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Contents

Caterpillar Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-65Caterpillar Acronyms and Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67-76P. C. Related Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77-82P. C. Related Acronyms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83-84Terms Pertaining to the Integration of Cat and MaK . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Abrasion Wearing or rubbing away of apart.Absolute Humidity Amount of moisture inthe air, indicated in grains per cubic foot.Absolute Pressure Gauge pressure plusatmospheric pressure (14.7 lb per in2).Absolute Temperature The temperaturemeasured using absolute zero as a reference.Absolute zero is -469.69 F (-273.16 C) andis the lowest point of temperature known.Absorber A device containing liquid forabsorbing refrigerant vapor or other vapors. Inan absorption system, that part of the low sideused for absorbing refrigerant vapor.Acceleration The rate of increase of velocityper time unit (example: feet per second).Accumulator A device used for storing liquidunder pressure (sometimes used to smooth outpressure surges in a hydraulic system).Active Power The real power supplied bythe generator set to the electrical load. Activepower creates a load on the sets engine and islimited by the horsepower of the engine.Active power does the work of heating,turning motor shafts, etc., and is measured inwatts, kilowatts, and megawatts.Actuator A device which uses fluid powerto produce mechanical force and motion.Additive 1. A compound which is added toimprove fuel. 2. A substance added to oil togive it certain properties. For example, amaterial added to engine oil to lessen itstendency to congeal or thicken at lowtemperatures.Advance To move the timing of the injectionpump or injectors to an earlier injection point.Advanced Diesel Engine Management(ADEM) The name for current generation ofthe electronic engine control system.

A/F Dynamic Setting The dynamic (enginerunning) setting of a device on the enginewhich limits the amount of fuel injected perstroke as a function of the boost.Aftercooler A heat exchanger inserted intothe induction system of an engine after anydevice used to compress combustion air.Air Bleeder A device used to remove airfrom a hydraulic system. Types include aneedle valve, capillary tubing to the reservoir,and a bleed plug.Air Cleaner A device (filter) for removingunwanted solid impurities from the air beforethe air enters the intake manifold.Air Compressor A device used to increaseair pressure.Air Conditioning The simultaneous controlof all or at least the first three of the followingfactors affecting the physical and chemicalconditions of the atmosphere within astructure: temperature, humidity, motion,distribution, dust, bacteria, odors, toxic gasesand ionization most of which affect, ingreater or lesser degree, human health orcomfort.Air Cooled Condenser Heat of compressionis transferred from condensing coils tosurrounding air. This may be done either byconvection or by a fan or blower.Air Diffuser Air distribution outlet designedto direct airflow into desired patterns.Air-Fuel Ratio The ratio (by weight or byvolume) between fuel and air.Air-Fuel Ratio Control (AFRC) A featureon Cat engines which measures actual enginespeed and boost pressure to reduce smoke andlower fuel consumption. Air Gap The distance between twocomponents; clearance between internalrotating member and stationary outsidemember. Refers to gap per side.

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Air Inlet Shutoff An engine protectionmeasure used to supplement the fuel shutoff,when blocking the air supply is the quickestway to stop the engine. Often this approach isused on larger engines when operating incombustible environments or to achieve fastshutdowns. Air shutoffs are not used forroutine shutdowns.Air Lock The presence of air in a pump orpipes which prevents the delivery of liquid.Air Pollution Contamination of the earthsatmosphere by pollutants such as smoke,harmful gases, etc.Air Return Air returned from conditioned orrefrigerated space.Air (Saturated) A mixture of dry air andsaturated water vapor all at the same dry-bulbtemperature.Air (Specific Heat of) The quantity of heatabsorbed by a unit weight of air per unittemperature rise.Air (Standard) Air with a density of0.075 lb per ft3 and an absolute viscosity of0.0379 x 10-5 lb mass per (ft) (sec). This issubstantially equivalent to dry air at 70 F and29.92 in. Hg barometric pressure.Air Starting Valve A valve which admitscompressed air to the air starter for startingpurposes.Air-to-Air Aftercooler (ATAAC) A meansof cooling intake air after the turbocharger,using ambient air for cooling. The intake air ispassed through an aftercooler (heat exchanger)mounted in front of the radiator before goingto the intake manifold.Aldehydes A chemical compound formed byincomplete combustion.Align To bring two or more components of aunit into the correct positions with respect toone another.Allowance The difference between theminimum and the maximum dimensions ofproper functioning.

Alloy A mixture of two or more differentmetals, usually to produce improvedcharacteristics.Alnico Magnet A magnet composed ofaluminum (Al), nickel (Ni), and cobalt (Co).Alternating Current (AC) An electriccurrent that reverses its direction at regularlyrecurring intervals such as 50 or 60 times persecond in 50 Hz and 60 Hz, respectively.Alternating Current (AC) Metering Module An apparatus which displays generator setvolts, amps, and frequency.Alternator An electromechanical devicewhich produces alternating current.Altitude Adjustment Adjusting refrigeratorcontrols so unit will operate efficiently ataltitude in which it is to be used.Ambient The surrounding atmosphere;encompassing on all sides; the environmentsurrounding a body but undisturbed orunaffected by it.Ambient Temperature Temperature of fluid(usually air) which surrounds object on all sides.Ammeter An instrument used to indicate, inamperes, the current flowing through thephases from a generator to the load.Ammonia Chemical combination ofnitrogen and hydrogen (NH3). Ammoniarefrigerant is identified by R-117.Amortisseur Windings Apparatus formedby copper rotor end plates and damper bars tohelp stabilize a generator set during paralleloperation.Amperage A measure of the current ornumber of electrons passing a given point perunit of time.Ampere (A) A unit of measurement definedas the current that 1 V can send through 1Wresistance.Ampere-hour Capacity (Ah) Ameasurement of the batterys capacity todeliver a specified current over a specifiedlength of time.

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Analog A continuous performance signalrepresenting the value of an engineperformance characteristic.Aneroid A pressure-measuring devicecontaining no liquid.Angle Inclination of two lines to each other.Angularity Having or being at an angle.Anneal To toughen metals by heating andthen cooling.Annular In the form of an annulus; ring-shaped.Annulus A figure bounded by concentriccircles or cylinders (e.g., a washer, ring,sleeve, etc.).Annunciator An alarm which producesaudible and/or visual signals to give warnings ofshutdown or fault conditions. Annunciators aretypically used in applications where theequipment monitored is not located in a portionof the facility that is normally attended.Anticipating Control One which isartificially forced to cut in or cut out before itotherwise would, thus starting the coolingbefore needed or stopping the heating beforecontrol point is reached, to reduce thetemperature fluctuation or override.Antifreeze A chemical such as alcohol,glycerin, etc., added to the coolant in order tolower its freezing point.Antifriction Bearing A bearing constructedwith balls, rollers or the like between thejournal and the bearing surface to providerolling instead of sliding friction.API Gravity Gravity expressed in units ofstandard API (hydrometer).Arc Portion of a curved line or of thecircumference of a circle.Air Gap The clearance between internalrotating member and stationary outside member.Refers to gap per side.Air Welding A method of utilizing the heatof an electric current jumping an air gap toprovide heat for welding metal.

Armature The movable part of a relay,regulator, or horn, or the rotating part of agenerator or starter.Asbestos A heat-resistant and nonburningorganic mineral.Asphalt Epoxy Additional protective coatingon winding coil heads on the intake end of agenerator.Aspirate To breathe (to draw out gas bysuction).Aspirating Psychrometer A device whichdraws a sample of air through it for humiditymeasurement purposes.Aspiration The method used to move inletair into the combustion chamber; e.g. NaturallyAspirated (NA), Turbocharged (T), andTurbocharged-Aftercooled (TA).ATA Link An analog terminal adaptor thatallows a Northern Transcom Norstar digitalphone system to use analog devices such as afax, answering machine, or modem.Atmosphere The mass or blanket of gasessurrounding the earth.Atmospheric Pressure (BarometricPressure) The pressure exerted by theatmosphere, averaging 14.7 psi at sea levelwith a decrease of approximately 1/2 lb per1,000 ft of altitude gained.Atom The smallest particle of an element.Atomizer A device which disperses liquid(e.g. fuel) into fine particles (pulverized spray).Attrition Wearing down by rubbing or byfriction: abrasion.Austempering A method of hardening steelby quenching from the austenitizingtemperature into a heat extracting medium(usually salt) which is maintained at someconstant temperature level between 400 F and800 F (usually near the higher temperature)and holding the steel in this medium untiltransformation is substantially complete andthen cooling to room temperature.

Austenite Solid solutions in which gammairon is the solvent.

Automatic Defrost System of removing iceand frost from evaporators automatically.

Automatic Expansion Valve (AEV) Pressure controlled valve which reduces highpressure liquid refrigerant to low pressureliquid refrigerant.

Automatic Synchronizer A magnetic-typecontrol relay which will automatically closethe generator switch/circuit breaker when theconditions for paralleling are satisfied.

Automatic Transfer Switch (ATS) Automatically switches electrical load from thenormal (or preferred) power source to analternate supply, should normal voltage fail or besubstantially reduced. It retransfers load to thenormal source when voltage has been restored.

Automatic Valve A valve assisted by a spring,which is opened by a difference of pressureacting in one direction and closed by a differencein pressure acting in the opposite direction.

Automatic Voltage Regulator Controls theoutput voltage produced by a generator bycontrolling excitation.

Auxiliary An aid to the main device whichmay only be used occasionally.

Avoided Costs The decremental cost for theelectric utility to generate or purchaseelectricity that is avoided through the purchaseof power from a cogeneration facility.

Axial Fan A shaft mounted fan on some designsbetween bearing and revolving field assemblyto provide additional air movement within theunit for cooling; also used for balancing.

Avoided Cost (Regulatory) The amount ofmoney that an electric utility would need tospend for the next increment of electricgeneration production to produce or purchaseelsewhere the power that it instead buys from acogenerator or small power producer.

Azeotropic Mixture Example of azeotropicmixture refrigerant R-502 is mixtureconsisting of 48.8% refrigerant R-22, and51.2% R-115. The refrigerants do not combinechemically, yet azeotropic mixture providesrefrigerant characteristics desired.

Babbitt An antifriction metal used to linebearings, thereby reducing the friction of themoving components.Backfire Ignition of the mixture in theintake manifold by flame from the cylindersuch as might occur from a leaking inlet valve.Backlash The distance (play) between twomovable components such as meshed gears.Backpressure A pressure exerted contrary tothe pressure producing the main flow. Alsocalled suction pressure or low side pressure.Back-Up Power Electric energy availablefrom or to an electric utility during anunscheduled outage to replace energyordinarily generated by the facility or theutility. Frequently referred to as standbypower.

Baffle or Baffle Plate A device which slowsdown or diverts the flow of gases, liquids,sound, etc.Bainite The structure that is obtained whensteel is quenched at a constant subcriticaltemperature.Balanced Valve A valve in which the fluidpressure is equal on both sides (i.e., theopening and closing directions).Ball Bearing A bearing using steel balls asits rolling element between the inner and outerring (race).Ball Check Valve A valve consisting of a ballheld against a ground seat by a spring. It is usedto check the flow or to limit the pressure.

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Banded Structure A segregated structure ofnearly parallel bands which run in thedirection of working.Barometer An instrument which measuresatmospheric pressure.Bars The term bars includes rounds,squares, hexagons, etc.; small standard shapes(angles, channels, tees, etc.) under 3"; flats 6"or under in width and 13/64" or over inthickness.Base Load The lowest level of powerproduction needs during a season or year.Base Load Unit A power generating facilitythat is intended to run constantly at nearcapacity levels, as much of the time aspossible.Base Loading Use of on-site generatingequipment to supply a set amount of power for aspecific time period usually on a daily basis.Baseline Forecast A prediction of futureenergy needs which does not take into accountthe likely effects of new conservation programsthat have not yet been started.Basic Size The theoretical or nominal standardsize from which all variations are made.Battery A connected group of cells storingan electrical charge and capable of furnishinga current from chemical reactions.Bearing The contacting surface on which arevolving part rests.Bearing Clearance The distance betweenthe shaft and the bearing surface.Bell Housing (Clutch Housing) The metalcovering around the clutch or torque converterassembly.Bendix-Type Starter Drive (Inertia StarterDrive) A type of starter drive that causes thegear to engage when the armature startsrotating and to automatically disengage whenit stops.

Bernoullis Principle Given a fluid flowingthrough a tube, any constriction or narrowingof the tube will create an increase in thatfluids velocity and a decrease in pressure.Bernoullis Theorem In a stream of liquid,the sum of elevation head, pressure head, andvelocity remains constant along any line offlow provided no work is done by or upon theliquid in its course of flow, and decreases inproportion to energy lost in the flow.Bessemer Process A process for makingsteel by blowing air through molten pig ironcontained in a suitable vessel. The process isone of rapid oxidation mainly of silicon andcarbon.Best Practice (BP) A business idea,procedure or process which describes themethod of improved efficiency and results.Bimetal Strip Temperature regulating orindication device which works on the principlethat two dissimilar metals with unequalexpansion rates, welded together, will bend astemperatures change.Black Smoke A soot-like substance emitted byengines resulting from incomplete combustion.Black Start Refers to the starting of a powersystem with its own power sources, withoutassistance from external power supplies.Blended or Heavy Fuel A mixture ofresidual fuel and a lighter fuel. This fuel typetends to create more combustion chamberdeposit formations which can cause increasedcylinder and ring wear, especially in smaller,higher- speed engines.Blister A defect in metal produced by gasbubbles either on the surface or formedbeneath the surface.Block Rate Schedules Utility rate schedulesthat charge different rates for certainincrements of energy consumed. For example:3 cents for the first 1000 kW-hr, 4 cents for thenext 1000 kW-hr, 5 cents for the next 1000kW-hr, etc.

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Block Wall A concrete structure which issometimes used to muffle the noise from anoperating generator set. Blowby Combustion gas leakage into theengine crankcase. The leakage is normallyfrom the combustion chamber past the pistonrings or through the valve guides. Specificblowby is the volume of blowby at atmosphericpressure divided by the engine power.Blower A low-pressure air pump, usually ofone rotary or centrifugal type.Blowhole A hole produced during thesolidification of metal by evolved gas which,in failing to escape, is held in pockets.Blue Brittleness Brittleness occurring insteel when worked in the temperature range of300-700 F or when cold after being workedwithin this temperature range.Boiling Point The temperature at whichbubbles or vapors rise to the surface of a liquidand escape.Boiling Temperature Temperature at whicha fluid changes from a liquid to a gas.Bond The holding together of different parts.Boost The gauge pressure as measured in theinlet manifold of a diesel engine. Adjustedboost is the calculated value of boost thatwould exist if an engine were running atnominal power. Boost is not synonymous withinlet manifold pressure.Bore The diameter of each cylinder in anengine. Boring Enlarging the cylinders by cutting orhoning them to a specified size.Boring Bar (Cylinder) A tool used tomachine the cylinders to a specific size.Bosch Metering System A metering systemwith a helical groove in the plunger whichcovers or uncovers ports in the pump barrel.Bottom Dead Center (BDC) The lowestpoint a piston reaches in its movement withina cylinder.

Bottoming Cycle A means to increase thethermal efficiency of a steam electricgenerating system by converting some wasteheat from the condenser into electricity ratherthan discharging all of it into the environment.Bound Electrons The inner-orbit electronsaround the nucleus of the atom.Boyles Law of Physics The absolutepressure which a given quantity of gas atconstant temperature exerts against the walls ofthe containing vessel is inversely proportionalto the volume occupied. Examples: If pressureis doubled on the quantity of gas, volumebecomes one-half. If volume becomes doubled,gas has its pressure reduced by one-half.Brake Horsepower (bhp) A measurementof the power developed by an engine in actualoperation. It subtracts the F.H.P. (frictionlosses) from the I.H.P. (pure horsepower).Brake Mean Effective Pressure (BMEP) Mean effective pressure acting on the pistonwhich would result in the given brakehorsepower output, if there were no losses dueto friction, cooling, and exhaustion. Equal tomean indicated pressure times mechanicalefficiency.Brake Specific Fuel Consumption (BSFC) The quantity of fuel burned to produce onehorsepower for one hour.Brake Thermal Efficiency Ratio of poweroutput in the form of brake horsepower toequivalent power input in the form of heatfrom fuel.Braze To join two pieces of metal using acomparatively high-melting-point material. Anexample is to join two pieces of steel by usingbrass or bronze as a solder.Break-in The process of wearing in to adesirable fit between the surfaces of two newor reconditioned parts.Breather A device that allows fumes toescape from the crankcase.Breather Pipe A pipe opening into thecrankcase to assist ventilation.

Brine Water saturated with chemical such assalt.Brinell Hardness The surface hardness of ametal, alloy, or similar material according toJ.A. Brinells method of measurement. Ametals surface is struck at a given force by arigid steel ball of given diameter, and theindentation is measured.British Gallon (Imperial Gallon, gal [Imp.]) A gallon measurement of 277.4 in3.British Thermal Unit (Btu) Approximatedefinition: The amount of heat required toraise 1 lb of water 1 F. Exact definition: Theamount of heat required to raise 1 lb. of waterfrom freezing to boiling at standardatmospheric pressure.Broad Voltage A term used to denote 12-leadunit, which allows low and high voltageconnections by customer.Brownout A controlled power reduction inwhich the utility decreases the voltage on thepower lines, so customers receive weakerelectric current.Brush The pieces of carbon or copper thatmake a sliding contact against the commutatoror slip rings.Brushless A synchronous machine having abrushless exciter with its rotating armature andsemiconductor devices on a common shaftwith the field of the main machine.

Buoyancy The upward or lifting forceexerted on a body by a fluid.Burning The heating of a metal totemperatures sufficiently close to the meltingpoint to cause permanent damage to the metal.Burnish To polish or shine a surface with ahard, smooth object.Bursts Ruptures made in forging or rolling.Bus Refers to the devices that connect thegenerators and loads in a paralleling system, orany point fed by multiple sources and/orsupplying multiple loads.

Bus Bars A set of common conductors on theload side of a circuit breaker used to conductgenerator output to the distribution system.

Bus Capacity The maximum load that can becarried on a system without causing degradationof the generator frequency. In other words, thefull load capacity of the system.Bushing A metallic or synthetic lining for ahole which reduces or prevents abrasionbetween components.Butane A hydrocarbon gas formedsynthetically by the action of zinc or ethyliodide. This gas becomes a liquid when underpressure.Butterfly Valve A valve in the venturi tocontrol the airflow.Bypass Filter An oil filter that only filters aportion of the oil flowing through the enginelubrication system.Bypass Valve A valve that opens when theset pressure is exceeded. This allows the fluidto pass through an alternative channel.

Cage A housing in which a valve operatesand seats.Calcium Sulfate Chemical compound(CaSO4) which is used as a drying agent ordesiccant in liquid line driers.Calibrate To make an adjustment to a meteror other instrument so that it will accuratelyindicate its input.Bus An electrical conductor that serves as acommon connection for two or more electricalcircuits.

Caliper A tool for measuring diameter,usually having curved legs and resembling apair of compasses.Calorie Heat required to raise temperatureof one gram of water one degree centigrade.

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Calorific Value The amount of heatproduced by burning one pound of fuel. (SeeHeating Value.)Calorimeter Device used to measurequantities of heat or determine specific heats.

Cam A component of irregular shape. It isused to change the direction of the motion ofanother part moving against it, e.g., rotary intoreciprocating or variable motion.

Cam Follower (Valve Lifter) A part whichis held in contact with the cam and to whichthe cam motion is imparted and transmitted tothe pushrod.

Cam-Ground Piston A piston ground to aslightly oval shape which under the heat ofoperation becomes round.

Cam Nose That portion of the cam thatholds the valve wide open. It is the high pointof the cam.

Camshaft The shaft containing lobes orcams to operate the engine valves.

Camshaft Gear The gear that is fastened tothe camshaft.

Capability The maximum load which agenerating unit, generating station, or otherelectrical apparatus can carry under specifiedconditions for a given period of time, withoutexceeding approved limits of temperature andstress.

Capacitor An arrangement of insulatedconductors and dielectrics for theaccumulation of an electric charge with smallvoltage output.

Capacity (electric utility) The maximumamount of electricity that a generating unit,power plant, or utility can produce underspecified conditions. Capacity is measured inmegawatts and is also referred to as thenameplate rating.

Capacity Credits The value incorporatedinto the utilitys rate for purchasing energy,based upon the savings due to the reduction orpostponement of new generation capacityresulting from the purchase of power fromcogenerators.

Capacity Factor The ratio of the actualannual plant electricity output to the ratedplant output.

Capacity-Net Cooling The cooling capacityof an air-conditioning system or heat pump onthe cooling cycle is the amount of Sensibleand Latent heat (total heat) removed from theinside air.Carbon One of the nonmetallic elementsconstituting fuel and lubricating oil.Carbon Dioxide (CO2) A greenhouse gasproduced as a result of combustion of anyhydrocarbon fueled engine, including ahuman. The highest efficiency engines producethe least CO2. Carbon Monoxide (CO) A poisonous gasformed by combustion taking place with ashortage of oxygen. Measured in parts permillion by volume.CO Concentration (ppm) =

1034 x CO mass emissions (g/hr)Exhaust mass flow (kg/hr)

Carbon Pile Carbon disks or plates capableof carrying high current.Carbon Tetrachloride A colorless liquid,the fumes of which are toxic. Used in fireextinguishers and for cleaning.Carbonize The process of carbon formationwithin an engine, such as on the spark plugsand within the combustion chamber.Carburetor A device for automaticallymixing gasoline fuel in the proper proportionwith air to produce a combustible vapor.Carburetor Icing A term used to describethe formation of ice on a carburetor throttleplate during certain atmospheric conditions.

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Carburizing (cementation) Adding carbonto the surface of iron-base alloys by heatingthe metal below its melting point in contactwith carbonaceous solids, liquids, or gases.

Cat Data Link A communication data linkwhich displays status of various engineparameters on the Computerized MonitoringSystem.

Ceiling The absolute maximum to which thehigh limit of an engine performancespecification may rise.

Cementite A compound of iron and carbonalways containing 6.68% carbon and 93.32%iron.

Central Cooling Same as central heatingexcept that cooling (heat removal) is suppliedinstead of heating; usually a chilled waterdistribution system and return system for airconditioning.

Central Heating Supply of thermal energyfrom a central plant to multiple points of end-use, usually by steam or hot water, for spaceand/or service water heating. Central heatingmay be large-scale as in plants serving centralbusiness districts, university campuses,medical centers, and military installations or incentral building systems serving multiplezones; also district heating.

Cetane Measure of ignition quality of dieselfuel at what pressure and temperature thefuel will ignite and burn.

Chamfer A bevel or taper at the edge of a hole.Charge Air Cooler (CAC) An air-to-air orwater-to-air heat exchanger to coolturbocharged combustion air.

Chase To straighten up or repair damagedthreads.

Choke A device such as a valve placed in acarburetor air inlet to restrict the volume of airadmitted.

Circuit The complete path of an electriccurrent including, usually, the source ofelectrical energy.

Circuit Breaker A device used to open andclose a circuit by nonautomatic means, and toopen the circuit automatically on apredetermined overload of current.

Closing Rating The maximum fault currentinto which an automatic transfer switch of agenerator set can close.

Coefficient of Expansion The change inlength per unit length or the change in volumeper unit volume per degree change intemperature.

Coefficient of Performance (COP) Theratio of the rate of heat removal to the rate ofenergy input in consistent units.

Cogeneration Utilizing a prime powergenerator set, this process involves harnessingfree heat energy from engine cooling andexhaust systems for heating or steamgeneration, or to power air conditioning,absorption chillers, or other equipment.

Cohesive Strength The strength property ofa metal that resists the tensile, disruptive stressacross a plane at right angles to the load applied.

Coil Spring A spring-steel wire wound in aspiral pattern.

Coil Wedge A mechanical device whichprevents coil bundle from coming out of rev.field slot passage during rotation of rev. field.Two types: expansion wedges 360, 440,and 580, 680 frames; compression wedges 800 frame.

Cold Cold is the absence of heat; atemperature considerably below normal.

Cold Drawing The process for finishing ahot rolled rod or bar at room temperature bypulling it through the hole of a die of the sameshape but smaller in size.

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Cold Finishing The process of reducing thecross sectional area without heating by coldrolling, cold drawing, cold drawing andgrinding, turning and polishing, or turning andgrinding.

Cold Rolling The cold working of hot rolledmaterial by passing it between power-drivenrolls. The process applies to flat bars of such asize that they cannot be pulled through a die.

Cold Working Plastic deformation of ametal at a temperature low enough to ensurestrain hardening.

Color Code Colored markings or wires toidentify the different circuits.

Combustion The process of burning.Combustion Chamber The chamber inreciprocating engines between the cylinderhead and piston, in which combustion occurs.

Combustion-Chamber Volume The volumeof the combustion chamber (when the piston isat TDC) measured in cubic centimeters.Combustion Cycle A series ofthermodynamic processes through which theworking gas passes to produce one powerstroke. The cycle is: intake, compression,power, and exhaust.

Comfort Air-Conditioning A simultaneouscontrol of all, or at least the first three, of thefollowing factors affecting the physical andchemical conditions of the atmosphere withina structure of the purpose of human comfort;temperature, humidity, motion, distribution,dust, bacteria, odors, toxic gases, andionization, most of which affect in greater orlesser degree human health or comfort.

Commercial Engine Featurization (CEF) A feature-based business process used byCaterpillar dealers that describes product incustomer terms (feature codes), eliminatinginternal Caterpillar terms (part numbers). Forthe dealer, it impacts the configuring, quotingand ordering processes. Internally, atCaterpillar, it is incorporated into Marketing,Orders, Pricing, and Accounting. CEF includes:1) part numbers changed to feature codes, 2)feature codes priced instead of part numbers, 3)PC software that mechanically checks productcompatibility, 4) weekly updates tocompatibility and pricing via the Internet, 5)electronic ordering via Internet or DBS.

Commutator A number of copper barsconnected to the armature windings butinsulated from each other and from thearmature. Rotation of the armature will, inconjunction with fixed brushes, result inunidirectional current output.

Compound A combination of two or moreelements that are mixed together.

Compressed Air Air that at any pressure inexcess of atmospheric pressure is consideredto be compressed.

Compressibility The property of a substance(e.g., air) by virtue of which its densityincreases with increase in pressure.

Compression The process by which aconfined gas is reduced in volume through theapplication of pressure.

Compression Check A measurement of thecompression of each cylinder at crankingspeed or as recommended by the manufacturer.

Compression Gauge A test instrument usedto test the cylinder compression.

Compression Ignition The ignition of fuelthrough the heat of compression.

Compression Pressure Pressure in thecombustion chamber at the end of thecompression stroke, but without any of the fuelbeing burned.

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Compression Ratio Compares the minimumand maximum volumes between the pistoncrown and the cylinder head.

Compression Release A device to preventthe intake or exhaust valves from closingcompletely, thereby permitting the engine to beturned over without compression.

Compression Ring The piston rings used toreduce combustion leakage to a minimum.

Compression Stroke That stroke of theoperating cycle during which air is compressedinto a smaller space, creating heat bymolecular action.

Compressor A mechanical device to pumpair, and thereby increase the pressure. Thepump of a refrigerating mechanism whichdraws a vacuum or low pressure eon coolingside of refrigerant cycle and squeezes orcompresses the gas into the high pressure orcondensing side of the cycle.

Compressor-Brake Horsepower A functionof the power input to the ideal compressor andto the compression, mechanical, andvolumetric efficiency of the compressor.

Compressor Efficiency A measure of thedeviation of the actual compression from theperfect compression cycle. Is defined as thework done within the cylinders.

Compressor, Hermetic Compressor inwhich the driving motor is sealed in the samedome or housing that contains the compressor.

Compressor, Open-Type Compressor inwhich the crankshaft extends through thecrankcase and is driven by an outside motor.

Compressor Outlet Pressure Gauge pressureof the combustion air at the turbochargercompressor outlet of a spark ignited engine.

Compressor, Reciprocation Compressorwhich uses a piston and cylinder mechanism toprovide pumping action.

Compressor, Rotary Compressor whichuses vanes, eccentric mechanisms, or otherrotating devices to provide pumping action.

Computerized Monitoring System (CMS) An electronic display for marine or industrialengines to display engine parameters anddiagnostics.Concentric Having the same center.Conceptual Design The specification of themajor components of a system and theiroperating characteristics, layout, space needs,and operating and maintenance requirements.

Condensate Fluid which forms on anevaporator.Condensate Pump Device used to removefluid condensate that collects beneath anevaporator.Condensation Liquid or droplets whichform when a gas or vapor is cooled below itsdew point.Condense Action of changing a gas or vaporto a liquid.Condenser, Air-Cooled A heat exchangerwhich transfers heat to surrounding air.Condenser, Electrical An arrangement ofinsulated conductors and dielectrics for theaccumulation of an electric charge.Condenser, Evaporative A condenser inwhich heat is absorbed from the surface by theevaporation of water sprayed or flooded overthe surface.Condenser, Thermal The part of arefrigeration mechanism which receives hot,high pressure refrigerant gas from thecompressor and cools gaseous refrigerant untilit returns to liquid state.Condenser, Water-Cooled Heat exchangerwhich is designed to transfer heat from hotgaseous refrigerant to water.Condensing Unit The part of therefrigerating mechanism which pumpsvaporized refrigerant from the evaporator,compresses it, liquifies it in the condenser, andreturns the liquid refrigerant to refrigerantcontrol.

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Conduction, Thermal The process of heattransfer through a material medium in whichkinetic energy is transmitted by the particles ofthe material from particle to particle withoutgross displacement of the particles.Conductivity, Thermal k factor Thetime rate of heat flow through unit area of ahomogeneous material under steady conditionswhen a unit temperature gradient is maintainedin the direction perpendicular to the area. InEnglish units its value is usually expressed inBtu per (hour) (square foot) (Fahrenheit degreeper inch of thickness). Materials areconsidered homogeneous when the value ofk is not affected by variation in thickness orin size of sample within the range normallyused in construction.

Conductor Any material whose propertiesallow electrons to move with relative ease.Typical examples are copper and aluminum.

Connecting Rod A reciprocating rodconnecting the crankshaft and piston in anengine.

Conservation Steps taken to cause lessenergy to be used than would otherwise be thecase.

Constant-pressure Combustion Combustionwhich occurs without a change in pressure. Inan engine, this is obtained by a slower rate ofburning than with constant-volume combustion.

Contaminant A substance (dirt, moisture,etc.) foreign to refrigerant or refrigerant oil insystem.

Contamination The presence of harmfulforeign matter in a fluid or in air.

Continuous Cycle Absorption System System which has a continuous flow of energyinput.

Continuous Power Output available withoutvarying load for an unlimited time. Continuouspower in accordance with ISO8528,ISO3046/1, AS2789, DIN6271, and BS5514.

Contour Outline.Contract To reduce in mass or dimension;to make smaller.

Control To regulate or govern the functionof a unit.Control Voltage Terminal Strip Stripsprovided to allow easy customer connectionsof generator sets to regulators, space heaters,or other devices.

Controlled Port Scavenging Scavengingmethod using ports which are controlled byvalves in addition to the power piston.Convection Transfer of heat by means ofmovement or flow of a fluid or gas.Convection, Forced Transfer of heatresulting from forced movement of liquid orgas by means of fan or pump.Convection, Natural Circulation of a gas orliquid due to the difference in density resultingfrom temperature difference.Conventional According to the mostcommon or usual mode.Converge To incline to or approach a certainpoint; to come together.Converter As used in connection with LP gas,a device which converts or changes LP gasfrom a liquid to a vapor for use by the engine.Convolution One full turn of a screw.Coolant A liquid used as a cooling medium.Cooling Load The rate of heat removedfrom the chilled water passing through theevaporator measured in tons.Cooling System The complete system forcirculating coolant.Cooling Tower Device which cools water bywater evaporation in air. Water is cooled to wetbulb temperature of air.Cooperative (electric utility) A jointventure organized by consumers to makeelectric utility service available in their area.

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Coproduction The conversion of energyfrom a fuel (possibly including solid or otherwastes) into shaft power (which may be usedto generate electricity) and a second oradditional useful form. The process may entaila series topping and bottoming arrangementfor conversion to shaft power and eitherprocess or space heating. Cogeneration is aform of coproduction; however, the conceptalso includes a single heat producer servingseveral different mechanical and/or thermalrequirements in parallel.

Core The central or innermost part of anobject.Correction Factor A number by which anengine performance characteristic is multipliedto show the value which would have beenobtained if the engine were operating undersome other set of conditions.

Corrosion The slow destruction of materialby chemical agents and electromechanicalreactions.Counterbalance A weight, usually attachedto a moving component, that balances anotherweight.Counterbore A cylindrical enlargement ofthe end of a cylinder bore or bore hole.Counterelectromotive Force (cemf) Theelectromotive force (voltage) that opposes theapplied voltage.Countersink To cut or shape a depression inan object so that the head of a screw may setflush or below the surface.Counterweight Weights that are mounted onthe crankshaft opposite each crank throw.These reduce the vibration caused by puttingthe crank in practical balance and also reducebearing loads due to inertia of moving parts.Coupling A device used to connect twocomponents.Crankcase The lower housing in which thecrankshaft and many other parts of the engineoperate.

Crankcase Dilution When unburned fuelfinds its way past the piston rings into thecrankcase oil, where it dilutes or thins theengine lubricating oil.Crankcase Scavenging Scavenging methodusing the pumping action of the power pistonin the crankcase to pump scavenging air.Cranking Rotating an engine with a sourceof power external to the engine.

Crankpin The portion of the crank throwattached to the connecting rod.Crankshaft The main drive shaft of anengine which takes reciprocating motion andconverts it to rotary motion.Crankshaft Counter-Balance A series ofweights attached to or forged integrally withthe crankshaft to offset the reciprocatingweight of each piston and rod.Crank Throw One crankpin with its twowebs (the amount of offset of the rod journal).Crank Web The portion of the crank throwbetween the crankpin and main journal. Thismakes up the offset.Crest The top surface joining the two sidesof a thread.Crest Clearance Defined on a screw form asthe space between the top of a thread and theroot of its mating thread.Critical Compression Ratio Lowestcompression ratio at which any particular fuelwill ignite by compression under prescribedtest procedure. The lower the criticalcompression ratio the better ignition qualitiesthe fuel has. (Gasoline engine, 4:1; oil engine,7:1; diesel engine, 12.5:1.)Critical Pressure Condition of refrigerant atwhich liquid and gas have the same properties.Critical Speeds Speeds at which thefrequency of the power strokes synchronizewith the crankshafts natural frequency ortorsional damper. If the engine is operated atone of its critical speeds for any length oftime, a broken crankshaft may result.

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Critical Temperature Temperature at whichvapor and liquid have the same properties.Crocus Cloth A very fine abrasive polishingcloth.Cross Current Compensating Transformer A unit which senses circulating currentsbetween generators in parallel operation.

Cross Current Compensation Method ofcontrolling the reactive power supplied bygenerators in a paralleling system so that theyequally share the total reactive load on the bus,without significant voltage droop.

Crowned A very slight curve in a surface(e.g. on a roller or raceway).Crude Oil Petroleum as it comes from thewell (unrefined).Crush A deliberate distortion of an enginesbearing shell to hold it in place duringoperation.

Cryogenic Fluid Substance which exits as aliquid or gas at ultra-low temperatures (-250 For lower).Cryogenics Refrigeration which deals withproducing temperatures at -250 F and lower.Current A flow of electric charge and therate of such a flow measured in amperes.

Current Transformer An auxiliaryinstrument used to reduce generator current tothat of the instruments and apparatus. Currenttransformers are used to step down the higherline current to the lower currents that thecontrol system is designed for. These signalsare utilized by AC meters, protective relays,and control devices.

Custom Alarm Module (CAM) A Cat unitwhich provides flexible annunciationcapabilities for engines.

Customer Communication Module (CCM) Apparatus which allows users of electronicengines to monitor up to eight Cat powersystems remotely, perform system diagnostics,and receive parameter readouts in real time.

Customer Interface Module (CIM) Adevice which decodes Cat electronic enginemonitoring information and provides a link toremote alarms and annunciators.

Cut-In Temperature or pressure valve whichcloses control circuit.Cut-Out Temperature or pressure valvewhich opens the control circuit.Cyaniding Surface hardening by carbon andnitrogen absorption of an iron-base alloyarticle or portion of it by heating at a suitabletemperature in contact with a cyanide salt,followed by quenching.Cycle One complete rise and fall of thevoltage of alternating current, from zero tomaximum positive/back to zero and from zeroto maximum negative and back to zero again.Cyclic Variation in the performancecharacteristics which vary as the engine runs;especially, but not exclusively, thosecharacteristics which vary in a repetitive fashion.Cyclic Irregularity A nondimensional ratiodescribing the degree of crankshaft twistoccurring between two successive firings ofcylinders of an engine during steady-stateoperation. Cyclic Irregularity = rpm (maximum) - rpm (minimum)

rpm (average)Cylinder The chamber in which a pistonmoves in a reciprocating engine.

Cylinder Block The largest single part of anengine. The basic or main mass of metal inwhich the cylinders are bored or placed.

Cylinder Head The replaceable portion ofthe engine fastened securely to the cylinderblock that seals the cylinder at the top. It oftencontains the valves, and in some cases, it ispart of the combustion chamber.

Cylinder Hone A tool used to bring thediameter of a cylinder to specification and atthe same time smooth its surface.

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Cylinder Liner A sleeve or tube interposedbetween the piston and the cylinder wall orcylinder block to provide a readily renewablewearing surface for the cylinder.

Cylinder, Refrigerant Cylinder in whichrefrigerant is purchased and dispensed. Thecolor code painted on cylinder indicates thekind of refrigerant the cylinder contains.

D Diode; Distance from plane of referenceto assembled unit center of gravity locationD1 Distance from plane of reference aft togenerator center of gravityD2 Distance from plane of reference forwardto engine centerDaltons Law Vapor pressure exerted oncontainer by a mixture of gasses is equal tosum of individual vapor pressures of gassescontained in mixture.Dead Bus The de-energized state of thepower connections between outputs ofparalleled generator sets. Dead Center Either of the two positionswhen the crank and connecting rod are in astraight line at the end of the stroke.Dead Front A term to used to describe the lackof accessibility of bare connections or apparatuson the panel face of controls or switchgear.Dealer Process Improvement (DPI) A three-part strategy that provides the format for dealersto identify, develop, and incorporate processimprovements in their business operations.Decarburization The removal of carbon(usually refers to the surface of solid steel) bythe (normally oxidizing) action of mediawhich react with carbon.Deceleration Opposite of acceleration; that is,implying a slowing down instead of a speedingup. Also called negative acceleration.

Decibel Unit used for measuring relativeloudness of sounds. One decibel is equal to theapproximate difference of loudness ordinarilydetectable by the human ear, the range ofwhich is about 103 decibels on a scalebeginning with one for faintest audible sound.Deferrable or Scheduled Loads Loadswhich can be disconnected for extendedperiods of time and restarted later without agreat effect on a facilitys operation. Delayingenergy use to a time of lower demand iseffective in minimizing peak demand. Deflection Bending or movement away fromthe normal position, due to loading.Deglazer A tool used to remove the glazefrom cylinder walls.Degree, Circle 1/360 of a circle.Degree-Day Unit that represents one degreeof difference from given point in averageoutdoor temperature of one day and is oftenused in estimating fuel requirements for abuilding. Degree-days are based on averagetemperature over a 24-hour period. As anexample, if an average temperature for a day is50 F, the number of degree-day for that daywould be equal to 65 F minus 50 F or 15degree-days (65-15 = 50) Degree-days areuseful when calculating requirements forheating purposes.Degree Wheel A wheel marked in degrees toset the lifter height.Dehumidifier Device used to removemoisture from air in enclosed space.Dehumidifier, Surface An air-conditioningunit, designed primarily for cooling anddehumidifying air through the action ofpassing the air over wet cooling coils.Dehumidify To remove water vapor fromthe atmosphere. To remove water or liquidfrom stored goods.Dehumidifying Effect The differencebetween the moisture contents, in pounds perhour, of the entering and leaving air,multiplied by 1.060.

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Dehydrate To remove water in all formsfrom matter. Liquid water, hygroscopic water,and water of crystallization or water ofhydration are included.

Dehydrated Oil Lubricant which has hadmost of water content removed (a dry oil).Dehydration The removal of water vaporfrom air by the use of absorbing or absorbingmaterials; the removal of water from storedgoods.

Delta Connection The connection of thethree windings of a generator into a triangularor delta configuration. Most commonly usedby utility companies. Has no neutral point.

Delta-T The temperature rise of the enginecoolant from the jacket water pump inlet to theengine coolant outlet.Demand (Utility) The level at whichelectricity or natural gas is delivered to users ata given point in time. Electric demand isexpressed in kilowatts.Demand, Annual The greatest of alldemands which occurred during a prescribeddemand interval in a calendar year.Demand, Billing The demand upon whichbilling to a customer is based, as specified in arate schedule or contract. It may be based onthe contract year, a contract minimum, or aprevious maximum and, therefore, does notnecessarily equal the demand actuallymeasured during the billing period.Demand Charge The sum to be paid by alarge electricity consumer for its peak usagelevel.Demand, Coincident The sum of two ormore demands which occur in the samedemand interval.Demand, Instantaneous Peak The maximumdemand at the instant of greatest load.Dendrites A crystal formed by solidification,or in any other way, having many branches anda tree-like pattern; also termed pine tree andfir tree crystals.

Density (Fuel) The mass of fuel per unitvolume. The units of density used in thisspecification are degrees API at 60 degreesFahrenheit. (API = American PetroleumInstitute)Depth of Engagement The depth of a threadin contact with two mating parts measuredradially. It is the radial distance by which theirthread forms overlap each other.

Desiccant Substance used to collect andhold moisture in a refrigerating system. Adrying agent. Common desiccants are activatedalumina, silica gel.

Design Voltage The nominal voltage forwhich a line or piece of equipment isdesigned. This is a reference level of voltagefor identification and not necessarily theprecise level at which it operates.

Detergent A compound of a soap-like natureused in engine oil to remove engine depositsand hold them in suspension in the oil.

Detonation Burning of a portion of the fuelin the combustion chamber at a rate faster thandesired (knocking).Dew Point Temperature at which vapor (at100 percent humidity) begins to condense anddeposit as liquid.

Diagnosis In engine service, the use ofinstruments to troubleshoot the engine parts tolocate the cause of a failure.

Dial Indicator (dial gauge) A precisionmeasuring instrument.

Diaphragm Any flexible dividing partitionseparating two compartments.

Dichlorodifluoromethane Refrigerantcommonly known as R-12. Chemical formulais CCl2F2. Cylinder color code is white.Boiling point at atmospheric pressure is-21.62 F.

Die, Thread A thread-cutting tool.

Dielectric A nonconductor of direct electriccurrent.

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Diesel Engine A type of internal combustionengine that burns fuel oil; the ignition isbrought about by heat resulting from aircompression, instead of by an electric spark, asin a gasoline engine.Diesel Index A rating of fuel according to itsignition qualities. The higher the diesel indexnumber, the better the ignition quality of the fuel.Differential As applied to refrigeration andheating, the difference between cut-in andcut-out temperature or pressure of a control.Differential Fuel Pressure The gas pressuresupplied to the carburetor of a spark ignitedengine minus the carburetor inlet pressure.Differential Pressure Fuel Valve A closedfuel valve with a needle or spindle valve whichseats onto the inner side of the orifices. Thevalve is lifted by fuel pressure.Differential Protection (Line) Leads passthrough current transformers for the purpose ofsensing current imbalance between line-leads.Digital A numeric value representing thevalue of an engine performance characteristic.Digital Voltage Regulator (D.V.R.) Amicroprocessor-based unit which regulatesvoltage output of a generator.Dilution Thinning, such as when fuel mixeswith the lubricant.Diode A device which allows current to passbut only in one direction.Dip and Bake The process of treating awound electrical element with varnish toprovide protection/insulation, and to secure thewinding insulation in place.Dipstick A device to measure the quantity ofoil in the reservoir.Direct Current (DC) An electric currentflowing in one direction only.Direct Expansion Evaporator An evaporatorcoil using a pressure-reducing device to supplyliquid refrigerant at the correct boiling point forheat absorption into the refrigerant.

Direct-cooled Piston A piston which iscooled by the internal circulation of a liquid.

Directional Control Valve A valve whichselectively directs or prevents flow to or fromspecific channels. Also referred to as selectorvalve, control valve, or transfer valve.Discharge A draw of current from thebattery.

Displacement or Swept Volume In a single-acting engine, the volume swept by all pistonsin making one stroke each. The displacementon one cylinder in cubic inches is the circulararea (in square inches) times the stroke (ininches) times the number of cylinders.Distillation Heating a liquid and thencondensing the vapors given off by the heatingprocess.

Distilling Apparatus Fluid reclaimingdevice used to reclaim used refrigerants.Reclaiming is usually done by vaporizing andthen recondensing refrigerant.

Distortion A warpage or change in formfrom the original shape.

Distribution Circuit Breaker A device usedfor overload and short circuit protection ofloads connected to a main distribution device.Distribution Switchgear May includeautomatic transfer switches, circuit breakers,fusible switches, or molded case breakers. Thisequipment distributes utility or generatorpower to the site electrical loads.Division Plate A diaphragm surrounding thepiston rod of a crosshead-type engine, usuallyhaving a wiper ring to remove excess oil fromthe piston rod as it slides through. It separatesthe crankcase from the lower end of thecylinder. Dog-Leg A colloquialism applied to theshape of a torque curve which has beenmodified to provide a steep torque rise at aspeed just above the full load point to preventexcessive shifting of transmissions.Double Acting An actuator producing workin both directions.18

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Double Flare A flared end of the tubinghaving two wall thicknesses.Dowel A pin, usually of circular shape like acylinder, used to pin or fasten something inposition temporarily or permanently.Down-Draft A type of carburetor in which thefuel-air mixture flows downward to the engine.

Draw-Out Relay An AC protective relay thatis door mounted, and can be removed from itscase without disturbing the wiring to the case, orinterrupting the connected circuits. This allowsfor easy testing and calibration of the relay.

Draw-Out Unit A structure that holds acircuit breaker in an enclosure. It has amovable carriage and contact structures thatpermit the breaker to be removed from theenclosure without manually disconnectingpower cables and control wires.

Drawbar Horsepower Measure of the pullingpower of a machine at the drawbar hitch point.

Dribbling Unatomized fuel running from thefuel nozzle.

Drier A substance or device used to removemoisture from a refrigeration system.

Drill A tool used to bore holes.

Drill Press A fixed machine to drive a toolin rotary motion.

Drive Flange Presses on shaft of revolvingfield rabbet pilot and mounting bolt pattern formounting to engine drive discs.

Drive-fit A fit between two components,whose tolerance is so small that the two partsmust be pressed or driven together.

Droop Load Sharing A method of makingtwo or more parallel generator sets share asystem kW load. This is accomplished by havingeach governor control adjusted so that the setshave the same droop (reduction of speed). Droop (or Speed Droop) The decrease fromno load speed to full load speed when full loadis applied to a generator set, expressed as apercentage of the full load speed.

Droop Transfer A small transformerprovided for mounting current flow throughoutput line leads. A loop of one or two turns ofone of the line leads passes through the coil/plane of the transformer to produce sensing.Drop-forged Formed by hammering orforced into shape by heat.Dry Bulb An instrument with a sensitiveelement which measures ambient (moving) airtemperature.Dry Bulb Temperature Air temperature asindicated by an ordinary thermometer.Dry Cell, Dry Battery A battery that usesno liquid electrolyte.Dry-Charged Battery A battery in aprecharged state but without electrolyte. Theelectrolyte ia added when the battery is to beplaced in service.Dry Sleeve A cylinder sleeve (liner) wherethe sleeve is supported over its entire length.The coolant does not touch the sleeve itself.Dual Element (DE) Number of elements inan assembly, especially filters. Dual Fuel A term used to describe an enginewhich starts on one type of fuel and runs onanother type.Dual Service Utilizing a prime powergenerator set for a regular, but noncritical load.When a utility outage occurs, the unitautomatically switches to provide emergencypower immediately.Dual Valves Refers to cylinders having twovalves performing one function, e.g. twointake valves, two exhaust valves.Dual Voltage The term used to denote 10-lead machine 240/480, 300/600.Ductility The ability of a metal to withstandplastic deformation without rupture.

Dynamic Balance Condition when theweight mass of a revolving object is in hesame plane as the centerline of the object.

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Dynamic Pressure The pressure of a fluidresulting from its motion, equal to one-half thefluid density times the fluid velocity squared.In incompressible flow, dynamic pressure isthe difference between total pressure and staticpressure.Dynamometer A device for absorbing thepower output of an engine and measuringtorque or horsepower so that it can be computedinto brake horsepower.

Ebullient Cooled Engine An engine cooledby boiling water. The cooling is accomplishedby turning water into steam. The latent heat ofevaporation absorbed in this process cools theengine.Ebullient System A type of high temperatureheat recovery system. Also known as solidwater system.Eccentric One circle within another circlebut with different center of rotation. Anexample of this is a driving cam on a camshaft.Economizer A device installed in acarburetor to control the amount of fuel usedunder certain conditions.Edge Filter A filter which passes liquidbetween narrowly separated disks or wires.Efficiency In general, the proportion ofenergy going into a machine which comes outin the desired form, or the proportion of theideal which is realized.Elapsed Time Meter Totals the hours ofgenerator set operation.Elastic Limit The greatest stress which amaterial is capable of developing without apermanent deformation remaining uponcomplete release of the stress.Electric Power Generation (EPG) Producingenergy through the use of a generator set.

Electric Power Generation Designer (EPGDesigner) A Cat software program whichguides Cat dealers and consulting engineersthrough specing and installing generator setpackages.Electrical Operator The electric motor-driven closing and tripping (opening) devicesthat permit remote control of a circuit breaker. Electrolyte A solution of sulfuric acid andwater.

Electromotive Force (emf) Forces thatmove or tend to move electricity.Electronic Control Analyzer Programmer(ECAP) An electronic service tool developedby Caterpillar used for programming anddiagnosing a variety of Caterpillar electroniccontrols using a data link.Electronic Control Module (ECM) Theengine control computer that provides power tothe truck engine electronics. It accepts inputsthat monitor and outputs that control or changeto act as a governor to control engine rpm.Electronic Modular Control Panel (EMCP) A microprocessor-based feature on all Catgenerator sets which provides improvedreliability through precise engine control. Electronic Technician (ET) A softwareprogram to run on a service tool like apersonal computer (PC). This program willsupplement and eventually replace ECAP.Element, Battery A group of plates negative and positive.Elongation The amount of permanentextension in the vicinity of the fracture in thetension test, usually expressed as a percentageof the original gauge length, such as 25 percentin two inches.Embedded Stator Temperature Detector Thermocouple embedded in a generatorsstator winding.Emergency System Independent powergeneration equipment that is legally required tofeed equipment or systems whose failure maypresent a hazard to persons or property.

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Emission Standard The maximum amountof a pollutant legally permitted to bedischarged from a single source.Emissions The gaseous products emitted inengine exhaust. Emulsify To suspend oil in water in amixture where the two do not easily separate.Encapsulation An impervious material tosurround and protect an item from theenvironment.End Mounted Terminal Box (EMTB) Thelatest design on very large generators; 580, 680,and 800 frames; for covering customer line leadconnections (bus bars or circuit breakers) andregulator assemblies.End Play The amount of axial movement ina shaft that is due to clearance in the bearingsor bushings.Endurance Limit A limiting stress, belowwhich metal will withstand without fracture anindefinitely large number of cycles of stress.Energize To make active.Energized Systems A system under load(supplying energy to load) or carrying ratedvoltage and frequency, but not supplying load.

Energy Capacity for doing work.Energy Charge That portion of the billedcharge for electric service based upon theelectric energy (kilowatt-hours) supplied, ascontrasted with the demand charge.

Energy Consumption The amount ofenergy consumed in the form in which it isacquired by the user (excluding electricalgeneration and distribution losses).Energy Efficiency Ratio (EER) The heattransfer ability of the refrigeration system,expressed in Btu/h, compared to watts ofelectrical energy necessary to accomplish theheat transfer. This comparison is expressed inBtu/h/Watt of electrical energy.Engine The prime source of powergeneration used to propel the machine.

Engine Coolant Level On the EMS II module,a flashing red light and horn annunciate when acustomer-provided coolant level switch isactivated. This information is provided to EMSII directly and then sent on the datalink. In theevent that coolant level input is not provided, theinput will be shorted on the terminal strip.

Engine Displacement The volume eachpiston displaces when it moves from BDC toTDC times the number of cylinders. (Also seeDisplacement.)Engine Investment Analysis A Cat serviceto aid potential buyers in the decision makingprocess, through qualifying fuel savings andcalculating return on investment.

Engine Load The engine power isdetermined as a function of manifold pressureand speed from dynamometer test data.

Engine Monitoring System (EMS) Anelectronic display for marine or industrialengines to display engine parameters anddiagnostics.

Engine Mounting Ring A rabbet fit ring withmounting holes on end of the stator frame forengine mounting.

Enthalpy Total amount of heat in one poundof a substance calculated from acceptedtemperature base. Temperature of 32 F is theaccepted base for water vapor calculation. Forrefrigerator calculations, the accepted base is-40 F.

Environmental Protection Agency (EPA) AFederal agency.

Erode To wear away.

Etching A process which determines thestructure and defects in metals.

Ether A volatile, colorless, and highlyflammable chemical compound which is usedas a starting aid.

Ethylene Glycol A compound added to thecooling system to reduce the freezing point.

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Eutectoid Nearly all iron contains somecarbon. In annealed steel, iron carbide mixeswith iron (ferrite) in alternate thin layers and iscalled pearlite. As the carbon contentincreases, it causes an increase in pearlite anda decrease in ferrite. At the point of increasewhere all the ferrite is in combination withcarbon, the structure will be entirely ofpearlite. This is called the eutectoid, and thestructure is the eutectoid composition.Evaporation The process of changing froma liquid to a vapor, such as boiling water toproduce steam. Evaporation is the opposite ofcondensation.Evaporative Cooling System A coolingsystem in which the heat finally passes to theatmosphere by evaporation. This system maybe either open or closed.Evaporator Part of a refrigeratingmechanism in which the refrigerant vaporizesand absorbs heat.Evaporator, Dry Type An evaporator intowhich refrigerant is fed from a pressurereducing device. Little or no liquid refrigerantcollects in the evaporator.Evaporator, Flooded An evaporatorcontaining liquid refrigerant at all times.Excess Air Air present in the cylinder overand above that which is theoretically necessaryto burn the fuel.Excess Oxygen The amount of free oxygen inthe products of combustion. It may be expressedas a percentage of either volume or mass.Excitation The power required to energizethe magnetic field of generators in an electricgenerating station.Excitation Current Amperage required bythe exiter to produce a magnetic field.Excite To pass current through a coil orstarter.

Exciter A generator or static rectifier assemblythat supplies the electric current used toproduce the magnetic field in another generator.

Exhaust Air removed deliberately from aspace by fan or other means, usually to removecontaminates from a location near their source.Exhaust Analyzer (Smoke Meter) A testinstrument used to measure the density of theexhaust smoke to determine the combustionefficiency.Exhaust Fan Normally shipped with MCEgenerators, designed to mount on engine drivedisc to run inside of generator exhaust opening.Exhaust Gas The products of combustion inan internal-combustion engine.Exhaust Gas Analyzer An instrument fordetermining the efficiency with which anengine is burning fuel.Exhaust Manifold The passages from theengine cylinders to the muffler which conductthe exhaust gases away from the engine.Exhaust Port The opening through whichexhaust gas passes from the cylinder to themanifold.Exhaust Valve The valve which, whenopened, allows the exhaust gas to leave thecylinder.Expansion An increase in size. For example,when a metal rod is heated it increases inlength and perhaps also in diameter. Expansionis the opposite of contraction.Expansion Ratio Ratio of the total volumewhen the piston is at BDC to the clearancevolume when the piston is at TCD. (Nominallyequal to compression ratio.)Expansion Valve A device in a refrigeratingsystem which maintains a pressure differencebetween the high side and low side and isoperating by pressure.Extended Service Coverage (ESC) A Catservice offering maintenance and or repair (upto five years) beyond that offered in aparticular products warranty.Eye Bolt A bolt threaded at one end and bentto a loop at the other end.

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Fahrenheit (F) A designated temperaturescale in which the freezing temperature ofwater is 32 F and boiling point 212 F (whenunder standard atmospheric pressure).Fatigue Deterioration of material caused byconstant use.

Fault (1) The failure of an operating piece ofequipment, and the specific reason for thefailure, or (2) an electrical distribution systemfailure, where there is a line-to-ground or line-to-line short circuit.

Federal Energy Regulatory Commission(FERC) An independent regulatorycommission within the U.S. Department ofEnergy that has jurisdiction over energyproducers that sell or transport fuels for resalein interstate commerce; the authority to set oiland gas pipeline transportation rates and to setthe value of oil and gas pipelines for ratemakingpurposes; and regulates wholesale electric ratesand hydroelectric plant licenses.

Feeder An electric line for supplying electricenergy within an electric service area or subarea.

Feeler Gauge A strip of steel ground to aprecise thickness used to check clearance.

Feature Based Ordering (FBO) Use offeature codes instead of part numbers todescribe/order product.

Feature Code A functional characteristic ofa product described in customer terms.

Ferrite Solid solutions in which alpha iron(or delta iron) is the solvent.Field A space or region where magnetismexists.

Field Coil An insulated wire wound aroundan (iron) pole piece.Fillet A curved joint between two straightsurfaces.

Filter: Oil, Water, Gasoline, etc. A unitcontaining an element, such as a screen ofvarying degrees of fineness. The screen orfiltering element is made of various materialsdepending upon the size of the foreign particlesto be eliminated from the fluid being filtered.

Fin (Flash) A thin fin of metal formed at thesides of a forging or weld where a smallportion of the metal is forced out between theedges of the forging or welding dies.

Finishing Stone (hone) A honing stone witha fine grid.

Fire Point Lowest temperature at which anoil heated in standard apparatus will ignite andcontinue to burn.

Firing Order The order in which thecylinders deliver their power stroke.

Firing Pressure The highest pressurereached in the cylinder during combustion.

Firm Energy Power supplies that areguaranteed to be delivered under terms definedby contract.

Fit The closeness of contact betweenmachined components.

Fixed Displacement Pump A type of pumpin which the volume of fluid per cycle cannotbe varied.

Flake Internal fissures in large steel forgingsor massive rolled shapes. In a fractured surfaceor test piece, they appear as sizeable areas ofsilvery brightness and coarser grain size thantheir surroundings. Sometimes known aschrome checks and (when revealed bymachining) hairline cracks. Not to beconfused with woody fracture.

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Flame Hardening (Shorterizing) A methodfor hardening the surface without affecting theremainder of the part, used mainly for gears orother parts where only a small portion of thesurface is hardened and where the part mightdistort in a regular carburizing or heat-treatingoperation. The operation consists of heating thesurface to be hardened by an acetylene torch tothe proper quenching temperature followedimmediately by a water-quench and propertempering. A special tool is required, and eitherthe torch or part may be rotated so that the flamepasses over the surface at a speed that willproduce the proper quenching temperature.Waterquenching follows immediately, and the part isneither scaled nor pitted by the operation.Flange A metal part which is spread out likea rim; the action of working a piece or partspread out.Flank, Side or Thread The straight part of thethread which connects the crest with the root.Flank Angles The angle between a specifiedflank of a thread and the plane perpendicularto the axis (measured in an axial plane).Flare To open or spread outwardly.Flaring Tool A tool used to form a flare on atubing.Flash Point The temperature at which asubstance, usually a fluid, will give off a vaporthat will flash or burn momentarily when ignited.Flat Crank A crankshaft in which one of thebearing journals is not round.Floating Piston Pin A piston pin which isnot locked in the connecting rod or the piston,but is free to turn or oscillate in both theconnecting rod and the piston.Float Level The height of the fuel in thecarburetor bowl, usually regulated by means ofa suitable valve or float.Flooded System Type of refrigerating systemin which liquid refrigerant fills the evaporator.Flooding Act of filling a space with a liquid.

Floor The absolute minimum to which thelow limit of an engine performancespecification may fall.Flow Control Valve A valve which is usedto control the flow rate of fluid in a fluidpower system.Flowmeter An instrument used to measurethe quantity or flow rate of a fluid in motion.Fluctuating Wavering, unsteady, not constant.Fluid A liquid, gas, or mixture thereof.Fluid Flow The stream or movement of afluid; the rate of a fluids movement.Fluid Power Power transmitted andcontrolled through the use of fluids, eitherliquids or gases, under pressure.Flush An operation to remove any materialor fluids from refrigeration system parts bypurging them to the atmosphere usingrefrigerant or other fluids.Flute The grooves of a tap that provide thecutting rake and chip clearance.Flutter or Bounce In engine valves, refers toa condition where the valve is not held tightlyon its seat during the time the cam is notlifting it.

Flux, Magnetic Magnetic force.

Flyball Governor Conventional type ofcentrifugal governor commonly called amechanical governor.

Flywheel A device for storing energy inorder to minimize cyclical speed variations.

Flywheel Ring Gear A circular steel ringhaving gear teeth on the outer circumference.

Foaming Formation of a foam in an oil-refrigerant mixture due to rapid evaporation ofrefrigerant dissolved in the oil. This is mostlikely to occur when the compressor starts andthe pressure is suddenly reduced.

Foot-pound (ft-lb) The amount of workaccomplished when a force of 1 lb produces adisplacement of 1 ft.

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Force The action of one body on anothertending to change the state of motion of thebody acted upon. Force is usually expressed inpounds (kilograms).Force Convection Movement of fluid bymechanical force such as fans or pumps.

Force-Feed Lubrication A lubricatingsystem in which oil is pumped to the desiredpoints at a controlled rate by means of positivedisplacement pumps.

Forged Shaped with a hammer or machine.

Fossil Fuel Oil, coal, natural gas, or theirby-products. Fuel that was formed in the earthin prehistoric times from remains of living-cellorganisms.

Foundation The structure on which anengine is mounted. It performs one or more ofthe following functions: holds the engine inalignment with the driven machine, addsenough weight to the engine to minimizevibration, adds to rigidity of the bed plate.

Four-cycle Engine Also known as Ottocycle, where an explosion occurs every otherrevolution of the crankshaft, a cycle beingconsidered as 1/2 revolution of the crankshaft.These strokes are (1) intake stroke, (2)compression stroke, (3) power stroke, (4)exhaust stroke.

Four-Stroke Cycle Cycle of events which iscompleted in four strokes of the piston, or twocrankshaft revolutions.

Frame The main structural member of anengine.

Free Electrons Electrons which are in theouter orbit of the atoms nucleus.

Free Flow Flow which encounters littleresistance.

Freon Trade name for a family of syntheticchemical refrigerants manufactured byDuPont, Inc.

Frequency The number of cycles completedwithin a one-second period, expressed as hertz.

Frequency Meter A unit which monitors agenerator sets output frequency.

Frequency Relay This relay can beconfigured to operate when the monitoredfrequency is above or below a given setpoint.

Friction The resistance to motion due to thecontact of two surfaces, moving relatively toeach other.

Friction Horsepower (FHP) A measure ofthe power lost to the engine through friction orrubbing of parts.

Fuel Cell A device or an electrochemicalengine with no moving parts that converts thechemical energy of a fuel, such as hydrogen,and an oxidant, such as oxygen, directly intoelectricity. The principal components of a fuelcell are catalytically activated electrodes forthe fuel (anode) and the oxidant (cathode) andan electrolyte to conduct ions between the twoelectrodes, thus producing electricity. Fuel-Flow Oil Filter All engine oil passesthrough this oil filter before entering thelubrication channels.

Fuel Knock See Detonation.

Fuel Level On the EMS II module, aflashing red light and horn annunciate when acustomer provided fuel level switch isactivated. This information is provided toEMS II directly and then sent on the datalink.In the event that coolant level input is notprovided, the input will be shorted on theterminal strip.

Fuel Mixture A ratio of fuel and air.

Fuel Pressure The fuel pressure supplied tothe injection pumps of a diesel engine.Fuel Rate (Diesel) The mass of fuel burnedby an engine in a specified time. Correctedfuel rate is the actual or observed fuel ratecorrected for fuel density.

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Fuel Rate (Spark Ignited) The volume offuel burned by an engine in a specified time atthe pressure and temperature being supplied tothe engine. Corrected fuel rate is the volumeof fuel at standard conditions multiplied by thelower heating value of the fuel.

Fuel Transfer Pump A mechanical deviceused to transfer fuel from the tank to theinjection pump.Fuel Valve A valve admitting fuel to thecombustion chamber. In a more general sense,this term may also apply to any manual orautomatic valve controlling flow of fuel.

Fulcrum The pivot point of a lever.

Full-Floating Piston Pin A piston pin free toturn in the piston boss of the connecting-rod eye.Full Load The maximum power an enginecan develop when running at rated speed withthe fuel system opened to its maximumspecified condition.

Gallery Passageway inside a wall or casting.Galvanic Action When two dissimilarmetals are immersed in certain solutions,particularly acid, electric current will flowfrom one to the other.Gas A substance which can be changed involume and shape according to thetemperature and pressure applied to it. Forexample, air is a gas which can be compressedinto smaller volume and into any shape desiredby pressure. It can also be expanded by theapplication of heat.Gasket A layer of material used betweenmachined surfaces in order to seal againstleakage.Gassing Hydrogen bubbles rising from theelectrolyte when the battery is being charged.Gate Valve A common type of manuallyoperated valve in which a sliding gate is usedto obstruct the flow of fluid.

Gauge Construction Shell is a cosmeticwrapper. Only advantage no varnish clean-up of shell required.Gauge, Low Pressure Instrument formeasuring pressures in range of 0 psig and50 psig.Gauge, High Pressure Instrument formeasuring pressures in range of 0 psig to500 psig.Gauge Pressure Pressure above atmosphericpressure.

Gauge Snubber A device installed in thefuel line to the pressure gauge used to dampenpressure surges and thus provide a steadyreading. This helps protect the gauge.Gear Ratio The number of revolutions madeby a driving gear as compared to the number ofrevolutions made by a driven gear of differentsize. For example, if one gear makes threerevolutions while the other gear makes onerevolution, the gear ratio would be 3 to 1.

Gear-type Pump A pump which uses thespaces between the adjacent teeth of gears formoving the liquid.

Generator, Electrical An electromagneticdevice used to generate electricity.

Generator, Cooling A device used inabsorption-type refrigeration systems to heatthe absorbing liquid to drive off the refrigerantvapor for condensing to a liquid beforeentering the evaporator.

Generator Power System (GPS) EPG powersystem that uses energy off an electric generator.Ghost (Ferrite Ghost) A faint band offerrite.Gland A device to prevent the leakage ofgas or liquid past a joint.Glaze As used to describe the surface of thecylinder, an extremely smooth or glossysurface such as a cylinder wall highly polishedover a long period of time by the friction ofthe piston rings.

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Glaze Breaker A tool for removing theglossy surface finish in an engine cylinder.Glow Plug A heater plug for the combustionchamber. It has a coil of resistance wire heatedby a low voltage current.Governor A device that maintains a constantengine speed under various load conditions.The governor must have provision foradjustment of speed (which controls generatorfrequency) and of the amount of speed droopfrom no load to full load. Grain A unit of weight equal to one 7000thof a pound. It is used to indicate the amount ofmoisture in the air.Grain Size There are two types of grains insteel which affect the physical properties ofsteel; the austenite grain and the ferrite grain.The ferrite grain tends to remain stable in sizeat temperatures below the transformation rangeunless the steel is cold worked a criticalamount, in which case the grains grow rapidly.When steel is heated above the transformationrange, the newly formed austenite grain issmall but tends to grow in size with increasingtemperature and time at temperature. Grainsize, as commonly used, is the size of the grainthat is developed in the austenite at the finalheat treating temperature and does not refer tothe ferrite grain. Except for the austeniticsteels, the austenite grain size does not exist atroom temperature; but its pattern can bedeveloped by special methods.Gravity The force which tends to draw allbodies toward the center of the earth. Theweight of a body is the result of allgravitational forces on the body.Gravity, Specific The specific gravity of asolid or liquid is the ratio of the mass of thebody to the mass of an equal volume of waterat some standard temperature. At the presenttime a temperature of a 4 C (39 F) iscommonly used by physicists, but the engineeruses 16 C (60 F). The specific gravity of agas is usually expressed in terms of dry air atthe same temperature and pressure as the gas.

Grid The electric utility companiestransmission and distribution system that linkspower plants to customers through high powertransmission line service (110 kilovolt [kV] to765 kV); high voltage primary service forindustrial applications and street rail and bussystems (23 kV to 138 kV); medium voltageprimary service for commercial and industrialapplications (4 kV to 35 kV); and secondaryservice for commercial and residentialcustomers (120 V to 480 V). Grid can alsorefer to the layout of a gas distribution systemof a city or town in which pipes are laid inboth directions in the streets and connected atintersections.Grid, Battery The lead frame to which theactive material is affixed.Grid Interconnection The intertie of acogeneration plant to an electric utilitys systemto allow electricity flow in either direction.Grinding Removing metal from an objectby means of a revolving abrasive wheel, disk,or belt.Grinding Compound Abrasive forresurfacing valves, etc.Ground, Battery The battery terminal thatis connected to the engine of the framework.Ground Fault Protection This function trips(opens) a circuit breaker or sounds an alarm inthe event that there is an electrical fault betweenone or more of the phase conductors and ground(earth). This ground fault protection functionmay be incorporated into a circuit breaker. Grounding Bar A copper or aluminum barthat electrically joins all the metal sections ofthe switchgear. This bar is connected to theearth or ground connection when the system isinstalled. The grounding or earthing protectspersonnel. Growler A test instrument used for testingthe armature of a starter or generator for open,short, and grounded circuits.GSC + Synchronizing General StatusControl plus Synchronizing

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Half-moon Key A fastening device in a shapesomewhat similar to a semicircle. (See Key.)Halide Refrigerants Family of refrigerantscontaining halogen chemicals.Hardenability This relates to the ability ofsteel to harden deeply upon quenching and takesinto consideration the size of the part and themethod of quenching. In testing for hardenability,standards are established governing the methodof quenching and the quenching medium whichmakes it possible to compare the hardenabilityof steels of various analysis and grain size.Hardness The ability of a metal to resistpenetration. The principal methods of hardnessdetermination are described under hardnesstesting and the correlation of thesedeterminations with the other mechanicalproperties are described under physical properties.Hardness Testing The determination of theability of a metal to resist penetration; thehardness of the metal may be determined byseveral methods (i.e. Brinell, Rockwell,Superficial).Harmonics Waveforms whose frequenciesare multiples of the fundamental (60 Hz) wave.The combination of harmonics andfundamental waves causes a non-sinusoidal,periodic wave. Harmonics in power systemsare the result of non-linear effects. Typically,harmonics are associated with rectifiers andinverters, arc furnaces, arc welders, andtransformer magnetizing current. There areboth voltage and current harmonics.Head Pressure Pressure which exists in thecondensing side of a refrigerating system.Head, Static Pressure of fluid expressed interms of height of column of the fluid, such aswater or mercury.Head, Velocity In flowing fluid, heat of fluidequivalent to its velocity pressure.Head-Pressure Control Pressure operatingcontrol which opens electrical circuit if highside pressure becomes excessive.

Heat Form of energy the addition of whichcauses substances to rise in temperature; energyassociated with random motion of molecules.Heat Balance Energy flow in a powergenerating system.Heat Coil A heat transfer device whichreleases heat.Heat Exchanger Device used to transferheat from a warm or hot surface to a cold orcooler surface. Evaporators and condensers areheat exchangers.Heat, Latent Heat characterized by a changeof state of the substance concerned, for a givenpressure and always at a constant temperaturefor a pure substance, i.e., heat of vaporizationor of fusion.

Heat Load Amount of heat, measured in Btu,which is removed during a period of 24 hours.

Heat of Compression Mechanical energy ofpressure transformed into energy of heat.

Heat of Fusion The heat released inchanging a substance from a liquid state to asolid state. The heat of fusion of ice is 144 Btuper pound.

Heat Pump A name given to an air-conditioning system that is reversible so as tobe able to remove heat from or add heat to agiven space or material upon demand.

Heat Pump Air Source A device thattransfers heat between two different airquantities, in either direction, upon demand.

Heat Pump Water Source A device thatuses a water supply as a source of heat or fordisposal of heat depending upon theoperational demand.

Heat Rate A measure of generating stationthermal efficiency, generally expressed in Btu(per net kilowatt-hour).Heat Recovery The capture and utilizationof heat energy which is normally wasted as aby-product of a diesel or gas engine.

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Heat, Sensible A term used in heating andcooling to indicate any portion of heat whichchanges only the temperature of the substancesinvolved.Heat Sink An aluminum plate or extrusionunder the rectifier assembly which dissipatesheat generated by the rectifier.Heat Source The material from which therefrigeration system extracts heat.Heat, Specific The heat absorbed (or givenup) by a unit mass of a substance when itstemperature is increased (or decreased) by1-degree Common Units: Btu per (pound)(Fahrenheit degree), calories per (gram)(Centigrade degree).