Summer Training Report: Amit Kumar Verma ECE (6th Sem)
Summer Training Report: Amit Kumar Verma ECE (6th Sem)
Summer Training Report: Amit Kumar Verma ECE (6th Sem)
:- Manometry lab
:- Protection and interlocks lab :- Automation lab :- Electronics lab :- Water treatment plant :-Furnaces Safety Supervisory System Lab
ACKNOWLEDGEMENT
WE HEREBY TAKE THIS OPPORTUNITY TO THANK NTPC LTD. TANDA FOR GIVING US THIS OPPORTUNITY TO CONDUCT OUR TRAINING IN NTPC LTD., TANDA. WE ARE GRATEFUL TO MR. SANJEEV GUPTA(DGM,C&I) FOR ALLOWING US TO CONDUCT OUR TRAINING IN THE CONTROL & INSTRUMENTATION DEPARTMENT.WE ARE HEARTLY INDEBTED TO OUR PROJECT GUIDE Mr. A. H. RIZVI FOR PROVIDING US WITH DETAILED IN DEPTH KNOWLEDGE AND VERY USEFUL INFORMATION ABOUT THE PROCESSES AND SYSTEMS USED IN THE PLANT.HIS SUPPORT WAS INSTRUMENTAL IN OUR TRAINING BEING FRUITFULL.WE ARE ALSO VERY TANKFUL TO ALL THE OFFICERS AND STAFF OF NTPC LTD., TANDA FOR EXTENDING A HELPING HAND WHENEVER WE NEEDED IT. WITH REGARDS, AMIT KUMAR VERMA DEO MANI SUKLA JOHN RIZVI
INTRODUCTION
NTPC is the largest power generation company in India, with comprehensive in-house capabilities in building and operating power projects. It is producing 28,644MW. Its family consists of 18 coal based power plant producing (23209 MW) and 8 gas based power plant having a capacity of (5435 mw). It is also setting up a hydro based power plants having capacity of 2471MW. It is one of the largest Indian companies with a market cap of more than US$50 BILLION and has total assets of around US$ 20 BILLION. In this firm government has 89.5% stake and 10.5% with public. NTPC is ranked 463rd biggest company in the world, 5th biggest Indian company and 2nd largest Asian power generator. It produces 26350MW which is 20.18% of the total 130,539MW of all India consumption. More than one-fourth of Indias generation with one-fifth capacity. The next largest power utility owns 7.9% of market share in terms of capacity and 8.12% of share in terms of units generated. NTPCs vision is to become world class integrated power major, powering Indias growth, with increasing global presence. It also develops and provides reliable power, related products and services at competitive prices, integrating multiple energy sources with innovative and eco-friendly technologies and contributes to society. This firm is also well concern about the environmental factors.
Saryu and West of the existing Mehripur pumping station of the Tanda canal system.
Necessary land, water and transport facilities are available. Land facility:1 .Land for Power Station including storage yard, Marshalling yard, Switching yard :- 120 hectares 2. Land for ash disposal 3. Land for colony 160 hectares 100 hectares
Water facility:1. Water for once thru cooling 2. Water for cooling tower 726.5 cusecs 45.0 cusecs
Transportation facility:- Power station is on Tanda-Faizabad also connected to AkbarpurFaizabad. Nearest railway station 13km far (surapur). Akbarpur is situated on Lucknow mughalsarai Railway track. The distance of plant from Akbarpur is 30km. Tanda town is about 8km far from plant. Production & Transmission:The 4*110MW power electricity is produced at the station using four different units. Each unit generates 110MW power. The arrangement of each unit is same. Since it is a thermal power plant, coal is used as the main source of energy. This coal is mainly supplied from the Dhanbad(Bihar) and other places.Generated electricity is supplied to following station:1.>Sultanpur 1 2.>sultanpur 2 3.>Gorakhpur 4.>Basti
Since this power plant had been undertaken by NTPC in 2000 its performance in terms of power factor load(PLF) is improved in a great manner and can be observed from the given graph:
to very large hyperboloid structures that can be upto 200 meters tall and 100 meters in diameter, or rectangular structure that can be over 40 meters tall and 80 meters long. Smaller towers are normally factory built while larger ones are constructed on site. The primary use of large, industrial cooling tower system is to remove the heat absorbed in the circulating water system used in power plants, petroleum refineries, petrochemical and chemical plants, natural gas processing plants and other industrial facilities. The absorbed heat is rejected to the atmosphere by the evaporation of some of the cooling water in mechanical forced draft or induced draft towers or in natural draft hyperbolic shaped cooling towers as seen at most nuclear power plants. 2. Three phase transmission lineThree phase electric power is a common method of electric power transmission. It is a type of polyphase system mainly used for power motors and many other devices. In a three phase system, three circuits reach their instantaneous peak values at different times. Taking one conductor as reference, the other two conductor are delayed in time by one-third and twothird of cycle of the electrical current. This delay between phases has the effect of giving constant power over each cycle of the current and also makes it impossible to produce a rotating magnetic field in an electric motor. At the power station, an electric generator converts mechanical power into a set of electric currents one from each electromagnetic coil or winding of the generator. The currents are sinusoidal functions of time, all at the same frequency but offset in time to give different phases. In a three phase system, the phases are spaced equally giving a phase separation of one-third of one cycle. Generators output at a voltage that ranges from hundreds of volts to 30,000 volts. At the power station. Transformers step-up this voltage for suitable transmission. After numerous further conversions in the transmission and distribution network, the power is finally transformed to standard mains voltage i.e. the household voltage. The power may already have been split into single phase at this point or it may be still three phase. Where the step-down is three phase. The output of the transformer is usually star connected with the standard mains voltage being the phase neutral voltage. 3. Electrical generatorAn electrical generator is a device that coverts mechanical energy to electrical energy, using electromagnetic induction whereas electrical energy is converted to mechanical energy with the help of electric motor. The source of mechanical energy may be a reciprocating turbine steam engine. Turbines are made in variety of sizes ranging from small 1 hp(0.75 kW) used as mechanical drives for pumps, compressors and other shaft driven equipment to 2,000,000 hp(1,500,000 kW) turbines used to generate electricity.
4. Boiler Feed PumpA Boiler Feed Pump is a specific type of pump used to pump water into steam boiler. The water may be freshly supplied or retuning condensation of steam produced by the boiler. These pumps are normally high pressure units that use suction from a condensate return system and can be of centrifugal pump type or positive displacement type. Construction and Operation feed water pumps range in size upto many horsepower and the electric motor is usually separated from the pump body by some form of mechanical coupling. Large industrial condensate pumps may also serve as the feed water pump. In either case, to force water into the boiler, the pump must generate sufficient pressure to overcome the steam pressure developed by the boiler. This is usually accomplished through the use of centrifugal pump. Feed water pumps usually run intermittently and are controlled by a float switch or other similar level-sensing device energizing the pump when it detect a lowered liquid level in the boiler substantially increased. Some pumps contain a two stage switch. As liquid lowers to the trigger point of the first stage, the pump is activated. If the liquid continues to drop (perhaps because the pump has failed, its supply has been cutoff or exhausted, or its discharge is blocked),the second stage will be triggered. This stage may switch off the boiler equipment (preventing the boiler from running dry and overheating), trigger an alarm or both. 5. Control valvesControl Valves are the valves used within industrial plants and elsewhere to control operating conditions such as temperature, pressure, flow and liquid level by fully or partially opening or closing in response to signals received from controllers that compares a set point to a process variable whose value is provided by sensors that monitor changes in such conditions. The opening or closing of control valves is done by means of electrical, hydraulic or pneumatic systems. 6. DeaeratorA Deaerator is a device for air removal and used to remove dissolved gases from boiler feed water to make it non-corrosive. A deaerator typically includes a vertical domed deaeration section as the deaeration feed water tank. A steam generating boiler requires that the circulating steam, condensate and feed water should be devoid of dissolved gases, particularly corrosive ones and dissolved or suspended solids. The gases will give rise to corrosion of the metal. The solids will deposit on heating surfaces giving rise to localized heating and tube ruptures due to overheating. Deaerator level and pressure must be controlled by adjusting control valves-the level by regulating condensate flow and pressure by regulating steam flow. Most deaerators guarantee that if operated properly, oxygen in deaerated water will not exceed 7ppb by weight.
7. Feed Water HeaterA feed water heater is a power plant component used to pre heat water delivered to a steam generating boiler. Feed water heater improves the efficiency of the system. This reduces plant operating costs and also helps to avoid thermal shock to boiler metal when the feed water is introduced back into the steam cycle. Feed water heaters allow the feed water to be brought upto the saturation temperature very gradually. This minimizes the inevitable irreversibility associated with heat transfer to the working fluid(water). A belt conveyer consists of two pulleys, with a continuous loop of material- the conveyer belt that rotates around them. The pulleys are powered, moving the belt and the material on the belt forward. Conveyer belts are extensively used to transport industrial and agricultural material, such as grain, coal, ores, etc. 8. PulverizerA pulverizer is a device for grinding coal for combustion in a furnace in a fossil fuel power plant. 9. Boiler Steam DrumSteam Drums are a regular feature of water tube boilers. It is reservoir of water/steam at the top end of the water tubes in the water-tube boiler. They store the steam generated in the water tubes and act as a phase separator for the steam/water mixture. The difference in densities between hot and cold water helps in the accumulation of the hotter-water/and saturated steam into steam drum. Made from high-grade steel (probably stainless) and its working involves temperatures 390C and pressure well above 350psi (2.4MPa). The separated steam is drawn out from the top section of the drum. Saturated steam is drawn off the top of the drum. The steam will re-enter the furnace in through a super heater, while the saturated water at the bottom of steam drum flows down to the mud- drum /feed water drum by down comer tubes accessories include a safety valve, water level indicator and fuse plug. A steam drum is used in the company of a mud-drum/feed water drum which is located at a lower level. So that it acts as a sump for the sludge or sediments which have a tendency to the bottom. 10.Super HeaterA Super heater is a device in a steam engine that heats the steam generated by the boiler again increasing its thermal energy and decreasing the likelihood that it will condense inside the engine. Super heaters increase the efficiency of the steam engine, and were widely adopted. Steam which has been superheated is logically known as superheated steam; nonsuperheated steam is called saturated steam or wet steam; Super heaters were applied to steam locomotives in quantity from the early 20th century, to most steam vehicles, and so stationary steam engines including power stations. 11.EconomizersEconomizer, or in the UK economizer, are mechanical devices intended to reduce energy consumption, or to perform another useful function like preheating a fluid. The term
economizer is used for other purposes as well. Boiler, power plant, and heating, ventilating and air conditioning. In boilers, economizer are heat exchange devices that heat fluids , usually water, up to but not normally beyond the boiling point of the fluid. Economizers are so named because they can make use of the enthalpy and improving the boilers efficiency. They are a device fitted to a boiler which saves energy by using the exhaust gases from the boiler to preheat the cold water used the fill it (the feed water). Modern day boilers, such as those in cold fired power stations, are still fitted with economizer which is decedents of Greens original design. In this context they are turbines before it is pumped to the boilers. A common application of economizer is steam power plants is to capture the waste hit from boiler stack gases (flue gas) and transfer thus it to the boiler feed water thus lowering the needed energy input , in turn reducing the firing rates to accomplish the rated boiler output . Economizer lower stack temperatures which may cause condensation of acidic combustion gases and serious equipment corrosion damage if care is not taken in their design and material selection. 12.Air PreheaterAir preheater is a general term to describe any device designed to heat air before another process (for example, combustion in a boiler). The purpose of the air preheater is to recover the heat from the boiler flue gas which increases the thermal efficiency of the boiler by reducing the useful heat lost in the fuel gas. As a consequence, the flue gases are also sent to the flue gas stack (or chimney) at a lower temperature allowing simplified design of the ducting and the flue gas stack. It also allows control over the temperature of gases leaving the stack. 13.PrecipitatorAn Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate device that removes particles from a flowing gas (such As air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices, and can easily remove fine particulate matter such as dust and smoke from the air steam. ESPs continue to be excellent devices for control of many industrial particulate emissions, including smoke from electricity-generating utilities (coal and oil fired), salt cake collection from black liquor boilers in pump mills, and catalyst collection from fluidized bed catalytic crackers from several hundred thousand ACFM in the largest coal-fired boiler application. The original parallel plate-Weighted wire design (described above) has evolved as more efficient ( and robust) discharge electrode designs were developed, today focusing on rigid discharge electrodes to which many sharpened spikes are attached , maximizing corona production. Transformer rectifier systems apply voltages of 50-100 Kilovolts at relatively high current densities. Modern controls minimize sparking and prevent arcing, avoiding damage to the components. Automatic rapping systems and hopper evacuation systems remove the collected particulate matter while on line allowing ESPs to stay in operation for years at a time.
14.Fuel gas stackA Fuel gas stack is a type of chimney, a vertical pipe, channel or similar structure through which combustion product gases called fuel gases are exhausted to the outside air. Fuel gases are produced when coal, oil, natural gas, wood or any other large combustion device. Fuel gas is usually composed of carbon dioxide (CO2) and water vapor as well as nitrogen and excess oxygen remaining from the intake combustion air. It also contains a small percentage of pollutants such as particulates matter, carbon mono oxide, nitrogen oxides and sulfur oxides. The flue gas stacks are often quite tall, up to 400 meters (1300 feet) or more, so as to disperse the exhaust pollutants over a greater aria and thereby reduce the concentration of the pollutants to the levels required by governmental environmental policies and regulations.
than as a solid, in the conventional domestic or industrial grate, with additional amount of air, called secondary air supply, by forced draft fan. As coal is ground so finally the resultant ash is also a fine powder. Some of it binds together to form pumps, which falls into ash pits at the bottom of the furnace. The water-quenched ash from the bottom is conveyed to pits for subsequent disposal or sale. Most of ash, still in fine partical form is carried out of boilers to the precipitator as dust, where electrodes charged with high voltage electricity trap it. The dust is then conveyed to water to disposal area or to bunker for sale while the clean flue gases are passed on through IP fans to be discharged through chimneys. The heat released from the coal has been absorbed by the many kilometers tubing which line the boiler walls. Inside the tubes the boiler feed water, which is transformed by heat into staemat high temperature and pressure.. The steam superheated in further tubes (superheaters) passes to turbine where it is discharged through the nozzle on the turbine blades. Just as the energy of wind turns the sail of the windmill, the energy of steam striking the blade makes the turbine rotate. Coupled to the end of the turbine is the rotor of the generator. The rotor is housed inside the stator having heavy coils of the bars in which electricity is produced through the movement of magnetic field created by the rotor. Electricity passes from stator windings to step-up transformer which increases its voltage so that it can be transmited efficiently over lines of grid. The staem which has given up its heat energy is cahnged back into water in a condenser so that it is ready for re-use. The condenser contains many kilometers of tubing through which cold water is constantly pumped. The staem passing around the tubes looses heat.Thus it is rapidly changed back into water. But, the two lots of water, that is, the boiler feed and cooling water must never mix. Cooling water is drawn from river- bed, but the boiler feed water must be absolutely pure, far purer than the water we drink (de-mineralized water), otherwise it may damage the boiler tubes.
1. Manometry lab Transmitters- Transmitter is used for pressure measurements of gases and liquids, its working principle is that the input pressure is converted into electrostatic capacitance and from there it is conditioned and amplified. It gives an output of 4-20 ma DC. It can be mounted on a pipe or a wall. For liquid or steam measurement transmitters is mounted below main process piping and for gas measurement transmitter is placed above pipe. Manometer- Its a tube which is bent, in U shape. It is filled with a liquid. This device corresponds to a difference in pressure across the two limbs. Bourden Pressure Gauge- Its an oval section tube. Its one end is fixed. It is provided with a pointer to indicate the pressure on a calibrated scale. It is of two types : (a) Spiral type : for low pressure measurement and (b) Helical type : for high pressure measurement
2. Protection and Interlock Lab Interlocking- It is basically interconnecting two or more equipments so that if one
equipments fails other one can perform the tasks. This type of interdependence is also created so that equipments connected together are started and shut down in the specific sequence to avoid damage. For protection of equipments tripping are provided for all the equipments. Tripping can be considered as the series of instructions connected through OR GATE. When The main equipments of this lab are relay and circuit breakers. Some of the instrument uses for protection are: 1. RELAY It is a protective device. It can detect wrong condition in electrical circuits by constantly measuring the electrical quantities flowing under normal and faulty conditions. Some of the electrical quantities are voltage, current, phase angle and velocity. 2. FUSES It is a short piece of metal inserted in the circuit, which melts when heavy current flows through it and thus breaks the circuit. Usually silver is used as a fuse material because: a) The coefficient of expansion of silver is very small. As a result no critical fatigue occurs and thus the continuous full capacity normal current ratings are assured for the long time. b) The conductivity of the silver is unimpaired by the surges of the current that produces temperatures just near the melting point. c) Silver fusible elements can be raised from normal operating temperature to vaporization quicker than any other material because of its comparatively low specific heat. Miniature Circuit Breaker- They are used with combination of the control circuits to. a) Enable the staring of plant and distributors. b) Protect the circuit in case of a fault. In consists of current carrying contacts, one movable and other fixed. When a fault occurs the contacts separate and are is stuck between them. There are three types of -MANUAL TRIP - THERMAL TRIP - SHORT CIRCUIT TRIP. Protection and Interlock System- 1. HIGH TENSION CONTROL CIRCUIT For high tension system the control system are excited by separate D.C supply. For starting the circuit conditions should be in series with the starting coil of the equipment to energize it. Because if even a single condition is not true then system will not start. 2. LOW TENSION CONTROL CIRCUIT For low tension system the control circuits are directly excited from
the 0.415 KV A.C supply. The same circuit achieves both excitation and tripping. Hence the tripping coil is provided for emergency tripping if the interconnection fails.
3.
Automation Lab
This lab deals in automating the existing equipment and feeding routes. Earlier, the old technology dealt with only (DAS) Data Acquisition System and came to be known as primary systems. The modern technology or the secondary systems are coupled with (MIS) Management Information System. But this lab universally applies the pressure measuring instruments as the controlling force. However, the relays are also provided but they are used only for protection and interlocks. 4.
Pyrometry Lab
Liquid in glass thermometer - Mercury in the glass thermometer boils at 340 degree Celsius which limits the range of temperature that can be measured. It is L shaped thermometer which is designed to reach all inaccessible places. Ultra violet censor- This device is used in furnace and it measures the intensity of ultra violet rays there and according to the wave generated which directly indicates the temperature in the furnace. Thermocouples - This device is based on SEEBACK and PELTIER effect. It comprises of two junctions at different temperature. Then the emf is induced in the circuit due to the flow of electrons. This is an important part in the plant. RTD(Resistance temperature detector) - It performs the function of thermocouple basically but the difference is of a resistance. In this due to the change in the resistance the temperature difference is measured. In this lab, also the measuring devices can be calibrated in the oil bath or just boiling water (for low range devices) and in small furnace (for high range devices).
5.
This lab has the responsibility of starting fire in the furnace to enable the burning of coal. For first stage coal burners are in the front and rear of the furnace and for the second and third stage corner firing is employed. Unburnt coal is removed using forced draft or induced draft
fan. The temperature inside the boiler is 1100 degree Celsius and its height is 18 to 40 m. It is made up of mild steel. An ultra violet sensor is employed in furnace to measure the intensity of ultra violet rays inside the furnace and according to it a signal in the same order of same mV is generated which directly indicates the temperature of the furnace. For firing the furnace a 10 KV spark plug is operated for ten seconds over a spray of diesel fuel and pre-heater air along each of the feeder-mills. The furnace has six feeder mills each separated by warm air pipes fed from forced draft fans. In first stage indirect firing is employed that is feeder mills are not fed directly from coal but are fed from three feeders but are fed from pulverized coalbunkers. The furnace can operate on the minimum feed from three feeders but under not circumstances should any one be left out under operation, to prevent creation of pressure different with in the furnace, which threatens to blast it.
6.
Electronics Lab
This lab undertakes the calibration and testing of various cards. It houses various types of analytical instruments like oscilloscopes, integrated circuits, cards auto analyzers etc.Various processes undertaken in this lab are: 1. Transmitter converts mV to mA. 2. Auto analyzer purifies the sample before it is sent to electrodes. It extracts the magnetic portion.
SYSTEM OVERVIEW
The control and automation system used here is a micro based intelligent multiplexing system This system, designed on a modular basis, allows to tighten the scope of control hardware to the particular control strategy and operating requirements of the process Regardless of the type and extent of process to control provides system uniformity and integrity for: Signal conditioning and transmission Modulating controls
Employees Machines So the Parameters to be monitored are : Speed Temperature Current Voltage Pressure Eccentricity Flow of Gases Vaccum Pressure Valves Level Vibration
PRESSURE MONITORING
Pressure can be monitored by three types of basic mechanisms Switches Gauges Transmitter type For gauges we use Bourden tubes : The Bourdon Tube is a non liquid pressure measurement device. It is widely used in applications where inexpensive static pressure measurements are needed. A typical Bourdon tube contains a curved tube that is open to external pressure input on one end and is coupled mechanically to an indicating needle on the other end, as shown schematically below.
For Switches pressure swithes are used and they can be used for digital means of monitoring as swith being ON is referred as high and being OFF is as low. All the monitored data is converted to either Current or Voltage parameter. The Plant standard for current and volta are as under voltage
Voltage : 0 10 Volts range Current : 4 20 milliAmperes We use 4mA as the lower value so as to check for disturbances and wire breaks. Accuracy of such systems is very high . ACCURACY : + - 0.1 % The whole system used is SCADA base baseD. Programmable Logic Circuits ( PLCs) are used in the process as they are the heardt of Instrumentation .
HL switch
Level High
pump
Stop OR
TEMPERATURE MONITORING
We can use Thernocouples or RTDs for temperature monitoring Normally RTDs are used for low temperatures. Thermocoupkle selection depends upon two factors: Temperature Range Accuracy Required Normally used Thermocouple is K Type Thermocouple: Chromel (Nickel-Chromium Alloy) / Alumel (Nickel-Aluminium Alloy)
This is the most commonly used general purpose thermocouple. It is inexpensive and, owing to its popularity, available in a wide variety of probes. They are available in the 200 C to +1200 C range. Sensitivity is approximately 41 V/C. RTDs are also used but not in protection systems due to vibrational errors. We pass a constant curre t through the RTD. So that if R changes then the Voltage also changes RTDs used in Industries are Pt100 and Pt1000 Pt100 : 0 0C 100 ( 1 = 2.5 0C ) Pt1000 : 0 0C - 1000 Pt1000 is used for higher accuracy The gauges used for Temperature measurements are mercury filled Temperature gauges. For Analog medium thermocouples are used And for Digital medium Switches are used which are basically mercury switches.
FLOW MEASUREMENT
Flow measurement does not signify much and is measured just for metering purposes and for monitoring the processes
ROTAMETERS:
A Rotameter is a device that measures the flow rate of liquid or gas in a closed tube. It is occasionally misspelled as 'rotometer'. It belongs to a class of meters called variable area meters, which measure flow rate by allowing the cross sectional area the fluid travels through to vary, causing some measurable effect.
A rotameter consists of a tapered tube, typically made of glass, with a float inside that is pushed up by flow and pulled down by gravity. At a higher flow rate more area (between the float and the tube) is needed to accommodate the flow, so the float rises. Floats are made in many different shapes, with spheres and spherical ellipses being the most common. The float is shaped so that it rotates axially as the fluid passes. This allows you to tell if the float is stuck since it will only rotate if it is not. For Digital measurements Flap system is used. For Analog measurements we can use the following methods : Flowmeters Venurimeters / Orifice meters Turbines Massflow meters ( oil level ) Ultrasonic Flow meters Magnetic Flowmeter ( water level ) Selection of flow meter depends upon the purpose , accuracy and liquid to be measured so different types of meters used. Turbine type are the simplest of all. They work on the principle that on each rotation of the turbine a pulse is generated and that pulse is counted to get the flow rate.
VENTURIMETERS :
Referring to the diagram, using Bernoulli's equation in the special case of incompressible fluids (such as the approximation of a water jet), the theoretical pressure drop at the constriction would be given by (/2)(v22 - v12). And we know that rate of flow is given by:
Flow = k (D.P)
Where DP is Differential Presure or the Pressure Drop.
CONTROL VALVES
A valve is a device that regulates the flow of substances (either gases, fluidized solids, slurries, or liquids) by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but usually are discussed separately.
Valves are used in a variety of applications including industrial, military, commercial, residential, transportation. Plumbing valves are the most obvious in everyday life, but many more are used. Some valves are driven by pressure only, they are mainly used for safety purposes in steam engines and domestic heating or cooking appliances. Others are used in a controlled way, like in Otto cycle engines driven by a camshaft, where they play a major role in engine cycle control. Many valves are controlled manually with a handle attached to the valve stem. If the handle is turned a quarter of a full turn (90) between operating positions, the valve is called a quarterturn valve. Butterfly valves, ball valves, and plug valves are often quarter-turn valves. Valves can also be controlled by devices called actuators attached to the stem. They can be electromechanical actuators such as an electric motor or solenoid, pneumatic actuators which are controlled by air pressure, or hydraulic actuators which are controlled by the pressure of a liquid such as oil or water.
So there are basically three types of valves that are used in power industries besides the handle valves. They are : Pneumatic Valves they are air or gas controlled which is compressed to turn or move them Hydraulic valves they utilize oil in place of Air as oil has better compression Motorised valves these valves are controlled by electric motors
The 95 MW boilers are indirect type boilers. Fire takes place in front and in rear side. Thats why its called front and rear type boiler. The 210 MW boilers are direct type boilers (which means that HSD is in direct contact with coal) firing takes place from the corner. Thus it is also known as corner type boiler. IGNITER SYSTEM Igniter system is an automatic system, it takes the charge from 110kv and this spark is brought in front of the oil guns, which spray aerated HSD on the coal for coal combustion. There is a 5 minute delay cycle before igniting, this is to evacuate or burn the HSD. This method is known as PURGING. PRESSURE SWITCH Pressure switches are the devices that make or break a circuit. When pressure is applied , the switch under the switch gets pressed which is attached to a relay that makes or break the circuit. Time delay can also be included in sensing the pressure with the help of pressure valves. Examples of pressure valves: 1. Manual valves (tap) 2. Motorized valves (actuator) works on motor action 3. Pneumatic valve (actuator) _ works due to pressure of compressed air 4. Hydraulic valve