Friday, October 3, 2014





In an effort to share my experience, I pulled out a few topics listed below  to get your feedback. My friends in the professions hopefully will take the pain in going  through the same and guide me in choosing a right path. Any review and valuable comments will help me in my learning process!  
1.0 OBJECTIVE                                                                                                                                                                                                                                                  
uch information is available at the stroke of computer key but one could not find in one book covering both         knowledge base as well as sharing the shop floor experience this book is solely written keeping in practical knowledge on Power Plant Engineering and Practices. Instrumentation & process control engineers practicing in the shop floor GLOBALLY will get the benefit of the various design aspect and data. It covers design, state of the art controls currently in practices at various parts of the world. With in depth discussions, one can develop control loop of one’s choice from the drawings given. On account of Author’s  working experience in India as well as in Europe, USA, and other countries, the book has been written to highlight GLOBAL practices which is very important in the perspective of globalization in the current era.  As far as possible Internationally practiced loop and methodologies have been discussed. Even the students in this discipline will immensely be benefitted from the book. This book unlike any hand book, starts with fundamental knowledge then slowly develops in to the practicing hand book with up to date relevant data It is expected that certainchapters would definitely help the Graduate students to accomplish their mission also, as it starts  from fundamentals and not empirical results. Engineers from other disciplines such as Chemical engineering, Mechanical engineering, Electrical engineering etc would find the same very handy. The top engineering managers would get the fundamentals in following up their day to day work.
The fundamental knowledge on the basic process is essential for any Control & Instrumentation ( henceforth referred to as C&I)  Engineer. Power Plant concepts are based on Laws of Thermodynamics depicting the relation amongst Heat, Work, Intensive and Extensive property of system, Specific Weight, Specific Volume, Path, Process, etc. Boyle’s Law & Charles Law with general and combined equations, Avogadro’s Law / Hypothesis, Universal Gas Constant, Enthalpy, Entropy, Rankin and other cycles are the natural topics related to thermal power plants along with Pressure – Volume and Temperature-Entropy Diagram for steam, different types Steam Generators or Boilers, Steam & Gas Turbines, Condensers and Regenerative cycles.
Steam generators and turbines require a condensing system (Condenser) maintained at vacuum to dump the steam from turbine after extracting work. Regenerative cycle, multistage turbines with single/double chambers are introduced to improve the efficiency. Condensate Extraction Pumps and Boiler Feed Pumps are necessary as the reversible cycle requirement.
For Gas Turbine, on the contrary, air/flue gas is utilized as working fluid and normally not recycled but discharged to atmosphere though exceptions do exist.
Requirement of vacuum in the condenser  in relation to  thermal efficiency  has been discussed but that every where same cannot be applied specially for combined Process cum power plants is also discussed . By the use of Pressure reducing and De superheating ( PRDS) in tandem with turbine extraction, the process steam can be supplied at various pressures .

1.0 MAIN EQUIPEMNT TYPES, FUNCTIONS AND ESCRIPTION                                                                                                                                                                                                                                           
like any other plant there are various types of main equipment  which are functionally unique. Again in the world there are several manufacturer having different design of the basic equipment with its own merits and demerits. As a consequence the control requirement of various types are different, naturally C&I engineer has to have acquaintance with such variations. Standard text books discuss about the normal reheat temperature control, with water, whereas in reality hardly much water is used to control Reheat steam temperature, instead these are controlled by tilting burners, or Bypass dampers-these are just example. In this chapter possible variation in type & functions of main equipment, such as TG, SG ,Heaters, etc have been discussed with description, so that reader will be able to fix the measuring point and /or control.
There are some fundamental variations in combustion type, burner configuration etc.  in the design of boilers from various manufacturers. Naturally all these necessitate different control system, and no of control loops. Again pulverization process in conventional boiler  is different for different design. In this book,  two main fundamental design from Babcock and CE design have been considered.  Depending on the design some use Bowl, some use Tube/ Ball mill obviously there will be different measuring and control points. Tube mills have more capacity so that even if the mill is tripped the boiler need not shade load. However this has some more complicated control. In order to enable C&I engineer to understand the variations, all these aspects have been covered in this book. Air flow measurement in FD fan is very critical , also C&I engineer must be able to suggest the suitability on the types of controls for the fans such as vane control, pitch control or Hydraulic scoop tube control or VFD, etc..  In Air flue gas various fundamentals about the Air heaters( Ljunstrom type/ Tubular type) have been discussed. While one has advantage of better heating but have more leakage,. Also Rotary type heats up air more hence flue gas cools more as a consequence there will be chance of corrosion , hence SCAPH need to be used Functionality of all these are discussed so that C&I engineer can assess why one measurement is essential. In pressure parts also, on account of heater configuration, burner types, the water circulation system etc. control system are  different, so a short discussion on the same has been done to enable the reader to recognize why there are different control systems are used even though  controlling parameter is the same. Also importance of MSCV, Safety valves- both mechanical and electrically operated, have been discussed to point out the protections.
3.0 TURBINE  : Type
Turbine cylinders  associated with stop valve, control valve and interceptor valves  have been discussed. Brief discussion of various  design types have been discussed. As this is a rotating system the Lub oil, Jacking oil system is very important. Almost all the turbine work on Electro hydraulic system so importance of control oil cannot be overestimated. In turbine, the measurements are very critical, as the gap of rotor & stator is very low, so turbovisory instrumentation, their use, location have been given due importance. Also functional aspect of EHG, Thermal stress evaluators have been discussed, in tandem with Automatic starting and running of the turbine. Different extraction steam at different operating conditions have tremendous impact on the heat rate as well as on heat cycle and so have been included. Bypass system, specially LP bypass is absolutely essential for turbine system, naturally the discussions could not be closed without having reference to these systems, which is very important to C&I engineer also. This part also covers seal steam pressure control system which is an important system.
Even though Generator is an electrical equipment from its control point of view since it has certain mechanical systems such as rotor H2 cooling and sealing, PW cooling of stator, there are some implication of these systems on C&I engineers, so these aspects have been covered along with Excitation system controls as it is also an electronic control.
5.0 BFP & CEP
After SG,TG the major main equipment in power station is BFP which are motor operated as well turbine operated. The speed control of the BFPs are responsible for the control of Boiler drum level. This along  with CEP has been discussed to understand the difficulties and importance of control of these pumps in power plant operations.

Deaerator and heaters are the backbones of the regenerative cycle. Deaerator has two fold functions, one it makes the condensate free from, dissolved O2 , as well as acts as a heater. At various turbine load the deaeration will be different so , it has both level as well as pressure control. All heaters level controls are important so as to have proper heat transfer. As the name suggests the terminal temperature difference is of high importance so that power cycle have better efficiency. Discussion on these will enable the reader to understand the whole system/cycle.
Apart from the main plant equipment there are  a number of off site plants like, CW  ACW  plant, Water treatment plant ( DM plant), Coal handling(CHP) & Ash Handling plant(AHP). All these are very important as these are like circulatory and excretory system in a human body. All of the plants in the current scenario, good amount of Instrumentation and controls are necessary. Almost all are PLC controlled, duly connected thru’ network with the main system. Switchyard and other electrical systems are also connected to the main system via PLC network. So C&I engineer need to have some basic idea about these plants. Again as there are many variation in design of these Plants so, generalized discussion, based Industrial system have been done.
CW system stands for Circulating Water which may be open circuit draining to the river nearby and or closed system, via, Cooling Tower. Whereas ACW stand s for closed Cooling system necessary for the main plant equipment. Pump / Valve selection, Start and stop etc are all controlled by PLC system.                                                                                              
Water treatment plant would encompasses Pre Treatment and Post treatment. While Pretreated water is supplied to many systems, but Post treated DM water is supplied to the main plant and ACW system. All these sequential operations are carried out by PLC.
 Main coal crushing, up to supply of coal at feeder floor of the main plant, is carried out in CHP. Various conveyors, stacker , reclaimers, crusher are controlled by a set of PLCs.
Ash handling system, comprising bottom ash, fly ash etc are also carried out by PLC. 


&ID is such a document which is developed at an early stage of systems design and is useful through out the life span of the plant. It is the fundamental document for Plant Hazard Analysis like HAZOP,FMEA. Naturally its importance cannot be overestimated! Most popular instrument  representation of P&ID is that from Instrument Society of America( ISA) and it will be followed here . For each system separate discussions have been presented to put due importance to it, and to make the reader understand how one is related to the other in a connected continued system. For each case Major important equipment involved is discussed so that reader can understand how main equipment discussed in the previous chapter constitute  the whole plant. Special emphasis has been made on measurement and control of the related parameters. Each of the system will be discussed in terms of the following points
  • System Design objective
  • Major  Component/Equipment
  • Parameters monitoring- measurement types, range of parameter etc.
  • Measurement & Control loop involved
  • Redundancy aspects for controls.
  • Various control parameters directly or indirectly involved in control loop.
Starting from, boiler super heater up to the turbine HP cylinder is the main line for Main steam( MS), Major components ( e.g MS SV, HP Stop valve at turbine , HP turbine control valve ) in this have been discussed. Now in this path major controlling parameter such as MS pressure & temperature are of immense importance from control point of view. What are these measuring points , what are their range, Instrument type etc in each case have been discussed. Hp Bypass --another system discussed  here is very important from Control as well as plant operation point of view.

HP turbine, exhaust and /or HP BYPASS outlet is the starting point of Cold reheat in a Reheat cycle. Part of the same is utilized for regeneration heating and Aux steam, but most of it is taken back to boiler Reheater in the boiler, to form, Hot reheat steam to be fed to the IP turbine. Depending on the turbine operating point the pressure, may be variable naturally the admission at IP casing is not same as that in the HP casing. Such conditions are discussed. Unlike steam temperature control, reheat temperature is mostly controlled by Burner tilt / Flue gas by pass damper so variations in controls have been discussed. LP BYPASS – the most essential system in turbine startup and shut down is a part of this system, hence LP BYPASS control has been discussed at length
It is the heart of regenerative cycle. Depending on the rating of the turbine, type of turbine, the extraction points and no of such extractions point varies. There are not much control on the extraction pressure (except power operated Valves opening /closing) as it depends on turbine load. Deaerator is essential to get minimum desired temperature of Feed water( FW), so it is supplied from Cross over steam in utility station, but it has other sources also like CRH, & AUX STM..
Even before the boiler is started it may be necessary, so in green field Projects, to have separate Aux Boiler. Aux steam has two side consumer such as Boiler Aux Steam( BAS)  cater to the requirement of HO heating, SCAPH etc, whereas for air extraction, deaerator in turbine side (TAS). This is very important as it basically consist of a number of Pressure Reducing and de superheating stations(PRDS ) taking in to account number of sensors, controllers, control valves, de super heaters. In large utility stations suitable judgment is necessary for the source of AS  from MS or CRH!
In the course of its journey from Boiler feed pump, till steam is formed in the drum, it has to pass thru’ a number of equipment. It is very important because complete boiler operation (also turbine operation in indirectly) depends on its Heat content, and quality. Feed water flow is the back bone for (Drum level control) boiler operation such as combustions  and an important variable for steam temperature control, Bypass operation, PRDS operation in AS etc. In this system there are a number of monitoring and control of  parameters (e.g. FW heater Temperature, Economizer temperature, BFP speed control etc.) for system operation. There are a number of control loops involved in this system.
It is the earlier form of Feed water, in the cycle, condensed from the turbine exhaust/ Process return. The water chemistry, here is very important maximum contamination is noted here. Starting from condenser it ends its journey at Deaerator to remove dissolved Oxygen. Condenser ,Deaerator level, are important controls here. All Systems some (~ 3%) make up and some time dumping is necessary. All these controls and associated monitoring takes place in this system.

 Heaters takes the . Extraction steam for heating the condensate / feed water , now upon exchanging the heat the extraction steam condenses, and same need to returned to the system!  Generally this is done in cascade draining of the heater for two purposes so that there is no thermal shock as well as heat transfer is uniform. However in certain emergencies and abnormalities, or different operating condition of the turbine , these may have high level &  emergency dumping to condenser/deaerator. Heater level controls are of utmost importance in this system
Air and Flue gas system is the heart of boiler operation. In this system some combustion, milling system need will also be .discussed. Since milling system is greatly related to the Primary air system milling system has been included in this system. There are some variation in air flue gas P&ID with type of PA chosen ( Hot/Cold PA) and with mill systems involved. Out of the total control system related to boiler control, major part shall be covered under this system. Main combustion control including Oxygen trim control, milling system control is connected to this system . Major boiler equipment such as fans, AH, Mills have been  covered here. Apart from main combustion control, Mill outlet temperature, mill  flow, Secondary air damper controls are major controls of this systems.
Gas Turbine (GT) in simple cycle and combined cycle are the back bone of the systems . Also there could be Co generations, where electrical generations shall be done by GT and steam shall be generated by use of these GT exhaust. Gas turbine types, HRSG , Diverter Damper etc are major systems involved here. In this section all these aspects from small unit generation to large units have been discussed. Controls of GTs and HRSGs are some what different from normal turbine so all these have been covered here.
In Power .plants there are a few other smaller system such as FO handling system,H2, Seal oil system, turbine oil system etc so all these have been  discussed in this section with special reference to monitoring and control aspects. The entire systems have been divided in to Steam Generator Auxiliary system and Turbo generator auxiliaries.

                                                      CHAPTER IV     GENERAL INSTRUMENTS


This chapter covers the fundamental of general instruments with special emphasis on calculation and data from leading world standards like ASME, BS, ISA and data from leading manufacturer, so that engineers can use it suitably. Since conventional analog transmitters have become obsolete we have used SMART instruments wherever possible. For each  type of Instruments we have covered
  • Basic working principle,
  • Types ( as are in use in power plants) 
  • ONE SPECIFICATION/DATA SHEET with various accessories.
  • Most importantly, it has been endeavored to cover material of construction for various types of instrument wetted parts.
Pressure instruments in power plants are of various types with Smart pressure transmitters, how they are categorized according to the ranges, so that inventory control is easier. Special emphasis has been put in selection of Pressure transmitters in DRAFT & VACUUM application. Various types of Pressure switches, gages have also been covered along with  all  the accessories necessary.
Temperature element selection according to the parameter, environmental condition is very important. Discussions take care criteria for selection of immersion length, extension length for temperature element, Thermowell (pressure rating & end connection of TW is very critical), Smart temperature transmitters etc., how they can be categorized according to the sensors, so that inventory control is easier.  Various types of Temperature switches, gages have also been covered. 
Flow element selection according to the parameter, line size is essential. Covered in this book is the calculation in accordance with ASME /BS practice in power station. Selection of tapping point, end connection for these are of utmost importance. Another important aspect is selection of flow meter for various medium such as Heavy fuel oil, Steam etc. There are a wide variety of flow meters are available as well as are in use but all are not suitable for all application—a discussion on the same has been presented. Similarly selection of flow element for air system is quite critical. Smart Flow pressure transmitters, how they can be categorized according to the ranges, so that inventory control is easier are included.  .
Types of level instruments are quite large which starts from Simple float type up to Hydrastep. Even Simple Drum level gage has some specialty. Apart from discussing all these special instruments , conventional level instruments such as displacer or float types have also been covered. Special DP type level gage. DP type transmitters have also been discussed to make the system complete in all respect. Keeping in mind the off site plants other level instruments such capacitance type in DM plant, , RF types instruments in Coal and Ash Handling plants have also been discussed.


ery consciously special instruments have been  clearly demarcated from the conventional ones, as these require special attention, on account of its variations use and maintenance. While Vibration, Turbovisory instruments are more mechanical type, Analyzer again requires some knowledge on Chemistry. For each  type of these SMART Instruments we have covered
  • Basic working principle,
  • Types ( as are in use in power plants) 
  • ONE SPECIFICATION/DATA SHEET with various accessories associated
  • Material of construction  for various types of instrument wetted parts have been covered .
Vibration measurement is  not only important for Turbines alone, these are of importance for large FANS, and Pumps Such as BFP, CW pump as this measurements give the indication for mechanical stability of the equipment. Bearing Vibration measurement of Turbine, BFP, ID/FD/PA fans, CW pumps are very common in utility stations. Velocity type probe is common, however some cases displacements are also in use. In turbine, other measurements such as eccentricity, absolute vibration (acceleration type) casing expansions are very common. Since clearance between rotor and stator in turbine is very small, Speed measurement (Hall Probe), Axial shift in turbine are almost mandatory measurement  for turbine system measurement. In all these instruments special application notes, installation details have been covered, to give special edge to the readers. A typical such Turbovisory measurements have been covered in the following diagram to give clear idea about condition monitoring systems for large steam turbines. In the book there are several such drawing for GTs and other application notes.

In this era of energy crisis, Gas analyzers play very important role to obtain optimum response from boiler. Oxygen analyzer (Zirconia type) is used for O2 trimming, whereas for finer control, CO ( some school of thoughts --CO2) analyzers are used in tandem in place of CO+H2  analyzer. At schtociometric ratio near unity,   CO shows best response. So in this book, O2, CO, CO2, H2 analyzers have been discussed. H2 Analyzer play important role, in TG side, as H2 Purity is important. For pollution control, gas analyzers discussed separately in the book.

Boiler – turbine operation depends very much depend on the steam water quality. Feed water chemistry is a subject by itself, since deposits scale formation &  corrosions are quite complex process. Depending on the cases AVT, OT systems are deployed to combat the situations. Therefore detailed  discussions with a number of Drawings have been presented to deal with the situations. In power plants there are a number of points where various types of analytical measurements are essential. Conductivity (with CAT Column  at condensate), pH , Dissolved O2, Residual Hydrazine measurements are essential. Silica analyzer for TG operation  and  H2 Analyzer in steam for boiler operation in utility stations. play important  role. All these analyzers along with sampling and sample conditioning systems have been discussed at length.  A typical list of SWAS points have been shown below, a detailed list of measuring points , tentative parameter value, instrument ranges have been presented in several tables & chart apart from various drawings for deposits, corrosion points dosing controls, CPU etc.:
The Analysis instruments are not only very costly these are  very sensitive to pressure and temperature etc. conditions, so it is essential that the sample before sending to the analyzers must be suitably conditioned. In order to make the SWAS effective sample conditioning system, which has been discussed in the book, is essential. Photographs of Standard SWAS panel have also been included.

Boiler blow down and system chemical  dosing systems now a days are no longer manual, so keeping in pace with the requirement the book contains discussion on boiler blow down from Conductivity measurement. Automatic control of Hydrazine, Phosphate, etc dosing system have been discussed.

In all the countries the pollution control is very strict, so for large utility station it has been made mandatory to install NOx, Sox, Particulate monitoring system and controlling the Over Air fire damper Vis a Vis gas recycling damper. All these aspects have been included in the book..


inal Control Element like, control valve/ damper with actuator  play key role in ascertaining the Performance of any control system. Again It is essential that the sizing, material , and other selection criteria are extremely important. In this chapter emphasis has been put to ensure that the reader is well aware of these aspects. Sizing as per ISA, material selection as per ANSI & Flange details have been well covered with special reference to power plant application. Controllability, actuator types and selection have been covered. For Control Valves and actuators SPECIFICATION SHEET have been included for directly use of the same in specification.
Out of final control elements Control valve is the most important one. There are a variety of control valves and desuperheaters . It is extremely important that correct types have been selected. Application wise various types have been discussed in the book so that designer can use the book to select the valve of his choice for the application. In one application also, there will be variation in the selection of valve e.g.main feed water control valve 0-30% load will be different from 0-100% valve in the same application, This is because of the Pressure and flow condition! Not only the valve types are different, also the Trim in the same type of valve will be different for various  applications. So, emphasis has been given on the discussions on Trim types, material and characteristics.
In Air & flue gas, path in Power plant there are a number of Dampers and other control devices (such as impeller control), so a brief discussion on the same have been presented so that the C&I engineer have an overall knowledge on the same, as this is basically a mechanical system
Actuator selection and sizing is important, because if it is not selected properly, then, it may be of lower size, or may be too big and sluggish!  While discussing actuator, both Diaphragm, and double acting cylinders have been discussed. . Motorized actuators have also been discussed. Control and power circuit have been presented, discussions have been limited as it is a part of MCC of electrical system.  Hydraulic Actuators, Smart EP Actuators have also been discussed as this is the trend today!
Out of various means to regulate the flow in the system, speed control of fan/pumps are always a better option from efficiency point of view. These speed control of various fans/Pumps (e.g. ID Fan, BFP) are carried out by Hydraulic scoop tube control and or by electronic speed control of the motor driving the fan/pump.  Complete details for Hydraulic scoop control and VFD have been presented with application note for ready made use in the actual field as well as for specification in design office.
There are a number of accessories necessary for control valves and actuators. I/P converter necessary to convert electronic signal  in to pneumatic signal. Solenoid valves , Positioner, Position transmitters, Limit switch, Torque switches are a few accessories discussed in this section of the book so that the reader can choose the same from here. Also a brief specification of each type shall be presented.



very thing likes to be smart or intelligent (if not wise)!  So is the control system. What is really intelligence? So called conventional systems were rather static, they could not sense the changes around it to trim its action. Intelligent systems do the same, so they can dynamically change its control action in uniformity with the changes in the surrounding. Book have put special emphasis on this aspect. It also deals with the various types of signal and its conditioning, necessary to interface with innumerable signals.  In this chapter  discussions starts from very basics such as signal conditioning ( e.g. interfaces RS 232,422),  protocols (such as ISO OSI model), and networking (e.g. point to point, Ethernet ) etc.  to finally do a complete integration of various systems. Alike the control systems sensors are now a days are smart , so that the cables are less. In view of the same there have been many field bus systems such as Foundation Fieldbus, Profibus (or HART protocol) etc. Networking and system integrations are the calls of the day!   However in view of different suppliers for Main plants and Off sites , there may be different networks, but these need to be integrated together with the help of various filed bus Profinet, OPC etc. Starting from a simple network complex network ( as an example following figure may be referred to). Artificial intelligence, Fuzzy logics find their applications in Power plant applications so, same have been duly covered with the help of example controls systems.
In small power plants the control system of the main plants are designed with PLC or PC  based system.. there is as such no problem in doing so, but it may not be cost effective if analog : Digital I/O is higher . However for many offsites like DM Plant, AH plant, CHP, where Digital signal processing is much higher than their counter parts in Analog signals. Independent PLC  operation with digital link to the main control system is quite common. Various aspect of PLC, such as Redundancies in Processors, I/O levels have been discussed. Use of Remote I/O have been discussed.   As in many cases  in main plants PLCs have been used in Burner management System( BMS) , Automatic Turbine Run Up system( ATRS), so in this book, same also been discussed. Apart from main plants there are discussions on PLC for various Off site plants like AHP, CHP, DM plants etc. Also Electrical system controls of PLC have been discussed.  HAZOP FMEA etc. are not uncommon now a days so, short discussion based around IEC 61511 have been included in  connection with discussion on BMS PLC.
As the name suggest it is very useful in plant trip analysis. Here time tagging in the resolution to the extent of 1ms is important. In power plant , following a trip there  will be series of events as power plant is a continuous connected system. In many plants a stand alone sequence event recorder (SER) is kept. In some place this in tandem with Alarm system are in use,. This section deals with the requirement of SER, the specification sheet etc.
In large utility stations an integrated DCS is kept to take care of Open Loop Control System(OLCS), for interlocked operations, and Closed Loop Control System(CLCS) for  modulating ( analog ) controls. This system is dedicated to discuss such control system of the main plant. In general now a days this type of control system is linked with OFF sites via Digital links and by system integrations. Again there are variations in this control systems, Some manufacturer use common controller for an equipment/system where both  CLCS & OLCS of the same sub system say BFP. Whereas some other manufacturer use separate CLCS and OLCS sub systems to deal interlock and modulating controls separately( also use PLC for OLCS. Special emphasis has been put in this book to discuss the pros and cons of both the systems. There are a number of small power stations especially combined process and power plants where Multi-functional/single loop stand alone controllers are in use, which are integrated thru standard RS link. This book discusses the same aspects also. It is quite common that ( especially for turbine controls) Main equipment supplier provides its controls system, whereas C&I engineers need to device a control system which need to be interfaced with the former one. The discussion in the book encompasses the same also.                                                                                                                                                                             
It is a challenging task for the designer to decide Man machine interface system for the control system. It is essential to keep in mind the following aspects
  • Man machine interface primarily is for the operator and/ operating personnel. who may not have enough knowledge on Instrumentation.
  • There shall be sufficient number of information arranged in a logical manner so that operator is well aware of all the happenings of the plant, at the same time it shall not be so much that the operator is overloaded with data.
  • Day by day on account of higher degree of Automation, no of operators are reduced, so in case of emergency operators has to cover a large control area , such display & emergency management is very important.
  • There shall be sufficient data , calculation, SER so that Trip Analysis , as well as quick start up is possible.
In this section special emphasis has been put to decide optimum no of Monitor, their division of duty and fall back facility. There is another aspect , types of displays, Information on each screen, some permanent important parameter always present at the top or bottom, of the display!  Suitable attentions have been put to take care that  hardware details about these monitors and printers are  not missed out, at the same time it does not burden the readers mind so basics with application details have been included.
Alike, Display,  the logging of data is very important. Certain Logging, are very easy such as Periodic log, Alarm log, Return to normal log! Problem arises, following a trip at what frequency which parameter need to be logged so that at later date such data can be used to analyze the system. Decision regarding periodicity of logging of each parameter is very important!  Presentation of data is very important, so that it becomes helpful to person analyzing the same . Importance have been put on Historic log, , data sampling during start up as well as  post trip condition as these form basis for analysis., fault detection etc.
With Modern control system it has become customary to have a monitor at the office of management personnel so that sitting at the office he/she can monitor the health and performance of the plant. At the same management personnel will be interested to get  a few other data such as cumulative consumption of fuel, steam loss etc. Down time, ( equipment wise) or may like to keep record maintenance management system, Inventory control system., Lubrication Program. All these aspects have been discussed in the section.
Performance calculation of equipment, or system is another aspect the system need to take care! As per ASME both Class I & II performance calculations have been discussed. This is very important for the plant superintendent to access the performance of the plant and equipment .


oiler Control philosophy is hinged around safe operation of boiler with safety regulation, and get the optimum efficiency at various operating points with minimum possible down time.  In order to achieve this goal a number of points are taken in to consideration, such as redundancy in sensor and controller etc. while strategizing the control philosophy.  This section of the book takes in to account of these factors as well as the pros and cons of integrating OLCS & CLCS together.  All the controls related to Boiler with several options have been presented in this chapter.
Boiler steam pressure is “THE” parameter for combustion control as well as for fixed pressure control of the turbine. Even in steam cum power plant this is the parameter which is maintained at set point to regulate combustion control. Steam pressure at steam Header or at turbine Inlet is measured and fed to the controller to compare with the desired set point. In order to enhance the performance vis a vis system response of  the loop boiler load index is taken as feed forward system. Now this boiler load index is very critical, in some cases of small, or medium sized boiler steam flow is considered as load index, in case of co ordinate control, unit demand is considered as load index, also for  larger boiler( >500MW),steam flow may not be measured to minimize Pressure loss and use unit demand as boiler load(1st stage turbine pressure with HP by pass flow) . The output of the controller in conjunction with load index creates the demand for combustion control. As a safety measure to ensure air enriched condition in the boiler , this demand is fed through Lead Lag circuit to air and fuel controllers as set point.
The set point generated from the above steam pressure control is compared at the controller with the total air flow, ( Air flow from Primary air as well as secondary  and / or tertiary air flow), this will generate the demand for Secondary air flow. (and not the demand for Primary air. which is guided by the pulverized coal flow). At Schtochiometric ratio (>near) 1 the is the best operating point for combustion. So  it is always aim to operate the  boiler at this point but to ensure air enrichment so that there is no accumulation of CO, it shall be >1 again if there is excess, amount of” excess air” there will be heat loss thru’ excess air. Therefore demand signal to Secondary air flow, is trimmed coarsely by Oxygen Analyzer ( Zirconia Probe) and fine tuned by CO analyzer.  After this trimming the signal through suitable scaling biasing unit goes to regulate the final control for Secondary( FD ) Fans.
The set point from the above steam pressure control is compared at the main fuel flow controller with the total fuel flow.  One thing shall be kept in mind  that the calorific value of all types of fuels are not same so in a multi fuel boiler necessary scaling factor need to put in the loop to take care of the same. (Again at every instant the calorific value of fuel may be changing however such changes are well taken care of by O2 controller). In practice depending on the mill, or fuel feeding configuration, it regulates the fuel flow to the boiler. Since fuel feeding to the mill (except Tube mill) is rather slower process so a good  response of this loop is inevitable for good performance of the Automatic Boiler Control(ABC). There are a few  complexity in selection and regulation of fuel flow in case of Multi fuel system. All such details have been discussed—whereas preferential tripping of mill has been discussed in connection with BMS.
A)Mill air flow: Generally Mill controls have two control loop e.g. Mill Air flow control and Mill Temperature control. As pulverized coal is used, it is driven away from the mill to the boiler by the primary air flow, thus it is obvious that the air flow shall be proportional to the  scaled demand  signal from the  fuel flow controller. However on account of complexity of air flow in tube mill, special emphasis has been put on tube mill discussions.               
B)Mill Temperature Control: Mill Outlet temperature control is not only important to maintain a set temp at the mill, but also necessary that the coal reaches boiler at a desired temperature so that spontaneous ignition is possible. Again at low temperature during monsoon there is possibilities of mill jamming. At the same time mill temperature in the mill shall not be to high so that there is possibility of getting Fire! These are maintained by operation of HOT & COLD AIR DAMPER.
C) Tube Mill Level control: In case of tube mill there is another control, mill level to regulate the speed of the feeder so that level inside the mill is maintained. This mill has an advantage that unlike other mill , the boiler can run unaffected for a certain time,  even if the mill trips.
Furnace Draft is very important parameter to be maintained at a desired set value! As the operation of the boiler and firing optimization take place at a desired set point. Normally set point is compared with the actual value to regulate Suction of ID fan to maintain desired set value for Furnace draft. Air flow is fed as feed forward signal so that wherever there will change in the boiler load first air flow will be affected , so that furnace pressure gets corrected accordingly receiving this feed forward signal. In large utility stations ID fan ( high vol. handling fan) play important role, so There have been many techniques such as Hydraulic scoop Tube, and VFDs  to regulate fan speed,  In let Damper control etc have been adapted. In power stations >500MW both systems have been in use! So detailed discussion on the same have been presented
Drum level control is one of the major control adapted in all boilers from  smallest boiler to the largest boiler. This is because if there is low level the boiler will starve , and if there is high level , then there will be a chance of water ingress to  turbine to cause over speed!— also Not as per regulation. In Drum level there are mostly two types of control. Single element ( Drum level only), or three element( drum level, steam flow, feed flow). The Desired set value is compared with actual level to regulate the feed flow. Feed control valves (because of valve controllability & selection criteria) are three types, Low load control valve(0-30%) Full load control valve (25-100%) and bypass valve (may be 0-100% high cost VRT type valve). In some cases, where there is speed control of BFP,  say up to 200MW drum level is maintained by the feed control valves and DP across feed control valve is kept constant by regulating the speed of BFP, so that Feed control station is not subject to tough operating condition. In larger stations >500 MW, Other than Low load control valve ( with one full flow by pass valve) is kept and drum level control directly regulates the speed  by means of  Hydraulic scoop tube or VFD.
All power station, whether fixed pressure or sliding pressure control, of turbine, have constant temperature of  main steam admitted to the turbine, so regulation of superheated Steam temperature is of utmost importance! Here one point need to be remembered that at low load when steam flow is smaller fixed set point may be lowered or could be given as a function of steam /air flow. As temperature is rather sluggish parameter so one need to take in to consideration a few feed forward signals like, Air flow as boiler load index so that steam temperature can be regulated in changing load condition. Generally in Boiler the super heater steam temperature is regulated in two stages thru’ attemperation  control ( feed flow).
Alike Super heater temperature, reheater temperature is regulated at a fixed point. However unlike above, reheater temperature is mainly regulated by Tilting of Burner or by operation of By pass dampers etc- depending on the boiler design. However provisions are kept for attemperation control also to cater. All these aspects along with re heater Protection methods have been discussed as emergency measure.

Also this section include discussions on a few other controls listed below            
  • Boiler Aux steam PRDS: Generation of Aux steam needed for boiler operation. Header developed from MS/CRH thru’PRDS
  • Soot Blowing steam Pressure control: Soot blowing is done thru’ low pressure  Aux steam, so there is a pressure control
  • Over fire Air Damper control to regulate the SOx & NOx emission from the boiler
  • F.O. pressure regulation: During start up and as support fuel Oil is used , whose pressure need to be regulated before firing.. 
Start up, shut down and also some time during emergency operation of boiler and turbine, HP Bypass system is necessary. Though this is related to both Boiler and turbine, yet it is discussed here as many a times these are included in SG package. As we are aware that the CRH pressure at HP turbine Outlet is a variable one depending on work done at turbine. It is the job of this control to match such pressure when they work in tandem. It has therefore three control, one Pressure control, temperature control, and FW pressure control ,somewhat similar to PRDS, but it has its significance of its operation for the interlock which are very vital e.g. no sooner the turbine trips it has to come in to operation so that boiler safety pop up is avoided. 12.0 BOILER OLCS
As stated earlier, there are a number of  Open Loop Control  System( OLCS) for boiler for interlock, sequential operation and protection. These have been encompassed in this section of the chapter.
  • BURNER MANAGEMENT SYSTEM(BMS): This part deals with the startup /shut down, and sequential operation for boiler and auxiliaries such as ID/ FD PA fans, Mills, Firing system. In case of Corner fire system, it deals with each elevation sequence also. In case of shut down and /or load shading  of boiler (and when HP Bypass comes in to operation) how the mills are cut of – Preferential cutting of mills. Similarly how mills are taken one by one etc.
  • SECONDARY AIR DAMPER CONTROL(SADC): This part deals with distribution of secondary air (SA) at various elevation and/or for each burner so that each burner gets the requisite amount of SA.
  • SOOT BLOWING CONTROL ( SBC) : For proper operation of boiler soot blowing is  essential otherwise heat transfer will be highly affected and is achieved through sequential operation

unning of turbine in unison with boiler to get optimum output is very critical. Alike boiler it also have a few regulation which need to be followed!. Also it is a heavy rotating machine with very narrow gap between rotor and stator, so, protection is of prime importance. Apart from mechanical protection since generator and excitation system is connected to turbine naturally electrical protection cannot be over estimated. Thus for this obvious reason, at sensor as well as at the control level adequate redundancies have been considered so as to avoid down time. In modern turbine control system there is provision for on line testing of the protective devices so that these are always active.
It is the heart of the turbine control system. In small turbo generator there may be simple hydraulic  governing system and  in larger machine two systems, electro hydraulic as well as Hydraulic governor system ( as back up) are deployed.  The system consist of Speed control, Load control and pressure control system with special feature like speed droop characteristic system. The Main function of the control system is to regulate the HP control valve in admitting the steam so as to regulate the speed (during start up and low load) & load control. During turbine follow mode HPCV will regulate the pressure of steam. In IP section, the in the initial period the valve may be regulating say up to 30 % load after the same the valve gets wide open and the steam admission is as per HRH pressure.. All these valve are interlocked with stop /interceptor valves also.. The speed is measured by speed probe may be Hall probe with redundancy. The EHG is well interlocked with the ATRS discussed later.
Turbine protection system generally include Mechanical and electrical over speed, axial shift, Bearing oil pressure, condenser vacuum, reverse power relay(Generator). Normally a separate control system different from main control system is provided for emergency.
For utility station Turbine start up /shut down are carried out with the help of  ATRS. Depending on the control system there may be a sub groups like evacuation system, Oil system, & turbine system. Each of these sub groups responsible for starting and control of various equipment and auxiliaries. ATRS operations are very much related to the EHG and TSE .L.O control, jacking  up operation, operation of evacuation system, Heat soaking of turbine are done in step by step mode thru’ ATRS.
It is of paramount importance to ensure all the basic protection system for the turbine is active and healthy at all the time. In order to ensure the same the protection points are tested on line through the redundant channel, only inhibiting actual tripping of the turbine during such testing by this independent OLCS  to carry out.
The turbine needs starting from conditions like cold condition  steam. Much care is taken towards admission of steam to the system, so that there is no mechanical fatigue in the metallurgy of the system. Apart from start up, shut down and during huge load fluctuation, turbine is subject to tremendous amount of thermal stress. In order  to protect the turbine, there is one thermal stress evaluator which measures the temperature at various places to check the stress developing in the system.                                  Based on safe operating condition it generates the speed ( during Start up & shut down) and load margin for the turbine! This also communicate with ATRS and EHG for their operation.
In most of the large size turbine especially the turbines from European manufacturers, need   LP BYPASS system for starting and shutting down of the turbines. This is a convenient system to operate turbine, independent of boiler.                                     Alike HP Bypass it bypasses the IP & LP Casing of the turbine, i.e HRH after pressure & temperature reductions dumped to the condenser. Generally the LP Bypass  is not a modulating control in true sense,  it works in close co ordination with the EHG system and have a number of protection input in this system so that the condenser vacuum is maintained
The glands in turbine leaks, so suitable sealing is essential. This sealing is two way, in HP side, the steam comes out whereas in the LP side air leaks in due to inside vacuum! It is therefore easier to develop a header so that the steam coming out at the HP side is to seal the same at the LP side. This control is done at turbine. However during start up and shut down External auxiliary steam is necessary for this purpose. However, the amount of steam coming out at HP may not match with the steam requirement at the LP side so, a seal pressure control system to supply/ drain  the required steam at all point of operation of the steam is done.
Many of the modern generator rotors are H2 cooled for better heat transfer. Now H2 coming in contact with air ( O2) may cause explosion so this is sealed by SEAL OIL whose pressure is controlled by a dedicated control loop.
This part deals with various discussion on Primary cooling water control and brief discussions on various excitation control system. This section also encompasses the Generator protections etc. The discussion here is short as this really pertains to electrical system, but to have idea on overall system by the reader a brief discussion has been presented
Condenser is part and parcel of the Turbine system, Vacuum maintenance is done through ATRS. Condenser level is another important part. Depending on P&ID configuration, Make Up and dumping of condensate may be done from condenser as well as at deaerator.  That is the reason these two level controls with available options are discussed here in turbine section. The major control valves involved are Make up valve, Dump valve and main condensate control valve. Also emergency make up and dump valve which may be ON OFF valves have been discussed here.
This sections discuss various configurations possible in a combined cycle plant. Also this section deals with GT integral control, Governor control, Starting up procedure, compressor and Hot gas generator control. This section also will cover Governor controls in smaller machine. Also this section of the chapter discusses about the turbine supervisory system.  Basically all miscellaneous discussion of TG system, left out,  have been covered here.
uring  operation of power plant in a grid, unit has to operate in closed co ordination with the Load Dispatch Center (LDC)  in a coordinated mode with its equipment. This give rise to have a coordinated control  system meaning that power generation is done in close coordination with the demand in the grid. This is more important for the larger utility stations..
 Smaller units or Captive plants may operate in boiler follow mode, but in Larger utility stations connected to the grid, involved in coordinate control system. The Load DEMAND signal for  each unit in the grid, is done thru’ Load dispatch center thru’ computation of the Grid demand, Grid frequency condition as well as No of units( and their respective unit size)in operation in the grid. In coordinated mode, this desired value is sent to the plant control room. This signal is sent to both Boiler and turbine control systems at the same time so that  both the systems can correct themselves to the desired condition so that waiting time is less but system response from both the systems should be very precise .
Turbine follow mode is one of the modes in Co ordinate control system. In this mode, the load demand signal  is sent to the boiler, whereas turbine control acts as inlet pressure control only. In this mode the boiler need to respond to the load demand signal to regulate the steam generation and the turbine governor will operate to maintain the header pressure. In sliding pressure operation, when the control valve is wide open above ( a low cut off of turbine load say 30%) this mode needs to be followed.
As discussed at the beginning, in this mode the turbine draws the steam from the header as per the load demand from LDC i.e the load control is with the turbine and boiler is just to follow the turbine by maintaining the master Pressure at the desired point. This mode is more common in the smaller units and in Captive generation units. Turbine responds to the varying load and  boiler to maintain steam pressure at fluctuating steam flow.
Run back is the situation when load demand exists but SG or TG may not respond accordingly on account of non availability of their auxiliaries and  run back to maximum possible load deliverable by the system.  Let there are 2X60% FD fan in the system and the boiler was operating based on the load demand say at 85% load, if a FD fan trips then it has to run back to 60% ( or the desired  load Run back point as programmed). Run Back is the operation which involve SG/TG to go back to the programmed load point  following a set back.
It is similar to the above situation, only difference is that here any major auxiliary may not trip but some  problem in the control system, and /or equipment (s) to attain to the desired load in either direction. These are termed as directional blocking also i.e. when even if there is requirement to change the load in either direction, but on account of limitation in the auxiliary and or due to control system same cannot be achieved.
A detailed discussion is presented on the pros and cons of the system,  Various mode selections and associated control system requirements.


enerally in small power plants many of the loops discussed below are considered as independent local control loop. However the effectiveness of these loops in overall performance of the power plant cannot be overestimated! However now a days for plant size > 200MW these are integrated with the main control system.
 BFP is a high pressure High flow (High power) pump, so for the safety of the same it is essential that min FW is pumped thru’ it even if there is very low demand for the main cycle, so FW is recalculated back to the deaerator. Flow of FW thru’ individual BFP is measured and compared with the Min value set  point , and controller O/P regulates the recirculation valve. Whenever the main cycle demand increases the recirculation valves closes automatically. In this control loop control valve is very critical for its duty cycle so special discussion on the same has been dedicated.
Alike BFP CEP may not be so much Hi power pump but it is essential that min Condensate( COND) is pumped thru’ it even if there is very low demand for the main cycle, so COND is recalculated back to the condenser.  Depending on the configuration of the regenerative system, This recirculation valve may act in tandem with the main condensate valve to deaerator or could be an independent control. In the former case the pump may be started with recirculation valve open and may close when system condensate requirement increases. All these variations in the P&IDs and their impact on the control loop has been discussed to choose best possible way for one’s system.
In certain configuration there is a separate gland steam condenser whose temperature need to be controlled.
Deaerator is one of the major equipment in the regenerative cycle. Level control of  deaerator has been covered above . However the pressure control is very important as it performs two major duties one is heating and other is removal of dissolved O2 from Condensate. Deaerator has steam supply from three sources viz, Aux. Steam during initial start up( ~1.5 Kg/cm2), and when CRH is established (either thru’ By pass operation or turbine started ), then from CRH ( ~3.5kg/cm2), finally when cross over steam is established it is supplied from there (This is uncontrolled and load dependent parameter). Change over amongst various sources are not always very smooth, naturally suitable protections need to be incorporated in the system which is well depicted in the control. loop.
In order to have proper functioning of the heaters, the level in the heater shell. Under normal condition the level is maintained in cascade draining system (exception LPH #1—located at the neck of the Condenser), i.e Heater VI drains to Heater V , LPH 3  to LPH 2 etc. In case of Hi level control the drains are put into the next vessel such as HPH to Deaerator, and LPH to condenser. etc. In extreme emergencies there will be draining facilities of HP drains to condenser. Again Direct draining to condenser may some other problems, such as Condenser Vacuum may fall. Naturally suitable means to be deployed and these have been shown and discussed in the book with required details.
7.0 Ejector Steam Control-- TAS
This section deals with PRDS controls to regulate the desired Pressure & temperature for steam needed  for Ejector and for TAS

eeping in mind the practical aspects of the book, a chapter dedicated for installation practices, has been assigned. Any instrument /system, however reliable it may be, can function properly only if proper installation practices have been followed.  . This chapter includes both  mechanical  Installation as well as electrical installation practices. Depending on applicability in mechanical installation, source point details, mounting and  impulse tube/pipe for  various instruments such as Pressure, Temperature level, flow and other special instruments like analyzers etc. have been discussed and shown with the help of a large nos. of drawings.   Naturally not much description of the same is necessary instead various diagrams have been presented with application note and note for good engineering practices. For each of the installation diagram each item is identified with a unique number and a complete Bill of Materials(BOM) have been presented so that from there the reader can choose the installation practices applicable for reader’s  application and by multiplying the same with no. of instrument of particular category reader can  draw up total erection hardware necessary. It is worth noting that in this  BOM basic specification such size, standard, rating etc. required for procurement have been included. Transmitter enclosure is quite common to group transmitters, process switches in power plant practices. Therefore detailed discussions, grouping philosophy, and detailed drawings  for the same have been included.
Earthing/ Grounding is an important factor for electrical installations, so a detailed discussion accompanied with a figures have been included in the system so CMRR NMRR etc could be avoided. Also standard practices in various cases, normally faced in the plant have been covered. There are a number of cables especially in the current era when there are nos. of field buses, so, all these kind of cables have been discussed along with their installation practices and grounding schemes.  Detailed specification of various kinds of cables normally used in present day power plant practices, such as Screen cable, Compensating cable, Extension cables special cables such as Profibus cable, Cat cable etc.

Above chapters cover good engineering practices necessary Instrumentation & Control Engineering in Fossil fuel Power plants. Some additional useful information  have been presented in the form of appendices listed below:

APPENDIX III ISA Standard, Materials, Human Engineering & Control room
he information appended here consists of various ISA standards mainly used for power plant applications. Brief presentation on various materials normally find their applications in instrumentation have been discussed with temperature range. Discussion on  any process /power plant remains in complete in case control concept is not touched upon. Ergonomics is very important for Control room concept, Control Panel design. A brief discussions on the same including temperature regulation, Light and sound effect for control room has been discussed. For control panel layout and vis a vis lighting design, human engineering play a great role so, short discussion on the Human Engineering to size various console their relative distance etc.

APPENDIX IV  Network Control and Communication
ome additional discussions have been presented on network control and communication. The discussion starts with Fiber optic communication methodology, Spectrum for long distance communication. With more and more system integration and internet the networks become vulnerable. So from security point of view suitable firewall needs to be developed for protection of the network of interest. A brief discussions on Firewall and security aspect have been covered. System availability is extremely important foe real time networks, therefore fault tolerant Ethernet enjoys some especial position. A short discussion on Fault tolerant Ethernet has been included.
hermal power plants can be divided into Subcritical, Super critical and Ultra supercritical category. Power plants operating at steam pressure below critical pressure i.e. 221MPa & temperature 374˚C are sub critical power plants. When plants operates at steam conditions are more than that of critical point, they are supercritical power plant.  In Supercritical stage there is no DISTINCTION between liquid ( water and Gaseous (steam) phase. In subcritical stage latent heat is necessary to convert water to steam, at supercritical state , it is not necessary. Ultra super critical plants are those plants where the steam is operated at higher pressure and Temperature (say, 300bar and 630˚C).  Efficiency and pollutant emission are much improved and can be seen from the table AP5/1 “Comparison amongst Typical subcritical /super critical & Ultra super critical plants”. Fire input /Feed water ratio is very important as these are necessarily once through boilers where100% Condensate polishing unit is a natural choice.
Separator units, storage vessels and recirculation pump are required for start-up / wet mode of operation.

Appendix VI Integrated Gasifier & Combined Cycle plant
(Pollution Control)
ntegrated Gasification Combined Cycle (IGCC) technology is the future promise to meet high energy demand with lesser pollution. A brief discussion on the same has been appended. The basic process for the same, and how synthesized gas is produced has been discussed. Various methods for gas cleaning  and other process details have been covered in this discussions. A brief discussions on the power block from this system has also been included to complete the discussions. Also brief detail about Circulating Fluidized Bed Combustion method has been included as a short note for readers benefit.

Appendix VII  A Few Operational Features of The Unit
nit Protection with various classes of trips under various conditions have been discussed with special reference to practical implementations have been discussed. House load operation is a specialized operation so its requirements have been covered. For thermal power plant operation under various electrical fault conditions require smooth bus transfer. Various methods of such transfer with pros and cons of each system have been covered with special reference to modern practices.

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