines, Kelanitissa Power Station) and Mr. U.K.L.

Chulakeerthi (Mechanical Engineer- GT 7 Gas Turbine) in Kelanitissa Power Station for

sharing their knowledge and giving some assignments during our training period. I would

especially like to thank Mr. A.P.K. Mutunayake (Mechanical Engineer- Frame 9E Gas

Turbine), Mr. Sudheera Wanisundara (Mechanical Engineer- Steam Turbine) in Kelanitissa

Combined Cycle Power Station for giving the knowledge of the process of the combined

cycle power plant and the individual projects during the training period in KCCPS. I wish to

extend my sincere thanks to Mr. Mani Albert (Mechanical Engineer-Mechanical overhaul,

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station B), Mr. Thilina Hettiarachchi (Mechanical Engineer-Mechanical maintenance, station

B), Mr. Chaminda Kodithuwakku (Mechanical Engineer- Overhaul, station A), Mr. Aruna

Salwathura (Mechanical Engineer-Mechanical maintenance, station A) and the Shift Charged

Engineers in Sapugaskanda Power Station for giving us valuable experience, lessons and

guiding during the training period and the support given to make my training period a true

success.

It is necessary to appreciate the kindness and the helpfulness shown by Training engineer

(Training Division) in Piliyandala and other officers in Ceylon Electricity Board for giving

the proper schedule to success of our in-plant training.

Finally, I would like to thank my colleagues W.H.P.Sampath, P.G.H.S.Rohanawansha and

H.M.C.K.M.B.Dehikumbura for being with me and sharing the experiences and knowledge

during the training.

Konthawardana K.A.M.K

Department of Mechanical Engineering

Faculty of Engineering

University of Moratuwa

Katubedda

Sri Lanka

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TABLE OF CONTENTS

PREFACE .................................................................................................................................. i

ACKNOWLEDGEMENT ....................................................................................................... ii

TABLE OF CONTENTS ....................................................................................................... iv

LIST OF FIGURES ............................................................................................................. viii

LIST OF TABLES ................................................................................................................... x

1 INTRODUCTION TO THE TRAINING ESTABLISHMENT ................................... 1

1. 1 Ceylon Electricity Board (CEB) .................................................................................. 1

1.1.1 Introduction about CEB ........................................................................................... 1

1.1.2 Vision ................................................................................................................... 2

1.1.3 Mission ................................................................................................................. 2

1.1.4 C.E.B. Organization Hierarchical Levels ............................................................ 3

1.1.5 Achievements and Awards .................................................................................. 4

1.1.6 SWOT Analysis of CEB ...................................................................................... 4

1.1.6.1 Present performance ..................................................................................... 4

1.1.6.2 Strengths ....................................................................................................... 5

1.1.6.3 Weaknesses ................................................................................................... 6

1.1.6.4 Opportunities for improvement .................................................................... 6

1.1.6.5 Threats of CEB ............................................................................................. 6

1.1.6.6 Profitability of CEB ...................................................................................... 7

1.1.6.7 Usefulness to the society .............................................................................. 7

1.1.6.8 Suggestions to improve the performance ..................................................... 7

1.2 Kelanitissa Power Station............................................................................................ 8

1.2.1 Introduction to Kelanitissa Power Station ........................................................... 8

1.2.2 Organizational structure and hierarchical levels ................................................ 10

1.2.3 The main purposes of the plant .......................................................................... 10

1.3 Kelanitissa Combined Cycle Power Station (KCCPS) ............................................. 10

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1.3.1 Introduction to Kelanitissa Combined Cycle Power Station ............................. 10

1.3.2 Organizational structure and hierarchical levels ................................................ 12

1.4 Sapugaskanda Power Station .................................................................................... 12

1.4.1 Introduction to Sapugaskanda Power Station .................................................... 12

1.4.2 Organizational structure and hierarchical levels ................................................ 13

2 TRAINING EXPERIANCES ........................................................................................ 15

2.1 Kelanitissa Power Station (KPS)............................................................................... 15

2.1.1 Observations and work carried out at Kelanitissa Power Station ...................... 15

2.1.2 Gas turbines ....................................................................................................... 16

2.1.3 The Brayton Cycle ............................................................................................. 17

2.1.4 Specifications of gas turbines in KPS ................................................................ 18

2.1.4.1 Fiat Avio TG50D5 (GT 7) Gas Turbine ..................................................... 18

2.1.4.2 Frame-V gas turbine ................................................................................... 19

2.1.5 Major parts in GT 7 gas turbine ......................................................................... 19

2.1.5.1 Intake air filters ........................................................................................... 19

2.1.5.2 Inlet silencers .............................................................................................. 21

2.1.5.3 Bell mouth and Inlet Guide Vane (IGV) .................................................... 21

2.1.5.4 Axial Compressor ....................................................................................... 22

2.1.5.5 Fuel injectors and Combustion chamber .................................................... 23

2.1.5.6 Transition Pieces......................................................................................... 25

2.1.5.7 Turbine........................................................................................................ 25

2.1.5.8 Exhaust diffuser and exhaust manifold ...................................................... 26

2.1.5.9 Stator motor ................................................................................................ 27

2.1.6 Consequences of Poor Inlet Filtration................................................................ 27

2.1.6.1 Foreign Object Damage (FOD) and Domestic Object Damage (DOD) ..... 27

2.1.6.2 Erosion ........................................................................................................ 27

2.1.6.3 Fouling ........................................................................................................ 29

2.1.6.4 Corrosion (hot and cold corrosion) ............................................................. 29

2.1.7 Vibration test run of GT7 gas turbine (Fr-IX) ................................................... 30

2.1.8 Compressor washing of GT7 gas turbine........................................................... 31

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2.1.9 Failure nature of the second stage nozzle of a Frame-V gas turbine ................. 32

2.1.10 Fuel Oil Treatment Plant (FOTP) ...................................................................... 33

2.1.10.1 Working principle of the centrifugal separator ........................................... 34

2.2 Kelanitissa Combined Cycle Power Station (KCCPS) ............................................. 35

2.2.1 Observation and work carried out at KCCPS .................................................... 35

2.2.2 Gas turbine in KCCPS ....................................................................................... 36

2.2.3 Steam turbine ..................................................................................................... 37

2.2.4 Rankine cycle ..................................................................................................... 38

2.2.5 Components of steam turbine ............................................................................ 38

2.2.5.1 Diverter damper .......................................................................................... 38

2.2.5.2 Heat Recovery Steam Generator (HRSG) .................................................. 38

2.2.5.3 Deaerator .................................................................................................... 39

2.2.5.4 Feed water tank ........................................................................................... 40

2.2.5.5 LP drum ...................................................................................................... 40

2.2.5.6 LP turbine ................................................................................................... 40

2.2.5.7 HP drum ...................................................................................................... 40

2.2.5.8 HP turbine ................................................................................................... 41

2.2.5.9 Stop valve ................................................................................................... 41

2.2.5.10 Governor ..................................................................................................... 41

2.2.5.11 Condenser ................................................................................................... 42

2.2.5.12 Cooling towers ............................................................................................ 42

2.2.6 Air inlet equipment of gas turbine ..................................................................... 42

2.2.6.1 Inlet system ................................................................................................. 42

2.2.6.2 Inlet air filter house ..................................................................................... 42

2.2.6.3 The silencer buffers .................................................................................... 43

2.2.6.4 Inlet plenum ................................................................................................ 43

2.2.7 Liquid fuel system (both naphtha and Diesel) of gas turbine ............................ 43

2.2.8 Water treatment plant ......................................................................................... 44

2.2.9 Chilled water central air conditioning system ................................................... 46

2.2.10 Making a Bill of Quantity (BOQ) for double wall naphtha tanks. .................... 47

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2.3 Sapugaskanda Power Station .................................................................................... 48

2.3.1 Observations and work carried out during the training at SPS .......................... 48

2.3.2 Station A ............................................................................................................ 48

2.3.2.1 Specification of the engine in station A ...................................................... 48

2.3.2.2 Designation of the cylinders ....................................................................... 49

2.3.2.3 Turbocharger .............................................................................................. 50

2.3.2.4 Cylinder head arrangement in station A Diesel engine .............................. 51

2.3.2.5 Piston heads and the cylinder liners in station A (Diesel engines) ............. 53

2.3.2.6 Connecting rod ........................................................................................... 54

2.3.2.7 Crank case pressure .................................................................................... 55

2.3.2.8 Schedule maintenance of PIELSTICK Diesel engines in station A ........... 55

2.3.3 Station B............................................................................................................. 55

2.3.3.1 Specifications of the Diesel engine in station B ......................................... 55

2.3.3.2 Designation of the cylinders ....................................................................... 56

2.3.3.3 Definition of Left Hand and Right Hand engine ........................................ 57

2.3.3.4 Crankshaft of MAN B&W Diesel engines in station B.............................. 57

2.3.3.5 Cylinder head arrangement ......................................................................... 57

2.3.3.6 Valve cages used in the MAN B&W Diesel engine ................................... 58

2.3.3.7 Schedule maintenance of the MAN B&W Diesel engine in station B ....... 58

2.3.4 Auxiliary systems............................................................................................... 58

2.3.4.1 Fuel oil system ............................................................................................ 58

2.3.4.2 Lubrication oil system ................................................................................ 59

3 CONCLUSION ............................................................................................................... 61

ABBRIVIATIONS .................................................................................................................. xi

ANNEXES ............................................................................................................................ xiii

Annex.1 The temperature and pressure variation on the HRSG .................................... xiii

Annex.2 Schematic diagram of the operation of the pulsing air skid ............................... xv

Annex.3 BOQ for double wall naphtha tank 1 & 2 ............................................................ xv

Annex.4 The piston rings kit for PIELSTICK engine PC4-2 ........................................... xxi

Annex.5 Check list for overhauls in station B Diesel engines .......................................... xxii

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LIST OF FIGURES

Figure 1.1 Logo of CEB............................................................................................................. 1

Figure 1.2 CEB Organizational Hierarchy................................................................................ 3

Figure 1.3 Organizational structure and hierarchy levels ........................................................ 10

Figure 1.4 Structural view of the KCCPS ................................................................................ 11

Figure 1.5 View (3D) of the cooling towers in KCCPS .......................................................... 12

Figure 1.6 Organizational structure and hierarchical levels in KCCPS................................... 12

Figure 1.7 A V-type Diesel engine in station A ....................................................................... 13

Figure 1.8 Organizational structure and hierarchical levels in SPS......................................... 14

Figure 2.1 Fuel Oil Treatment Plant (FOTP) in KPS .............................................................. 15

Figure 2.2 A Gas turbine .......................................................................................................... 16

Figure 2.3 A Schematic diagram of an open cycle gas turbines .............................................. 17

Figure 2.4 Closed cycle gas turbine engine ............................................................................. 18

Figure 2.5 Process diagrams of the Brayton cycle ................................................................... 18

Figure 2.6 Schematic diagram of GT7 gas turbine .................................................................. 18

Figure 2.7 Schematic diagram of the Fr-V gas turbine ............................................................ 19

Figure 2.8 Air intake of GT 7 gas turbine …………………………………………………...20

Figure 2.9 Pre filter (filter pad and filter cone) ........................................................................ 20

Figure 2.10 A fine filter in GT7 gas turbine ............................................................................ 21

Figure 2.11 Part of the bell mouth and the IGV of GT7 gas turbine ....................................... 22

Figure 2.12 IGV arrangement of GT7 gas turbine ................................................................... 22

Figure 2.13 Axial compressor of GT7 gas turbine .................................................................. 23

Figure 2.14 Compressor rotating and stator blades ................................................................. 23

Figure 2.15 Fuel injector of GT7 gas turbine .......................................................................... 24

Figure 2.16 Arrangement of the combustion chamber and transition pieces .......................... 24

Figure 2.17 Fuel injector nozzles cleaning .............................................................................. 25

Figure 2.18 Turbine stator and rotating blades ........................................................................ 26

Figure 2.19 Exhaust diffuser of GT7 gas turbine .................................................................... 26

Figure 2.20 The comparison of the particle size rang for erosion and fouling ........................ 28

Figure 2.21 Erosion on the leading edge of the turbine blade ................................................. 28

Figure 2.22 FOD on the compressor diaphragm ...................................................................... 29

Figure 2.23 Fouling on the compressor blade .......................................................................... 29

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Figure 2.24 Balancing weights arrangement of the turbine rotor ............................................ 31

Figure 2.25 Main rotor of the GT7 gas turbine ........................................................................ 31

Figure 2.26 Label of a detergent used for compressor washing .............................................. 32

Figure 2.27 Thermal cracks on the nozzle vanes ..................................................................... 33

Figure 2.28 Second stage nozzle segments .............................................................................. 33

Figure 2.29 Centrifugal separators in FOTP at KPS................................................................ 34

Figure 2.30 Main components of the gas turbine .................................................................... 36

Figure 2.31 Overall process of the combined cycle power station .......................................... 37

Figure 2.32 HP circuit ……………………………………………………………………….38

Figure 2.33 LP circuit .............................................................................................................. 38

Figure 2.34 Efficiency of the HRSG varies with the pressure levels ...................................... 39

Figure 2.35 Governor in HP steam turbine .............................................................................. 41

Figure 2.36 Overall path of the GT liquid fuel system ............................................................ 44

Figure 2.37 Clarifier in water treatment plant ......................................................................... 46

Figure 2.38 A chilled water central air conditioning system ................................................... 47

Figure 2.39 Turbocharger and intercooler in station A Diesel engine ..................................... 50

Figure 2.40 Exhaust valve cage (station A) ............................................................................. 51

Figure 2.41 Cracks on the valve seat ....................................................................................... 51

Figure 2.42 Cylinder head configuration in station A Diesel engines ..................................... 52

Figure 2.43 Cylinder head assembly ........................................................................................ 52

Figure 2.44 Inside of the rotor cap ........................................................................................... 53

Figure 2.45 Cylinder liner of the PIELSTICK Diesel engine in station A .............................. 54

Figure 2.46 Connecting rod of The PIELSTICK Diesel engine .............................................. 55

Figure 2.47 Crankshaft of the MAN B&W Diesel engine in station B ................................... 57

Figure 2.48 Cylinder head arrangement of the MAN B&W Diesel engine ............................. 58

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LIST OF TABLES

Table 1.1 Future Major Generation Projects in Sri Lanka ......................................................... 2

Table 1.2 Difference between the gas turbine and hydro turbine plants ................................... 5

Table 2.1 Specification of the Diesel engine in station A ........................................................ 49

Table 2.2 Specification of the Diesel engine in station B ........................................................ 56

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1 INTRODUCTION TO THE TRAINING ESTABLISHMENT

1. 1 Ceylon Electricity Board (CEB)

1.1.1 Introduction about CEB

Figure 1.1 Logo of CEB

Ceylon Electricity Board was established on the 1st of November 1969 under the control of

Ministry of Power and Energy by the Ceylon Electricity Board Act No. 17 in 1969. It can be

introduced as the government organization which handling the fields of electrical power

generation, transmission of it and distribute it to consumers and collect the revenue in Sri

Lanka. CEB always tries to satisfy the consumers with focusing on the availability, reliability

and quality of the power. It is the largest electricity company in Sri Lanka. The electricity is

generated using hydro power, thermal power (coal, Diesel, naphtha, Heavy Fuel Oil (HFO))

and wind power. Opened in 1969, the company now has a total installed capacity

of approximately 2,800 MW.

It is empowered to generate electrical energy, transmit the same and distribute it to reach all

categories of consumers and to collect the revenue. It is also empowered to acquire assets,

including human resources following the approved procedures. It is the duty of the CEB to

make the optimal use of the resources through the application of pragmatic and time-tested

managerial methods. Accordingly, the Ceylon Electricity Board (CEB) was entrusted with

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the uphill task of providing 24 hours uninterrupted electricity supply, throughout the island,

with a minimum burden to its consumers. So they introduced some electrification program to

provide electricity supply for the rural villages in Sri Lanka and some programmes were

introduced to provide loans for those who are in need of the financial assistance to obtain

electricity connections. The Ceylon Electricity Board has decided to complete several major

generation projects in future. The following table shows the details of the future major

generation projects in Sri Lanka.

Table 1.1 Future Major Generation Projects in Sri Lanka

Project Capacity

/MW

Expected

annual Avg.

Energy/GWh

Expected

Years of

Commissio

ning

location

Uma Oya Hydropower

project

120 231 2017 Reservoirs in Welimada and Puhulpola

in Uma Oya and underground power

station near Randeniya in Wellawaya.

Broadlands Hydropower

project

35 126 2017 Boundary of Central and Sabaragamuwa

Provinces, Kegalle and Nuwara Eliya

Districts.

Wind Park 100 300 2018 Southern Coast Mannar Island

Trincomalee Coal Power

Plant

3182 2019 Sampur, Trincomalee District

Moragolla Hydropower

Plant

27 98 2020 Near Ulapane in the Mahaweli River

Advanced Sub Critical

Coal Power Plant (Phase 1)

3784 2021 Sampur, Trincomalee district

1.1.2 Vision

Enrich Life through Power

1.1.3 Mission

To develop and maintain an efficient, coordinated and economical system of electricity

supply to the whole of Sri Lanka, while adhering to our core values:

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Quality

Service to the nation

Efficiency and effectiveness

Commitment

Safety

Professionalism

Sustainability

1.1.4 C.E.B. Organization Hierarchical Levels

Minister of Power and

Energy

Chairman & Board of Directors

Secretary of the Board

General Manager

AGM Generation

DGM

(TC)

CE (KPS)

CE (KCCPS)

CE (SPS)

CE (LVPS)

CE (UJPS)

DGM

(MC)

DGM

(LC)

DGM

(OH)

DGM

(M)

DGM

(GP)

DGM

(CA)

DGM

(ES)

DGM

(EM)

AFM

(Generation)

DGM

(ECM & DS)

AGM Transmiaaion

AGM Distribution

Region 1

AGM Distribution

Region 2

AGM Distribution

Region 3

AGM Distribution

Region 4

AGM Project and Centralized

Servises

Senior Project Director

(Puttalam Coal plant)

Finance Manager

Chief Internal Auditor

Figure 1.2 CEB Organizational Hierarchy

Figure 1.2 CEB Organizational Hierarchy

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1.1.5 Achievements and Awards

* ISO 14001:2004 Certification:-

Samanalawewa Power Station of CEB has emerged as the first Government Entity in Sri

Lanka to be awarded with the ISO 14001:2004 certification by Sri Lanka Standards

Institution for its Environmental Management System in 2007.

1.1.6 SWOT Analysis of CEB

1.1.6.1 Present performance

Ceylon Electricity Board (CEB) is established on the 1969, mainly to generate electrical

energy, transmit and distribute it to all categories of consumers and also to collect the

revenue. Three methods are used in power generation in Sri Lanka, which are hydro power

and thermal power generation and wind power. Electricity generation by CEB is primarily

done by hydro power. Hydro power is the oldest and most dependant source of electricity

generation in Sri Lanka. When we are considering the thermal power generation method, the

hydro power generation is the most suitable method to generate electricity because of the unit

cost for generating electricity and the environmental pollution have minimized comparing the

thermal power generation. But the generation capacity using hydro power is not sufficient for

daily consumption in Sri Lanka. Because of that the thermal power plants are used to

generate electricity power. Under hydro power there are Mahaweli hydro complex

comprising of Kothmale, Victoria, Ukuwela, Bowatenna, Randenigala, Rantambe, upper

Kothmale and Nilambe power stations, Laxapana Complex comprising of New Laxapana,

Old Laxapana, Wimalasurendra, Canyon and Polpitiya power stations and Samanala complex

comprising Samanala wewa, Udawalawe, Inginiyagala and Kukuleganga power station.

Thermal complex comprises with Kelanitissa, Sapugaskanda, Chunnakam, Uthuru Janani

power station and Lak Vijaya coal power stations. A wind power plant is installed at

Hambantota area.

The total installed capacity of all hydro power stations in Sri Lanka is around 1357 MW

while total installed thermal capacity is around 560 MW which is owned by CEB. Today the

installed capacity of LakVijaya coal power station is 900 MW and it is one of the largest

thermal power plants in Sri Lanka. 3 MW of power is given to the system by wind power.

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This wind plant is located at Hambantota. Still Sri Lanka very much depends on the Hydro

Power but still Hydro Power alone is not sufficient so government has taken steps to go for

Thermal and Renewable energy. Recently Renewable Energy Authority launched a Solar

Power pilot project in Hambantota and the Ceylon Electricity Board aimed to launch several

major generation projects in Sri Lanka (refer the Table 1.1). Private sector is also joined to

produce electricity in Sri Lanka. There are many thermal private power plants and CEB hires

the power from them. All the power stations of the system are interconnected and operations

of these stations are coordinated by the System Control Center, which is acting as the heart of

the power system. Power is transmitted via a National Grid System operated by the CEB.

The following Table shows the different between gas turbine plant and the hydro turbine

plant in Sri Lanka.

Table 1.2 Difference between the gas turbine and hydro turbine plants

Gas Turbine Hydro Turbine

Efficiency (%) 25-30% 96-98%

Weather condition Minimum effect Dependent

Unite cost Rs. 25-65 Rs. 2

Capital cost Very high Low

1.1.6.2 Strengths

A main strength of the CEB is; it’s a state owned company. The monopoly of the power

sector in Sri Lanka is govern by the CEB and it can be identified as another major strength of

it. Although CEB makes some loss, currently it shows steady growth in indicators and it

could provide a reliable, continuous and quality-full electricity supply than the other South

Asian countries. CEB has lot of expert engineers and qualified administration officers.

Another one is the Property which is owned by the CEB of billions of Rupees is a great

strength of CEB. It's all in generation, transmission and distribution in addition to having a

license for three. The transmission is only allowed to CEB. It is the major strength for the

Ceylon Electricity Board. This makes CEB the most powerful establishment in the energy

sector in Sri Lanka.

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1.1.6.3 Weaknesses

Most of the power plants owned by CEB have less efficiency due to lack of proper

maintenance. There may have some unwanted political influences to the management

decisions as it’s a government company. The delays of commissioning of Norechcholei and

Sampoor power plants were happened due to that reason and it has makes large loss to the

CEB. Today the Uma Oya Hydropower Project gets the bad influences to the environment

and there are many houses destroyed due to the environmental damages caused by the Uma

Oya Multi-purpose Development Project. The wells in these areas had completely dried up.

While some of the wells have completely dried up, some other wells were found with water

unfit for consumption. The Iranian Company is engaged in the construction of the Uma Oya

Project.

Ceylon electricity board is belonged to the government sector of Sri Lanka. So, rights of

employees are stronger than considering private sector. Therefore the wrong union actions

have badly affected to the performance of CEB as well as the country. The conflicts among

the unions are the major problem to CEB. CEB has the very tall organizational structure. As

the weaknesses we can consider like seniority gets the place but not the talent, more workers

and engineers than the requirement, number of workers and engineers are higher than the

requirement, lot of personals in between the latter and higher part of the hierarchy. Many

executives try to maintain their hierarchy rather than taking useful steps in order to develop

the organization.

1.1.6.4 Opportunities for improvement

New power plant projects like wind park (location- Southern Coast Mannar Island),

Trincomalee Coal Power Plant and Moragolla Hydropower Project are new opportunities to

the CEB to meet the increasing demand of the electricity achieve profits through that. Targets

like rural electrification also can be achieved by those projects. There is a trend to use

Renewable Energy Sources like wind power, solar power, geothermal power.etc. The Ceylon

Electricity Board has the opportunity to use Renewable Energy. If we can increase power

generation, we can even earn by selling power to India.

1.1.6.5 Threats of CEB

Power theft incidents are directly influence to the profits of the company and to the system

efficiency indicators as well. There for power theft incidents are one of the major threats to

the CEB. Still CEB is mostly depend on the thermal power plant and therefore the volatility

in Petroleum fuels (Diesel, Naphtha, Heavy Fuel Oil) is influence to the electricity prices and

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hence to the profits. And regulatory obligations like drinking and irrigation water supply and

other contract basis obligations to the renewable power producers are also limits the function

of CEB. Politicians and non-technical authorities tend to take funny technical decisions in

order to win their hidden political agendas and narrow desires. This causes major damages to

CEB and it is directly affected to the society in Sri Lanka. When we examined the past period

of time, the bad political decisions were the major threads to CEB as well as the country.

1.1.6.6 Profitability of CEB

Ceylon Electricity Board is conducted under huge losses. This had made the organization

unprofitable. Electricity supply is handled as a social service by the government because the

electricity is a necessary to develop the society as well as the country. The total capacity of

hydro power stations is not enough to fulfill the highly forecasting demand. Hence the

thermal power is used to fulfill that demand in Sri Lanka. The capital cost of thermal power

plants is much higher than the hydro power plants. Because of this reasons are directly

affecting to the organizational unprofitability. The price of an electricity unit sell by CEB is

lesser than the price it produces and buys. Proposals had come out to improve the

profitability. But due to some reasons, these attempts have been restrained.

1.1.6.7 Usefulness to the society

The Ceylon Electricity Board is a government company which is under a statutory duty to

develop and maintain an efficient, coordinated and economical system of Electricity Supply

for the whole of Sri Lanka. Therefore, CEB is required to generate or acquire sufficient

amount of electricity to satisfy the demand. CEB methodically plans its development

activities in order to provide reliable, quality electricity to the entire nation at affordable

prices and other thing is providing huge job opportunities to the Sri Lankan society. This is a

huge opportunity for engineers to get the maximum knowledge about the power generation,

transmission and distribution and help to work foreign companies such as ALSTOM

ATLANTIQUE, JOHN BROWN ENGINEERING, MAN B&W and PIELSTICK etc.

Several programs such as Vidulamu Lanka, Viduli Athwela, Grama Shakthi were held to

supply electricity for remote areas in Sri Lanka and locate the Renewable Energy Plant in

rural and other locations.

1.1.6.8 Suggestions to improve the performance

There are many suggestions to improve the performance and the profitability in CEB.

Recruitments should be in transparency and proper method without influences of politicians

P a g e | 8

or any others and corruptions must be stopped in CEB. Training programs should be

implemented to recruited employees at right time and their promotions should be at right time

and proper schedule. Also the correct and suitable plans for the future should be implemented

without any delay at right time such as building plants. Maintenance should be carried out

regularly to keep the no of breakdowns, failures at a low rate. The important factor is that the

CEB should be looking forward to use renewable energy resources.

1.2 Kelanitissa Power Station

1.2.1 Introduction to Kelanitissa Power Station

The Ceylon Electricity Board is the largest electricity company in Sri Lanka. With a market

share of nearly 100%, it controls the major functions of generation, transmission, distribution

and retailing in Sri Lanka. CEB has several numbers of thermal power plants in Sri Lanka.

They are,

* Kelanitissa Power Station

* Kelanitissa Combined Cycle Power Station

* Sapugaskanda Power Station

* Chunnakam Power station

* Uthuru Janani Power Station

* Lakvijaya Power Station

Kelanitissa Power station is one of the largest thermal power plants in Sri Lanka. Kelanitissa

power station is established as the first thermal power station in Sri Lanka in 1964. It is

located near the new Kelani Bridge in Wellampitiya. At the beginning this power plant

consisted of two steam turbine units. Two steam turbines were generated 20 MW each. They

were stopped in 2002 because of the retirement of the plant and the harmful effect to the

environment. KPS generates 195 MW electricity power to the national grid, especially

covering the Colombo area in a blackout situations.

Two gas turbine projects were commissioned in this power station in two steps. In the first

step, three gas turbines were commissioned in 1980 and these gas turbines were known as

Phase 1. The manufacturing company of Phase 1 gas turbines was John Brown Engineering

Pvt.Ltd in England. In the second step, another three gas turbines were commissioned in 1981

P a g e | 9

and they were known as Phase 2 gas turbines which were manufactured by Alstom Atlantique

in France. The installed capacity of each small gas turbine is 20 MW. These gas turbines are

dropped to the open cycle category because exhaust gases (flue gases) which have higher

temperature value (about 520 ), have not used to generate steam. The small gas turbines are

known as Frame V gas turbines which were named as GT1, 2, 3, 4, 5 and GT6. But GT 3 &

GT 6 gas turbines are not working. In 2001, GT 6 was damaged completely due to turbine

blades were damaged, making a huge loss to the CEB. Now it is out of use and even it can’t

be repaired again. In the present these gas turbines are working with efficiency about 20

percent. Even they cannot be loaded up to the full load of 20 MW. The phase 1 gas turbines

have wet air filters and the phase 2 gas turbines have dry air filters.

In 1997, another gas turbine project was commissioned in this power station. A gas turbine

from Fiat Avio in Italy was established and it is GT 7 in the power station. This gas turbine is

known as Frame IX gas turbine. The installed capacity of GT 7 gas turbine is 115 MW. The

entire unit in GT 7 gas turbine is controlled and monitored using computerized system. A

major inspection (MI) for GT 7 gas turbine has been carried out once complete a 48,000 EQH

and the least of its major inspection was carried out in the year 2012 where the whole rotor

was removed and inspected for defects, cavities etc. This gas turbine is dropped to the open

cycle category.

There is a yard with 8 fuel storage tanks with 12000 m3 and 5000 m3 to store auto Diesel and

naphtha. The double wall naphtha tanks are situated separately when considering the Diesel

storage tanks. Liquid naphtha is extremely flammable and high vaporizable. Therefore

naphtha storage tanks were designed to sustain this vaporization and explosive properties of

naphtha fuel. More details of double wall naphtha tanks are described in chapter 2. There are

two fuel oil treatment plants in order to purify diesel. One fuel oil treatment plant was

commissioned with phase 1 and phase 2 gas turbines with 6 centrifugal separators while the

newer one was commissioned with the gas turbine Fiat Avio. It consists of 6 centrifugal

separators (Veronesi Separatori) which are high speed machines that have been used in

industry for several years. The tanks no 3 and 4 are used to store the untreated Diesel while

tank no 5 and 6 are used to store the purified Diesel coming from the fuel oil treatment plant.

In the power plant premises there is a 132 kV switch yard and there are current transformers,

potential transformers, inter bus transformer, circuit breakers and bus bars in a switch yard. In

the power plant there are many workshops (Machine shop, Welding shop, Injector Nozzle

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repairing shop etc) to repair gas turbine parts and other auxiliary equipments such as pumps,

compressors, cooling fans etc.

1.2.2 Organizational structure and hierarchical levels

The following diagram shows the hierarchical levels of Kelanitissa Power Station.

Figure 1.3 Organizational structure and hierarchy levels

1.2.3 The main purposes of the plant

The main purpose of this plant is to generate 195 MW electricity power to the national grid,

especially covering the Colombo area in a blackout situations and other important factor is to

supply excess electricity power during the peak hours, drought seasons and unavailable of

other plants. The small gas turbines (Fr-V gas turbines) use to generate reactive power which

is utilized to stabilize the system voltage.

1.3 Kelanitissa Combined Cycle Power Station (KCCPS)

1.3.1 Introduction to Kelanitissa Combined Cycle Power Station

Kelanitissa Combined Cycle Power Station is only one of the combined cycle power plant in

CEB. Kelanitissa combined cycle power station started its operation at the beginning of 2002

from simple cycle operation and by 2003 becomes with combined cycle operation. Today it

plays a major role for power generation in Sri Lanka. The total capacity of the KCCPS is

around 165 MW electricity power. The installed capacity of the gas turbine (Frame IX-E) is

115 MW. But the capacity is depend on the ambient temperature of the air. Air density is

directly connected for generation process. The total capacity of the steam turbine is around 55

CE(KPS)

SOE

SCE (3)

ES (OP)

CRO ED

EE(EM)

ES (EM)

ELEC

FITTER

EE

(I&c- GT)

EA

(I&C-GT)

ELEC

FITTER

EE

(GT 7)

ES

(GT 7)

ELEC

FITTER

ME

(GT 7)

MS

(GT 7)

MEC

FITTER

EE

(Fr-5)

MS

(Fr-5)

MEC

FITTER

ME

(FS)

MS

(FS)

FITTER

P a g e | 11

MW. There are two types of steam turbines which are known as a HP steam turbine and a LP

steam turbine. According to the system requirement, the gas turbine can operate in combined

cycle and in open cycle because there is diverter toward an exhaust stack (that avoids the

Heat Recovery Steam Generator- HRSG). But operation in combined mode gives better and

higher efficiency. The exhaust system is that portion of the gas turbine in which the exhaust

gases used to drive the turbine are redirected and released to atmosphere when the plant is

operated in an open cycle mode. When the plant is operated in a combined cycle mode, the

exhaust gases are used to generate the superheated steam. The Heat Recovery Steam

Generator (HRSG) is an energy recovery heat exchanger that recovers heat from the flue

gases. There is a two pass box type condenser to do the condensing process and the cooling

towers are used for cooling the condenser cooling water. There is a well maintain water

treatment plant in KCCPS to produce demineralized water for generating steam and uses as

the condenser cooling liquid. The KCCPS takes makeup water from a Kelani river and water

treatment plant is used to treat water before it was used. Water treatment is the process of

removing undesirable chemicals, biological contaminants, suspended solids and dissolved

impurities etc.

Figure 1.4 Structural view of the KCCPS

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Figure 1.5 View (3D) of the cooling towers in KCCPS

1.3.2 Organizational structure and hierarchical levels

Figure 1.6 Organizational structure and hierarchical levels in KCCPS

1.4 Sapugaskanda Power Station

1.4.1 Introduction to Sapugaskanda Power Station

Sapugaskanda Power Station is a thermal power plant. It generates around 160 MW

electricity power to the national grid. In Sapugaskanda Power Station there are two stations

called station A & station B. Station A was commissioned in 1984 and it consists of four V

type Diesel engines to generate electricity power. The installed capacity of each Diesel

engine is 20 MW. The section B consists of eight In- Line Diesel engines which are

generated 10 MW per engine. The station B was commissioned in two separate units (B1 &

B2). The station Section B1 was commissioned in 1997 September with four In-Line engines.

Section B2 was commissioned in 1999 October with four In-Line engines.

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The Sapugaskanda Power Station (SPS) is a base load plant. Both engines are used to get

Diesel and heavy fuel oil as the fuel. Diesel is used only at the movements of the startup and

shut down processes. HFO is used to get the peak load and generate electricity power.

Exhaust gases (flue gases) is used to produce hot water which is applicable to increase the

temperature value (about 60 of HFO. The engine manufacturer of Diesel engines in

station A was PIEISTICK and MAN B&W was the engine manufacturer of Diesel engines in

station B. The following figure shows the V type Diesel engine in station A.

Figure 1.7 A V-type Diesel engine in station A

There are several auxiliary systems attached to the engine in both station A &B. They are a

fuel system, lubrication oil system, cooling water system, hot water system, control air

system, sludge system, electrical system etc. The HFO is sent to this plant from the

Sapugaskanda oil refinery that is located nearby power station. Actually this plant was

designed to get some use from the waste of the oil refinery. There are two yards of fuel

storage tanks and two fuel treatment plants in the premises to treat the heavy fuel oil.

1.4.2 Organizational structure and hierarchical levels

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Figure 1.8 Organizational structure and hierarchical levels in SPS

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2 TRAINING EXPERIANCES

2.1 Kelanitissa Power Station (KPS)

2.1.1 Observations and work carried out at Kelanitissa Power Station

According to my training schedule Kelanitissa Power Station was my first training place

under DGM- Thermal complex in CEB. In the first week of our in-plant training period, we

trained under the supervision of shift charged engineers and got the basic information of the

switch yard, Frame v gas turbines and GT 7 (Fr-IX) gas turbine. After we reported to the

mechanical engineer (Fr-V gas turbines, Mr. A.P.Sampath) and the mechanical engineer (GT

7 gas turbine, Mr. U.K.L.Chulakeerthi) and they gave us a training schedule to cover the

scope in Kelanitissa Power Station. It is helpful to get the idea of the systems in the plant

such as fuel system, lubrication system, atomizing air system etc. in gas turbines and

drawings and manuals are helpful to refer the systems and to observe on location. We

observed and examined the basic functions of the gas turbines such as Fr-V and GT 7(Fr-IX)

gas turbines. Further we inspected the different kinds of bearings used in gas turbines and

their failure criteria and also examined the offline and online compressor blades washing and

reasons for washing compressor blades. After we observed the operation of the Fuel Oil

Treatment Plant (FOTP) and looked over the operation of the centrifugal separator (Veronesi

Separatori) and the basic mechanical process to treat Diesel fuel and visited the yard which is

located oil tanks. There are two untreated diesel oil tanks in capacity 12,000 m3 per tank, two

treated diesel oil tanks in capacity 12,000 m3 per tank and two naphtha storage tanks in

capacity 5,000 m3 in the yard.

Figure 2.1 Fuel Oil Treatment Plant (FOTP) in KPS

We participated to the vibration test run of GT7 (Fr-IX) gas turbine and examined the

fluctuation of the blade path temperature values of 18 combustors. After that we observed the

wet filers and the exhaust stack of Fr-V (phase 1) gas turbines under the guidance of the

P a g e | 16

mechanical engineer (Fr-V gas turbine) and further beheld the dry filtering process of GT 7

gas turbine under the guidance of the mechanical engineer (GT7 gas turbine). We went

through the Operation and Maintenance manual of Fr-v gas turbine as well as the GT7 gas

turbine.

We observed basic components and system in gas turbines under the guidance of mechanical

engineers and mechanical superintendents. We wrote several reports about the compressor,

bearings and the failure nature of the second stage nozzle blades of a Frame Vgas turbine

under the supervision of mechanical engineers.

2.1.2 Gas turbines

Gas turbine is a device which converts the chemical energy of the fuel to mechanical energy.

It consists of a compressor, combustion chamber and turbine. Considering both gas turbines

and reciprocating internal combustion engine, gas turbines are better in both performance and

use. For a same output, the ratio between horse power and weight is higher in gas turbine

when compared to reciprocating internal combustion engine. Also the wear and tear is much

higher in IC engines due to reciprocating action. In IC engines, balancing process in much

more difficult. Furthermore, the operation of gas turbine is smooth.

Figure 2.2 A Gas turbine

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2.1.3 The Brayton Cycle

The Brayton cycle is the ideal cycle for gas turbine engines, named after George Brayton who

proposed it around 1870. Gas turbines usually operate on an open cycle, as shown in Figure

2.3 and explained below.

Figure 2.3 A Schematic diagram of an open cycle gas turbines

The T and P of the fresh ambient air drawn into the air intake are raised in the

compressor.

The high pressure air is mixed with fuel and burnt at constant pressure in the

combustion chamber.

The higher temperature gases expand to the ambient pressure through the turbine thus

producing power.

The exhaust gases are thrown out through the turbine.

The open gas turbine cycle described above can be modified to a closed cycle as shown in

Fig. 2.4, using the air standard assumptions. Here the compression and expansion processes

remain the same, but the combustion process is replaced by a constant pressure heat addition

process from an external source and the exhaust process is replaced by a constant pressure

heat rejection process to the ambient air. In this ideal cycle, the working fluid undergoes the

following process. They are 1-2 isentropic compression, 2-3 constant pressure heat addition,

3-4 isentropic expansion and 4-1 constant pressure heat rejection. Although the heat addition

process is under constant pressure, practically a pressure loss of about 5% can be seen. This

closed loop ideal cycle is the Brayton Cycle. All the four processes in the Brayton cycle are

steady and reversible processes.

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Figure 2.4 Closed cycle gas turbine engine

Figure 2.5 Process diagrams of the Brayton cycle

2.1.4 Specifications of gas turbines in KPS

2.1.4.1 Fiat Avio TG50D5 (GT 7) Gas Turbine

Figure 2.6 Schematic diagram of GT7 gas turbine

RPM of both generator and turbine= 3000 rpm

Number of combustors= 18

Number of Compressor stages= 19

Number of Turbine stages= 4

Number of spark plugs= 2

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Number of fire detectors= 4

Number of journal bearings (radial bearings)= 5

Number of Thrust bearings= 1

2.1.4.2 Frame-V gas turbine

Figure 2.7 Schematic diagram of the Fr-V gas turbine

Maximum generator speed= 3000 rpm

Maximum Turbine speed= 5200 rpm

Number of Compressor stages= 17

Number of Turbine stages= 2

Number of combustors= 10

Efficiency= 25%

Phase 1 gas turbines have wet filter and phase 2 gas turbines have dry filters

Turbine exhaust temperature= 520

Input- Air = 98.5 m3/ sec

Fuel= 0.75 L/sec

Output- Power= 20 MW

Voltage= 11 kV

2.1.5 Major parts in GT 7 gas turbine

2.1.5.1 Intake air filters

The air intake is the major part of the gas turbine. The inlet filtration system cleans the air

entering the gas turbine. The effects of inlet air filtration are both positive and negative. The

negative side of filtration is that whatever is placed in the path of air coming into the gas

P a g e | 20

turbine causes a pressure loss, resulting in reduced performance or efficiency of the machine.

However, inlet filtration will help sustain the gas turbine’s performance above an acceptable

level and minimize the occurrence of the degradation effects such as foreign object damage,

erosion, fouling and corrosion etc. Properly selecting and maintaining the filtration system

can increase the performance and life of the gas turbine and minimize the required and

unexpected maintenance. When considering the path of air initially it comes through the

filter. Filter is consists of four sections. They are

1. Stainless steel mesh

2. Louvers

3. Pre filtering

4. Fine filtering

In industrial areas, air consists of dust, water mist when raining, solid particles etc. Therefore

the stainless steel mesh is used to avoid some particles such as leaves, insects etc. It is

important to have louvers to avoid water droplets or water mist entering the duct. In louver

designing, the angle of the louver and the distance between louver blades has to be designed

for avoiding water droplets. The air has a mixture of large and small dirt particles. Pre filters

are used to capture the large solid particles and this will increase the life of fine filtering. Pre

filtering is done with filer pads surrounded by filter cones. Figure 2.9 shows a part of the pre

filter. This prevents the erosion of compressor blades. Fine filtering is done to remove smaller

particles which lead to corrosion and fouling.

Figure 2.9 Pre filter (filter pad and filter cone) Figure 2.8 Air intake of GT 7 gas turbine

P a g e | 21

Figure 2.10 A fine filter in GT7 gas turbine

2.1.5.2 Inlet silencers

The inlet silencers reduce the level of sound pressure transmitted through the working fluid

(air) of the gas turbine plant. The inlet silencers are the essential part of the gas turbines.

2.1.5.3 Bell mouth and Inlet Guide Vane (IGV)

At the inlet bell mouth to the compressor, the air pressure decrease slightly due to the

increase in velocity from the converging cross section of the mouth. This decrease in pressure

causes a decrease in temperature which can lead to the water vapor in the air condensing and

freezing on the bell mouth, inlet guide vanes, and initial compressor stage blades.

The Inlet Guide Vane (IGV) blades are the only curved surface vanes in the entire machine

and were designed to modulate the air flow inward to the combustors in the function of the

demand, a fundamental operation during the transitional phases of the rotor starting and

stopping. The IGV is a ring of guide vanes that can be adjusted through an angle of 370 with a

hydraulic actuator. When the machine is not running the IGV vanes are at 370 closed

position. At the start up the IGV angle is set to 30 degrees (blade tangent angel of 70in normal

operation). Again when the gas turbine is running at 2850 rpm IGV is closed. When the

machine is loaded to 5 MW the IGV is gradually being opened with the fuel regulating

valves. When the gas turbine is loaded to 21 MW the IGV angle is set to zero giving

opportunity to extract more fresh air. The following figures show the bell mouth and the Inlet

Guide Vane (IGV) in GT7 gas turbine.

P a g e | 22

Figure 2.11 Part of the bell mouth and the IGV of GT7 gas turbine

Figure 2.12 IGV arrangement of GT7 gas turbine

2.1.5.4 Axial Compressor

The axial compressor is a mechanical component in which the pressure of the working fluid

(air) is increased. There are 19 stages in the compressor. There are stationery blades which

are called compressor diaphragms in the housing and fixed to the inner housing and rotating

blades are fixed on the rotor. The compressor inlet casing contains the first two series of axial

compressor stator blades (diaphragms). The compressor cylinder provides the location of the

compressor diaphragm from 2nd

to 11th

stage and chambers collecting air bled off in stages

from 6 through 11 for cooling of the 4th

and 3rd

turbine blades. There is a compressor-

combustor cylinder and the compressor diaphragms of stages from 12 through 19 are located

inside of the compressor-combustor cylinder. A ring shape chamber collecting air bled off in

stage 14 for cooling the 2nd

of the turbine blades. There are 19 compressor stages in the axial

compressor. Stationary blades guide the air flow towards the rotating blades. The axial air

compressors can produce higher compression ratios. This is the most commonly used one.

The GT7 axial compressor has a compression ratio of 1:14. The pressure is 14 bars while the

P a g e | 23

temperature is 379°C. The following figure shows the compressor blades and diaphragms in

GT7 gas turbine.

Figure 2.13 Axial compressor of GT7 gas turbine

Figure 2.14 Compressor rotating and stator blades

2.1.5.5 Fuel injectors and Combustion chamber

A combustion chamber is required to mix and ignite the fuel and according to this

arrangement, more compressed air will come into the chamber to complete the combustion

process. There are eighteen combustion chambers or combustors in the machine positioned

around the axis of the rotor. Combustion chambers are provided the space to burn by mixing

the gaseous or the liquid fuel and compressed air and the spark plugs give the spark for the

ignition. Here a constant pressure heat addition to the compressed gas occurs. The outer

jacket of the combustor has the flanges with which the combustors are connected through

flexi hoses (cross-flame) that allows the flame to be propagated from one combustor to the

next. These combustors are the most heat affected areas in a gas. When the machine is

running on base load the firing temperature is about 1085°C. So, hot corrosion may be

P a g e | 24

occurred in these combustion chambers. The 18 combustors are basically all the same but

differ in the shape of the dome and the number of cross-flame connecting flanges. It result

that,

a. The combustors in position 8 and 9 have two spark plugs

b. The combustors in position 17 &18 have a way in their domes for the piston of the

two flame detectors.

On the machine are 18 fuel injectors, consisting essentially of the internal nozzle for the

liquid fuel, a concentric outer chamber for the atomizing air and the demineralized water.

After mixing of the atomizing air and the fuel, ignition was carried out using the spark plugs.

Figure 2.15 Fuel injector of GT7 gas turbine

Figure 2.16 Arrangement of the combustion chamber and transition pieces

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Figure 2.17 Fuel injector nozzles cleaning

2.1.5.6 Transition Pieces

Eighteen in numbers, these are duly shape conveyors that take the product of combustion

from the combustor to the turbine 1st stage blade areas. It also subjected to the high

temperature of the hot gas flow. So they were made of metal that was stable in high

temperatures about 600 . A new material which is a nickel base alloy called, Nimonic 263

was used for the transition pieces. Further the thermal barrier coating was applied on the

transition pieces to hot corrosion. Figure 2.16 shows the transition pieces in GT7 gas turbine.

2.1.5.7 Turbine

Turbine is the most important part of the gas turbine. A turbine is a mechanical component in

which energy of the working fluid (air) is converted into mechanical energy by kinetic action

on the rotating blades. Turbine type is Fiat Avio TG 50 DS and consists of four stages. It

consists of four stationary stages which are called the nozzle rings and four rotating stages

which are called buckets. The combustion gas flow coming through the transition pieces are

directed in to the first stage nozzle ring. The first stage nozzle ring guides the gas flow

directly to the first stage buckets for better performance.

A turbine blade is the individual component which makes up the turbine section of a gas

turbine. The blades are responsible for extracting energy from the high temperature, high

pressure gas produced by the combustor. The turbine blades are often the limiting component

of gas turbines. Because of the high temperature, Turbine vane segments (fixed blades of the

turbine) and the turbine rotating blades were cooled using the compressed air extracted by the

compressor. The first stage vane segment is a single vane sector and it has 60 blades per

complete ring. Inside the blades there are 3 cooling chambers and also the outer surface of the

blades are cooled through film cooling. The second stage vane segment has 3 blades per

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sector and 20 sectors have for a complete ring and these blades have cooling chambers. The

3rd

and 4th

stage vane segments have 64, 73 blades respectively. The 3rd

and 4th

blade surfaces

are not cooled.

The turbine cylinder has a number of inlets for the cooling air bled from the compressor for

the cooling of the turbine rotating blades. To survive in this difficult environment, turbine

blades often use exotic materials like super alloys and many different methods of cooling.

The following figures show the turbine vane segments and turbine rotating blades.

Figure 2.18 Turbine stator and rotating blades

2.1.5.8 Exhaust diffuser and exhaust manifold

The turbine exhaust diffuser is the final section of the turbine in which diffusion of the gas

takes place through recovery of the kinetic energy in the exhaust. The turbine diffuser section

is also the location of the over speed safety mechanism.

The exhaust manifold is the appendix to the exhaust diffuser, where combusted gases

terminate their expansion before being conveyed to the stack.

Figure 2.19 Exhaust diffuser of GT7 gas turbine

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2.1.5.9 Stator motor

The gas turbine has a 6kV starting motor. The gas turbine is started by this motor. The starter

motor gives the required initial power to the gas turbine till the engine comes to its sustaining

speed. At the speed of 2100 rpm the starting motor decoupled from the turbine. Thereafter the

engine accelerates up to 3000rpm with by the power produced by combustion process.

2.1.6 Consequences of Poor Inlet Filtration

Proper inlet filtration is designed based on the required application in order to prevent a

decrease in gas turbine performance and even destruction of the gas turbine. The gas turbine

is affected by various substances in the inlet air depending upon their composition and their

particle size. Discussed below are six common consequences of poor inlet air filtration:

foreign object damage and domestic object damage, erosion, fouling, turbine blade cooling

passage plugging, particle fusion, and corrosion (hot and cold).

2.1.6.1 Foreign Object Damage (FOD) and Domestic Object Damage (DOD)

Foreign Object Damage (FOD) can be significant in a gas turbine if there is not proper

protection. Large objects or relatively large particles can be trapped or screened to avoid their

entry into the compressor section of a turbine. This accomplishment is a significant gain,

because FOD has the greatest potential for secondary and extensive damage to the

compressor and later parts in the air flow path. The filter system and its components are

designed to prevent FOD. Poorly designed filters or systems and other aspects lead to a risk

of FOD.

The Domestic Object Damage (DOD) is another failure which is occurred to the compressor

blades as well as the turbine blades. Some rupturing parts of the intake air duct and the rust

parts of duct and other components are directly impacted on the compressor or turbine blades.

The impact effect is the Domestic Object Damage.

2.1.6.2 Erosion

Hard particles 5 to 10 microns or larger create erosion of the metal surfaces bounding the air

flow path. Sand is one of the most common causes of erosion due to its prevalence at the

installations of gas turbine. Impingement of small, hard particles against blade and stator

aerodynamic airfoil shapes repeatedly removes tiny particles of metal, eventually re-shaping

portions of the parts. Re-shaping aerodynamic surfaces changes the air flow paths, roughens

the surfaces, changes clearances, and eventually reduces the cross-sectional areas that provide

the strength necessary to resist the very high stresses of parts with minimal margins of safety.

P a g e | 28

Also, changing the blade shape can create stress concentrations that reduce the fatigue

strength, thus leading to high cycle fatigue failures. The efficiency of the gas turbine is

reduced until excessive stress takes over as the main cause of problems. Erosion is a non-

reversible problem. The only method of bringing blades back to their original condition is

with replacement. The figure 2.20 shows the comparison of the particle size rang for erosion

and fouling.

Figure 2.20 The comparison of the particle size rang for erosion and fouling

Figure 2.21 Erosion on the leading edge of the turbine blade

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Figure 2.22 FOD on the compressor diaphragm

2.1.6.3 Fouling

As particle size and hardness reduce, the potential problems change from erosion to fouling.

Fouling is the build-up of material in cavities and low flow-rate locations along the air flow

path. The small particles such as vapor water, oil and other sticky substances are coursed for

fouling. This small particles stick on the compressor blades as well as the turbine blades

cooling passages. It is a major problem to operate the gas turbine. Fouling courses many

problems such as change clearances, disrupt rotating balance, obstruct and plug flow paths,

and reduce smoothness of rotating and stationary blade surfaces.

Fouling is, however, usually recoverable since there are methods available to remove these

deposits with online or offline compressor washing or mechanical cleaning.

Figure 2.23 Fouling on the compressor blade

2.1.6.4 Corrosion (hot and cold corrosion)

Corrosion is a chemical process and if the types of material ingested into the machine are

chemically reactive, especially involving the metal in the turbine parts, the result is corrosion.

P a g e | 30

There are two classification of corrosion in gas turbine such as cold corrosion and hot

corrosion. Cold corrosion occurs in the compressor due to wet deposits of acids, steam,

aggressive gases such as chlorine, sulfides etc. This can result in reducing cross sectional

properties by removal of material over an area or concentrated corrosion resulting in pitting.

Hot corrosion occurs in the turbine area of the gas turbine. It is also the chemical reaction.

This section is exposed to materials that may intrude not just from the air, but also from the

fuel or water/ steam injection which can be difficult to filter. These include metals such as

sodium, potassium, vanadium, and lead that react with sulfur and oxygen during combustion.

After combustion, these will deposit themselves on combustor liners, nozzles, turbine blades,

and transition pieces and cause the normally protective oxide film on these parts to oxidize

several times faster than without it. It is a form of accelerated oxidation deposited on their

surfaces. The rate of the hot corrosion is highly depended on the temperature.

2.1.7 Vibration test run of GT7 gas turbine (Fr-IX)

GT7 gas turbine is the largest gas turbine in Kelanitissa Power Station. The entire unit is

controlled and monitored using computerized system. A Major Inspection (MI) for GT7 gas

turbine plant has been carried out once complete a 48,000 EQH (equal hours) and the least of

it’s major inspection was carried out in year 2012 where the whole rotor was removed and

inspected defects, cavities etc. In these days GT7 gas turbine plant has been started some

unusual vibration of the rotor. The rotor was rearranged to minimize the vibration effect. The

main rotor can be divided into three parts. They are compressor shaft, intermediate shaft and

the turbine shaft. Engineers have tried to minimize this vibration using balancing weights

which were attached to the particular discs (plates) on the rotor. The figure 2.24 shows the

balancing weights arrangement of the turbine rotor.

The vibration test run was conducted by the engineers. The purpose of this test run was to

determine the amount of vibration of the rotor. The turbine has been programmed to trip-off

automatically when the vibration is exceeding one present value. When the plant was started

then the turbine speed was continuously increasing. When the turbine speed was around 1400

rpm, the machine was suddenly tripped-off due to the increasing of the blade path

temperature difference. There are 18combustors in GT7 gas turbine and 18 thermocouples

measure the temperature of each combustor and get the average blade path temperature as

well as the maximum blade path temperature difference etc. To overcome this problem they

conducted an off-line compressor blades washing.

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Figure 2.24 Balancing weights arrangement of the turbine rotor

Figure 2.25 Main rotor of the GT7 gas turbine

2.1.8 Compressor washing of GT7 gas turbine

Compressor blades are subjected to deposit tiny dust particles that are coming through the

intake air filter. This is known as fouling which is described under the sub section about the

Consequences of Poor Inlet Filtration. Reasons for washing compressor blades are as follows.

Decreasing the compressor discharge pressure.

Increasing the blade path temperature difference.

Washing is done with a detergent and water mixture that stored in a pressurized tank. Online

and offline washing methods are used to clean the compressor blades.

Off line cleaning- This is done when the turbine is in unload mode. Here the turbine

is rotated by the starting motor.

Online cleaning- This is done when the gas turbine is running with a load

The mixture of water and a detergent (chemical composite-FYREWASH F2) were used for

compressor blades washing process. The ratio of adding water and detergent is 4:1. The

detergent (FYREWASH F2) was supplied as a concentrate and is normally diluted with four

P a g e | 32

parts of distilled water before used. For online cleaning water must be demineralised,

deionised or distilled. For offline cleaning water must be of quality required by engine

manufacturer. Online washing helps to avoid performance loss and increases fuel

consumption and reduces the need for off line cleaning.

Figure 2.26 Label of a detergent used for compressor washing

2.1.9 Failure nature of the second stage nozzle of a Frame-V gas turbine

We have been given a second stage nozzle of a frame V gas turbine (phase-I) located at the

KPS and it is having several cracks in nozzle vanes. Figure 2.28 shows the second stage

nozzle in Fr-V gas turbine. Nozzle segments in gas turbine engines tend to degrade during

engine service, with degradation modes ranging from oxidation, corrosion and creep, thermal

fatigue cracks and the foreign object damage. An example of the thermal fatigue cracks on

the outer sidewall of the second stage turbine nozzle segments and the thermal fatigue cracks

on the blades of the nozzle segments. The nozzle under evaluation was the second stage

nozzle of 20 MW Diesel combustion, 2 stage turbine which is having the gas inlet

temperature around 1000 . The full nozzle consists of several nozzle segments and each

nozzle segment is composed by two vanes. The nozzle was made of cobalt base super alloy

(FSX-414) by means of conventional investment casting.

By visual inspection, it was obviously shown some thermal cracks on nozzle vanes and near

the nozzle internal and external shroud. The gas turbine nozzle is a stationary element and its

operational stresses are generated only due to gas flow pressure and thermal load originated

by temperature gradient through the nozzle elements wall thickness. The cracks in nozzle

segments were originally repaired using manual arc welding with processes such as GTAW

or PAW and the cobalt base filler metal is known as Nozzalloy.

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Figure 2.27 Thermal cracks on the nozzle vanes

Figure 2.28 Second stage nozzle segments

2.1.10 Fuel Oil Treatment Plant (FOTP)

There are two fuel oil lines to the plant from Ceylon Petroleum and from the port directly.

The oil must be treated before using, since the oil may consists water and sludge. So, there is

a process to purify the fuel oil and remove all other unnecessary components. Separators have

been used for this purpose. Centrifugal separators are high speed machines that have been

used in industrial for several years. Operations are based on very simple principle and the

continual technical and technological progress has made their characteristic of efficiency,

reliability and strength possible. There are 6 centrifugal separators (Veronesi Separatori), fuel

oil feed pumps, pneumatic pumps (fixed capacity pumps), filters, valves, gear boxes (worm

and wheel drive), electric motors and treated and untreated fuel oil treatment tanks. In

Kelanitissa Power Station maximum 4 separators and minimum two separators are used to

get the treated fuel oil. The untreated Diesel fuel is stored in the untreated fuel tanks 3 & 4

and each of having a capacity of 12,000 m3. Then it is kept some times to allow the water in

oil to get deposited in the bottom of the tanks. After the fuel is filtered using duplex filters

and pump to the separators to do the purifying process. We saw that each feeding process,

P a g e | 34

two fuel oil feed pumps are used. But one of the fixed capacity pumps is used as a stand by

pump. The FOTP can be operated in two ways such as the manual and the automatic method.

A motor is used to rotate the centrifugal discs in the separator. The motor rpm is 1500 rpm.

There is a gearbox which is having a worm and wheel drive, to increase the rotational speed

up to 5100 rpm. The hydraulic network for bowl lifting, water must have a pressure of 0.5 bar

and a capacity of 200 l/h at least. There is water consumption for bowl opening and closing as

well as for washing away the separated sludge. To avoid pipes clogging and consequent

troubles in bowl closing and opening, the water must be mud, sand or other contaminants

free. So cartridge filters are used to filter the water. When the bowl was not closed or opened

properly, then it is called a pocket loss.

2.1.10.1 Working principle of the centrifugal separator

By applying a rotational velocity, then it is replaced the gravity force with the centrifugal

force which is thousand times higher. Then the liquid is subjected to the centrifugal force, the

separation and the sedimentation will be continuous and very fast. This is the pure

mechanical system. The mixture to be separated is fed by means of a pipe into the distributor.

From the distributor is subdivided in the spaces among the disc where the mixture

components are separated by the centrifugal force. The treated fuel (light fuel) is collected

toward the bowl center and the heavy liquid (water) is flown toward the disc outer diameter.

The separation is possible only if the bowl is previously filled with heavy liquid (water) to

form a hydraulic sealing to prevent the flowing out of the light liquid (treated fuel) over the

outer edge of the dividing cone. The solids (sludge) are ejected through the slots machined in

the blow bottom cylindrical wall.

Figure 2.29 Centrifugal separators in FOTP at KPS

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2.2 Kelanitissa Combined Cycle Power Station (KCCPS)

2.2.1 Observation and work carried out at KCCPS

My second training place was the KCCP station after trained at the KPS. I reported chief

engineer in KCCPS and he assigned three sections for me. First week of my in-plant training,

we trained under the supervision of the shift charged engineers and discussed about the basic

introduction and the operation of the combined cycle power plant at Kelanitissa Combined

Cycle Power Plant (KCCPS). Also we observed and examined an inlet fuel pipe line of

naphtha and Diesel, an auxiliary compartment and the turbine compartment of gas turbine

and a Heat Recovery Steam Generator (HRSG).

After that, we were assigned to the mechanical engineer of the gas turbine, Mr. A.P.K.

Mutunayake. He guided us very well to study mechanical engineering sections in gas turbine.

He introduced Mr. A.W. Gunawardhana and Mr. K.D.I.T. Kiriwaththuduwa who are the

mechanical superintendents in section GT to get the help from them to study the systems. We

observed the GT liquid fuel system including naphtha and Diesel tank farm, naphtha/Diesel

forwarding skid, filtering skid, super lubricant skid as well as the governor and the flow

divider. After that we beheld and examined the GT air intake system, pulsing air skid, GT

bell mouth and IGV and also examined the online and offline compressor washing system

and their operating sequence. Further we referred the design of compartment ventilation to

avoid cabinet temperature increment, exhaust plenum and the exhaust duct. The mechanical

engineer (gas turbine) gave individual projects and I did a project about making a Bill of

Quantity (BOQ) for double wall naphtha tank 1&2 which is having a capacity of 5000 m3.

After we trained under the supervision of the mechanical engineer (Steam turbine), Mr.

W.M.S.M.B. Wanisundara and the mechanical engineer of the steam turbine guided me to

study about the steam turbines, the HRSG, the condenser, the cooling towers and the

operating sequence of a governor valve and a stop valve. Then After two weeks I was

assigned to the third section of the plant BOP. Mechanical engineer of the BOP section, Mr.

Neranjan Desilva and his superintendent guided me to study about the water treatment plant,

central AC system and chillers and several systems in the power station and we observed the

overall process of the water treatment plant and further studied the coagulation, flocculation

and sedimentation of the suspended solid in river water and participated to the discussion

conducted by a chemist about the removing suspended particles and dissolve impurities in

river water.

P a g e | 36

2.2.2 Gas turbine in KCCPS

KCCP has a Frame 9E gas turbine. This consists of 17 compression stages and 3 turbine

stages. It has 14 injector nozzles, 2 spark plugs and 4 flame detectors. Turbine entry

temperature is 1200 and the exhaust temperature of gas turbine is 560 . Both the

compressor and the turbine rotate at 3000 rpm. Figure 2.30 shows the main components of

gas turbine. In this gas turbine, there are shaft driven pumps: atomizing air pump, lubrication

oil pump (A/C & D/C), hydraulic pump and fuel pump. The total capacity of the gas turbine

is around 110 MW. It is depend on the ambient temperature of the environment (air) which is

directly connected with the air density of the environment. The Inlet Guide Vane (IGV) is

used to control the exhaust temperature of the gas turbine. There are three main journal

bearings used to support the gas turbine rotor. Also there is a thrust bearing to maintain the

rotor to stator axial position. One bearing assembly is located at the inlet. It has loaded and

unloaded thrust bearings and journal bearing. Second bearing assembly is at compressor

discharge casing. Third bearing assembly is located at end of the turbine shaft. It consists of a

tilting pad bearing.

Figure 2.30 Main components of the gas turbine

This gas turbine can run with the fuel diesel and Naphtha. Usually, diesel is taken to startup

and shut down of the plant. But, it is decided whether it is converted to naphtha or not

according to the price of diesel in the market. Diesel is taken from the treated diesel storage

tank in the KPS fuel storage tank yard on the same premises. This turbine is in a covered

turbine hall. It is a main advantage in maintenance. In any weather condition the turbine can

be taken into maintenance. During the operation of the gas turbine, air is extracted from

various stages of the axial flow compressor to cool the turbine parts subject to high

P a g e | 37

temperatures, seal the turbine bearings, provide an operating air supply for air operated

valves and also use as fuel nozzle atomizing air. The combustion system of the gas turbine is

of the reverse-flow type and consists of canted combustion chamber liners arranged around

the periphery of the compressor discharge casing. This system also includes the fuel nozzles,

spark plug ignition system, flame detectors and crossfire tubes. There are 14 combustors in

this gas turbine.

2.2.3 Steam turbine

Kelanitissa Combined Cycle Power Plant (KCCPS) can be operated in an open cycle mode or

a combined cycle mode. When the power plant is operating in a combined cycle mode, the

total capacity of electricity generated is around 165 MW. The total capacity of electricity

generated using steam turbines (HP steam turbine and LP steam turbine) is around 55 MW.

The high pressure steam turbine rotates at 3,000 rpm. The low pressure steam turbine rotates

at the speed 9417 rpm and coupled to the gear box to get the speed 3,000 rpm in the shaft

which is connected to the generator.

Figure 2.31 Overall process of the combined cycle power station

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2.2.4 Rankine cycle

The Rankine cycle is an ideal cycle for vapour power cycle. Many of the impracticalities

associated with the Carnot cycle can be eliminated by superheating the steam in the boiler

and condensing it completely in the condenser. In order to increase the efficiency of the

cycle, the area of the curve has to be increased. Since the exhaust gas temperature of the GT

is around 560 . It is not possible to move the curve more upwards. Therefore the only

possible way to increase the area of the curve is to reduce the feed water temperature. Here it

is maintained at 50 under pressure. Here after you can see the steam cycle of its high

pressure circuit and also for its low pressure circuit. It can be also seen the association

between the thermodynamic transformation and the equipment on a process diagram (Figure

2.31).

Figure 2.32 HP circuit Figure 2.33 LP circuit

2.2.5 Components of steam turbine

2.2.5.1 Diverter damper

The maker of the steam turbine is Alstom Vega 109E. In combined cycle plant there is a

diverter damper to control the path of the flue gas. The flue gas goes out to atmosphere

through stack when the diverter damper is closed. In order to send the gas through steam

generator, diverter damper has to be opened. The sequence of opening the diverter damper is

34%, 54% and 84%. The flue gas temperature is 560 .

2.2.5.2 Heat Recovery Steam Generator (HRSG)

A Heat Recovery Steam Generator (HRSG) is an energy recovery heat exchanger that

recovers heat from a hot gas steam. It produces steam (LP steam & HP steam) that can be

used to drive steam turbine. The Heat Recovery Steam Generator is a vertical boiler with a

drum for each of the two pressures. Pressure of the LP drum is around 7 bar and the pressure

P a g e | 39

of the HP drum is around 70 bar. The HRSG consists of four major components that are the

economizer, the evaporator, the super heater and the water pre-heater. The HRSG has 7

stages which are illustrated in Figure 2.32. It is required to keep the exit temperature of the

gas from HRSG at a predefined value. If the Naphtha is used as the fuel, the value is

110/120 . When the fuel is Diesel the value should be 145/150 . This is done in order to

avoid condensation of H2SO4 which may lead for corrosion in the HRSG walls. The HRSG

can be categorized by a number of ways such as direction of the exhaust gas flow or number

of pressure levels. Based on the flow of exhaust gases, it can be categorized into vertical and

horizontal type. In horizontal type HRSG’s, the exhaust gas flows horizontally over vertical

tubes whereas into vertical type HRSG’s, the exhaust gas flows vertical over horizontal tubes.

In horizontal type HRSG, the circulation water pumps should always not be operated.

Because of the water tubes are vertical and water is continually flowing due to the gravity.

But the circulation water pumps are always used in vertical type HRSG due to the horizontal

type water tubes.

The temperature and pressure variation along with the 2 stages on the HRSG is shown in

annex 1. The following diagrams show that more the HRSG has pressure levels and then

higher can be the efficiency of the power plant. But if the number of pressure levels

increases, then the number of heat exchangers increases too and therefore its complexity also.

The optimum is a boiler with two pressures. After the initial investment there is a longer

period of time before a return on money can occur.

Cheap/ low efficiency Standard Expensive/high efficiency

Figure 2.34 Efficiency of the HRSG varies with the pressure levels

2.2.5.3 Deaerator

The function of deaerator is to remove all non-condensable gases using the LP steam.

Condensed feed water goes into this before it goes to feed water tank. Before come to the

deaerator, the condensed water is per-heated using the pre-heater coli which is situated at the

P a g e | 40

top of the HRSG and then it helps to maintain the exit temperature of the HRSG as described

above.

2.2.5.4 Feed water tank

The demineralized water is stored in the feed water tank and it is pumped by two impeller

type feed water pumps in duplex mode, from different stages to LP and HP drum. This

system is a closed cycle. But some amount of water is pulled out because of the leakage of

the water lines and other factors such as vaporizing the water to the atmosphere. To overcome

this problem some amount of demineralized water is added to the water lines (both LP & HP

lines) after the feed water tank.

2.2.5.5 LP drum

LP drum is filled with saturated water at 7 bar and the LP drum maintains a pressure of 7 bar

and temperature 165 °C. Then water is pumped to LP evaporator coil using LP circulation

pump. There are two circulation pumps; duty and stand by. Generated low pressure saturated

steam sent to LP drum.

2.2.5.6 LP turbine

The low pressure saturated steam in the LP drum is sent through the LP super heater and the

LP super heated steam is fed into the LP turbine with 7 bar pressure. The LP turbine has 8

stages and each stage consists of a stationary set of blades mounted on the periphery of a

diaphragm and a moving set of blades mounted on the periphery of a moving disc. It also has

the thrust bearing collar and two journal bearings on the both side of the turbine which helps

to support the turbine rotor. Super heated steam admission pressure and the discharge

pressure are 9 bar and 0.127 bar respectively. Steam admission temperature into the LP

turbine is 239 and the steam discharged temperature is 50 . Maximum rotational speed of

the LP turbine is 3000 rpm.

2.2.5.7 HP drum

High pressure water line passes through the two economizer coils in the HRSG and then goes

to HP drum. Saturated water at 70 bar is pumped again to the evaporator coil to get the

saturated steam. After then saturated water is sent through the super heater coli and then

generated HP steam is forwarded to HP turbine. The HP drum maintains a pressure of 70 bar

and the temperature of 289

P a g e | 41

2.2.5.8 HP turbine

HP turbine type is TM2 41.7 and it has 7 stages and HP diaphragm is located in front of each

disk. The purpose of this diaphragm is to direct the steam flow into the rotating blades. The

steam admission diameter is 250 mm and casing is made by cast steel. 1st stage diaphragm is

one piece and centered on the steam admission annular. This nozzle ring is machined from a

piece of a metal because it always exposes to the high pressure steam of 70 bar with a high

temperature of 510 °C. To reduce the effects of thermal stresses is made as one part. The

other diaphragms are consisting with 2 parts. The rotor blades are made by mild from

chromium alloy steel and rotor is made of forged steel. The rotor is supported on two journal

bearing and there is a thrust bearing that the axial load on the rotor is bear. The HP turbine

rotor shaft is directly couple to the reduction gear box. Because the HP turbine speed is 9000

rpm.

2.2.5.9 Stop valve

The steam turbine (HP turbine) stop valve is automatically and manually operated. Its

function is to provide HP steam to the governing valve from live steam into the inlet pipe

from the HP drum.

2.2.5.10 Governor

The operating sequence of the governor has a fully mechanical process. There are 4

governing valves and when the turbine shafts are at a standstill, the four governing valves are

in the closed position. There are 4 governing valves, each in turn providing steam to one

quarter of the first diaphragm nozzles in the HP turbine. The purpose of the valves is to adjust

the flow of steam admitted into the turbine according the power demand. The figure 2.37

shows the Governor used in HP turbine.

Figure 2.35 Governor in HP steam turbine

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2.2.5.11 Condenser

A two pass box type condenser is used to condense the steam after the isentropic expansion

process (outlet steam of the LP turbine). There is a vacuum pump for air extraction to reduce

the pressure in condenser. So that the condensate water temperature can preserve a low value

(around 50 ).

2.2.5.12 Cooling towers

Cooling tower is a type of an induced draft counter flow tower. It consists of four fans. The

steam in the condenser is cooled by the cooling water that comes from the cooling tower. The

water in the condenser is a closed system. There are three type of chemicals are added to the

cooling water and one of the chemicals is used to prevent scaling in the water tubes in the

cooling towers. Weedicide is added to the cooling water to prevent planting in the reservoir

and Br2 is used as an anti-bacterial agent. This cooling water cools the lube oil that circulates

in the steam turbines. Lube oil cooling system is a closed cycle system. The water that cools

lube oil is cooled by the cooling tower water in a separate heat exchanger system. The

cooling water is also used to generator cooling.

2.2.6 Air inlet equipment of gas turbine

2.2.6.1 Inlet system

The turbine air inlet system is the means of receiving, filtering and directing the ambient air

flow into the inlet of the compressor. The system consists of an inlet filter house, ducting

silencing, elbows and inlet plenum.

2.2.6.2 Inlet air filter house

The inlet air filter house contains the filtration equipment and an access door for

maintenance. The filter equipment can be of different type with either;

A static multi-stage filter which includes a front separator (dust louvers or initial

separator), a pre-filter, a coaleacent filter and a final high efficiency fixed media filter.

The assembly depends on environment, temperature and weather conditions.

A self cleaning filter, utilizing cylindrical filter cartridges sequentially cleaned by

reverse flow pulses of 7 bar compressed air. This pulsing air skid is used to clean the

filters. In this system clean air is sent to filters as pulse, duration of 0.1 s and with a

break of 8 s. Then the blower will remove the dirt out. Annex.2 shows the operation

of the pulsing air skid and the pressure loss curve over time on a Self-Cleaning Filter.

P a g e | 43

Rain hoods (weather louvers)

2.2.6.3 The silencer buffers

The silencers are of baffle-type construction to assist in attenuating the high frequency tones

from the compressor. Elbows and transition sections are acoustically lined to aid in sound

reduction.

2.2.6.4 Inlet plenum

The inlet plenum is a lined sheet metal box type structure that is mounted on the turbine base

and encloses the compressor inlet casing. It is open at the top where is connects to the inlet

ducting and is mounted and welded to the turbine base I-beam.

2.2.7 Liquid fuel system (both naphtha and Diesel) of gas turbine

We observed GT liquid fuel system including naphtha/Diesel storage tanks, forwarding skid,

filtering skid, super lubricant skid, main fuel pump, stop valve, governor valve and the flow

divider. In Kelanitissa Combined Cycle Power Station, there are two double wall naphtha

tanks which have a capacity of 5000 m3. The figure 2.38 shows the overall path of the GT

liquid fuel system. Liquid naphtha is extremely flammable and highly vaporizable. Therefore

the naphtha storage tanks were designed to sustain this vaporization and explosive properties

of naphtha fuel.

The forwarding skid is used to supply naphtha and Diesel near to the gas turbine plant. There

are two impeller pumps (centrifugal pumps), duplex filters and valves in the forwarding skid.

The special design in naphtha centrifugal pump is having a powerful permanent magnetic

coupling between the pump and the motor. The reason of this is to prevent sparking effect.

The filtering skid is used to remove any foreign particles left in the fuel lines after

installation. There are two filtering skids to both naphtha and Diesel fuel. There are a regulate

valve and an accumulator in both filtering skids. An accumulator acts as fluid reservoir. It

helps to avoid the use of a quantity of fluid may be required at short notice. Low pressure fuel

strainer prevents contaminants from entering the fuel oil stop valve and the fuel feed pump

(main fuel pump or warrant pump). After there is a 3 way valve and then super lubricant is

injected to reduce the viscosity of the naphtha fuel using the super lubricant skid. The fuel oil

stop valve is an emergency valve operated from the protection system used to shut-off the

supply of the fuel oil to the turbine during normal or emergency shutdowns. The main fuel

pump is the positive displacement screw type pump which is used to compress the fuel oil

P a g e | 44

around 37 or 38 bar. The governor by-pass valve assembly is used to control the high

pressure fuel flow from the pump. The by-pass valve is connected between the inlet and the

discharge sides of the main fuel pump and meters the flow of fuel to the turbine by

subtracting excess fuel delivered by the fuel pump by passing it back to the fuel pump inlet.

After the fuel flow is entered to the high pressure fuel filter or fuel strainer and it flows from

the fuel pump to the flow divider. The flow divider equally distributes inlet fuel flow to the

14 combustion nozzles. The important factor is to be mentioned that the machine starting and

stopping operations are done using Diesel fuel.

Figure 2.36 Overall path of the GT liquid fuel system

2.2.8 Water treatment plant

Kelanitissa Combined Cycle Power Station (KCCPS) can be operated in an open cycle mode

or a combined cycle mode. When the plant is operated in a combined cycle mode, the steam

is generated using the exhaust gases (temperature is around 560 ) produced by the gas

turbine and the steam is condensed using a box type two pass condenser after it passed

through the LP steam turbine. The demineralized water is used as the generating steam and

the condenser cooling liquid. The KCCPS takes make-up water from a Kelani river. Initially

it comes through coarse bar screen. Then it passes through travelling screen which keeps

unnecessary particles further. Water flow rate is 450 m3/h. Then the water is pumped through

raw water pumps. They are engine driven and motor driven. Pump which is driven by Diesel

engine is used for fire water. Also there are jockey pumps which also known as pressure

maintenance pump. This exerts with a fire pump. This is designed to maintain an elevated

pressure when the system is not in use.

P a g e | 45

The water treatment plant is used to make demineralized water for steam generation and

fulfill the water requirement of the plant. This system is used to filter in four categories at its

stages. Water treatment is the process of removing micro-organism, suspended solids,

dissolve impurities and organic materials. First Sodium Hypo Chloride (NaOCl) is added into

the river water pipe line to remove the micro-organisms. After then coagulation, flocculation

and sedimentation of suspended solids are done in a clarifier. Coagulant (Al2(SO4)3) and

NaOH are added to the river water to coagulate small solid particles of silts and Al(OH)3

precipitate which have a little positive charge. Flocculation is done by adding synthetic

organic polymer (coagulant aid) to the clarifier. Flocculation refers to water treatment

processes that combined or coagulate small particles into large particles because the polymer

is a negative charged. Water is retained for a sufficient period of time to allow the flow to

settle at the bottom of the clarifier. After the clariflocculation process, sludge is being

discharged. The figure 2.39 shows the clarifier in the KCCPS. Purpose of clarifier is to

reduce the turbidity. Turbidity is the parameter of measuring the amount of solid particles in a

solution. Unit of turbidity is ppm or NTU (Nephelometric Turbidity Units). Turbidity of

clarified water should be less than 5 NTU. After the water enters the clarified water tank and

then it passes through the vertical type pressure filter with gland and sand. Filtration is the

process of removing of non-settle able flocks remaining after chemical coagulation and

flocculation through a granular media. Turbidity of filtered water should be less than 2 NTU.

Filtered water is sent to the filtered water tank and then passed through the multimedia filter.

Water comes out from that filter has a turbidity less than 1 NTU. In order to remove those

dissolved impurities, water is sent through the reverse osmosis membrane. Reverse osmosis is

used to reduce the conductivity in water and this results in the separation of water and ions.

The reverse osmosis layer is a semi-permeable layer and it helps to reduce the conductivity

less than 100 µS/cm. After the water enters to the buffer tank and then it enters to the mixed

bed polisher which is the ions exchanging filter made of cationic and anionic resins, to

produce demineralized water. The conductivity of the demineralized water should be less

than 0.1µS/cm. H2SO4 and NaOH are used to regenerate the resins. The demineralized water

is stored in 9,000 m3 capacity storage tank.

P a g e | 46

Figure 2.37 Clarifier in water treatment plant

2.2.9 Chilled water central air conditioning system

Chilled water central air conditioning systems are commonly used in applications that need

large cooling capacity such as industrial process, commercial air conditioning such as offices

and factories. This chilled water air conditioning system is very cost effective method and no

hazard of having refrigerant pipes all over the building. In KCCPS both chilled water and air

are separately used as a cooling medium in a central air conditioning system. Chilled water is

used to produce the cooling effect needed to reduce the interior temperature of rooms and

offices. The refrigerating machine is the chiller or evaporator. Water is supplied to the chiller

and then the liquid refrigerant (R407C) absorbs heat from the water. Then a temperature of

the water is reduced around 9 . This chilled water then flows to the coils in the fan coil unit

(heat exchanger). Pumps are used to move the water between the chiller and the air handling

equipment. After the water is heated by the room air that that is pulled over the chiller

(evaporator). This process is repeated. The water is absorbed heat as it is exposed to the room

air being drawn into the unit by blowers. After the cooled air is supplied to the air

conditioned spaces. Evaporated refrigerant is condensed using a condenser. Water is used as

a condensing liquid and cooling tower is used to reduce the temperature of that condensing

water. The compressor is used to compress the refrigerant vapour and pumped the refrigerant

through the condenser which is removed heat from the refrigerant vapour and condensed it to

the liquid. The thermostatic expansion valve is used to reduce the pressure of the liquid

refrigerant.

P a g e | 47

Figure 2.38 A chilled water central air conditioning system

2.2.10 Making a Bill of Quantity (BOQ) for double wall naphtha tanks.

Mr.A.P.K.Muthunayake who is the mechanical engineer of gas turbine at Kelanitissa

Combined Cycle Power Station, gave us individual projects to gain extra knowledge during

the in-plant training and he gave me to carry out a BOQ (Bill of Quantity) for double wall

naphtha tanks 1 & 2. These storage tanks should be held schedule maintenance.

The Bill of Quantity is that a tender document produced by a Designer at the design stage

which translates relevant information on construction drawings into bill of quantities (BOQ)

that fully describes the quality and quantities of work to be carried out by a Contractor or

Principal Contractor during the construction stage. It is basically a list of work items with

brief detailed descriptions and firm quantities for different elements of work to be carried out.

First I examined the production drawings of the double wall naphtha tank 1&2 and their

design specifications and studied the maintenance procedure, surface preparation method, the

recommended electrodes for welding purposes and the recommended anti-corrosive paints

using the ISO/EN 12944 standard. After I listed down all the work items to be carried out

with the brief detailed description and calculated the quantities for different element work

such as the outer surface area, surface area of the spiral stairway, Walkway and platform on

roof etc. A full report is shown in the annex.3.

P a g e | 48

2.3 Sapugaskanda Power Station

2.3.1 Observations and work carried out during the training at SPS

According to my training schedule Sapugaskanda power station was my third training place

under DGM- Thermal complex in CEB. We reported to the chief engineer of Sapugaskanda

Power Station and he scheduled our five weeks training period in station A & station B. First

week we trained under the supervision of shift charged engineers and obtained the basic

introduction of the power plant and the process of electricity power generation as well as the

Diesel engines and their auxiliary systems in station A and B. After we were assigned to the

mechanical engineer (station A) of the power station, Mr. Aruna Salwathur and trained under

the supervision of the mechanical engineer and got an idea about v-type high duty marine

Diesel engines and the working principles of the turbocharger and the intercooler. After we

observed and examined the auxiliary systems attached to the engine and also examined the

cylinder head configuration, the piston rings arrangement and the cylinder liner and its

lubrication and cooling system. Finally we were assigned to mechanical engineers of section

B of the power station Mr. Mani Albert and Mr. Thilina Hettiarachchi. They welcome us

warmly and explained the system that we should have to study and maintenance. In here, we

got a great opportunity to observe the major overhaul of station B inline Diesel engine. Then

we got an idea about the high duty marine in-line Diesel engines and also understood about

the HP compressors, heat exchangers, the different type of pumps, filters, boilers, cooling

towers etc. Also we examined the different types of bearings used in Diesel engines and their

lubrication system.

2.3.2 Station A

In station A, there are four v-type high duty marine Diesel engines and each engine has an

installed capacity of 20 MW. Therefore the installed capacity and the current running

capacity of station A are 80 MW (4 20 MW) and 66 MW (3 . Each

Diesel engine has 18 cylinders and two turbochargers. In this engine, loading is done at a rate

of 1 MW per 3 minutes. The starting and the stopping are done using Diesel fuel like as the

gas turbine and the Heavy fuel oil is used to get the peak load value. De-loading is done at a

rate of1 MW per 1.5 minutes. Each has a generator with 14 poles and a rated voltage of 11

kV.

2.3.2.1 Specification of the engine in station A

P a g e | 49

Table 2.1 Specification of the Diesel engine in station A

Description Station A

Installed capacity (MW) 4

Current running capacity (MW) 3

Engine manufacturer Pielstick

Engine type PC4-2 18V

Number of cylinders 18

Number of stroke Four

Piston configuration V-type

Cylinder bore diameter (mm) 570 mm

Stroke length (cm) 620 mm

Rated speed (rpm) 428 rpm

Compression ratio 11.79:1

Number of turbochargers and manufacturer Two / Brown, Boveri & Company Ltd.

Plant efficiency

D/F 26%

H/F 40%

Fuel consumption (l/kWh) D/F 0.26

H/F 0.24

Fuel consumption at current running load

(m3/h)

D/F 4.072

H/F 3.916

Approx. Unit cost (Rs./kWh) 24.00

Auxiliary consumption (%) 3.5%

2.3.2.2 Designation of the cylinders

There is a special designation type of the cylinder numbering, in the case of V-type engines

by a combination of a capital letters and a number, the left hand cylinder bank by the letter A

and the right hand bank by the letter B, when looking on the coupling end (A1-A2-A3 or B1-

B2-B3 etc).

The firing sequence of the V-type Diesel engine is A1B1 A2B2 A4B4 A6B6 A8B8 A9B9

A7B7 A5B5 A3B3.

P a g e | 50

2.3.2.3 Turbocharger

Turbocharger is called a force induction system and it is used to increase the specific power

for a given size. Power output can be increased by having larger bore diameter and stroke

length. But in this case large space is required to have an engine with higher power output.

Therefore the specific power can be increased with less space using turbo chargers. Speed of

the turbo charger in section A is 12500 rpm. The turbocharger consists of two parts such as

the turbine section and the compression section. The turbine consists of the turbine wheel and

the turbine housing. It is the job of the turbine housing to guide the exhaust gas into the

turbine wheel. The energy from the exhaust gas turns the turbine wheel and the gas then exits

the turbine housing through an exhaust outlet area. The compressor also consists of two parts

such as the compressor wheel and the compressor housing. The compressor’s mode of action

is opposite that of the turbine. The compressor wheel is attached to the turbine using a forged

steel shaft and as the turbine turns the compressor wheel, the high-velocity spinning draws in

air and compresses it. The compressor housing then converts the high-velocity, low-pressure

air stream into a high-pressure, low-velocity air stream through a process called diffusion.

Turbocharger increase the air intake pressure to 2.5 bar and then the air temperature is

increased because of the compression process. The intercooler is utilized to decrease the

temperature of the intake air from 280 and it helps to increase the air density of the

intake air flow. The turbine driven forced induction device increases an engine efficiency

power by forcing extra air into the combustion chamber.

Figure 2.39 Turbocharger and intercooler in station A Diesel engine

P a g e | 51

2.3.2.4 Cylinder head arrangement in station A Diesel engine

When we considering the cylinder head of a Diesel engine in station A, cylinder head is

situated above the cylinder linear on the top of the cylinder block. It closes in the top of the

cylinder liner forming the combustion chamber. Basically the cylinder head is acting as a host

to several important used in heavy duty marine Diesel engines. It consists of starting air

valve, inlet and exhaust air valves, fuel injector hole, cooling water ports and lubrication oil

drain ports. There are two intake air valves and two exhaust air valves in cylinder head. The

exhaust valves are in valve cages in the engines of plant A and inlet valves are in valve

guides. The valve cages are repaired in an overhaul to proper seal with valve seat. The valves

cages are used because the valves are exposed to high temperature continuously. If there are

no cages in the cylinder head, the head has to expose to the hot temperature directly. As the

result the cylinder head can damage quickly. So having the valve cage in an exhaust side is

more important than in an inlet air side. There are cooling water lines to cool the valve cage

and the cylinder head. Both inlet valves and the exhaust valves are rotating when the Diesel

engine is started. The reason of the rotation is to prevent valve seating damagers. The NDT

test is carried out to check the valve seat damagers. The figure 2.42 shows the valve cage

used in station A and the Figure 2.43 shows the cracks occurred on the valve seat which is a

part of a valve gauge.

Figure 2.40 Exhaust valve cage (station A)

Figure 2.41 Cracks on the valve seat

There are two springs in a valve cage assembly. These springs bring the valve to the closed

position after the valves are opened and also they give a rotation for the valve during the

compression and the expansion and there is a rotor cap in a valve cage assembly. It helps to

rotate the intake and exhaust valves to prevent valve seating damagers. The center of the

P a g e | 52

cylinder head there is a fuel injector nozzle which is used to inject the fuel to the combustion

chamber and nozzle cooling water lines are also situated in a cylinder head. The starting air

valve is held near to the injector nozzle and the 30 bar stating air supply through the cylinder

head to rotate the crank during the engine start-up. When the crank speed is around 90 rpm,

starting air supply must be stopped. The plugged valve is used in an emergency situation. The

clog valve is used to measure the peak mean pressure inside the cylinder. Reasons for gain

low peak mean pressure are the damages of the inlet/exhaust valves and wear/ damage of the

piston rings.

Figure 2.42 Cylinder head configuration in station A Diesel engines

Figure 2.43 Cylinder head assembly

P a g e | 53

Figure 2.44 Inside of the rotor cap

2.3.2.5 Piston heads and the cylinder liners in station A (Diesel engines)

The piston head consists of two parts as such as the crown and the skirt and the crown and the

skirt are made of different materials. The crown is the top part of the piston and it is made of

heat resisting steel forging which may be alloyed with chromium, molybdenum and nickel to

maintain strength at high temperatures and resist corrosion (hot corrosion). The skirt of the

piston is made to reduce the weight and the inertia. The gudgeon pin of the connecting rod

small end bearing is located in the piston skirt. The piston rings are located both the crown

and the skirt and there are 5 piston rings used in V-type Pielstick Diesel engines. They are a

top ring, three compressor rings and the final is the oil scraper ring which is used to scrape

the excess lubrication oil on the inner surface of the cylinder liner. The piston rings kit for

Pielstick engine PC4-2 is shown in an Annex. 4. The piston is oil cooled. This is achieved by

various means; the simplest is for a jet of oil to be directed upwards from a hole in the top of

the con rod onto the underside of the crown. This process is used the Diesel engines in station

A at Sapugaskanda Power Station.

The cylinder liner is cast separately from the main cylinder frame. There are several reasons

for that. They are,

The cylinder liners should be manufactured using a super material to the cylinder

block. While the cylinder block is made from a grey cast iron, the liner is

manufactured from a nodular cast iron alloyed with chromium, vanadium and

molybdenum. This alloy elements help to increase the wear resistance as well as the

corrosion (hot corrosion) resistance at elevated temperatures.

The cylinder liner will wear with use, and therefore may have to be replaced.

At a working temperature the cylinder liner is a much hotter than the cylinder block.

Then the liner will expand more and is free to expand diametrically and lengthwise. If

P a g e | 54

they were cast as one piece, then unacceptable thermal stresses would be set up,

causing fracture of the material.

The cylinder liners employ bore cooling at the top of the liner where the pressure stress is

high and therefore the liner wall thickness has to be increased. This brings the cooling water

close to the liner surface to keep the liner wall temperature within acceptable limits. The

figure 2.47 shows the cylinder liner of the Pielstick Diesel engines in station A.

Figure 2.45 Cylinder liner of the PIELSTICK Diesel engine in station A

2.3.2.6 Connecting rod

The connecting rod consists of two bearings. They are a big end bearing and a small end

bearing. The big end bearing is connected to the crank shaft and the small end bearing is

connected to the gudgeon pin. The big end bearing can be separated into two parts and the

lubrication oil flows through the connecting rod to lubricate the inside area of the cylinder

liner. Because of the large diameter of the crankpin to increase bearing area and decrease

bearing load, the width of the bottom end of the connecting rod is greater than the diameter of

the cylinder liner.

Big end bearing temperature:

Normal value- 75

Alarm value- 85

Tripping value- 90

P a g e | 55

Figure 2.46 Connecting rod of The PIELSTICK Diesel engine

2.3.2.7 Crank case pressure

Crank case pressure is occurred because of the damages of the piston rings. The normal crank

case pressure is around 0.3 mbar. Alarm value of the crank case pressure is 3 mbar and the

tripping value is around 5 mbar.

2.3.2.8 Schedule maintenance of PIELSTICK Diesel engines in station A

Maintenance in section A is done at 3000, 6000, 12000, 24000 running hours. In major

overhaul which is done at 24000 hours, main bearing, big end bearings and fuel pumps are

replaced. Auxiliary systems are maintained under planned maintenance

2.3.3 Station B

There are 8 heavy duty marine Diesel engines in station B at Sapugaskanda Power Station.

The engine type is 8L 58/54 and these engines are inline Diesel engines. The total installed

capacity of each Diesel engine is 10 MW and the current running capacity of station B is

9 . Engine manufacturer of these inline Diesel engines is MAN B&W. In this engine,

loading is done at a rate of 1 MW per 1:5 minutes. De-loading is done at a rate of 1 MW per

1 minute. Each has a generator with 14 poles and a rated voltage of 11 kV. This inline Diesel

engine has one turbocharger and one intercooler.

2.3.3.1 Specifications of the Diesel engine in station B

P a g e | 56

Table 2.2 Specification of the Diesel engine in station B

Description Station A

Installed capacity (MW) 8

Current running capacity (MW) 8

Engine manufacturer MAN B&W

Engine type 8L 58/64

Number of cylinders 8

Number of stroke Four

Piston configuration Inline

Cylinder bore diameter (mm) 580 mm

Stroke length (cm) 640mm

Rated speed (rpm) 428 rpm

Compression ratio 13.2:1

Number of turbochargers and manufacturer MAN B&W

Plant efficiency

D/F 38%

H/F 44%

Fuel consumption (l/kWh) D/F 0.23

H/F 0.21

Fuel consumption at current running load

(m3/h)

D/F 2.16

H/F 2.16

Approx. Unit cost (Rs./kWh) 21

Auxiliary consumption (%) 4%

Sludge disposal Burn by incinerator

Ave. Lubrication oil consumption per hour

per engine (l/hr)

8.5 l/hr

2.3.3.2 Designation of the cylinders

The individual cylinders are designated by numbers (numbering consecutively 1, 2, 3, etc),

when looking on the coupling end.

The firing sequence of the in-line four stroke Diesel engines is 1-4-7-6-8-5-2-3-1

P a g e | 57

2.3.3.3 Definition of Left Hand and Right Hand engine

For the definition of “Left-hand engine” and “Right-hand engine”, the locating of the exhaust

side of the engine is the deciding factor. The engine will be known as the Left-hand engine

when the exhaust manifold is mounted on the left side or as the Right-hand engine when it is

mounted on the right hand side when looking on the coupling end. This differentiation is

normally applicable to single bank engines only.

2.3.3.4 Crankshaft of MAN B&W Diesel engines in station B

The Crankshaft for a medium speed 4 stroke Diesel engine is made from a one piece forging.

The figure 2.49 shows the crankshaft arrangement of MAN B&W Diesel engine in station B.

The ten main bearings are supported to the crankshaft and there are 8 crank pins consist of

the crankshaft. The crankshaft is forged and equipped with counterweights on the crank webs

for good mass equilibrium. The driving gearwheel for the timing gear is attached to the

crankshaft between the first two bearing points on coupling end.

Figure 2.47 Crankshaft of the MAN B&W Diesel engine in station B

2.3.3.5 Cylinder head arrangement

The cylinder head arrangement of MAN B&W Diesel engine is the same as the Pielstick

Diesel engine. The individual cylinder heads of gray cast iron are secured to the crankcase

and cylinder block by 8 bolts and nuts each. Mounted in a cylinder head are two each inlet

and exhaust valves, one each starting valve and fuel injection valve and an emergency valve.

The indicator valve is fitted on the outside on the cylinder head.

P a g e | 58

Figure 2.48 Cylinder head arrangement of the MAN B&W Diesel engine

2.3.3.6 Valve cages used in the MAN B&W Diesel engine

Mainly there were used to aligned and positioned valve cones in side of the cylinder heads.

The exhaust valve cage made into a single part as it should withstand to high temperature and

high pressure developed inside the exhaust side of the cylinder head. At the inlet valve cage

there is a valve seat part.

2.3.3.7 Schedule maintenance of the MAN B&W Diesel engine in station B

Maintenance of the MAN B&W Diesel engines are done at 1500, 3000, 6000, 12000, 24000

and 36000 Rhr. The Annex.5 is shown the check list for overhauls.

2.3.4 Auxiliary systems

Both plants consist of several auxiliary systems such as;

Fuel oil system

Lubrication oil system

Hot water system

Engine cooling water system

Charge air cooling water system

2.3.4.1 Fuel oil system

The Diesel engines both section A and section B are used both the Diesel and heavy fuel oil.

The fuel is supplied from the petroleum refinery near by the plant. Diesel oil is used only to

startup and shut down processes. After synchronizing to the system, the load is greater than

or equal to 25 % of rated power output and engine cooling water temperature is greater than

P a g e | 59

or equal to 70 °C the heavy fuel supply is opened gradually. The Diesel is not subjected to

any special purification system other than the filters.

The heavy fuel oil from Sapugaskanda Oil Refinery is pumped to the HFO storage tanks A

and B which have 1500 m3 capacity in station A and after it is sent to the service tank (E)

(capacity-150 m3) through the suction duplex filter. After then HFO is sent to the fuel

treatment house. The purification and clarification is done in the FOTP and then the treated

HFO is sent to the treatment fuel tanks F &G. The heaters are used to decrease the viscosity

of the HFO. The treated fuel is sent to the fuel module by ring main pumps. There are a

Diesel storage tank (c) and the Diesel service tank (D). Both Diesel and HFO are sent to the

mixing tank. There is a three way valve to supply either Diesel or HFO to the mixing tank.

Finally HFO is sent to the engine through the viscosity controller, course duplex filter and the

fine duplex filter.

Fuel oil system of station B is same as used in the station A. But I observed some different

factors comparing the both fuel systems. The HFO storage tanks P & Q stored and are sent to

the settling tanks R & S. After it is sent through the duplex filters to the Separator house. The

clarifying process is done by six separators and sent to the treated oil tank T. There are hot

water distribution lines (water temperature is around 160 inside the bottom of the storage

tanks. They are used to increase the temperature of the treated HFO around 60 . After the

HFO is pumped through a heater, a simplex filter and an auto filter to the fuel module. The

booster pumps are used to supply the fuel from the mixing tank to the engine through the

duplex filters.

2.3.4.2 Lubrication oil system

The lubrication oil system is one of the major auxiliary systems attached to the engine. There

are many types of equipment used for the lubrication oil system. There are two lubrication oil

systems for each station and these lubrication systems are quit same. But the two systems

have different equipments such as the filters etc. The lubrication oil system consists of two

lubrication storage tanks, Lubrication oil pumps (gear pumps), a lubrication oil separator,

lubrication oil sump tank and the used lubrication tank in both stations A &B. Lubrication is

an integrated engine component. The primary purpose of lubrication is to keep a clean layer

of lubrication oil film between the contacting areas of the running parts in order to prevent

friction, heat and the metal to metal wear (abrasive wear). The second purposes of the

lubrication system are described as follows;

P a g e | 60

Cooling- In passing through the engine, part of the heat is absorbed by the

circulating oil. Therefore it is made to pass through the cooler before being re-

circulated.

Neutralization of acid products of combustion (sulfuric acid).

Cleaning-Washing away of wear particles due to surface friction.

Preventing from corrosion

Lubrication oil for an engine is stored in the bottom of the crank case, knows as the lub oil

sump tank. The oil is drawn from this tank through the lub oil cooler and the moti filters and

entered to the engine in station A. But in station B, auto filters and the duplex filters are used

to do the filtering process.

P a g e | 61

3 CONCLUSION

As I described in above chapters, I have trained in three power generation plant under the

CEB as it is considered the largest power generation organization in Sri Lanka. I and my

friends started our training session from Kelanitissa Power Station in Wellampitiya. Actually

having training from a power plant like this is a rare and valuable chance. It was a great

challenge to me to adapt industrial environment. As an Engineering Undergraduate Trainee, it

is indeed a wonderful and successful period of my career. During this bunch of time I met

different types of people, learnt loads of things in a diversified manner, get exposure to the

industry. The mechanical engineer (Fr-V gas turbine) and the mechanical engineer (GT7 gas

turbine) always guided us to complete our in-plant training period in KPS successfully.

During this period there was no considerable maintenance or major overhaul. So, it is very

hard to see the components of gas turbines. I observed system and components from the

outside of it. During this period we learnt lots of practical knowledge about the open cycle

gas turbines and their operating sequences. But we had learnt only the theoretical knowledge

about the gas turbines in university. So, the in-plant training is the most suitable session to

gain the practical understanding about the thermal power generation. When we trained under

the supervision of the mechanical engineers, they gave us some presentations about the daily

load pattern in Sri Lanka and the brief introduction of the open cycle and the combined cycle

power plants. The major drawback in KPS session is no proper schedule to the engineering

undergraduate apprentices to gain the knowledge successfully.

We were assigned to the Kelanitissa Combined Cycle Power Station as the second power

plant in CEB. I had the chance of learning how to apply the theoretical knowledge I learned

at faculty to practical situations and undeniably I have gone through plenty of lessons which I

haven’t ever heard. It is good opportunity to see the theoretical knowledge and some concepts

are in practical situation. In KCCPS we were appointed in several places to grant us to have

an overall process of the combined cycle power plant. The mechanical engineers of gas

turbine, steam turbine and BOP were always guided us to gain the knowledge about the gas

turbine, HRSG, steam turbine as well as the water treatment plant. But there was not a

considerable maintenance or major overhaul during this in-plant training session. It was a

disadvantage to gain a practical knowledge about the maintenance of the gas turbine section

as well as the steam turbine section. All the engineers and other people who we met in CEB

spent their time as much as they can with their busy schedules. I must thankful to

Mr.A.P.K.Muthunayake (mechanical engineer-gas turbine) for giving us a proper training

P a g e | 62

schedule and the individual project about making a BOQ for Double Wall Naphtha Tanks.

Because of this I could gain a good knowledge about a construction of the double wall

naphtha tanks. There are some subjects I did not learn before in the university. So, I feel it is

better to have theoretical knowledge before like air conditioning and chiller systems as well

as the air filtration system, to study in depth. But, now I am happy in my final year because

these subjects are easy to understand with applications. The major disadvantage was to gain a

lack of knowledge about the automation part and the pneumatic system of the power plant. I

think the special training schedule must be conducted to gain the practical knowledge about

the automation part and the pneumatic system of the power plant.

We were assigned to the Sapugaskanda Power Station as our third power plant in CEB. We

had an extremely great chance to participated a major engine overhaul of both V-type and

inline engines. Also I learned how to deal with the engineers, superintendents and the people

in low level (fitters/welders). I have fueled that the knowledge of the marine high duty Diesel

engines and auxiliary systems attached to the Diesel engine and hence I decided to pay my

attention to those areas in future more than before. The major drawback was a time limitation

to spend each station hence we had not gained the high level of knowledge about the

maintenance procedure of the Diesel engine. All the engineers and other people who we met

in SPS spent their time as much as they can with their busy schedules. But they shared their

experiences and knowledge about the plant. I specially thanks to Mr. Thilina Hettiarachchi to

spend their valuable time for us as our friend.

This training program was helped me to improve my technical, non-technical and soft skill. It

gave me a good exposure to the industry both in technology-wise and handling people-wise.

Therefore this overall training program was a great opportunity for me to apply the

theoretical knowledge we gathered from university into practice. And hence it was a great

experience to me which I have never had before. When we are considering the overall in-

plant training in CEB, the major disadvantage for the mechanical undergraduates is the lack

of knowledge about the hydro power stations. There must be a proper training schedule for

mechanical undergraduates to train in thermal power plants as well as hydro power plants.

As a conclusion the overall training session which is organized by University of Moratuwa

and National Apprentice and Industrial Training Authority (NAITA) is very successful and

we could gather a plenty of experience during this small time period. I think that I could gain

the maximum benefits out of it.

P a g e | xi

ABBRIVIATIONS

CEB Ceylon Electricity Board

GM General Manager

AGM Assistance General Manager

DGM Deputy General Manager

CE Chief Engineer

TC Thermal Complex

KPS Kelanitissa Power Station

KCCPS Kelanitissa Combined Cycle Power Station

SPS Sapugaskanda Power Station

LVPS Lakvijaya Power Station

UJPS Uthuru Janani Power Station

SOE Senior Operational Engineer

SCE Shift Charge Engineer

ME Mechanical Engineer

EE Electrical Engineer

MS Mechanical Superintend

ES Electrical Superintend

GT Gas Turbine

HRSG Heat Recovery Steam Generator

ST Steam Turbine

BOP Balance of Plant

IGV Inlet Guide Vane

MI Major Inspection

EQH Equal Hours

FOD Foreign Object Damage

DOD Domestic Object Damage

P a g e | xii

FOTP Fuel Oil Treatment Plant

LP Low Pressure

HP High Pressure

NTU Nephelometric Turbidity Unit

NDT Non Destructive Test

BOQ Bill of Quantity

P a g e | xiii

ANNEXES

Annex.1 The temperature and pressure variation on the HRSG

P a g e | xv

Annex.2 Schematic diagram of the operation of the pulsing air skid

P a g e | xv

No. Item Description Unite of

measureme

nt

Quantity

of work

Rate Total

amount

Price schedule for double wall naphtha tank 1

1 Inspect the outer shell plates for corrosion

and deformation

2 Inspect the outer shell plates circumferential

and longitudinal welding joints for corrosion

and cracking

3 Replace the rust on the corroded areas on

outer shell of naphtha tank

square

meter

1206.37

4 Inspect the cracks and the damaged plates

5 Replace/ repair the damaged outer shell

plates

6 Weld 25 cm LG cracks appearing on the

outer shell plates

7 Inspect the roof plate and central drum (total

weight 4000kg) for corrosion/ deformation.

(All dimensions are taken using the roof plate

and central drum drawings and directly go

through the specifications to get the reference

drawing no :)

square

meter

327

8 Repair/replace the damaged roof plates and

central drum structure

square

meter

327

9 Inspect the floating roof plate for corrosion

and deformation

square

meter

210

10 Examine the welding joints of floating roof

plate(aluminum plate) for corrosion and

cracking

11 Examine the sealing system (rubber seal/

sealing plates) of floating roof plate

12 Remove the rust on the floating roof and the

welding joints

square

meter

210

13 Weld 25cm LG cracks appearing on the

floating roof and the welding joints of the

floating roof

14 Remove the rust on the spiral stairway (total

weight is around 1758.194kg) for double

wall naphtha tank (spiral stairway has 73

steps and four landings. They are lower mid

landing, mid landing, upper mid landing and

finally top landing)

square

meter

73.87

Annex.3 BOQ for double wall naphtha tank 1 & 2

PRICE SCHEDULE

P a g e | xvi

15 Remove the rust on the outer shell manholes.

(Total weight per set is 505.6kg) (There are

two sets of outer shell manholes and they

both have same dimensions. Complete all as

described in the Specifications and as shown

on the Drawings and as directed by the

Engineer.)

square

centimeter

1871.796

16 Remove the rust on the roof manholes. (total

weight per set is 149.85kg) (There are two

sets of roof manholes M5 /M6 and they both

have same dimensions. Complete all as

described in the Specifications and as shown

on the Drawings and as directed by the

Engineer.)

square

centimeter

1831.898

17 Inspect the wind girder for double wall

naphtha tank for corrosion and deformation.

18 Remove the rust on the wind girder for

double wall naphtha tank. (Dimensions are

taken using drawing and directly go through

the specifications to fine the reference

drawing no :)

square

meter

22.9

19 Remove the rust on the walkway and

platform on roof for double wall naphtha

tank 1.

(All dimensions are taken using the drawings

of the walkway and the platform on roof and

directly go through the specifications to get

the reference drawing no:)

square

meter

65.765

20 Inspect the concrete foundation for cracking

and repair the 30 cm LG cracks.

21 Inspect the cathodic protection of the double

wall naphtha thank 1.

22 Apply primary coating (tough up coating) on

the outer shell, roof plate and central drum,

spiral stairway, outer shell manholes, roof

manholes (M5 & M6), walkway and platform

on roof.

square

meter

23 Apply secondary coating (tough up coating

and full coating) on the outer shell, roof plate

and central drum, spiral stairway, outer shell

manholes, roof manholes (M5 & M6),

walkway and platform on roof.

square

meter

1701.275 (for full coat)

24 Apply final coating (full coating) on the outer

shell, roof plate and central drum, spiral

stairway, outer shell manholes, roof

manholes (M5 & M6), walkway and platform

on roof.

square

meter

1701.275

P a g e | xvii

No. Item Description Unite of

measurement

Quantity of

work

Rate Total

amount

Price schedule for double wall naphtha tank 2

1 Inspect the outer shell plates for corrosion and

deformation

2 Inspect the outer shell plates circumferential and

longitudinal welding joints for corrosion and

cracking

3 Replace the rust on the corroded areas on outer

shell of naphtha tank

square meter 1206.37

4 Inspect the cracks and the damaged plates

5 Replace/ repair the damaged outer shell plates

6 Weld 25 cm LG cracks appearing on the outer

shell plates

7 Inspect the roof plate and central drum (total

weight 4000kg) for corrosion/ deformation.

(All dimensions are taken using the roof plate and

central drum drawings and directly go through the

specifications to get the reference drawing no :)

square meter 327

8 Repair/replace the damaged roof plates and central

drum structure

square meter 327

9 Inspect the floating roof plate for corrosion and

deformation

square meter 210

10 Examine the welding joints of floating roof

plate(aluminum plate) for corrosion and cracking

11 Examine the sealing system (rubber seal/ sealing

plates) of floating roof plate

12 Remove the rust on the floating roof and the

welding joints

square meter 210

13 Weld 25cm LG cracks appearing on the floating

roof and the welding joints of the floating roof

14 Remove the rust on the spiral stairway (total

weight is around 1758.194kg) for double wall

naphtha tank (spiral stairway has 73 steps and four

landings. They are lower mid landing, mid

landing, upper mid landing and finally top

landing)

square meter 73.87

15 Remove the rust on the outer shell manholes.

(Total weight per set is 505.6kg) (There are two

sets of outer shell manholes and they both have

same dimensions.Complete all as described in the

Specifications and as shown on the Drawings and

as directed by the Engineer.)

square

centimeter

1871.796

PRICE SCHEDULE

P a g e | xviii

SPECIFICATIONS

Specifications for the double wall naphtha tank 1 &2:-

Nominal diameter= 24000/20000mm

Nominal capacity= 4712

Nominal height= 16000mm

Design liquid level= 15000mm

Maxi: operating temperature= 40

16 Remove the rust on the roof manholes. (total

weight per set is 149.85kg) (There are two sets of

roof manholes M5 /M6 and they both have same

dimensions.Complete all as described in the

Specifications and as shown on the Drawings and

as directed by the Engineer.)

square

centimeter

1831.898

17 Inspect the wind girder for double wall naphtha

tank for corrosion and deformation.

18 Remove the rust on the wind girder for double

wall naphtha tank. (Dimensions are taken using

drawing and directly go through the specifications

to fine the reference drawing No.)

square meter 22.9

19 Remove the rust on the walkway and platform on

roof for double wall naphtha tank 2.

(All dimensions are taken using the drawings of

the walkway and the platform on roof and directly

go through the specifications to get the reference

drawing no :)

square meter 65.765

20 Inspect the concrete foundation for cracking and

repair the 30 cm LG cracks.

21 Inspect the cathodic protection of the double wall

naphtha thank 1.

22 Apply primary coating (tough up coating) on the

outer shell, roof plate and central drum, spiral

stairway, outer shell manholes, roof manholes (M5

& M6), walkway and platform on roof.

square meter

23 Apply secondary coating (tough up coating and

full coating) on the outer shell, roof plate and

central drum, spiral stairway, outer shell

manholes, roof manholes (M5 & M6), walkway

and platform on roof.

square meter 1701.275 (for full coat)

24 Apply final coating (full coating) on the outer

shell, roof plate and central drum, spiral stairway,

outer shell manholes, roof manholes (M5 & M6),

walkway and platform on roof.

square meter 1701.275

P a g e | xix

Material of construction= IS: 2062 Gr.t

Recommended electrodes:-

Following electrodes are recommended for Tank welding job

Low hydrogen electrodes shall be used for all manual metal arc welding of sell course

having a thickness of 12mm and above and for attachment of shell course to bottom

plates.

For all other welding types, rutile type electrodes as per AWS classification SFA 5.1

acceptable.

Recommended surface preparation:-

HP fresh water washing to be done to remove surface contamination/ chalking

Corroded spots are to be spot power tool cleaned to ISO St 3 standard (very thorough

power tool cleaning). Recommend using sand disc for power tool cleaning.

Coating cracks and top coat to be removed by using the sand disc.

Surface must be dry and free from any contamination prior to paint application.

Slow to be done to obtain specified Dry Film Thickness (DFT) when using brush /

roller.

Fresh water cleaning to be done prior to apply subsequent coatings.

Stripe coating to be gone on all the weld lines/ joints, brackets, nuts & bolts etc.

Recommended anti-corrosive paints:-

As per ISO 12944 C4 (Industrial and coastal)- C5M (Uncontrollable high industrial pollution/

Marine coastal and chemical water sprays from nearby cooling water plant) it is

recommended for minimum of 250 Microns-320 Microns DFT(Dry Film Thickness) of paint

system governed by internationally approved specification. If water film is created it can be

considered as ISO 12944 Im1-2 (Immersed).

Applied recommended coating system:-

For the outer shell of double wall naphtha tank 1 @2, roof plate and central drum, spiral

stairway, outer shell manholes, roof manholes (M5 @ M6), walkway and platform on roof.

P a g e | xx

1. Primary coating

* Tough up coating SigmaPrime 200 Yellow green (DFT- 75mic)

2. Secondary coating

* Tough up coating-SigmaShield 420 Green Dark (DFT - 100mic)

* Full coating-SigmaShield 420 Green Dark (DFT - 100mic)

3. Final coating

* Full coating- SigmaDur 188 white 7000 (DFT - 100mic)

Drawings details:-

* Outer shell- Drawing no:-KEL01MK11- -DD018

* Roof plate and central drum- Drawings no:-KEL01MK11- -SW001 & SW004

* Spiral stairway- Drawings no:-KEL01MK11- -DD014 & DD015

* Outer shell manholes- Drawings no:-KEL01MK11- -DD010 & DD011

* Roof manholes (M5@M6)- Drawings no:-KEL01MK11- -DD012 & DD013

* Walkway and platform on roof- Drawings no:-KEL01MK11- -DD016 & DD028

P a g e | xxi

Annex.4 The piston rings kit for PIELSTICK engine PC4-2

P a g e | xxii

Annex.5 Check list for overhauls in station B Diesel engines

i. 1500 Rhr check list

Replace all baffle screws

Cleaning of Duplex filters (fuel module)

Tappet clearance checking/ adjusting

ii. 3000 Rhr check list

Replace all baffle screws

Cleaning of Duplex filters (fuel module)

Servicing and pressurizing fuel injectors

Check/ adjust tapper clearance

iii. 6000 Rhr check list

Replace all baffle screws

Replace fuel injector nozzle and pressurizing

Tappet clearance checking/ adjusting

Remove all valve cages dismantling, regrinding and re installation

Inspection of no: 5 injector pump

Sample inspection of no: 5 main and big end bearings

Sample inspection cam bearings 0, 1, 2

Check oil, air, fuel filters

LOC servicing

Inspection of sample head and piston (head no: 5)

iv. 12000 Rhr check list

In addition to the 6000 Rhr inspection,

Servicing and inspection of all engine heads

All injector pumps servicing

Cylinder liner measuring and horning

Servicing the turbo charger

v. 24000 Rhr check list

In addition to the 12000 Rhr inspection,

Check vibration damper springs of the crank and the cam shaft

vi. 36000 Rhr check list

In addition to the 12000 Rhr inspection,

Changed all cam/ main/ big end bearings