Engineering Dictionary C
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Table of contents Power Plant Dictionary


Carnot Cycle - The most efficient heat engine cycle is the Carnot cycle, consisting of two isothermal processes and two adiabatic processes. The Carnot cycle can be thought of as the most efficient heat engine cycle allowed by physical laws

CALCAREOUS COATING OR DEPOSIT - A layer consisting of a mixture of calcium carbonate and magnesium hydroxide deposited on surfaces being cathodically protected against corrosion, because of increased pH adjustment to the protected surface.

CO - Carbon monoxide (CO) is a colorless, odorless, poisonous gas. It is produced by the incomplete burning of solid, liquid, and gaseous fuels. Appliances fueled with natural gas, liquefied petroleum (LP gas), oil, kerosene, coal, or wood may produce CO. Burning charcoal produces CO. Running cars produce CO

CO2 - is an atmospheric gas composed of one carbon and two oxygen atoms. Carbon dioxide results from the combustion of organic matter if sufficient amounts of oxygen are present. It is also produced by various microorganisms in fermentation and is breathed out by animals. Plants absorb carbon dioxide during photosynthesis, using both the carbon and the oxygen to construct carbohydrates. It is present in the Earth's atmosphere at a low concentration and acts as a greenhouse gas. It is a major component of the carbon cycle.

CALCIUM - A scale forming element found in boiler feed water.

CALCIUM CHLORIDE - A substance used to obtain calcium chloride brine.

CALCIUM SULFATE - Chemical compound (CaSO4) which is used at a drying agent or desiccant in liquid line dryers.

CALIBRATION - A process of dividing and numbering the scale of an instrument; also of correcting or determining the error of an existing scale, or of evaluating one quantity in terms of readings of another.

CALORIE - It is equal to the amount of heat required to raise the temperature of one gram of water one degree Celsius.

CALORIMETER - Device used to measure quantities of heat or determine specific heats.

CHANGE OF STATE - Change from one phase, such as solid, liquid or gas, to another.

CAPACITANCE - The property of an electric current that permits the storage of electrical energy in an electrostatic field and the release of that energy at a later time.

CAPACITOR, (CONDENSER) - A device that can store an electric charge when voltage is applied.

CAPACITY - The adsorption activity possessed in varying degrees by ion-exchange materials. This quality may be expressed as kilograms per cubic foot, gram-milliequivalents per gram, pound-equivalents per pound, gram-milliequivalents per milliliter, and so on, where the numerators of these ratios represent the weight of the ions adsorbed and the denominators represent the weight or volume of the adsorbent.

CAPILLARY - The name given to the thin tube attached to the bulb which transmits the bulb pressure changes to the controller or indicator. The cross sectional area of the capillary is extremely small compared to the cross section of the bulb so that the capillary, which is usually outside of the controlled fluid, will introduce the smallest possible error in the signal being transmitted from the bulb.

CAPILLARY TUBE - The capillary tube is a metering device made from a thin tube approximately 0.5 to 6 meter long and from 0.025 to 0.090 inches in diameter which feeds liquid directly to the evaporator. Usually limited to systems of 1 ton or less, it performs all of the functions of the thermal expansion valve when properly sized.

CARBON DIOXIDE - Compound of carbon and oxygen (CO2) which is sometimes used as a refrigerant. Refrigerant number is R-744.

CARBON FILTER - Air filter using activated carbon as air cleansing agent.

CARBON RINGS -  To minimize steam leakage, gland sealing arrangement features an angle-type, carbon ring design with a packing case that is an integral part of the turbine case. Inconel springs hold the rings in place.

CARBON TETRACHLORIDE - Colorless nonflammable and very toxic liquid used as a solvent. It should never be allowed to touch skin and fumes must not be inhaled.

CARBONACEOUS EXCHANGER - Ion-exchange materials of limited capacity prepared by the sulfonation of coal, lignite, peat, and so on.

CARBONATE - An ion or salt of carbonic acid, containing carbon and oxygen such as calcium carbonate. (CaC03)

CARBONATE HARDNESS - That hardness caused in water by bicarbonates and carbonates of calcium, and magnesium.

CARBONATE-POLYMER TREATMENT - A treatment method using synthetic polymers, generally used with high hardness (60-70) ppm and high alkalinity.

CARBOXYLIC - A term describing a specific acidic group (COOH) that contributes cat ion-exchange ability to some resins.

CARRYOVER - The moisture and entrained solids forming the film of steam bubbles, as a result of foaming in a boiler. This condition is caused by a faulty boiler water condition. See also foaming.

CASCADE - A series of stages in which the output of one stage is the input of the next stage.

CASCADE SYSTEMS - Arrangement in which two or more refrigerating systems are used in series; uses evaporator of one machine to cool condenser of other machine. Produces ultra-low temperatures.

CATHODE - In electrolysis or electrochemical corrosion, a site on a surface where actions in solution are neutralized by electrons to become elements that either plate out on the surface or react with water to produce a secondary reaction.

CATHODE PROTECTION - A method of preventing corrosion by making the metal a cathode in a conducting medium by means of a direct electrical current that is galvanic.

CATHODIC PROTECTION - Reduction of corrosion rate by shifting the corrosion potential of the electrode towards less oxidizing potential by applying an external electromotive force.

CATION - A positively charged ion that migrates through the electrolyte toward the cathode under the influence of a potential gradient.

CATION-EXCHANGE SOFTENERS - Ion exchange units are known primarily as water softeners. But they can also remove nitrates, sulfates, and various toxic metals from water.  ion exchangers. PDF

CATIONIC - The condition of a polymer, colloid, or large particle having exchangeable anions on its surface and an opposite, positive charge on the substrata.

CAUSTIC CRACKING - A form of stress-corrosion cracking most frequently encountered in carbon steels or iron-chromium-nickel alloys that are exposed to concentrated hydroxide solutions at temperature of 200 to 250C.

CAUSTIC EMBRITTLEMENT - An obsolete term replaced by caustic cracking.

CAUSTIC SODA - A common water treatment chemical, sodium hydroxide.

CAVITATION - The formation and collapse, within a liquid, of cavities or bubbles that contain vapor or gas or both. In general, cavitation originates from decreases in static pressure in the liquid. In order to erode a solid surface by cavitation, it is necessary for the cavitation bubbles to collapse on or close to that surface.


CAVITATION EROSION - Progressive loss of original material from a solid surface due to continuing exposure to cavitation.

CELSIUS TEMPERATURE SCALE - A thermometric scale in which the freezing point of water is called 0C and its boiling point 100C at normal atmospheric pressure.

CENTANE NUMBER - A measure of ignition quality of a fuel or petroleum with reference to normal centane high-ignition quality fuel with an arbitrary number of 100.

CENTRIFUGAL COMPRESSOR - Pump which compresses gaseous fluids by centrifugal force.

CENTRIFUGAL FORCE - is actually not a force but the experience of an inertial force experienced in a rotating reference frame acting away from the center of the rotation. It is equal in magnitude but opposite to the centripetal force required to constrain the body to move in a circular motion. s actually not a force but the experience of an inertial.

CENTRIFUGAL FORCE -On a centrifugal pump, it is that force which throws water from a spinning impeller.

CENTRIFUGAL PUMP - A pump consisting of an impeller fixed on a rotating shaft and enclosed in a casing, having an inlet and a discharge connection. The rotating impeller creates pressure in the liquid by the velocity derived from centrifugal force.

CENTRIFUGAL PUMP - Pump which produces fluid velocity and converts it to pressure head.

Centripetal force - is the force that causes an object to move in a circle, acting towards the centre of the circle. In the case of a satellite the centripetal force is gravity, in the case of an object at the end of a rope, the centripetal force is the tension of the rope.

CHANGE OF STATE - Condition in which a substance changes from a solid to a liquid or a liquid to a gas caused by the addition of heat. Or the reverse, in which a substance changes from a gas to a liquid, or a liquid to a solid, caused by the removal of heat.

CHANNELING - Cleavage and furrowing of the bed due to faulty operational procedure, in which the solution being treated follows the path of least resistance, runs through these furrows, and fails to contact active groups in other parts of the bed, (water treatment).

CHARGE - Amount of refrigerant placed in a refrigerating unit.

CHARGING BOARD - Specially designed panel or cabinet fitted with gauges, valves and refrigerant cylinders used for charging refrigerant and oil into refrigerating mechanisms.

CHECK VALVE - Device which permits fluid flow in one direction.

CHELATE - Is a molecule, similar to an ion exchanger, capable to withdraw ions from their water solutions into soluble complexes.

CHEMICAL CLEANING - Using a solvent solution to remove mill scale and corrosion products.

CHEMICAL FEEDLINE - The line which feeds the boiler treatment chemicals into the boiler.

CHEMICAL PRECIPITATION - When the chemicals react with the dissolved minerals in the water to produce a relative insoluble reaction product. A typical example of this takes place with the lime-soda softening process.

CHEMICAL REFRIGERATION - System of cooling using a disposable refrigerant. Also called an expendable refrigerant system.

CHEMICAL STABILITY - Resistance to chemical change which ion-exchange resins must possess despite contact with aggressive solutions.

CHILL FACTOR - Calculated number based on temperature and wind velocity.

CHILLED-WATER SYSTEM - A re-circulating water system using water chilled in a refrigeration machine as a source for cooling.

CHILLER/HEATERS - A unit that supplies either chilled water for cooling or hot water for heating, (HVAC).

CHLORIDE - An ion, compound, or salt of chlorine, such as sodium chloride (NaCl) or calcium chloride (CaCl2).

CHLORINATION - A process in which chlorine gas or other chlorine compounds are added to the water for the purpose of disinfecting.

CHOKE TUBE - Throttling device used to maintain correct pressure difference between high-side and low-side in refrigerating mechanism. Capillary tubes are sometimes called choke tubes.

CHORDAL THERMOCOUPLE - A thermocouple installed in furnace tubes, designed to measure the effectiveness of water treatment within the boiler.

CIRCUIT - An electrical arrangement requiring a source of voltage, a closed loop of wiring, an electric load and some means for opening and closing it.

CIRCUIT BREAKER - A switch-type mechanism that opens automatically when it senses an overload (excess current).

CLAY - Finely suspended earth mineral sometimes found as an impurity in water.

CLEARANCE SPACE - Space between top of piston and the valve plate.

CLEARANCE VAPOR - The vapor remaining in the clearance space at the end of each discharge stroke.

CLOSED CYCLE - is the gas turbine arrangement, in which the exhaust is directed back again to compressor without coming in contact with the atmospheric air.

CLOSED FEED WATER HEATER - An indirect-contact feed water heater. Steam and water are separated by tubes.

CLOSED RE-CIRCULATING WATER SYSTEM - A system using as a heat-transfer medium water that continuously circulates through closed piping and heat exchanger without evaporation.

CO COAGULANT - A substance that promotes the clumping of particulate matter in water, forming a larger mass and thus promoting settling of particulates and clarification of the water.

COAGULATION - Is the process whereby finely divided particles of turbidity and color, capable of remaining in suspension indefinitely, are combined by chemical means into masses sufficiently large to effect rapid settling.

COALESCENCE - The gathering together of coagulated colloidal liquids into a single continuous phase.

CODE INSTALLATION - Refrigeration or air conditioning installation which conforms to the local code and/or the national code for safe and efficient installations.

CO-EFFICIENT OF CONDUCTIVITY - Measure of the relative rate at which different materials conduct heat. Copper is a good conductor of heat and, therefore, has a high coefficient of conductivity.

COEFFICIENT OF EXPANSION - A measure of the change in length or volume of an oject, specifically, a change measured by the increase in length or volume of an object per unit length or volume.

COEFFICIENT OF FRICTION - The dimensionless ratio of the friction force (F) between two bodies to the normal force (N) pressing these bodies together - m (f) = (F/N)

COEFFICIENT OF PERFORMANCE (COP) - Ratio of work performed or accomplished as compared to the energy used under designated operating conditions.

COEFFICIENT OF THERMAL EXPANSION - The fractional change in length (or sometimes in volume, when specified) of a material for a unit change in temperature.

COGENERATION - A term used to describe the combination of different thermodynamic cycles for the purpose of increasing all-over cycle efficiency.

CO-GENERATION GENERATION - a term applied to identify the generation of people interested in co-generation.

COLD - The absence of heat; a temperature considerably below normal.

COLD DECK -The cooling section of a mixed air zoning system.

COLD JUNCTION - That part of a thermoelectric system which absorbs heat as the system operates.

COLD PROCESS - A water treatment process carried out at room temperature.

COLD WALL - Refrigerator construction which has the inner lining of refrigerator serving as the cooling surface.

COLLOIDAL - A state of suspension in a liquid medium in which extremely small particles are suspended and dispersed but not dissolved.

COLLOIDS - Organic matter of very fine particle size, usually in the range of 10-5 to 10-7 cm in diameter. It tends to inhibit the formation of dense scale and results in the deposition of sludge, or causes it to remain in suspension, so that it may be blown from the boiler.

COLUMN OPERATION - Conventional utilization of ion-exchange resins in columns through which pass, either upflow or down flow, the solution to be treated.

COMBINED FEEDER CUTOFF - A device that regulates makeup water to a boiler in combination with a low-water fuel cutoff.

COMBINED STEAM-GAS PLANT - where a gas turbine is combined with steam plant in order to utilize the waste heat.

COMBINED TREATMENT - A method of physical treatment , followed by the addition of chemicals to remove oxygen.

COMBUSTION - The act or process of burning.

COMFORT CHART - A chart showing effective temperatures with dry-bulb temperatures and humidity's (and sometimes air motion) by which the effects of various air conditions on human comfort may be compared.

COMFORT COOLER - System used to reduce the temperature in the living space in homes. These systems are not complete air conditioners as they do not provide complete control of heating, humidifying, dehumidification, and air circulation.

COMFORT COOLING - Refrigeration for comfort as opposed to refrigeration for storage or manufacture.

COMFORT ZONE - (Average) the range of effective temperatures over which the majority (50 percent or more) of adults feels comfortable; (extreme) the range of effective temperatures over which one or more adults feel comfortable. An area on the psychometric chart which shows conditions of temperature, humidity and sometimes air movement in which most people are comfortable.

COMMON NEUTRAL - A neutral conductor that is common to, or serves, more than one circuit.

COMPOSITION - The elements or chemical components that make up a material and their relative proportions.

COMPOUND - They are chemically combined elements with definite proportions of the component elements.

COMPOUND GAUGE - Instrument for measuring pressures both above and below atmospheric pressure.

COMPOUND REFRIGERATING SYSTEMS - System which has several compressors or compressor cylinders in series. The system is used to pump low pressure vapors to condensing pressures.

COMPRESSION - Term used to denote increase of pressure on a fluid by using mechanical energy.

COMPRESSION RATIO - Ratio of the volume of the clearance space to the total volume of the cylinder. In refrigeration it is also used as the ratio of the absolute low-side pressure to the absolute high-side pressure.

COMPRESSION, ADIABATIC - Is compressing a gas without removing or adding heat.

COMPRESSOR - Pump of a refrigerating mechanism which draws a low pressure on cooling side of refrigerant cycle and squeezes or compresses the gas into the high-pressure or condensing side of the cycle.

COMPRESSOR - The pump which provides the pressure differential to cause fluid to flow and in the pumping process increases pressure of the refrigerant to the high side condition. The compressor is the separation between low side and high side.

COMPRESSOR DISPLACEMENT - Volume, in cubic inches, represented by the area of the compressor piston head or heads multiplied by the length of the stroke.

COMPRESSOR SEAL - Leak proof seal between crankshaft and compressor body in open type compressors.

COMPRESSOR SURGING - An instability of air flow with axial compressor on the first stages of these compressors. Air flow might even be reversed that point.

COMPRESSOR TURBINE - in terms of a gas turbine arrangement, it is the turbine which drives the compressor only.

COMPRESSOR, CLEARANCE POCKET - Small space in a cylinder from which compressed gas is not completely expelled. This space is called the compressor clearance space or pocket. For effective operation, compressors are designed to have as small a clearance space as possible.

COMPRESSOR, ROTARY BLADE - Mechanism for pumping fluid by revolving blades inside cylindrical housing.

COMPRESSOR, SINGLE-STAGE - Compressor having only one compressive step between low-side pressure and high-side pressure.

COMPRESSIBILITY - The ease which a fluid may be reduced in volume by the application of pressure, depends upon the state of the fluid as well as the type of fluid itself.

CONDENSATE - The liquid formed by condensation of a vapor. In steam heating, water condensed from steam; in air conditioning, water extracted from air, as by condensation on the cooling coil of a refrigeration machine.

CONDENSATE POLISHER - A device used to clean the returning condensate to the boiler feedwater system.

CONDENSATE PUMP - Device to remove water condensate that collects beneath an evaporator.

CONDENSATION - Process of changing a vapor into liquid by extracting heat. Condensation of steam or water vapor is effected in either steam condensers or dehumidifying coils, and the resulting water is called condensate.

CONDENSE - Action of changing a gas or vapor to a liquid.

CONDENSER - An apparatus used to transfer heat from a hot gas, simultaneously reducing that gas to a liquid.


CONDENSER TUBE - The heat transfer surface in a condenser.

CONDENSER-WATER SYSTEM - A re-circulating cooling water used as a heat transfer fluid for the condensation of a gas.

CONDENSING TEMPERATURE - The temperature at which the condensing gas is returned to a liquid at the same pressure.

CONDENSING TURBINE - With this turbine, the steam exhausts to the condenser and the latent heat of the steam is transferred to the cooling water. The condensed steam is returned to the boiler as feedwater.

CONDENSING UNIT - Part of a refrigerating mechanism which pumps vaporized refrigerant from the evaporator, compresses it, liquefies it in the condenser and returns it to the refrigerant control.

CONDENSING UNIT SERVICE VALVES - Shutoff valves mounted on condensing unit to enable service technicians to install and/or service unit.

CONDENSING UNIT, REFRIGERANT - An assembly of refrigerating components designed to compress and liquefy a specific refrigerant, consisting of one or more refrigerant compressors, refrigerant condensers, liquid receivers (when required) and regularly furnished accessories.

CONDUCTANCE, ELECTRICAL - The reciprocal (opposite) of resistance and is the current carrying ability of any wire or electrical component. Resistance is the ability to oppose the flow of current.

CONDUCTANCE, SURFACE FILM - Time rate of heat flow per unit area under steady conditions between a surface and a fluid for unit temperature difference between the surface and fluid.

CONDUCTION - Transfer of heat by direct contact.

CONDUCTIVITY (ELECTRICAL) - The ability of a liquid to conduct an electrical current and indicating the presence of cat ions and anions. Conductivity is usually expressed in Micromos per cm.

CONDUCTIVITY (THERMAL) - The time rate of heat flow through unit thickness of an infinite slab of homogeneous material in a direction perpendicular to the surface, induced by unit temperature difference. (W/m K)

CONDUCTIVITY METER - An electric instrument used to measure the conductivity of water to determine its content of dissolved solids.

CONDUCTIVITY, THERMAL - The time rate of heat flow through unit area and unit thickness of a homogeneous material under steady conditions when a unit temperature gradient is maintained in the direction perpendicular to area. Materials are considered homogeneous when the value of the thermal conductivity is not affected by variation in thickness or in size

CONDUCTOR - Substance or body capable of transmitting electricity or heat.

CONDUIT - A round cross-section electrical raceway, of metal or plastic.

CONGEALER - Also known as freezer.

CONGRUENT PHOSPHATE CONTROL - Similar as a coordinated phosphate control but more restrictive where the equilibrium is based on maintaining a ratio of 2.6 Na/1.0 PO4, instead of 3.0/1.0 PO4.

CONNECTED LOAD - The sum of all loads on a circuit. (1) Connection in Parallel: System whereby flow is divided among two or more channels from a common starting point or header. (2) Connection in Series: System whereby flow through two or more channels is in a single path entering each succeeding channel only after leaving the first or previous channel.

CONSTRICTOR - Tube or orifice used to restrict flow of a gas or a liquid.

CONTAMINATION - The introduction into water of microorganisms, chemicals, toxic materials, waste water in a concentration that makes the water unfit for its next intended use.

CONTROL - A device for regulation of a system or component in normal operation, manual or automatic. If automatic, the implication is that it is responsive to changes of pressure, temperature or other property whose magnitude is to be regulated.

CONTROL POINT - The value of the controlled variable which the controller operates to maintain.

CONTROL VALVE - Valve which regulates the flow or pressure of a medium which affects a controlled process. Control valves are operated by remote signals from independent devices using any of a number of control media such as pneumatic, electric or electro hydraulic.

CONTROLLED DEVICE - One which receives the converted signal from the transmission system and translates it into the appropriate action in the environmental system. For example: a valve opens or closes to regulate fluid flow in the system.

CONTROLLER - A device capable of measuring and regulating by receiving a signal from a sensing device, comparing this data with a desired value and issuing signals for corrective action.

CONVECTION - The movement of a mass of fluid (liquid or gas) caused by differences in density in different parts of the fluid; the differences in density are caused by differences in temperature. As the fluid moves, it carries with it its contained heat energy, which is then transferred from one part of the fluid to another and from the fluid to the surroundings.

CONVECTION, FORCED - Convection resulting from forced circulation of a fluid, as by a fan, jet or pump.

CONVECTION, NATURAL - Circulation of gas or liquid (usually air or water) due to differences in density resulting from temperature changes.

CONVERGENT NOZZLE - Impulse Turbine - Stationary convergent nozzles are used for smaller pressure drops where the minimum exit pressure is 0.577 x the inlet pressure (the critical pressure for nozzles.) If the exit pressure is less than 0.577 x inlet pressure, eddy-currents are developed and the exit velocity will be less than calculated.

-  Impulse Turbine - Stationary convergent-divergent nozzles prevent eddy-currents and the calculated velocity will be obtained even at large pressure drops.

COOLER - Heat exchanger which removes heat from a substance.

COOLING EFFECT, SENSIBLE - The difference between the total cooling effect and the dehumidifying effect, usually in watts.

COOLING EFFECT, TOTAL - Difference between the total enthalpy of the dry air and water vapor mixture entering the cooler per hour and the total enthalpy of the dry air and water vapor mixture leaving the cooler per hour, expressed in watts.

COOLING TOWER - Device for lowering the temperature of water by evaporative cooling, in which water is showered through a space through which outside air circulates. A portion of the water evaporates, its latent heat of vaporization cooling that portion of the water which does not evaporate.

COOLING, EVAPORATIVE - Involves the adiabatic exchange of heat between air and water spray or wetted surface. The water assumes the wet-bulb temperature of the air, which remains constant during its traverse of the exchanger.

COOLING, REGENERATIVE - Process of utilizing heat which must be rejected or absorbed in one part of the cycle to function usefully in another part of the cycle by heat transfer.

COORDINATED PHOSPHATE CONTROL A treatment to prevent caustic gauging. Free caustic is eliminated by maintaining an equilibrium between the sodium and phosphate. Control is based on maintaining a ratio of 3.0 Na to/1.0 PO4.

CORROSION - The chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties.

CORROSION, ANODE - The dissolution of an metal acting as an anode.

CORROSION, ATMOSPHERIC - The gradual degradation or alteration of a material by contact with substances present in the atmosphere, such as oxygen, carbon dioxide, water vapor, and sulfur and chlorine compounds.

CORROSION, BIOLOGICAL - Deterioration of metals as a result of the metabolic action of microorganisms. Also often named fouling.

CORROSION, CATHODIC - Corrosion resulting resulting from a cathodic condition of a structure usually caused by the reaction of an amphoteric metal with the alkaline products of electrolysis.

CORROSION, CAVITATION - A process involving conjoint corrosion and cavitation.

CORROSION, CONCENTRATION ATTACK - A form of corrosion caused by the concentration of caustic or phosphate salts under porous deposits, generally iron oxide. Sometimes found at welded tubes and due to steam blanketing.

CORROSION, CONCENTRATION-CELL - Pitting type of corrosion caused by an electrical potential differential between surfaces of a metal as a result of deposits or differences in the solution concentration in contact with the metal.

CORROSION, COUPONS - Pre-weighed metal strips installed into fluid systems for the purpose of monitoring metal losses.

CORROSION, CREVICE - Localized corrosion of a metal surface at, or immediately adjacent to an area that is shielded from full exposure to the environment because of close proximity between metal and the surface of another metal.

CORROSION, DEACTIVATIONS - The process of prior removal of the active corrosive constituents, usually oxygen, from a corrosive liquid by controlled corrosion of expendable metal or by other chemical means, thereby making the liquids less corrosive.

CORROSION, DEPOSIT (also called poultice corrosion) - Corrosion occurring under or around a discontinuous deposit on a metallic surface.

CORROSION, EFFECT - A change in any part of the corrosion system caused by corrosion.

CORROSION, ELECTROCHEMICAL - Corrosion that is accompanied by a low of electrons between cathodic and anodic areas on metallic surfaces.

CORROSION, EMBRITTLEMENT - The severe loss of ductility of a metal resulting from corrosive attack, usually intergranular and often not visible.

CORROSION, EXTERNAL - A chemical deterioration of the metal on the fireside of boiler heating surfaces.

CORROSION, FATIGUE - The process in which a metal fractures prematurely under conditions of simultaneous corrosion and repeated cyclic loading at lower stress levels or fewer cycles than would be required in the absence of the corrosive environment.

CORROSION, FILIFORM - Corrosion that occurs under organic coatings on metals as fine wavy hairlines.

CORROSION, FRETTING - A type of corrosion which occurs where metals slide over each other. Long tubes in heat exchangers often vibrate, causing metal to metal contact, tube supports etc.. The metal to metal rubbing causes mechanical damage to the protective oxide coating.

CORROSION, GALVANIC - Corrosion of a metal caused by its contact with a metal of lower activity; this contact results in an electron flow or current and dissolution of one of the metals.

CORROSION, GASEOUS - Corrosion with gas as the only corrosive agent and without any aqueous phase on the surface of the metal. Also called dry corrosion.

CORROSION, GENERAL - A form of deterioration that is distributed more or less uniformly over a surface.

CORROSION, GRAPHITIC - Corrosion of grey iron in which the iron matrix is selectively leached away, leaving a porous mass of graphite behind. This type of corrosion occurs in relative mild aquous solutions and on buried piping.

CORROSION, HOT - An accelerated corrosion of metal surfaces that results from the combined effect of oxidation and ractions with sulfur compounds or other contaminants such as chlorides, to form a molten salt on a metal surface that fluxes, destroys or disrupts the normal protective oxide. (commonly found in pulp mills)

CORROSION, IMPINGEMENT - A form of erosion-corrosion generally associated with local impingement of a high velocity, flowing fluid against a solid surface.

CORROSION, INFLUENCED - The corrosion cause by organisms due to their discharge containing sulfur compounds and the depolarization with other types of discharge due to the presence of the microorganisms.

CORROSION, INHIBITORS - Substances that slow the rate of corrosion.

CORROSION, INTERCRYSTALINE -(see intergranular cracking)

CORROSION, INTERGRANULAR - Localized attack occurring on the metal grain boundaries. This is commonly found with stainless steels which have been improperly heat treated.

CORROSION, INTERNAL - Usually refers to the internal corrosion and is considered an electrochemical deterioration of the boiler surface at or below the water surface.

CORROSION, LOCALIZED - Corrosion at discrete sites, for example, crevice corrosion, pitting, and stress-corrosion cracking.

CORROSION, LOCALIZED - Non-uniform corrosion of a metal surface highlighted by spotty or pitting-type corrosion.

CORROSION, MICROBIAL - (see biological corrosion).

CORROSION, OXYGEN DEFICIENCY - A form of crevice corrosion in which galvanic corrosion proceeds because oxygen is prevented from diffusing into the crevice.

CORROSION, POTENTIAL - The voltage between a corroding metal and a reference electrode.

CORROSION, POULTICE - (see corrosion, deposit)

CORROSION, POULTICE - A term used in the automotive industry to describe the corrosion of vehicle body parts due to the collection of road salts and debries on ledges and in pockets that are kept moist by weather and washing.

CORROSION, PROTECTION - Modification of a corrosion system so that corrosion damage is mitigated.

CORROSION, RESISTANCE - The ability of a material to resist deterioration by chemical or electrochemical reaction with its environment.

CORROSION, STRAY CURRENT - A form of attack caused by electrical currents going through unintentional path.

CORROSION, STRESS - Preferential attack of areas under stress in a corrosive environment, where such a environment alone would not have caused corrosion.

CORROSION, STRESS CORROSION CRACKING - Material deterioration due to cracking, by being under static stress either applied or residual.

CORROSION, SWEET - The deterioration of metal caused by contact with carbon dioxide in water.

CORROSION, THERMO-GALVANIC - Corrosion resulting from an electrochemical cell caused by a thermal gradient.

CORROSION, UNIFORM - The simplest form of corrosion. It attacks all surfaces exposed to a corrodent.

CORROSIVE WEAR - A material deterioration due to the co-joint action of corrosion and mechanical action.

CORROSIVITY - An indication of the corrosiveness of the water of material. The corrosivity of a water as described by the waters pH, alkalinity, hardness, temperature, total dissolved solids, dissolved oxygen concentration and the Langerier Index.

COUNTER-FLOW HEAT EXCHANGER - When the fluid to be cooled flows against the direction of the coolant. In heat exchange between two fluids, opposite direction of flow, coldest portion of one meeting coldest portion of the other.

COVALENT BOND - A bond in which two atoms share pair of electrons.

CRANKSHAFT SEAL - Leak proof joint between crankshaft and compressor body.

CRAZE CRACKING (OR CHECKING) - Irregular surface cracking of metal associated with thermal cycling.

CREEP - Time dependent permanent strain under stress. This is used to rate the resistance of a material to plastic deformation under sustained load.

CREEP STRENGTH - The constant nominal stress that will cause a specified quantity of creep in a given time at constant temperature. Creep strength is expressed as the stress necessary to produce 0.1% strain in 1000 hours.

CREEP, DYNAMIC - Creep that occurs under conditions of fluctuating load or fluctuating temperatures.

CRISPER - Drawer or compartment in refrigerator designed to provide high humidity along with low temperature to keep vegetables, especially leafy vegetables - cold and crisp.

CRITICAL HUMIDITY - The relative humidity above which the atmospheric corrosion rate of some metals increase sharply.

CRITICAL POINT - A point at which the saturated liquid and saturated vapor states are identical. Also, the latent heat of evaporization is zero at this point.

CRITICAL PRESSURE - The pressure at the critical temperature above which the fluid no longer has the properties of a liquid, regardless of further increase of pressure.

CRITICAL TEMPERATURE - That temperature above which the vapor phase cannot be condensed to liquid by an increase in pressure.

CRITICAL VELOCITY -  Maximum velocity is obtained and no further pressure drop is obtained. (Acoustic Velocity).

CROSS COMPOUND TURBINE -  These turbines are large turbines with parallel shafts with a generator on each shaft. The steam flows through the high pressure turbine, then is crossed-over to the low pressure turbine

CRT - Cathode ray tube terminal.

CRYOGENIC FLUID - Substance which exists as a liquid or gas at ultra-low temperatures - 157C.

CRYOGENIC SUPERCONDUCTOR SYSTEM - Uses helium to cool conductors to within few degrees of absolute zero where they offer no electric resistance.

CRYOGENICS - Refrigeration which deals with producing temperatures of -157C below zero and lower.

Crystal Formation, Zone of Maximum: Temperature range in freezing in which most freezing takes place, i.e., about 25F to 30F for water.

CRYSTALLITES - Atoms arranged in a repeating and definite structure.

CRYSTALLIZATION - The separation, usually from a liquid phase on cooling, of a solid crystalline phase.

CURRENT (I) - The electric flow in an electric circuit, which is expressed in amperes (amps).

CURRENT DENSITY - The current flowing to or from a unit area of an electrode surface.

CURTIS METHOD or Curtis stage - Velocity Compounding - This turbine design consists of one set of nozzles in which the steam is expanded from initial to exhaust pressure. The velocity of the steam resulting from this expansion is absorbed in two or more rows of moving blades. Rows of fixed or guide blades, attached to the casing, are set between rows of moving blades and receive and redirect the steam to the next row of moving blades. As the velocity is absorbed in more than one row of moving blades, the blade speed is less than if the velocity was all absorbed in one row of blades.

CYCLE - A series of thermodynamic processes during which the working fluid can be made to undergo changes involving energy transition and is subsequently returned to its original state.

CYCLE, REVERSIBLE - Theoretical thermodynamic cycle, composed of a series of reversible processes, which can be completely reversed.

CYCLE, WATER TREATMENT - A complete course of ion-exchange operation. For instance, a complete cycle of cation exchange would involve regeneration of the resin with acid, rinse to remove excess acid, exhaustion, backwash, and finally regeneration.

CYCLES - A system that undergoes a series of processes and always returns to its initial state.

CYCLES OF CONCENTRATION - The number of times the soluble mineral salts in a water supply have been concentrated in, a system.

CYLINDER HEAD - Plate or cap which encloses compression end of compressor cylinder.

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Table of contents Power Plant Dictionary