Glossary Power Plant

BOILER SECTION
Balanced draft system A boiler that uses an induced draft fan to maintain the boiler furnace under a pressure that is less than at mospheric pressure
Boiler A component in the plant cycle consisting of a closed vessel that uses the heat produced by the combustion of fuel to efficiently transform water into steam
Boiler water Water used in a boiler to produce steam
Critical conditons Temperature and pressure above the critical point
Critical point Condition of 705 F (373.8 C ) and 3206 psia (221.0 bar ) , where there is no disthinguishable difference between water and steam
Downcomers Large pipes that supply water from the steam drum to the inlet headers and waterwall tubes
Economizer Section of boiler tubes where feed water is first introduced into the boiler and where flue gas is used to raise the temperature of the water
Flash tank A closed vessel used for seperation of water and steam during the start up and shutdown of once through boilers
Latent heat vaporation Heat must be added to water to transform it into steam
Primary air Air used to transport fuel to a burner
Ramp rate Change in temperature per unit time
Reheaters Bundles of boiler tube that receive steam from the high pressure turbine section and then used heat from flue gas to superheat the steam
Saturation temperature The tmperature at which water boils at given pressure
Secondary air Additional air added to ensure the complete mixing of fuel and air for complete combustion
Steam drum A closed vessel used to hold a large quantity of water for the production of steam in a drum type boiler and to separate water from steam
Superheated steam Steam heated above saturation temperature
Superheaters Bundles of boiler tubes that receive dry saturated steam and use the heat in flue gas to raise the temperature of the steam
Turbulance Movement of scendary air necessary to ensure the complete mixing of air and fuel
Waterwall tubes Section of tubes that line the inside of the boiler and transfe heat to the boiler water to produce steam

POWER GENERATION
AC Exciter An exciter that produces alternating current ; also called an alterex
Amplidyne A device that automatically controls generator field voltage
Apparent power The amount of power that a generator would produce if inductive reactance or capacitive reactance were not present
Automatic load frequency controller A device that automatically increases or decreases generator load within a specified band to meet system demands for power
Brushless exciter An exciter that does not have brushes or slip rings
Capability curve A chart that can be used to calculate a generator’s ability to produce power safely under specific operating condition
Capacitance A physical property of AC circuits that opposes change in voltage
Capacitive reactance The effect of capacitance on an AC circuit
Capacitor A component used to control or increase the amount of capacitive reactance in an AC circuit
Circuit breaker A switch that opens to interrupt current flow through a circuit
Commutator A device in a DC exciter that change that changes AC to DC
Core Monitor A device used to mesure the amount of particulate matter in the hydrogen inside a hydrogen-cooled generator
Counter electromotive force (CEMF) Voltage induced in an operating circuit that opposes the existing applied voltage . Also called self induction
Cross-compound unit A generating unit consisting of two or more generators that are electrically connected so that they function as one unit
DC exiciter An exciter that produced direct current for the rotor windings of a main generator
Detraining tanks Tanks in a seal oil system that remove hydrogen and air trapped in oil
Dielectric An insulating material that seperates the parallel plates inside a capacitor
Disconnect swicth A switch that , in most case , is operated to isolate a CB after the CB has been opened ; usually not designed to open under load
Dispatcher A person who controls the distribution of electricity within a power system
Effective value A measure of the amount of work that can be accomplished by an AC circuit in relation to an equivalent DC value; mathematically determined by mulplying the peak AC value times 0.707 ; also called the root mean square (RMS) value
Exiciter A device that produces and supplies direct current to generator’s rotor winding
Frequency The number of cycles completed each second by given AC voltage
Generating unit A plant boiler , turbine , generator ,and associated systems and equipment
Generator load The number of megawatts produced by a generator
Grid A network of power stations , power lines , and power users
Hertz A unit of frequency ; one cycle per second
Hydrogen dryer A dvice that removes moisture from the hydrogen circulating inside a hydrogen – cooled generator
Inductance A physical property of AC circuits that opposes changes in current flow
Inductive reactance The effect of inductance on in AC circuit
Isolated-phase bus Conductors that connect a generator to a main trasformer
Load shedding The cutting off of electricity to a specific consumers in a power system in in response to load demand in excess of generating capacity;done to prevent damage to generating units
Peak value The maximum positive or negative value in AC sine wave
Pilot exciter A generator that supplies current for the electromagnet in a stator of a DC exciter
Power The rate at which work is done
Power factor The relatinship between true power and apparent power: true power divided by apparent power
Power grid A group of interrelated power system ,also known as anetwork,or a power pool
Purity nalyzer A device tha measures the percentage of hidrogen in air inside a hydrogen cooled generator
Ramp rate For generator ,the speed at wichthe generator changes load
Rate voltage The amount of voltage that a generator is desgned to produce
Reactive power Power that must be supplied to a load to a conpensate for the effects of inductive reactance or capacitive reactance
Rectifier An electronic device that allows alternating currentto flow in only one direction ,that is ,changes alternating current into direct current
Regenenation A procedure for removing moisture from the desiccant inside a hydrogen dryer
Rheostat A device that control current flow by increasing or decreasingthe amount of resistance in a circuit
RMS(Root Mean Square )value See effective value
Rotor The movable part of a generator
Seal oil system A generator auxiliary system that maintains oil flow through seals at each end rotor ;seals the inside of the generator from the outside
Sine wave A wave form that represents an oscillating signal ;for example ,an AC sine wave
Single phase generator Agenerator that has only one group of stator windings
Solenoid Acoil of wire that surrounds a movable metal core
Satic exciter An exciter tha has no moving part
Station service system An electrical circuit thatsupplies power to a plant’s electrical equipment
Sator The fixed ,or nonmoving ,part of a generator
Stator cooling system A water cooling system that provides cooling for the stator bars in larg hydrogen-cooled generators
Switchyard The area of a plant where the combined outputs of plant’s generating units are directed to a power system
Synchroscope A device used to match a generator’s output voltage and frequency with that of the grid
System load The total demand for power from the grid
Terminal voltage The amount of voltage that a generator is desgned to produce
Three phase generator A generator that has three sets of stator windings and produces three outputs
True power The amount of power that is actually doing work in an AC circuit
Unity power factor An operating condition in which true power and apparent power are equal

BASIC POWER PLANT OPERATION
Air preheater A component that transfers heat from the flue gas leaving a boiler to the combustion air flowing into the boiler
Axial movement End – to-end movement
Balanced draft boiler A boiler that uses both forced draft fans and induced draft fans to provide the necessary air and flue gas flow through it
Bearing A component that carries loads ,reduce friction , and positions moving parts
Blade A rotating or fixid part of turbine . Rotating balase convert energy in steam into mechanical energy , which cause rotation of the turbine shaft ; fixed blade direct the steam into the rotating blades.
Blowdown A type of drain that may be opened during boiler operation for specific purposes,such as to remove contamination that has built up in drum
Boiler The component in power plant that burns fuel to produce heat and uses that heat convert water into steam.
Boiling The process of converting water into steam
Carbon seal A methode of trubine sealing in which springs hold carbon rings against the shaft
Circuit A complete path for current flow
Combustion air system The support system that supplies the air necessary for the proper combustion of fuel in a boiler
Condensate The water that is collected in a condenser as steam is condesed
Condensate-feedwater system The support system that removes condensate from the condenser and sends it back to the boiler
Condenser A large heat exchanger that removes heat from steam and thus converts the steam into water
Condenser circulating water system The support system that supplies cooling water to the condenser tubes
Controlled circulation A process that uses boiler water circulation pumps to move steam and water through boiler tubes
Critical condition The point at which the density of water and density of steam are the same ; 705 F ( 373.8 C ) and 3206 psi (221 bar )
Current The movement , or flow ,of electricity through a circuit
Diaphragm A stationary part of turbine ; a diaphragm contains blades or nozzles that direct steam from one set of rotating blades to the next
Downcomers The large pipes in drum-type boilers that recirculate water from the steam drum to the waterwalls
Economizer A type boiler that transfers heat from flue gas leaving boiler to feed water flowing into the boiler
Electro-hydraulic control system A trubine control system that uses an electronic governor and oil from an independent oil supply to monitor and control turbine speed .
Extraction steam Steam that is extracted from the turbine and used by the feedwater heaters to heat the fesswater that is being sent to the boiler
Feedwater The water that is pumped into the boiler to replace the water that leaves the boiler as steam
Feed water control valve A valve used to control the amount of water pumped to the boiler
Film lubrication A process that maintains a wedge of oil between a bearing and a shaft
Flue gas The exhaust gas produced when fuel burns in a boiler furnace ; flue gas must be pushed or drawn out the furnace and discharge from the plant through the stacks
Fossil fuel plant A power plant that uses energy from coal , oil , or natural gas to produce electric power
Friction The resistance to motion that exists between two bodies in contact with each other
Fuel system The support system that delivers fuel to boiler furnace
Furnace The open area in a boiler where fuel is burned
Generator A machine that converts mechanical energy into electrical energy
Gland The collective term for the gland seals used at a particular sealing point
Gland seal A seal ,usually composed of several labyrinth seals , designed to prevent leakage of air or steam around a turbine shaft
Gland seal exhaust system A system that prevents steam from leaking out along the turbine shaft by drawing off the steam and condensing it for reuse
Gland seal system A system that supplies low-pressure steam to keep outside air from leaking into the turbine
Gland steam condenser A part of the gland seal exhaust system in which steam leaking paast the turbine shaft is collected and condensed ; the condensate may be drained to the condenser
Galnd steam exhauster A vacuum pump that draws air and steam from turbine glands to gland steam condenser
Hydroelectric plant A power plant that uses energy from water stored behind dams to produced electric power
Impulse turbine A turbine in which the force of high-pressure steam cause the rotating blades to turn.
Labyrinth seal A seal made up of a set of grooves and ridges that correspond to another set of grooves and ridges on , for example ,turbine shaft .
Load change The process of changing the amount of power produced by a power plant to meet a change in demand
Load dispatcher The individual who predicts the demand for power ,monitors the condition of a power system , and coordinates the outputs of the plants in the system so that supply always equals demand .
Main steam system The system that transports steam from a boiler to its turbine
Makeup water system The support system that replinishes water lost from the steam cycle as a result of leakage
Mechanical-hydraulic control system A turbine control system that uses a mechanical governor and oil from the turbine lube oil system to monitor and control turbine speed .
Mega watt One million watt
Natural circulation The process by which water and steam mose through some drum-type boilers based on fact that cold water is heavier than hot water or steam , so colder water in downcomers pushes hot water and steam upward through boiler tube
Nuclear plant A power plant that use energy from uranium to produce elctric power
Once- through boiler A boiler in wich water goes through only once;water is pushed through this tyipe of boiler by boiler feed pumps
Particulates Small unburned solid paticles that are left in flue gas after combastion
Power station A facility tha produce electricity
Power system The system thst connets all the plants owned by a power company
Precipitator A device use to separate particulates from flue gas leaving a boiler
Pressurized furnce boiler A boiler in wich the pressure of the incoming air from a force draft fan pushes flue gas out through the stacks
Pyrometer An instrument used to make temperatur readings and bearings and other component
Radial movement Side to side movement
Reaction turbine A turbine in wich the expansion of steam cause the rotating blade to turn
Reheater A boiler component that adds heat to steam after it has move through a portion of the turbine The reheated steam then flow through the remainder of the turbine
Rolling contact bearing A bearing in wich one surface roll over another survace ;there is lubricant between the two surface to reduce friction
Rotor The moving parts of a turbine
Saturation temperature The temperature at which water will boil at a given pressure
Scrubber A device that uses chemical process to reduce the amount of pollutants such as sulfur oxides in flue gas leaving a boiler
Sliding surface bearing A bearing in which two surfaces with lubricant between them ,slide over each other
Sootblower A device that uses steam or compressed air to blow off soot that collects on boiler tubes
Spray attemperator A device that sprays water into the steam flowing through a superheater or reheater to prevent the final outlet steam from exceeding established limit
Steam control valve A valve used to control the amount of steam flowing through the turbine
Steam cycle In apower plant , the complete loop from the boiler ,through the turbine , through the condenser , and back to the boiler .
Subcritical conditions Steam condition below the critical condition of 705 F (373.8 C) and 3206 psi (221 bar )
Substation A facility in which electric power from several sources is combined in one location for local distribution
Supercritical condition Steam condition above the critical condition of 705 F (373.8 C ) and 3206 psi (221 bar )
Superheated steam Steam that has been heated above the saturation temperature
Superheater A component that heats steam above the saturation temperature
Support system A system that supports the operation of another system . For example , several systems outside the steam cycle are needed to make the steam cycle work .
Switchyard A facility that combines the output from numbe of generators and transmits the combined output to different service areas.
Transformer A device that increases or decreases AC voltage
Turbine The component in a power plant that converts the the energy stored in steam or falling water into the mechanical energy needed to turn a generator .
Turbine lube oil system The turbine system that provides oil for lubrication and ,in some cases ,for turbine control .
Turbine trip A sudden shutdown of the turbine in response to emergency situation
Turning gear A motor and gear arrangement that keeps the turbine shaft rotating slowly during cooling down
Unit A term commonly used used to refer to each generator and its system in a power plant
Vacuum A pressure less than atmospheric pressure
Vibromotor An instrument used to check bearings and other component s for vibration
Voltage The driving force that causes current to flow
Water seal A type of turbine seal that uses water to fill the opening between the turbine shaft and the casing , and thus prevent leakage
Waterwalls Vertical tubes filled with water that line the inside of a boiler furnace
Watt The unit used to measure electric power
Wheel A row of rotating blades in a turbine

PLANT CYCLE
Absolute pressure Pressure measured on scale where zero is equal to the total absence of presure
Atmospheric pressure Pressure exerted on the surface of the earth by air in the at mosphere
Attemperator/desuperheater A component that controls steam temperature by spraying a fine mist of water into steam pipe
Backpressure The difference between atmospheric pressure and condenser vacuum
Barometer A device used to measure atmospheric pressure
Boiling The process of changing the state of water from a liquid to a vapor
British thermal unit (BTU) A unit of thermal energy equal to the amount of heat required to raise the temperature of one pound of water at standard conditions one degree fahrenheit
Condensing The process of changing the state of water from a vapor to a liquid
Efficiency The relationship between the energy that goes into a process and the energy that comes out of the process (energy out /enrgy in ) ;usually expressed as a percentage
Enthalpy Thermal energy or heat content of one pound of a subtance
Entropy A calculated property used to evaluate the effeciency of a process
Flashing A rapid change of state from water to steam
Gauge pressure Pressure measured from a zero refernce point of atmospheric pressure
Heat rate A direct measure of the amount of chemical energy required to produce each kilowatt-hour of electricity
Heating value The btu content of fuel
Latent heat of vaporization The amount of heat required to turn a quantity of saturated water completely into steam
Moisture content The percentage of water in a steam /water mixture
Mollier diagram A graph of entropy vs enthalpy that indicates most of the properties of wet steam and superheated steam
Net generation The amount of electrical energy produced per hour ; also called net electrical output
Pressure Measure of force per unit area
Quality The percentage of steam in a steam /water mixture
Saturated steam Steam at the saturation temperature that has no water
Saturated water Water at the saturation temperature that is not boiling
Saturation temperature The temperature at which boiling occurs
Shrink The dcrease in water level that occurs when boiling sops and the number of bubbles is reduced
Specific heat The amount of heat , in BTU’s , required to raise the temperature of one pound of a substance one degree Fahrenheit
Specific volume The measurement of the amount of space occupied by one pound of substance
Steam table Ttable that list the values for the properties of wate and steam at various temperature and pressures
Steam trap A component in asteam system that removes condensation without removing steam . Steam traps minimize water hammer
Swell The increase in water level that occurs during boiling , when the number of bubbles increase rapidly
Temperature Measurement of warmth or coolness in relation to a scale
Transition zone All the conditions at which water and steam coexist
Vacuum Pressure below atmospheric pressure
Vacum manometer A device commonly used to measure condenser vacuum
Water hammer One of the conditions that cause pipes to rattle and vibrate

WATER TREATMENT EQUIPMENT
Acid A solution that contains hydrogen inos and has a pH less than 7
Abrasive balls Small balls coated with an abrasive that are forced through condenser tubes to scrape off buildup
Acid attack Corrosion cause by an acid
Acid dosing A water treatment method in which acid is injected into circulating wate to control pH and neutralize alkaline impurities
Activated carbon Carbon that has been processed to increase its surface area ; used as a filter medium
Alkali A solution that contains hydroxyl ion and has a pH more than 7
Anion A negatively charged ion
Anion resin beads Resin beads in an ion exchanger that attract negatively charges ions
Backwashing A process of reversing the flow of water through a component such as a filter or an ion exchanger to remove trapped material
Biocide A chemical , such as chlorine , used to prevent biological organisms in water from growing into slime deposite
Biological fouling An accumulation of deposits resulting from the growth of boilogical organisms
Blowdown A process for removing impurities from water that involves removing part of water
Breakthrough A condition that occurs when ion exchange resin is exhausted and water containing dissolved solids flows through the ion exchanger without being treated
Carbon filter A filter containing an activated carbon filter medium ; typically used to remove suspended soilds , chlorine, and organic material from water before water enters an ion exchanger
Carryover The process by which impurities in boiler water are picked up in steam and deposited elsewhere in the plant cycle
Cation A positively charged ion
Cation resin beads Resin beads in an ion exchanger that attract positively charges ions
Caustic attack Corrosion cause by an alkali
Caustic embrittlement A condition caused by a combination of excessively alkaline boiler water and leaks in boiler tube ; changes the molecular structure of boiler tube metal so that the metal becomes brittle
Channeling A condition that can result from improper diffusion of water entering an ion exchanger ; water flows through only part of the resin bed , and the overall efficiency of the ion exchanger is reduced
Chemical feed rate control A device that regulates the amount of chemicals added to clarifier
Chlorinator A piece of equipment a chlorine injection system that regulates the pressure of shlorine gas and controls its flow rate so that it is mixed with water in the correct proportions
Chlorine evaporator A piece of equipment in typical chlorine injection system that provides a safe means for changing liquid chlorine into a gas
Clarification A wate treatment process in which chemicals are used to cause charged particles in raw water to come together in heavier clumps and settle out
Clarifier A piece of equipment used to remove large concentration of suspended solids from raw water
Closed cooling system A cooling water system that is not exposed to atmosphere
Coagulant A chemical added to raw water in a clarifier to form a positively charged precipitate that attracts negatively charged particles suspended in the water
Coagulant aids Substances such as fine clay and syntehetic polymers that are added to a clarifier to increase the effectiveness of the calrification process
Coagulation The first stage of the clarification process , in ehich a chemical coagulant is rapidly mixed into raw water
Condensate polishing mixed –bed ion exchanger A specially designed mixed –bed ion exchanger used to remove dissolved solid from condensate ; usually contains 2-3 times as much cation resin as anion resin
Conductivity A measure of a solution’s ability to conduct electrical current
Conductivity cell A device that passes an electrical current through a solution to measure the solution’s conductivity
Cooling canal An evaporative cooling arrangement consisting of a long channel through which warm circulating water passes and is expossed to air
Cooling tower An evaporative cooler in which warm circulating water is broken into droplets that are cooled by a flow of air
Corrosion The deterioration of substance as it reacts with its anviroment ; a chemical attack on metal surface
Corrosion inhibitor A chemical , such as hydrazine , chromates , or nitrites , that protects metal surfaces from corrosion by forming a protective coating on the surfaces or by neutralizing corrosion-causing impurities in water
De-aerator A component used to remove dissolved gases from water in plant cycle
Degasfier A component that removes carbon dioxide and other gases from water
Diffuser The part of an ion exchange that spreadds the incoming water water over the entire resin bed
Effluent The water leaving an ion exchanger
Entraiment The process by which water containing impurities is picked up and pushed along by steam
Erosion The wearing away of metal surfaces caused by the flow of a substance
Evaporator A piece of equipment that removes suspended solids and dissolved solids from water by heating the water to produce steam
Filter A device that allows liquid to pass through it while it traps solids
Filter demineralizer A component that uses a layer of resin beads on top of a filter medium to remove dissolved solids from water
Filter medium The part of a filter that traps solids
Flocculation The second stage of the clarification process, in which a slow mixing action causes negatively charged suspended particles to come together with the positively charged precipitate formed during coagulation
Foaming A condition in which a blanket of foam created by impurities covers the surface of the water in a boiler drum
Gravity filter A filter used to trap suspended solids by passing water through a filter medium that is usually a granular material
Hardness salts Compounds made of calcium or magnesium
Horizontal flow clarifier A clarifier that is essentially a large basin that is devide into three section : a flash mixer , a flocculator , and a settling basin
Hydrogen embrittlement A condition caused by interaction of dissolved hydrogen and the carbon in boiler metal ; loss of carbon causes the metal to become brittle
Ion A charged particles formed when a solid dissolves in water
Ion exchange A methode of removing dissolved solids from water by exchanging the ions of the solids for ions that will not cause problems in the systems using the water ; an example of such ions are those that combine to form pure water
Ion exchanger A component that uses the principles of ion exchange to remove dissolved solids from water ;also called a demineralizer
Ion exchange resin The medium in an ion exchange takes places ; small, porous ,plastic beads that contain areaas called sites ,which are occupied by ions
Jar test A test used ti determine the minimum amount of chemical addition that will provide the desired amount of settling in clarifier
Magnetite An iron oxide formed during a self –limiting type of corrosion that occurs under low oxygen condition ; the iron oxide layer prevents further corrosion
Makeup train An iron exchanger system with single-bed exchangers and mixed-bed exchangers functioning together ;used to supply make u water to boiler
Mixed-bed ion exchanger An ion exchanger in which the resin bed consists of anion and cation resin beads mixed together
Mixing tee A device used to dilute regenerant before it flows into an ion exchanger
Once –through cooling system A cooling water system in which water is drawn from asource, used for cooling ,and then rened to the source
Open system A cooling water system that is exposed to atmosphere
pH A measure of the acidity or alkalinity of solution on a scale from 1 ( most acidic ) ti 14 ( most alkaline )
Pressure filter A filter that uses pressure to force water through the filter medium
Priming A conditon in which slugs of water flood the moisture separators in a boiler and enter the superheater
Raw water Water that has not been treated
Recirculating cooling system A cooling water system in which water continuously recycled
Regenerant a chemical Soution used for regenerating resin
Regeneration The process of restoring an ion exchanger’s capability for exchanging ions
Resin bead A small, porous bead ( usually plastic ) that contains electrically charged areas where ions are exchanged ; may be either an anion bead or cation bead
Resin column A device used in condensate systems to aid in the measurement of conductivity ; contains specially color –coded resin
Resin exhaution A condition in which the exchange –able ions on resin besd sites have become depleted so that sufficient ion exchang ecan no longer take place
Reverse osmosis unit A device that uses semipermeable membranes to filter dissolved soilids out of water
Scale A buildup of impurities on metal surface
Sedimentation The third stage of the clarification process, in which floc particles that have settled to the bottom of the clarifier form an accumulation called sludge
Selectivity A property of resin beads based o the degree of attraction between the chrged sites on the resin besds and different kinds of ions
Service water system A cooling water system that supplies cooling water to shell and tube heat exchangers
Side stream filtering and softening A water treatment system for recirculating systems in which part of the water is reis removed and treated and then to the main flow
Singli –bed ion exchanger A ion exchanger that contains either anion resin or cation resin
Sites Charged areas on resin beads that are occupied by ions
Slime A deposit formed by the growth of biological organisms
Sludge The sediment at the bottom of a clarifier ; made up of floc particles
Sludge blanket A layer of sludge in an upflow clarifier at the point where the rate of upward flow of freshly flocculated water equals the rate at which the floc particles settle out ; serves to trap additional suspended particles
Sludge rake Flat boards connected by a chain and used to collect sludge from the bottom of a horizontal flow clarifier
Spray pond An evaporative cooling arrangement consisting of a pond, a pump , and spray nozzles, which allow more of the water’s surface to be exposed to air
Stator cooling system A cooling system that uses extremely pure cooling water to prevent the stator windings of a generator from overheating
Trash rake A device used to remove large debris from water before the water enters the plant
Trveling screes Loops of screen segments that prevent leaves and debris in raw water from entering the plant
Throughput The amount of raw water passing through a clarifier
Turbidity The cloudiness of water
Vaporization A process in which an impurity in boiler water reaches its boiling point and changes to a gas
Voltile chemical A chemical that vaporizes easily
Zeolite softener A component that softens water by removing dissolved hardness solids such as calcium and magnesium

TURBINES
AC turning gear oil pump An electrically powered oil pump in the turbine lubricating oil system that serves as a backup to the auxiliary ( motor –driven ) oil pump
After –seat pressure ( stop valve ) The pressure of the steam between the main stop valve bypass and the control valve
Auxiliary ( motor –driven ) oil pump A pump in turbine lubricating oil system ; used to provide hydraulic and lubricating oil during startups and shutdowns , when turbine speed is too slow for the main oil pump to be effective ; driven by an electrically powered motor
Bearings Turbine component designed to support the rotor and allow it to rotate while preventing metal –to-metal contact between stationary and moving parts
Bearing padestals ( standards ) Supports for turbine bearings and turbine casings
Before –seat pressure ( stop valve ) The pressure of the steam between the boiler and the main stop valves also called “ throttle “ pressure
Boote oil pump A pump in aturbine lubricating oil system ; designed to draw oil from an oil resevoir and pump it to themain oil pump
Booster oil turbine A drive mechanism in turbine lubricating oil system ;designed to drive the booster pump
Casing ( shell ) The outer covering of a turbine
Centrifuge A device used to purify oil by spining it to sparate the impurities
Control stage The first stage of a turbine , consisting of nozzle block and a row of moving blading
Control valves Steam valves leading to a turbine’s inlet that regulate the amount of steam supplied to the turbine and consequently the amount of energy that turbine receive ; valves designed to regulate the flow of steam into the HP turbine during normal operation , and to serve as a backup to the main stop valves during shutdowns , to shut off the flow of steam into the HP turbine ; some times called govenor valves
Counter flow A turbine clinder arrangement in which steam flows through one cylinder in one direction and through another cylinder in the opposite direction , or from the center of one cylinder to each end
Critical speed A turbine speed at which the rotor will vibrate excessively
Cross –compound A turbine cylinder arrangement consistng of two cylinders and two shafts that drive two generators ,which are tied together electrically
Cylinder A turbine rotor assembly and casing as a unit
DC turning gear oil pump A pump in the turbine lubricating oil system ; often powered by station battery and designed to supply lubricating oil when AC power is unavailable
Diaphragm A row of fixed blading that consists of an inner ring ,which surrounds the shaft , and an outer ring , which attaches the row to the turbine casing
Differential expansion The difference between the rates at which a turbine rotor and aturbine shell expand or contract in response to temperature change
Disc type rotor A type of turbine rotor in which the moving blades are mounted on discs , called wheels, that are raised up from the shaft
Double casing A turbine casing consisting of two walls : an inner casing and an outer casing
Double flow A steam flow arrangement in which steam enters a turbine cylinder in the center and flows in two directions
Drain valves Manual or motor –operated valves designed to remove moisture from a turbine
Drum type rotor A turbine rotor that consists of an enlarged portion of the shaft , called drum . The turbine’s moving blades are mounted directly onto the drum
Eccentrcity The degree of deviation from absolute roundness; the amount that the rotor deviates from its normal center of rotation
Electronic governor A governor that typically consists of three element : a speed sensor , electronic circuitry designed to develop an error signal ,and a torque motor
Emergency blowdown valve A turbine valve designed to prevent overspeeding and steam leakage through the mid –span seal in the event of a turbine trip or shutdown
Error signal A signal that is derived by comparing the difference between a signal that indicates the actual value of quantity and s reference signal that indicates the desired value for that quantity
Exhaust hood The exhaust section of the outer casing in the LP turbine
Exhaust hood cooling system A turbine support system designed to minimize exhaust hood expansion and thus reduce stress on turbine parts
Fixed blading ( stationary blading ) Turbine blading that is fixed to the casing ; consists of nozzle –shaped blades that direct steam flow through the turbine and supply igh velocity steam to the moving blades
Flow indicator A device that provides a means of visually checking the oil leaving a bearing ; also called a sight box or a sight glass
Flyweights Parts of some mechanical governors ; consisting of a set of weighted arms connected together by spring
Full arc admission A methode of starting a turbine in which steam is distributed equally through the control valves to each section of the nozzle block so that the turbine is heated evenly
Gland A component of the gland seal system made of grooves and ridges designed to help seal the turbine ; usually suplied with steam or water ,which provides sealing
Gland seal system A turbine support system designed to prevent air from leaking into the turbine and prevent steam from leaking out ; sealing is accomplished by supplying steam to a series of glands located along the turbine shaft
Governor A device used to maintain the speed of a turbine at a desired value
Governor control switch A switch used to operate the turbine control valves and thus regulate load changes
Heat soak A procedure in which the speed of aturbine is held constant for a specified length of time ; a method used to bring steam –to-metal temperaure mismatches back to normal
High vibration trip A circuit designed to activate a solenoid trip when turbine vibration exceeds the maximum limit established by the turbine manufacture
Hydraulic actuator A device , consisting of casing , a piston , and a spring ,that is commonly used to operate a control valve
Hydraulic governor A goveernor that typicall consists of a centrifugal pump mounted on , and driven by , the shaft of a turbine . A relay connected to the hydraulic governor converts the discharge pressure of the hydraulic governor to a mechanical action
Impulse blading Moving blading in which the space between blades is the same size at the blading inlet and the blading outlet . Energy transfer in impulse blading results in decrease in steam velocity
Intercept valves Trubine steam valves designed to admit reheated steam to the IP turbine during normal operation , and to regulate or shut off the flow of steam to the IP turbine during emergencies or shutdowns; also designed to minimize turbine overspeed cause by a load rejection
Internal byapss valve A turbine valve that is part of the main stop valve ; designed to regulate the control of the steam flow into turbine during startups
Journal bearing A bearing that surrounds a turbine shaft and maintains the rotor’s radial position
Labyrinth A component of the gland seal system made of grooves and that form a maze or tortuos path to restrict the passage of a fluid such as air or steam
Linear variable differential transformer (LVDT) A device that transmita an electrical feedback signal to an electronic governor ; the signal is proportional to the movement of control valve
Load The amount of electrical usage in a power system
Load rejection A sudden reduction in the amount of electrical usage in the power system , which may cause a turbine to over speed
Low vacuum trip A circuit designed to activate a solenoid trip when vacuum in a condenser decrease to a preset limit
Lubricating oil system A turbine support system designed to provide lubricating oil to the turbine . Lubrication prevents metal-to metal contaact between stationary and rotating parts and abnormal due to friction
Lube oil trip A circuit desgneed to activate a selonoid trip when the lubrication oil pressure fals bellow a certain value
Main oil pump A componen of the turbine’s lubricating oil system ;an oil pump that is attach to and driven by the turbine rotor ,and whose discharge pressure is dependent on rotor speed ;design to provide turbine lubricating oil during normal operation
Main stop valves Turbine steam valvs designed to admit steam to the HP turbine during normal operation ,shut off the flow of steeeam during shutdown ,and reulted the flow of steam during start up also called “throtle valves”
Manual trip A trip that is iniatiated by an operator
Megawatt reacorder An intrument designed to measure the amount of load a turbine ia carrying
Mid-span seal A seal between the HP and IP section of the turbine;prevents steam from leaking between the two section during normal operation
Moving blading (buckets) Turbine blading that is attached to the shaft and converts the thermal energy in steam into mecanical energy
Multi –cylinder turbine A turbine consisting of two or more cylinders
Nozzle A set of fixed blade
Nozzle block The first row of fixed blading in control stage of turbine . The blades are usually separated into groups so that each group can be supplied with steam from an individual control valve
Overspeed mechanism A deice consisting of wheel and a bolt –spring assembly that activates the trip finger of the turbine trip system
Over speed trip A trip that is activated when the speed at which the turbine rotates exceeds a specific rated value
Partial arc admission A conditon occurs after the transfer point in a turbine start up ; a state in which steam is admitted through only part of the nozzle block at atime , as a result of the sequential opening and closing of the control valves
Peening The process in which shrouding is attached to arow of moving blading by hammering tenons on the blades through holes in the shrouding to rivet the shrouding to the blading
Pilot valve A device that is commonly used to regulate the flow of oil into and out of a hydraulic actuator
Pre –warming A period during which a turbine is warmed while still o turning gear ; a turbine warmup phase expressed in terms of minimum length of time required to reach a certain temperature
Pulling vacuum A turbine start up procedure in which a vacuum is created in the main condenser
Ramp rate The rate at which turbine metal temperature can be increased eadh hour during startup or decrease each hour during shutdown
Reaction blading Moving blading in which the space between blades is smaller at the exhaust than at the inlet . Energy transfer in reaction blading results in a decrease in steam pressure and velocity
Reheater A section of the turbine where steam is given additional heating , enabling the steam to perform more useful work in the rest of the turbine
Reheat stop valves Turbine steam valves designed to admit reheated stemto the IP turbinr during normal operation and to shut off the flow of steam during shutwdowns or emergencies
Rotor A turbine shaft and attached blading that convert the energy in steam into mechanical energy
Rotor –long condition A condition in which the rotor of a turbine expands faster than shell
Rotor –short condition A condition in which the rotor of a turbine contracts faster than the shell
Shrouding A metal band attached to the outer edge of turbine’s moving blading to dampen blade vibration
Single casing A type of turbine casing in which all the turbine elements are contained within a sigle enclosure
Solenoid trip A trip activated by electrical inputs from various circuits designed to protect the turbine
Sounding out The act of listening for any unusual or abnormal noises in a turbine
Speed changer A device designed to adjust the speed of a turbine and to control the amount of the steam admitted
Stage One row of fixed blading and one row of moving blade
Steam –to –metal temperature mismatch The difference in temperature between the steam and the metal in a turbine
Tandem –compound A turbine cylinder arrangement in which one shaft (or several shafts that are coupled together ) , drives on generator
Tenon A raised knob on the end of a moving blade that is peened over shrouding to rivet the shrouding to the blading
Throttle pressure The steam pressure between the boiler and the main stop valves; also called “before seat “ pressure
Thrust A force created when moving steam strikes the blades in the turbine ; the thrust is in the direction of the steam flow
Thrust bearing A bearing consisting of two thrust plates , which surround a turbine shaft and ,one thrust runner , which is an integral part of the shaft . Axial rotor movement is prevented by the thrust plates blocking the movement of the thrust runner
Thrust bearing trip A circuit designed to activate a solenoid trip when turbine movement exceeds a certain preset value
Transfer point A point during start up when control of steam flow is transferred from stop valves to the control valves
Turning gear A turbine component designed to turn the rotor slowly during startups and shutdowns , thus minimizing rotor eccentricity
Turbine trip An immmediate closure of the turbine steam valves
Vacuum breaker A valve connected to the main condenser that , when opened ,lets air into the condenser ; closed during start ups and ususlly opened during shutdowns
Vapor extractor A component of the turbine lubricating oil system designed to remove potentially dangerous vapors from the oil reservoir
Ventilator valve A turbine valve designed to prevent the turbine from overheating during turbine trip or shutdown by discharging hot , trapped steam to a low pressure area
Water induction The entrance of water into a turbine
Water seal system A turbine support system that uses water to seal air out of the turbine and seal steam in

BASIC WATER CHEMISTRY
Acid A solution that contains hydrogen inos and has a pH less than 7
Acid attack Corrosion cause by an acid
Activated charcoal Charcoal that has been processwf to increase its surface area ; used as a filter medium
Alkali A solution that contains hydroxide ions and has a pH more than 7
Alloy A man –made subtance composed of two or more metals combined by heating
Anion resin beads Resin beads in ion exchanger that attract negative ion
Anthrancite coal Charcoal that can be used as a filter medium
Atom The smallest division of an element that still retains the chemical properties of the element
Atomic number The number of protons in one atom of an element
Atomic weight The weight of an element with respect to the weight of carbon
Avagadro’s number The number of atoms in agram atom of any element or the number of moleculs in amole of any compound ; equal to 6.023 x 1023
Backwashing A process of revesing the flow of water through a filter or an ion exchanger
Blanketing A process using a layer of steam or nitrogen to limit the dissolved oxygen in water
Blowdown A process for removing impurities from water that involves removing part of water
Carry over The process by which impurities in boiler water are transported into the steam areas by water droplets
Cation resin beads Resin beads in an ion exchanger that attract positive ions
Caustik attack Corrosion caused by an alkali
Clarifier A type of water treatment equipment used to remove large concentrations of suspended solids from raw water
Closed system A water system that is not exposed to atmosphere