All-volatile treatment program (AVT) - A treatment program in which all of the treatment components are fully volatile.

Cascading blowdown - Cascading blowdown generally refers to the process in which the highest-pressure drum continuous blowdown is directed to a lower-pressure steam drum to improve cycle efficiency.

Cation conductivity - The conductivity of a sample after passing it through an acid- form strong acid cation resin column, whereby all cations have been replaced by hydrogen ions.

Combined cycle - A combined cycle is any combination of a gas turbine, steam generator (or other heat recovery equipment), and steam turbine used to improve cycle efficiency in the power generation process.

Combustion turbine (CT) - Gas turbine. A turbine that uses the products of combustion to spin the turbine.

Combustion turbine steam power augmentation - The practice of injecting steam to increase the mass flow through the combustion turbine.

Cycling service - Operation at variable load.

Degassed cation conductivity - Degassed cation conductivity either heats the sample to boiling or purges the sample with nitrogen prior to the measurement of cation conductivity, thereby driving off gases and other volatile components.

Dry running condition - Condition of running without water in the tubing of once- through steam generators, especially during start-up.

Duct burner - A supplemental burner located within the gas turbine exhaust used to increase exhaust temperature and the amount of steam which can be produced by the heat recovery steam generator.

Equilibrium phosphate treatment (EPT) - A phosphate-pH control treatment program that typically maintains a phosphate concentration <2 ppm (mg/l).

evaporative cooling - The practice of cascading water across loose media perpendicular to the airflow to reduce the air temperature. Used to cool combustion turbine inlet air.

Flow accelerated corrosion (FAC) - A process whereby the normally protective oxide surface dissolves into a moving fluid. Metal loss occurs by the interaction of electrochemical and physical effects. In the case of carbon steels, this occurs under very specific, well-defined conditions. When the rate of oxide growth is unable to keep up with the metal dissolution rate, then rapid corrosion rates can ensue. The phenomenon typically occurs in areas of high local flow turbulence.

Fluxing chemical - A chemical that removes surface metal oxides.

Grab sample - A grab sample is a sample collected over a single, relatively short, interval of time.

Heat recovery steam generator (HRsG) - A steam generator that sits in the gas turbine exhaust and is designed to recover the thermal energy remaining after the gas turbine.

Hideout - Apparent loss of boiler water phosphate in high-pressure water-tube boilers operating under high load conditions. The salts reappear when the load is reduced.

Inlet fogging - The practice of spraying water directly into the turbine inlet air stream.

integral deaerator - A deaerator that sits on top of the low-pressure drum and uses its drum for storage.

Low-level phosphate treatment - A phosphate-pH control treatment program that usually operates with a range of phosphate between 2-6 ppm (mg/l).

once-through steam generating units (oTsGs) -The water is pumped into the unit as a subcooled liquid, passes over the heating surfaces, and is converted to steam as it absorbs the heat. There is no recirculation of the water within the unit and no conventional drum for the separation of water and steam. Water flows sequentially through the economizer, evaporator and superheater.

oxygenated treatment program (oT) - A treatment program that uses oxygenated high-purity water to minimize corrosion and/or flow assisted corrosion in the feedwater train. It can only be used in all-ferrous systems with feedwater cation conductivity <0.15 pS/cm.

Mixed metallurgy - Plants with a mixture of ferrous and copper-bearing alloys in the steam/water cycle.

Phosphate Gouging - The dissolution of carbon steel by localized high concentrations of mono- or disodium phosphate to form maricite (NaFe- PO4) and other sodium iron phosphate compounds. Crusty alternating black-and-white layered deposits may remain with knife-edge-like surfaces in the gouged area. Corrosion also requires a phosphate concentrating mechanism, such as steam blanketing or boiling within porous deposits, and buildup of a thermal barrier from the boiler water.

Simple cycle gas turbine - A combustion gas turbine without a heat recovery steam generator.

Steam host - A user of the steam produced by a combined cycle system.

Steam purity - Steam purity is an expression of the quantity of nonwater components contained in the steam. These components can be dissolved in the steam, dissolved in water droplets entrained in the steam, or carried as discrete solid particles with the steam.

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