Theme:

1. Theme: Power plant C&I (IPC) systems & Tending to Zero Forced Outage by Internalization of Best Practices

2. Presentation Outline: 1.Some definitions & basics of Pressure, Flow & Temp. measurement 2. Categorization of C&I systems based on location of application 3. Division of power plant C&I systems based on functionality & type of application 4.Evolution of C&I systems and latest trend in technology 5.NTPC at a glance and maintenance practices of C&I systems 6. Some case studies

3. Measurement: Pressure Outline: • Some Definitions • Pressure Units • Manometers • Elastic Pressure Sensors • Electrical Pressure Sensors • Pressure Switches • Snubbers & Siphon Tubes

4. Measurement: Pressure Terminology • Accuracy : Closeness with which an instrument reading approaches the true value of the variable being measured. • Precision : A measure of reproducibility of the measurements; i.e. given a fixed value of a variable, precision is a measure of the degree which successive measurements differ from one another. • Sensitivity :The ratio of output signal or response of the instrument to a change of input or measured variable. • Resolution :The smallest change in measured value to which the instrument will respond. • Error :Deviation from the true value of the measured variable.

5. Measurement: Pressure Repeatability refers to the ability of a pressure sensor to provide the same output with successive applications of the same pressure. Hysteresis is a sensor's ability to give the same output at a given pressure while increasing and decreasingthe pressure.

6. Measurement: Pressure Pressure : Definitions • Definition: Force per unit area • Absolute pressure • Atmospheric pressure • Differential pressure • Gauge pressure Importance : Pressure measurement is critical for safe and optimum operation of processes such as steam generation, hydraulic equipment operation, air compression, vacuum processing etc.

7. Measurement: Pressure Zero Reference , Gauge, Absolute, Atmospheric Pressure • Any pressure above atmosphere is called gauge pressure • Any pressure below atmosphere is a vacuum (negative gauge pressure) • Absolute pressure (psia) is measured from a perfect vacuum Differential Pressure has no reference to either absolute vacuum or atmospheric pressure

8. Measurement: Pressure Units • The SI unit for pressure is the Pascal (Pa);1Pa= 1 N·m-2 • Non-SI unit pound (Lb) per square inch (psi) and bar are commonly used • Pressure is sometimes expressed in grams-force/cm2or as kgf/cm2 (KSC) 1 atm=1.03 ksc=14.696 psi=760mmHg=10000 mmWC =101325 Pa Standard pressure:Pressure of normal (standard) atmosphere is defined as standard pressure

9. Measurement: Pressure PressureMeasuring devices • Manometers • using water ,mercury and other liquids of known density • For measuring low pressures. • Mechanical/Elastic Pressure Sensors • Electrical Pressure Transducers • For measuring pressure of all ranges for telemetering purposes. Manometer: • A simple pressure standard • May be used for gauge, differential, and absolute measurements with a suitable reference. • Useful mainly for lower pressure work because the height of the column of mercury will otherwise become very high. • The difference in column heights gives the pressure reading

10. Measurement: Pressure Elastic Pressure Sensors The basic pressure sensing elements: A: C-shaped Bourdon tube , B: Helical Bourdon tube , C: flat diaphragm D: Convoluted diaphragm, E: Capsule , F: Set of bellows

11. Measurement: Pressure Electrical Pressure Sensors • Potentiometer Sensor • Inductive • Capacitive • Piezoelectric • Strain Gauge • Usually generate output signals in the mV range (spans of 100 mV to 250 mV). • In transmitters, these are amplified to the voltage level (1to 5 V) and converted to current loops, usually 4-20 mA dc

12. Set Point Sensing Element Conditioning Circuit Bourdon Tube Bellows Diaphragm Strain Gauge Mechanical Switch Transistor Measurement: Pressure Pressure Switches Applications • Alarm (Status) • Shutdown (Hi/Lo Limits) • Control (ON/OFF) A “switch” is an instrument that automatically senses some process variable (such as pressure) and provides an on/off signal relative to some reference point.

13. Measurement: Pressure High Pressure In High Temperature * When high process temperatures are present, various methods of isolating the pressure instrument from the process are used. * These include siphons, chemical seals with capillary tubing for remote mounting, and purging. • Snubbers & its use • Chemical Seal • Siphon

14. Measurement: Pressure Pressure Snubbers • To filter out pressure spikes, or to average out pressure pulses, snubbers are installed between the process and the instrument • Instrument indicates avg pr. Snubber Before use After use when one is interested in the measurement of fast, transient pressures (such as to initiate safety interlocks on rising pressures), snubbers must not be used, as they delay the response of the safety system.

15. Measurement: Pressure Chemical Seal or diaphragm Protector Chemical seals are used when media can falsify the pressure measurements due to high temperature, high viscosity or their property to crystallise

16. Measurement: Pressure Siphon A siphon is a coiled tube. This coil provides a large cooling surface and the trap created prevents the condensate from draining away. A siphon is required for hot condensing. fluids, such as steam, to assure a liquid trap. It is used to prevent live steam from entering and damaging the device. It is used to protect the instrument from hydraulic or thermal shocks. The two most common forms of siphon tube are the 'U' and Pigtail types.

17. Measurement: Flow Types of flow meters: • Orifice Flow meter • Vortex flow meter • Ultrasonics flow meter • Coriolis Mass Flow meter • Major issues for selecting flow meters Orifice Flow-meters Several sensors rely on the pressure drop or head occurring as a fluid flows by a resistance. The relationship between flow rate and pressure difference is determined by the Bernoulli equation.

18. Measurement: Flow Orifice Flow-meters • An orifice plate is a restriction with an opening smaller than the pipe diameter which is inserted in the pipe; the typical orifice plate has a concentric, sharp edged opening. • Because of the smaller area the fluid velocity increases, causing a corresponding decrease in pressure. • The flow rate can be calculated from the measured pressure drop across the orifice plate, P1-P3.   • The orifice plate is the most commonly used flow sensor, but it creates a rather large non-recoverable pressure due to the turbulence around the plate, leading to high energy consumption.

19. Measurement: Flow Venturi Tube The change in cross-sectional area in the venturi tube causes a pressure change between the convergent section and the throat, and the flow rate can be determined from this pressure drop.  Although more expensive that an orifice plate; the venturi tube introduces substantially lower non-recoverable pressure drops

20. Measurement: Flow Pitot Tubes Pitot tubes were invented by Henri Pitot in 1732 to measure the flowing velocity of fluids. Basically a differential pressure (dp) flow meter, a pitot tube measures two pressures: the static and the total impact pressure. • Pitot tubes are used to measure air flow in pipes, ducts, stacks, and liquid flow in pipes, open channels. • While accuracy and rangeability are relatively low, pitot tubes are simple, reliable, inexpensive, and suited for a variety of environmental conditions, including extremely high temperatures and a wide range of pressures.

21. Measurement: Flow Pitot Tubes • A single-port pitot tube can measure the flow velocity at only a single point in the cross-section of a flowing stream. • The probe must be inserted to a point in the flowing stream where the flow velocity is the average of the velocities across the cross-section, and its impact port must face directly into the fluid flow.

22. Measurement: Flow Pitot Tubes The point velocity of approach (VP) can be calculated by taking the square root of the difference between the total impact pressure (PT) and the static pressure (P) and multiplying that by the C/D ratio, where C is a dimensional constant and D is density: • The pitot tube measures the static and dynamic (or impact) pressures of the fluid at one point in the pipe.  • The flow rate can be determined from the difference between the static and dynamic pressures which is the velocity head of the fluid flow.

23. Measurement: Flow Vortex Flow-meters • This measuring principle is based on the fact that vortices are formed downstream of an obstacle in a fluid flow, e.g. behind a bridge pillar. • This phenomenon is commonly known as the Kármán vortex street.

24. Measurement: Flow Vortex Flow-meters This is detected by a sensor, such as capacitive sensor and fed to the electronic processor as a primary, digitized, linear signal. Capacitive sensors with integrated temperature measurement can directly register the mass flow of saturated steam as well. • Universally suitable for measuring liquids, gases and steam • Largely unaffected by changes in pressure, temperature and viscosity • High long-term stability (lifetime K factor), no zero-point drift • No moving parts • Marginal pressure loss

25. Measurement: Flow Ultrasonic flow-meters Swimming against the flow requires more power and more time than swimming with the flow. Ultrasonic flow measurement is based on this elementary transit time difference effect. • Two sensors mounted on the pipe simultaneously send and receive ultrasonic pulses. • At zero flow, both sensors receive the transmitted ultrasonic wave at the same time, i.e. without transit time delay. • When the fluid is in motion, the waves of ultrasonic sound do not reach the two sensors at the same time.

26. Measurement: Flow Ultrasonic flow-meters • This measured "transit time difference" is directly proportional to the flow velocity and therefore to flow volume. • By using the absolute transit times both the averaged fluid velocity and the speed of sound can be calculated. • Ultrasonic flow metersmeasure the difference of the propagation time (transit time) of ultrasonic pulses propagating in (normally an inclination angle around 30 to 45° is used) flow direction and against the flow direction. • This time difference is a measure for the averaged velocity of the fluid along the path of the ultrasonic beam

27. Measurement: Flow Ultrasonic flow-meters Advantages: • With homogeneous fluids, the principle is independent of pressure, temperature, conductivity and viscosity • Usable for a wide range of nominal diameters Direct meter installation on existing pipes • Non-invasive measurement • No pipe constrictions, no pressure losses • No moving parts. Minimum outlay for maintenance and upkeep

28. Measurement: Flow Coriolis Mass Flow-meters • If a moving mass is subjected to an oscillation perpendicular to its direction of movement, Coriolis forces occur depending on the mass flow. • A Coriolis mass flow meter has oscillation measuring tubes to precisely achieve this effect. Coriolis forces are generated when a fluid (= mass) flows through these oscillating tubes. Sensors at the inlet and outlet ends register the resultant phase shift in the tube's oscillation geometry.

29. Measurement: Flow Coriolis Mass Flow-meters The processor analyzes this information and uses it to compute the rate of mass flow. Advantage This principle is used in a huge range of industry sectors, including pharmaceuticals, chemicals and petrochemicals, oil and gas, food etc.

30. Measurement: Flow Major issues for selecting flow-meters Accuracy Repeatability Linearity Reliability Range/Span Dynamics(Response time) Safety Maintenance Cost

31. Measurement: Temp. Measurement Devices • Thermocouples • Resistance Thermometers • Thermistors • Bimetallic Thermometers • Acoustic Pyrometers • Local Instruments

32. Measurement: Temp. Thermocouple IT IS BASED ON ‘SEEBECK’ EFFECT WHICH SAYS THAT WHEN HEAT IS APPLIED TO A JUNCTION OF TWO DISSIMILAR METALS AN ‘EMF’ IS GENERATED WHICH CAN BE MEASURED AT THE OTHER JUNCTION T/C Connection COMPENSATING CABLE HOT JUNCTION TO DDC CARDS TERMINAL END CJC BOX

33. Measurement: Temp. Thermocouple Types of T/C:E,J,K,T,R,S,B K (Chromel & Alumel; Ni-Cr &Ni-Al) Type: mostly used in power plant for low temp. application ) R (Platinum & Platinum-Rhodium) Type: Used for high temp. application. Highly resistant to oxidation & corrosion Advantages: - Disadvantages:- - Low Cost - Sensitivity low & low voltage output - No moving parts, less likely to be broken. susceptible to noise -Wide temperature range.   - Accuracy not better than 0.5 °C -Reasonably short response time.   -Requires a known temperature - Reasonable repeatability and accuracy. reference

34. Measurement: Temp. RESISTANCE THERMOMETER (RTD) THE RESISTANCE OF A CONDUCTOR CHANGES WHEN ITS TEMPERATURE IS CHANGED .THIS PROPERTY IS UTILISED TO MEASURE THE TEMPERATURE. Rt = Ro (1+βdT) WHERE β = TEMP CO- EFFICIENT OF RESISTANCE ; dT= TEMPERATURE DIFFERENCE When discussing RTDs, following must be considered: • Wiring configuration (2, 3 or 4-wire) • Self-heating • Accuracy RTD types: • Stability 1. Platinum (Range -200 °C to 600 °C ) • Repeatability 2. Copper (Range -100 °C to 100 °C ) • Response time 3. Nickel (Range -60 °C to 180 °C )

35. Measurement: Temp. THERMISTORS THERMISTORS ARE GENERALLY COMPOSED OF SEMICONDUCTOR MATERIALS.THEY HAVE A NEGATIVE COEFFICIENT OF TEMPERATURE SO RESISTANCE DECREASES WITH INCREASE IN TEMP. Making use of Negative Temperature Coefficient characteristics, thermistor and can be applied in temperature compensation, inrush current limit, precision temp. control (temp. coefficient very large compared to RTC & T/C) etc. BIMETALLIC THERMOMETERS • ALL METALS EXPAND OR CONTRACT WITH TEMPERATURE • THE TEMPERATURE COEFFICIENT OF EXPANSION IS NOT THE SAME FOR ALL METALS AND SO THEIR RATES OF EXPANSION AND CONTRACTION ARE DIFFERENT USAGE:IN PROCESS INDUSTRIES FOR LOCAL TEMPERATURE MEASUREMENTS OVERLOAD CUTOUT SWITCH IN ELECTRICAL APPARATUS

36. Measurement: Temp. ACOUSTIC PYROMETER • Acoustic Pyrometer is a non-contact measurement device that obtains highly accurate instantaneous gas temperature data in any area of the boiler, helping improve combustion efficiency. • For measurement of temperatures across large spaces of known distance in a noisy, dirty and corrosive environment such as a coal-fired utility boiler, or a chemical recovery boiler. • The Velocity of Sound in a medium is proportional to the Temperature. LOCAL INDICATION • LIQUID IN GLASS THERMOMETER • MERCURY IN STEEL THERMOMETER • BIMETALLIC THERMOMETER

37. Power Plant C&I systems 1.Field instruments/ input & output instruments • Various measuring instruments like Transmitters, RTD, Thermocouples, Pr. & temp. gauges, speed & vibration pick ups etc. (Analog inputs) • Various Pr., Temp. & limit switches, for Interlock , protections & feedback of control element (Binary inputs) • Output devices like solenoids, EP converters, Positioners etc. for controlling final control element • Final control elements like Power cylinder, Pneumatic/ motorized actuators etc.

38. Power Plant C&I systems 2. Control Systems • Various control cabinets for acquiring field signal (both analog & binary inputs), processing the signals as per control logic and issuing output command to output devices (Binary & analog). • Various control desk devices like command consoles, Push button modules, indicators, recorders, CRTs, PC based Operator Work Stations (OWS) etc. for human machine interface for monitoring & control of the plant • Power supply system(UPS)/ chargers with battery backups to ensure uninterrupted power supply of desired quality for the control system

39. Power Plant C&I systems 3. Analyzers The availability, reliability & efficiency of boiler unit hinge around the close control of chemical regimes of working fluid i.e. water/steam as well as combustion in the boiler. The instruments monitoring the chemical regimes and combustion are generally called analytical instruments. These instruments fall under three category • Water/ Steam Analyzers • Gas analyzers • Smoke monitors HIGH PURITY WATER IS ESSENTIAL TO MINIMISE • SCALING • CORROSION • CARRY OVER • EMBRITTLEMENT

40. Power Plant C&I systems ANALYZERS AND MEASURMENT LOCATION • ON LINE gas analyzers for measurement of flue gas oxygen, carbon mono-oxides, carbon di-oxides, oxides of sulpher & nitrogen at various location of boiler. • ON LINE analyzers for measurement of conductivity, pH, silica, dissolved oxygen, phosphate, hydrazine, chloride, sodium etc. at various points in the water & steam cycle of boiler & turbine area (SWAS-steam & water analysis system). • ON-LINE opacity monitors for measurement of dust concentration in flue gas • ON LINE analyzers for measurement of conductivity, pH, silica, dissolved oxygen etc. at various ION exchangers of DM plant .

41. SAMPLE PARAMETER UNIT LIMIT DM WATER a) Conductivity b) Cation Conductivity µS/cm <0.3 Condensate pump discharge (CEP) µS/cm <5 <0.3 a) Conductivity b) Cation Conductivity c) pH 9.0-9.2 ppb d) Na+ <5ppb ppb e) Dissolve oxygen (DO) <10 µS/cm Economizer Inlet a) Conductivity b) Cation Conductivity <5 <0.3 ppb c) Hydrazine 10-20 a) Conductivity Boiler water µS/cm 100 b) pH 9.1-9.4 ppb c) Silica 100 Sat & Main steam a) Conductivity b) Cation Conductivity µS/cm <5 <0.3 Power Plant C&I systems TYPICAL VALUES OF CHEMICAL PARAMETERS BEING MEASURED (SWAS)

42. Power Plant C&I systems 4. Laboratory Instruments & Setup Activities of C&I Lab • CALIBRATION • REPAIR • TESTING with proper documentation & records CALIBRATION: • Pressure switch , Transmitter , Gauge • Temperature switch , Transmitter , Gauge • Flow Transmitter • Level Switch

43. Power Plant C&I systems 4. Laboratory Instruments & Setup REPAIR: 1. ELECTRONIC CARDS 3. POWER SUPPLY MODULES TESTING: 1. ELECTRONIC MODULES 2. RELAYS 3. POWER SUPPLY MODULES

44. Power Plant C&I systems 4. Laboratory Instruments & Setup • Different standard instruments with traceability up to national standard . These insts. include Standard Gauges, Multimeters, Resistance boxes, mA sources, oscilloscope, signal generator etc. for calibration of measuring instruments. • Dead Weight tester, Comparator, Temperature bath, Vacuum pump, manometer, soldering stations etc. • Test benches with standard power supply sockets (e.g. 24VDC, 48VDC, 220VDC, 110VAC, 230VAC etc.) in each bench depending on requirement. • Laboratory should be air-conditioned with monitoring of temp., humidity and barometric pressure. Also, proper provision for handling electronic cards (floor mats, ESD protective bags/ anti static bags etc.)

45. Power Plant C&I systems 4. Laboratory Instruments & Setup Essential Tools/ Infrastructure for Repairing & testing 1. IN-CITCUIT IC TESTER 2. ESD WORK STATION 3. ULTRASONIC CARD CLEANER 4. STORRAGE OSCILLOSCOPE 5. LOGIC ANALYSER 6. THERMOCOUPLE SIMULATOR 7. VIDEO PATTERN GENERATOR 8. EPROM PROGRAMMER

46. Power Plant C&I systems C&I systems of Boiler • FSSS (Furnace safeguard supervisory system) • Open loop control system (interlock & protections) of boiler auxiliaries • Secondary Air Damper control system (SADC) • Hydrastep for drum level measurement • Measurements, Protection & Control of Coal Feeders

47. Power Plant C&I systems FSSS FUNCTIONS OF F.S.S.S 1. FURNACE PURGE SUPERVISION 2. OIL GUNS ON/OFF CONTROL 3. PULVERISERS/FEEDERS ON/OFF CONTROL 4. SECONDARY AIR DAMPERS CONTROL 5. FLAME SCANNER INTELLIGENCE 6. BOILER TRIP PROTECTIONS

48. Power Plant C&I systems FSSS WHY AT ALL A PROTECTIVE SYSTEM IS REQUIRED FOR THE BOILER? THE BOILER’S FURNACE IS CONTINUOUSLY FED WITH HIGH CALORIFIC VALUE ATOMISED FUEL WHICH IS IN THE PROCESS OF CONTINUOUS BUT CONTROLLED COMBUSTION. COMBUSTION-THE PROCESS COMBUSTION IS A RAPID BURNING OF OXYGEN WITH FUEL RESULTING IN RELEASE OF HEAT. AIR IS ABOUT 21% OXYGEN AND 78% NITROGEN BY VOLUME. MOST FUELS CONTAIN CARBON, HYDROGEN AND SULPHUR. A SIMPLIFIED COMBUSTION PROCESS COULD BE CARBON+OXYGEN=CARBONDIOXIDE+ HEAT HYDROGEN+DO =WATER VAPOUR + HEAT SULPHUR +DO =SULPHURDIOXIDE+ HEAT WHICH MEANS THAT THE FINAL DESIRED PRODUCT OF THE PROCESS IS HEAT WHICH WE REQUIRE TO BOIL THE WATER

49. Power Plant C&I systems FSSS COMBUSTION-THE PROBLEM : WHEN THIS CONTROLLED BURNING GOES OUT OF CONTROL DUE TO AN IMBALANCE IN THE FUEL/AIR RATIO, THERE IS EITHER A FUEL RICH MIXTURE OR A FUEL LEAN MIXTURE. IN BOTH CASES THE FLAME QUALITY BECOMES POOR. THERE IS A CHANCE OF FUEL ACCUMULATION WHICH CAN LATER ON IGNITE SUDDENLY AND CAUSE EXPLOSIONS. SO FSSS IS USED FOR SAFE AND ORDERLY STARTUP AND SHUTDOWN OF BOILER THROUGH VARIOUS INTERLOCKS AND PROTECTIONS THE PROTECTIVE SYSTEM IN THE BOILER IS DESIGNED BASICALLY TO PREVENT OCCURRENCE OF SUCH SITUATIONS BY TAKING ADVANCE ACTIONS.

50. Power Plant C&I systems N.F.P.A Guide line & Boiler Protection • N.F.P.A- National Furnace Protection Association, USA • Deals with protection for various types of furnace • Protection of Pulverized fuel fired boiler is governed by Section-85c • Different categories of protection: • a) Mandatory, b)Mandatory & automatically generated, c) Optional but alarm has to be there