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ABSOLUTE PRESSUREPressure measured with respect to zero pressure, as distinct from pressure measured with respect to some standardpressure such as atmospheric pressure. Thus, 2 Bar gauge (i.e. atmospheric) is equivalent to 3 Bar absolute.(Atmospheric pressure being 1 bar absolute).ABSOLUTE TEMPERATUREA temperature at which zero is a condition absolutely free of heat and equivalent to -459oF or 273oC. To converttemperature on Fahrenheit or centigrade scales to degrees absolute, add 459 or 273 respectively.ACIDA member of an important and fundamental category of chemical substances characterised by having an availablereactive hydrogen and requiring an alkali to neutralise them. Acid solutions usually have a sour, biting and tart taste,like vinegar.ADDITIVEA substance added to a product in order to improve its properties.ADSORPTION PROCESSA fractionation process based on the fact that certain highly porous materials preferentially adsorb certain types ofmolecules on their surface, e.g. PSA units.ALIPHATIC HYDROCARBONSHydrocarbons in which the carbon atoms are arranged in open chains, which may be branched. The term includesparaffins and olefins and provides a distinction from aromatics and naphthenes which have at least some of theircarbon atoms arranged in closed rings.ALKALIIn chemistry, any substance having marked basic properties. In its restricted and common sense, the term is appliedonly to hydroxides of ammonium, lithium, potassium, and sodium. They are soluble in water, they have the power ofneutralising acids and forming salts with them and of turning red litmus blue. In a more general sense, the term isalso applied to the hydroxides of the so-called alkaline earth metals - barium, calcium, and strontium.ALKALI TESTA test to determine the presence or absence of free alkali in finished oils after chemical purification.ALKALINEHaving the properties of an alkali; opposite to acidic.ALKALINITYThe amount of free alkali in any substance.ALKYLATIONA reaction in which a straight-chain or branched-chain hydrocarbons group, which is called an alkyl group or radical,is united with either an aromatic molecule or a branched-chain hydrocarbon. Used for detergent or petroleummanufacture. Usually catalysed by Hydrofluoric or Sulphuric acid.

ALLOYA substance composed of two or more metals, or of a metal and a nonmetal, intimately united, usually by being fusedtogether and dissolved in each other when molten.

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AMINEHydrocarbon with attached Ammonia group having absorbent properties, making it useful in treatment processes (ADIP, SULFINOL).

AMMONIA NH3Ammonia is manufactured by the direct combination of hydrogen and nitrogen under pressure over a catalyst. Anhydrous ammonia ismainly used for the manufacture of nitrogenous fertilisers, but is used at NZRC for pH control in various processes. A colourless,gaseous compound, NH3 is of extremely pungent smell and taste and is very soluble in water.

ANALYSISThe process of determining the composition of a substance by chemical or physical methodsv ANILINE POINTThe minimum temperature for complete miscibility of equal volumes of the chemical aniline and a petroleum product. In conjunctionwith API gravity the aniline point may be used to calculate the net heat of combustion of aviation fuels or the diesel index of dieselfuels. The lower temperature at which an oil product is completely miscible with aniline in a 1:1 volumetric ratio.

ANTIFOAM AGENTAn additive used for controlling foam. Antifoam agents are used in some lubricating oils. At NZRC, used as additives in ADIP,Sulphinol and BDU Units.

ANTI-KNOCKAn adjective signifying resistance to detonation (pinking) in spark-ignited internal combustion engines. Anti-knock value is measuredin terms of octane number of gasoline engines and of cetane number for diesel fuels.

ANTI-KNOCK AGENTA chemical compound such as tetramethyl-lead which, when added in small amounts to the fuel charge of an internal-combustionengine, tends to lessen knocking.

ANTIOXIDANTA chemical added to gasoline, lubricating oil, etc. to inhibit oxidation.

ANTI-STATIC ADDITIVEAn additive for reducing static properties, notably in Kerosene.

API GRAVITYIn the USA an arbitrary scale known as the API degree is used for reporting the gravity of a petroleum product. The degree API isrelated to the specific gravity scale (15C/15C) by the formula:

141.5

Degree API = Sp. Gr. 15C/15C - 131.5

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AROMATIC BLENDA mixture made by the addition of a component or stock essentially aromatic in nature to impart to the mixture some property of thearomatic.

AROMATICSA group of hydrocarbons characterised by their having at least one ring structure of six carbon atoms, each of the latter having onevalency outside the ring. If these valencies are occupied by hydrogen atoms, hydrocarbon radicals, or inorganic groups one speaks ofcondensed aromatics. These hydrocarbons are called aromatics because many of their derivatives have an aromatic odour. They are ofrelatively high specific gravity and possess good solvent properties. Certain aromatics have valuable anti-knock characteristics.Typical aromatics are: benzene, toluene, xylene, phenol (all mono-aromatics) and naphthalene (a di-aromatic). Aromatics can causesmoke and freeze point problems in Kerosene.

ASHThe solid residue left when combustible material is thoroughly burned.

ASH CONTENTThe percent by weight of residue left after combustion of a sample of a fuel oil or other petroleum oil.

ATMOSPHERIC PRESSURE1. The pressure of air.

2. More specifically, the pressure of the air at sea level.

3. As a standard, the pressure at which the mercury barometer stands at 760mm, or 30in. (equivalent to approx. 14.7 psi).

ATOMThe smallest complete particle of an element which can be obtained, yet retain all physical and chemical properties of the element.According to present theory, the atom consists of a nucleus of neutrons and positively charged protons, surrounded by negativelycharged particles called electrons.

AUTO IGNITION POINTThe temperature at which the vapour given off by a sample will ignite in air without any ignition source.

AVERAGE BOILING POINTUnless otherwise indicated, the sum of the ASTM distillation temperatures in steps of 10C from the 10-percent point to the 90-percentpoint, inclusive, divided by 9. Sometimes half the initial and half the maximum distillation temperatures are also added, and the sumthen divided by 10.

AZEOTROPETwo (or more) components are said to form an azeotrope if there is a mixture of those components which has no boiling range butwhose boiling point and dew point are the same.

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AZEOTROPIC DISTILLATIONA distillation process characterised by the fact that the relative position of the components boiling points is influenced by the additionof a compound which selectively forms an azeotrope with one or a group of the components. The added compound is called theazeotrope former. E.g. furfural, used in the extraction of aromatics, forms an azeotrope with water.

BAROMETERAn instrument employed to determine atmospheric pressure.

BAROMETRIC CONDENSERA device for condensing steam by direct contact with water. It produces a partial vacuum in refinery equipment such as a vacuumdistillation unit.

BATTERYA series of individual items of refinery equipment operated as a unit.

BATTERY LIMITSA term used when a unit or a battery is to be built in a refinery by an outside contractor or construction company. It specifies the areawithin which the contractor shall supply all services, and defines the limits beyond which this shall be done by the refinery. Alsodefines plant interface limits.

BEARINGA support for holding a shaft in its correct position. Examples: journal bearings to confine radial motion, thrust bearings to controlaxial movement, and "rolling element" bearings which are used in both services.

BENZENE C6H6The parent compound of the aromatic hydrocarbon series. It is used in the manufacture of a large number of chemicals includingphenol, styrene, detergent alkylate and insecticides and is a major component of platformate.

BIOCHEMICAL OXYGEN DEMAND (BOD)Important water test that shows the amount of bio-degradable matter in the water. Amount of oxygen required by aerobic organismsfor breakdown of organic matter in water over a 5 day period.

BOILING POINT (AT A GIVEN PRESSURE)The temperature at which a liquid, contained in a closed vessel under a given pressure, will form a first bubble of vapour on theaddition of heat. Further heating of the liquid at its boiling point results in evaporation of part or all of the liquid.

BOND1. Chemically, a unit link between atoms. In graphic chemical formulas, it is often represented by a short line or dash.

2. Electrically, a common grounding system e.g. Bonding wires used between fuel tanker and petrol station ground tanksor airport delivery systems and aircraft.

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BUFFER1. A vessel for temporary storage of liquid (buffer drum).

2. A chemical used to maintain another within set limits of (e.g.) pH.

A device to polish the floor.

An old Navel name for a person in-charge of the deck of a Ship.BULK DENSITYThe weight of solid particles which can be held by a container of known dimensions compared to the weight of water which can beheld by the same container.

BUTANE C4H10Commercial butane is a mixture of two gaseous paraffins, normal butane and isobutane. When blended into gasoline in smallquantities it improves volatility and octane number. Butane can be stored under pressure as a liquid at atmospheric temperatures("bottled gas") and it is widely used for cooking and domestic heating. Used at NZRC in the reformer and BDU.

BUTANE DE-ASPHALTINGA solvent extraction process whereby a short residue is split into components having low (D.A.O.) and high (Asphalt) asphaltic contentby contact with liquid butane.

BYPRODUCTA secondary or additional product not of primary importance. (e.g. Sulphur).

C1,C2,C3,C4,C5A common way of representing fractions containing a preponderance of hydrocarbons of 1, 2, 3, 4 or 5 carbon atoms, respectively,without reference to hydrocarbon type.

CALIBRATIONThe determination of fixed reference points on the scale of any instrument by comparison with a known standard and the subsequentsubdivision or graduation of the scale to enable measurements in definite units to be made with it. Also the process of measuring orcalculating the volumetric contents or capacity of a receptable.

CALORIEThe amount of heat required to raise the temperature of 1 gram of water through 1 the kcalorie, equal to 1,000 calories is often used. 1,000 kilocalories = 3,968 Btu.

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CALORIFIC VALUEThe calorific value of a combustible material is the quantity of heat produced by complete combustion of unit weight of the material.The units in which the calorific value is usually given are (a) calories per gram and (b) British Thermal Units per pound. The systemsmay be converted by the relationship:

1 calorie per gram = 1.8 Btu per lb.

CARBONA nonmetallic element existing in diamonds, graphite, and numerous amorphous forms; combined as carbon dioxide, carbonates, andin all living things. Carbon is unique in forming an almost infinite number of compounds (it is present in all organic compounds).

CARBON (FIXED CARBON)In the case of coal, coke, and bituminous materials, the solid residue other than ash contained by destructive distillation.

CARBON DEPOSITEngine deposits containing soot from over-rich fuel mixtures and the carbon residue and tars from decomposed lubricating oil. Roaddust, metal particles, gum and tarry substances also form a part of such deposits.

CARBON DIOXIDEA heavy, colourless gas, CO2, which will not support combustion. Dissolved in water, it forms carbonic acid. It is exhaled bylung-possessing animals as a waste gas, but is inhaled by certain plants which absorb its carbon and release its oxygen as a waste gas.

CARBON MONOXIDEA colourless, odourless gas, CO; a product resulting from the incomplete combustion of carbon. It is very poisonous.

CATALYSISThe alteration of the rate of a chemical reaction by the presence of a "foreign" substance (catalyst) that remains unchanged at the end ofthe reaction.

CATALYSTIn technology this word means a substance added to a system of reactants which will accelerate the desired reactions, while emergingvirtually unaltered from the process. The catalyst allows the reaction to take place at a temperature at which the uncatalyzed reactionwould proceed too slowly for practical purposes. Used extensively in secondary processes.

CATALYST POISONGenerally, coverage of the catalyst surface with nonreactants. If a large fraction of the catalyst surface is covered selectively by anyone strongly adsorbed chemical, the catalytic reaction will be drastically reduced in rate. This circumstance is called poisoning, andself-poisoning can result when one reactant or product is much more strongly adsorbed than another reactant. May be reversible, butcan destroy entire catalyst inventory.

CATALYTIC PROCESSAny process which employs catalysis. Examples : Hydrocracking, Platforming and hydrotreating.

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CENTRIFUGAL COMPRESSORA machine in which pressure is built up by means of rotating fans or blades.

CENTRIFUGAL PUMPA pump that derives its pressure increase from the centrifugal force generated when the impeller throws the liquid outwards at highspeed.

CENTRIFUGEA whirling instrument for separating liquids and solids or liquids of different specific gravity by use of centrifugal force.

CERAMIC BALLSBalls of chemically inert ceramic, used as filler and support in reactors etc.

CETANE NUMBERThe cetane number of a diesel fuel is a number equal to the percentage by volume of cetane in a mixture with alph-methyl-naphthalenehaving the same ignition quality as the fuel under test.

CHEMICAL OXYGEN DEMAND (COD)Total amount of oxygen needed for oxidation of all organic matter in water to CO2 and H2O.

CHLORINATIONA chemical reaction in which chlorine reacts with hydrocarbon and one or more of the hydrogen atoms are replaced by atoms ofchlorine, or chlorine reacts with an unsaturated hydrocarbon and two chlorine atoms (one molecule) are added to the double bond.

CLOUD POINTThe temperature at which a fuel, when cooled, begins to congeal and present a cloudy appearance owing to the formation of minutecrystals of wax.

COAGULATIONThe precipitation from solution or suspension of fine particles which tend to unite in clots or curds.

COALESCERA vessel packed with steelwool, glasswool, polypropylene wool or felt used to remove fine droplets of treating liquids or water from apetroleum product.

COKEHard carbon deposit, usually formed by the unintentional thermal cracking of heavy residues.

COMPOUNDA substance formed by the combination of two or more ingredients in definite proportions by weight, and possessing physical andchemical properties entirely different from those of the ingredients. e.g. table salt, paint.

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COMPRESSIONIn general, the act of increasing the pressure on gas or vapour. It is usually 0attended by a reduction in volume.COMPRESSORA device which draws in air or other gases, compresses it and discharges it at a high pressure.

CONDENSATELiquid hydrocarbons which are sometimes produced together with natural gas. In general: the liquid that is formed when a vapourcools.

CONDENSATION (PHYSICAL)The transfer of a material from the vapour phase into the liquid phase, for example by the withdrawal of heat.

CONDENSERA special type of heat exchanger for the removal of heat from e.g. the top of a fractionating column.

CONDUCTIVITYA materials ability to conduct an electrical charge. Important in water treatment (as an indication of impurities) and somehydrocarbons (static risk).

CONGEALTo change from a liquid to a semi-solid or solid state.

CONTINUOUS CATALYST REGENERATORsee Fluid bed operation.

CONTINUOUS DISTILLATIONAn operation in which the steps of charging, heating, vapourisation, fractionation, and collection of products are performedcontinuously rather than in a batchwise manner. The unit employed is known as a continuous still.

CONVECTIONThe flow of heat through liquid or gas by actual mixing of the fluids (physical turbulence).

CONVECTION SECTIONThat portion of the furnace in which tubes receive heat by convection from the flue gases (contrast with radiant section).

CONVENTIONAL PRODUCTSPetroleum products which are manufactured from crude oil by physical separation processes. (See primary processes).

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CORROSIONThe gradual eating away of metallic surfaces as the result of chemical action such as oxidation. It is caused by corrosive agents such asacids.

COUNTERCURRENT FLOWA system in which one fluid flows in one direction and another fluid flows in the opposite direction e.g. in a heat exchanger, in whichthe direction of flow of the cold oil is opposite to that of the hot oil.

CRACKINGProcess whereby the large molecules of the heavier oils are converted into smaller molecules of the gasoline type. When this isbrought about by heat alone, the process is known as thermal cracking. If a catalyst is also used the process is referred to as catalyticcracking (in speech generally abbreviated to cat. cracking) or Hydrocracking if the process is conducted over special catalysts in ahydrogen atmosphere - other processes include visbreaking and hycon

CRITICAL PRESSUREThe pressure necessary to condense a gas at the critical temperature.

CRITICAL TEMPERATUREThe maximum temperature at which a gas can be liquefied by pressure (critical pressure); above this temperature the gas cannot beliquefied, no matter what pressure is applied.

CRITICAL VELOCITYThe rate of flow in a pipe at which streamline flow changes into turbulent flow.

CRYSTALISATIONA fractionation process based on the difference in freezing point of the various constituents of the mixture to be fractionated. Theprocess is, for example, used in the separation of paraffins from lube oil (de-waxing).

DECOMPOSITIONThe breaking up of compounds into smaller chemical forms through the application of heat, change in other physical conditions, orintroduction of other chemical bodies.

DEHYDRATIONThe removal of water from crude oil, from gas produced in association with oil, or from gas from gas-condensate wells.

DEHYDROGENATIONA reaction process in which hydrogen atoms are eliminated from a molecule.

DEIONIZED WATERWater that has had all the free ions removed by ion-exchange, also called demineralised water.

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DEISOLATIONThe opposite of isolation i.e. To energise a piece of equipment.

DEMISTERAny device used to stop passage of liquid droplets e.g. a demister section in a vacuum column is to stop the asphaltenes from theresidue getting into the waxy distillate.

DEMULSIFIERAn additive used to prevent the formation of an emulsion - applicable in crude/water emulsions in desalter.

DENITRIFICATIONRemoval of nitrogen compounds on feedstock by hydrogenation. N2 + 3H2 = 2NH3.

DEOXYGENATIONRemoval of oxygen on feedstock by hydrogenation. 02 + 2H2 = 2H20.

DEW POINT (at a given pressure)The temperature at which a vapour, contained in a closed vessel under the given pressure, will form a first drop of liquid on thesubtraction of heat. Further cooling of the vapour at its dew point results in condensation of part or all of the vapour as liquid. Thedew point of a normal gasoline is approximately the same as the temperature at which 70% by volume distils over in theASTM-distillation test. The dew point of a pure compound is the same as its boiling point

DISTILLATION (fractional)A fractionation process based on the difference in boiling point of the various constituents of the mixture to be fractionated. It iscarried out by evaporation and condensation in contact with reflux. When applied to the separation of gasoline, kerosene, etc., from acrude oil, to leave a residual fuel oil or asphaltic bitumen, the process is frequently called topping. Distillation is normally carried outin such a way as to avoid decomposition (cracking); in the case of the higher boiling distillates, such as long residue, this isaccomplished by carrying out the distillation under vacuum (which requires a lower temperature).

DOCTOR SOLUTIONA solution (sodium plumbite) made from lead oxide and sodium hydroxide, used to treat gasoline or other light petroleum distillates toremove mercaptan sulphur. The "doctor test" is used for the detection of sulphur compounds in light petroleum distillates which reactwith sodium plumbite.

DRY GASNatural gas which does not contain liquid hydrocarbons at storage pressure. Also often used for a petroleum gas consisting of no othercompounds than inert gases (e.g. hydrogen, nitrogen, etc) and the light hydrocarbons methane, ethane, ethene, propane, propene(sometimes also: hydrogen sulphide).

EJECTORA device that uses the venturi effect to pull a partial vacuum. Usually driven by steam and associated with condensing plant.

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ELECTROLYSISChemical decomposition by the action of an electric current.

EMULSIFIERA substance used to promote or aid the emulsification of two liquids and to enhance the stability of the emulsion.

EMULSIONA dispersion of fine droplets of a liquid (the disperse phase) in the bulk of another liquid (the continuous phase) with which it is immiscible. A

third substance, the emusifier, is sometimes necessary to keep the droplets dispersed as a stable emulsion.

ENDOTHERMICRelating to or designating a reaction which occurs with the absorption of heat, so that the temperature of the reacting bodies is lowered (i.e.

heating is required).

ENDOTHERMICRelating to or designating a reaction which occurs with the absorption of heat, so that the temperature of the reacting bodies is lowered (i.e.

heating is required).

EXOTHERMICRelating to or designating a reaction which occurs with the evolution of heat, so that the temperature of the reacting bodies is raised (i.e. cooling

is required).

EXTRACTIONA fractionation process based upon the difference in solubility, in a given solvent, of the various constituents of the mixture to be fractionated.

The process is, for example, used in the separation of de-asphalted oil from short residue (see butane de-asphalting).

EXTRACTION DEPTHDepth to which DAO may be extracted from short residue on BDU unit - the greater the extraction depth, the higher the DAO yield, although too

deep an extraction may affect DAO specification.

EXTRACTORColumn in which an extraction process (e.g. BDU) is carried out.

EXTREME PRESSURE LUBRICANTSA term applied to lubricating oils or greases which contain a substance or substances specifically introduced to prevent metal-to-metal contact in

the operation of highly loaded gears and bearings. In some cases this is accomplished by the substances reacting with the metal toform a protective film.

FILTERA porous material on which solid particles are largely caught and retained when a mixture of liquids and solids is passed through it.

FILTRATEThe liquid which has passed through a filter; the product from a filtration process.

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FLASH DISTILLATIONThe process of heating a liquid to a temperature within the boiling range of the liquid which causes the evaporation of part of the liquid. The

vapour may then be taken off and condensed.

FLASH POINTThe lowest temperature under closely specified conditions at which a combustible material will give off sufficient

vapour to form an inflammable mixture with air in a standardised vessel. Flash point tests are used to assess the volatilities ofpetroleum products.

FLUE GASGas from the combustion of fuel, the heating effect of which has been substantially spent and which is, therefore, discarded to the flue or stack.

Its constituents are principally CO2, CO, 02, N2 and H20.

FLUIDNon rigid substance consisting of particles that move freely amongst themselves (includes particulate, liquids and gases).

FLUID BED OPERATIONWhere catalyst is continually moved from the reactor to a regenerator and back again, as in the continuously regenerated platformer or cat cracker

processes.

FOAMA preparation designed to smother oil fires. It consists of a solution which, on mixing with water, produces a mass of foammany times the

volume of the original liquids.

FOAMING1. The formation of froth or foam on lubricating oils or other oils as a result of aeration or release of gas dissolved in the oil.

2. The formation of bubbles on the surface of boiled water. The foam may entirely fill the steam space of the boiler or may be of minordepth; in either case, it causes appreciable entrainment of boiler water with steam.

3. Caused in Adip systems by presence of liquid hydrocarbons or fines affecting surface tension of solution.

FORCED DRAUGHTAir forced into a furnace by means of a fan or blower to improve combustion (compare induced draught).

FRACTIONA portion of petroleum separated from other portions in the fractionation of petroleum products. It is often characterised by a particular boiling

range.

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FRACTIONAL CONDENSATIONA separation of the components of vapourised oil coming off during distillation by condensing the vapours in stages (partial condensation). The

oil of highest boiling point will condense first and may be removed in the liquid stage, allowing the portion still in the vapour state topass on to the next stage condenser.

FRACTIONATIONThe general name for a physical process of separating a mixture into its constituents, or into groups of these constituents, called fractions.

Examples are: absorption, azeotropic distillation, crystallisation, decanting, distillation, extraction, extractive distillation and flotation.

FREEZE POINTAn important characteristic of aviation fuels. The test for Jet A1 is to cool until solid then reheat, the temperature at which the solid MELTS is

called freeze point.

FREEZING POINTThe temperature at which crystals first appear when a liquid is cooled under specified conditions.

FRESH GASIn the HYDROCRACKER, Fresh H2 from the reformer to replace H2 used up in the process. Otherwise any imported gas as distinct from

recycle gas.

FRICTIONResistance to the motion of one surface against another.

FUEL AIR RATIOThe ratio of the weights of fuel to air supplied to an engine, furnace or boiler at any time.

FUEL CELLAn electrochemical device to convert chemical energy directly into electricity. It is similar in some respects to a storage battery or a dry cell.

Like a battery, the fuel cell produces electricity by a chemical reaction. Unlike a storage battery, however, the fuel cell continues toproduce electricity as long as fuel is added. In a fuel cell chemical energy is directly converted to electrical energy by a process that isthe reverse of electrolysis. A fuel gas is fed into one or two hollow porous electrodes in a liquid electrolyte whilst oxygen or air issupplied to the other electrode.

FUEL GASAny gas used for heating by combustion.

GAS TURBINEAn engine in which gas (as distinct from steam) is directed, under pressure, against a series of turbine blades. The

energy contained in the rapidly expanding gas is converted into rotary motion.

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GOVERNORA device used to control the speed of a turbine, the best known example being the Woodward Governor.

HEAT EXCHANGERAn apparatus for transferring heat from one fluid to another. Specifically, a piece of equipment having a tubular piping arrangements which

affects the transfer of heat from a hot to a relatively cool material by conduction through the tube walls.

HEAT OF COMBUSTIONThe heat created when a substance is burned in oxygen. The calorific, thermal, or heating value of a fuel is the total amount of heat developed by

the complete combustion of a unit quantity of fuel; it is reported as calories per gram or Btu per pound.

HEATERThe furnace-and-tube arrangement which normally furnishes the principal heating element in a processing unit.

HUMIDITYA measure of the moisture contained in the atmosphere.

HYDRATEA compound formed by the chemical union of water with a molecule of some other substance such as gypsum, from which water may be

separated by a simple readjustment of the molecular structure. Gas hydrates, formed from water and, for example methane, may causeplugging of the tubing and flow lines of gas wells.

HYDRATIONThe addition of water to a double bond, no breakdown of the molecular structure being involved.

HYDRAULIC FLUIDSFluids used in the hydraulic systems of aircraft and industrial equipment etc.

HYDROCARBONA compound containing only hydrogen and carbon. The simplest hydrocarbons are gases at ordinary temperatures; but with increasing molecular

weight, they change to the liquid form and, finally, to the solid state. They form the principal constituents of petroleum.

HYDROCHLORIC ACIDA strong mineral acid, HCL. It is also called muriatic acid.

HYDROCRACKINGA process in which hydrocarbons are converted under hydrogen pressure into products of lower molecular weight, in the presence of an acidic

catalyst.

HYDRODEALKYLATIONA process to remove side-chains on aromatic molecules, either thermally or catalytically, under hydrogen pressure.

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HYDRODESULPHURIZATIONThe elimination of sulphur containing molecules in crudes or distillates by the action of hydrogen under pressure over a catalyst.

HYDROGENThe lightest of all gases, occurring chiefly in combination with oxygen in water, also in acids, bases, alcohols, petroleum and other

hydrocarbons.

HYDROGEN BLISTERINGA form of corrosion. Blistering of steel is caused by trapped molecular hydrogen formed as atomic hydrogen during attack of steel by hydrogen

sulphide.

HYDROGEN SULPHIDEA compound of hydrogen and sulphur, specifically the monosulphide; a colourless, flammable, poisonous gas, H2S, having a disagreeable odour;

also called sulphureted hydrogen.

HYDROGENATIONThe filling of the "free" places in unsaturated structures by hydrogen atoms. The chemical addition of hydrogen to a material. In non-destructive

hydrogenation, hydrogen is added to a molecule only if, and where, unsaturation with respect to hydrogen exists. In destructivehydrogenation, the operation is carried out under conditions which result in rupture of some of the hydrocarbon chains (cracking);hydrogen is added where the chain breaks have occurred. This process is known as hydrocracking.

HYDROLYSISThe decomposition of a molecular structure by the action of water. A chemical decomposition in which a compound is broken up and resolved

into other compounds by reaction with water. In many cases, it is induced by the presence of a small amount of dilute acid.

HYDROMETERA graduated instrument for determining the gravity of liquids, usually made of hollow glass and weighted at one end so as to

float upright. On immersion, the lighter the liquid, the lower the instrument sinks because the buoyancy.

HYDROTREATINGA vapour phase process used to treat petroleum fractions boiling up to approximately 250 r a fixed bed of

catalyst (usually prepared by depositing the metals COBALT and MOLYBDENUM on an alumina base) in a hydrogen atmosphere.The process achieves:

1. Hydrogenation of the sulphurous contaminants in the feedstock to hydrogen sulphide.

2. Saturation of unsaturated component compounds such as olefins.

IGNITION POINTThe point or temperature at which a substance takes fire.

IMMISCIBLENot capable of mixing; tending to form two layers, e.g. oil and water.

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INDUCED DRAUGHTAir drawn into a furnace by means of a fan to improve combustion (compare forced draught).

INJECTORA mechanism which may be used in different forms for spraying fuel oil into the combustion chamber, or for feeding water into steam boilers.

INORGANICPertaining to substances not organic, nonliving, i.e. which are not carbon compounds, with the possible exception of the oxides and sulphides of

carbon.

ION EXCHANGE RESINSPreparation used in water softening - Anion and Cation resins are used.

ISOLATEAny means of positive separation from a risk source:-

1. To electrically disconnect.

2. To valve/spade isolate a piece of linework/equipment.

ISOMERTwo substances composed of equal amounts of the same elements but differing in properties owing to variation in structure are called isomers.

ISOMERISATIONThe conversion of a compound into its isomer. For example, butane may be converted into isobutane. A reaction which alters the fundamental

arrangement of the atoms in the molecule without adding or removing anything from the original compound. In the petroleumindustry, straight-chain hydrocarbons are converted catalytically to branched-chain hydrocarbons of substantially higher octanenumber by isomerisation.

ISO-OCTANE C8H18 (2,2,4-TRIMETHYLPENTANE)A colourless liquid used with n-heptane to prepare standard mixtures to determine anti-knock properties of gasoline.

ISOTOPEAny one of a number of atomic species differing in atomic weight but having the same atomic number.

Used in some Refinery instruments and for radiography.

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KELVINThe unit used as the Absolute temperature scale, i.e. zero Kelvin is absolute zero, 273K is 0oC. The Kelvin degree has the same dimensions as

the Celsius degree. The o symbol is not used on the Kelvin scale.

KEROSENEAny petroleum product with a boiling range between the approximate limits of 140 oC and 270oC which satisfies certain quality requirements (for

lamp oil or jet fuel).

KETTLE REBOILERA reboiler with facilities for separation of liquid and vapour.

KNOCKRelated to internal combustion engines the noise associated with detonation of a portion of the fuel-air mixture in a cylinder ahead of the

advancing flame front.

KNOCKOUT (DRUM OR VESSEL)A vessel, constructed with baffles, through which a mixture of gas and liquid is passed to disengage one from the other. As the mixture comes in

contact with the baffles, the impact frees the gases and allows them to pass overhead; the heavier substance falls to the bottom of thedrum.

LASER ALIGNMENTMethod of aligning rotating equipment shafts using a laser beam.

LATENT HEATHeat required for a change of state without a change of temperature.

1. The latent heat of fusion, or the amount of heat necessary to change a unit mass of solid into a liquid without change of temperature.

2. The latent heat of vapourisation, or the amount of heat necessary to change a unit mass of liquid into vapour without change oftemperature.

2. The latent heat of condensation. Effectively the opposite of 2 (above).LEADIndustry parlance for the motor fuel anti-knock additive compounds tetraethyl-lead, tetramethyl-lead, or for other organometallic lead anti-knock

compounds. Not used in NZ.

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LEAD ACETATE TESTA method of detecting the presence of hydrogen sulphide in a sample using lead acetate paper, which will change from white to brown upon

detection.

LIQUEFIED PETROLEUM GAS (LPG)of the gaseous hydrocarbons, propane and the butanes can be liquefied under relatively low pressure and at ambient temperature and are then

known as liquefied petroleum gas. Light hydrocarbon material, gaseous at atmospheric temperature and pressure, held in the liquidstate by pressure to facilitate storage, transport and handling. Commercial liquefied gas consists essentially of propane, butane, ormixtures thereof.

LUBRICANTA substance, especially oil, grease, or a solid such as graphite, which may be interposed between moving parts of machinery, thus reducing

friction by preventing contact between the bearing surfaces. The lubricant has an important function in removing heat and dirt fromthe region of the bearing surfaces.

MASS SPECTROMETERA device for analysing a substance in terms of the mass-to-charge ratios of its constituents. It is so designed that the beam constituents of a

given-mass-to-charge ratio are focused on an electrode and detected or measured electrically. The mass spectrum shows thedistribution in mass or the mass-to-charge ratio of ionised atoms, molecules, or molecular fragments.

MELTING POINTTemperature at which a solid substance melts or fuses. For asphalt, the melting point is defined as the temperature at which the asphalt is soft

enough to permit a steel ball to drop through a disk of asphalt supported in a ring suspended in water (ring-and-ball method). Thegrease melting point is determined by placing a small amount of the grease on the bulb of a thermometer and heating in hot air until thegrease begins to run off.

MERCAPTANSMercaptans or alkyl-hydrosulphides are organic compounds of carbon, hydrogen and sulphur. They have a bad odour and frequently occur in

unrefined gasoline. Mercaptans must be removed from gasoline or converted to the unobjectionable disulphides by suitable refining(e.g. by sweetening).

METHANE CH4A light, odourless inflammable gas. It is the chief constituent of natural gas. It is also often produced by a partial decay of plants in swamps

(marsh gas), so that its occurrence is commonly misinterpreted by the layman as an indication of the presence of petroleum.

METHANE SERIESA homologous series of open-chain saturated hydrocarbons of the general formula CnH2n+2 of which methane (CH4) is the first member of the

type; generally called the paraffins.

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METHANOLMethylalcohol, CH3OH. The first member of the class of organic compounds known as alcohols. It is a liquid boiling at 66

inflammable and poisonous. It is used in the production of synthetic gasoline - see synfuel.

METHYL CHLOROFORMUsed as a catalyst promotor in the platformer.

METHYL TERTIARY BUTYL ETHER (MTBE)An oxygenated compound which can be used as a blending compound in gasoline to boost octane.

MISCIBLECapable of being mixed (stability and uniformity throughout the mixture are usually inferred).

MOLECULAR WEIGHTThe sum of the atomic weights of the atoms composing a molecule.

MOLECULEThe smallest portion of an element or a compound which retains chemical identify with the same particular substance en masse, e.g. unit of

water.

MOTOR OCTANE NUMBER (MON)The Octane number of a Motor Gasoline determined in a special laboratory test engine under high "engine-severity" conditions, giving a rough

measure of the high-speed knock properties of the gasoline.

MULTISTAGE PUMPPump with more than one impeller. Generally used in high pressure/medium flow applications.

NAPHTHANaphthas are straight-run gasoline fractions boiling below kerosene. Being generally unsuitable as a blending component for premium

gasolines, they are used as a feedstock for Platforming. Other important outlets for naphthas are their use as chemical feedstock (e.g.ethylene manufacture) and as feedstock for town gas manufacture.

NAPHTHENEA class of saturated cyclic hydrocarbons of the general formula CnH2N. One of a group of cyclic hydrocarbons, also termed cycloparaffins or

cycloalkanes. Polycyclic members are found in the higher boiling fractions of crude oil.

NAPHTHENIC ACIDNaturally occurring acidic compounds commonly found in Naphthenic crudes NATURAL DRAUGHT

A flow of air into the combustion chamber of a heater which is neither induced nor forced but derives solely from the fact that the pressure insidethe heater is lower than that of the ambient atmosphere (due to effect of stack).

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NATURAL GASNaturally occurring mixtures of hydrocarbon gases and vapours, the more important of which are methane, ethane, propane, butane, pentane, and

hexane. The gas which occurs naturally with crude oils, but also in reservoirs which contain only a few heavier constituents. Itconsists mainly of the lighter paraffin hydrocarbons. Natural gas is usually classified as wet or dry, depending on whether theproportions of gasoline constituents which it contains are large or small. Most gas reaches the surface through the tubing, but in somepumping wells it is taken off at the top of the casing (casinghead gas).

NEUTRALNeither acid nor alkaline.

NEUTRONAn uncharged particle having the mass of the proton. Generally, together with the protons, neutrons make up the nucleus of atoms.

NITROGENElement of atomic number 7, in group V of the periodic system; colourless, odourless, tasteless diatomic gas constituting approximately

four-fifths of the air; chemically rather inert; soluble in water. Derived from liquid air by fractional distillation. Used extensively inrefineries for inerting process plants (air exclusion).

NITROGEN BASEA compound, such as amine, which may be considered a substitution product of ammonia; a compound containing trivalent nitrogen, capable,

like ammonia, of combining with acids in the formation of salts containing pentavalent nitrogen.

OCTANEThe octane number of a fuel is a number equal to the percentage by volume of iso-octane in a mixture of iso-octane and normal heptane having

the same resistance to detonation as the fuel under consideration in a special test engine. It is a measure of anti-knock value of agasoline and, in the case of the special test engine, the higher the octane number the higher the anti-knock quality of the gasoline.

OLEFINSA class of unsaturated, non-cyclic, aliphatic hydrocarbons of the general formula CnH2n (mono-olefins). Ethene is the parent member of the

group. Not very abundant in crude oils.

ORGANICDesignation for a branch of chemistry; treating, in general, of the compounds produced in plants and animals, or of carbon-hydrogen compounds

of synthetic origin; contrasted with inorganic.

ORIFICE METERAn instrument which measures the flow through a pipe by use of the difference in pressure on the upstream and downstream sides of an orifice

plate.

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ORIFICE PLATEA device for restricting the flow through a pipe.

OSMOSISMigration of ions or species from an area of high concentration to one of lower concentration.

OUTPUTThe pneumatic or electronic control signal sent from the control instrument to the valve.

OVERHEADSIn a distilling operation, that portion of the charge which is vapourised and removed as the total stream from the top of the column.

OXIDATIONThe reaction of oxygen with a molecule that may or may not already contain oxygen. Oxidation may be partial, resulting in the incorporation of

oxygen into the molecule or in the elimination of hydrogen from it, or it may be complete, forming carbon dioxide and water(combustion) - contrast with reduction.

OXIDIZING FLAMETerm applied to a flame in which there is an excess of air or oxygen.

PARAFFINSStraight(N) or branched (ISO) open chain saturated hydrocarbons.

PARTIAL CONDENSERA heat exchanger, which condenses part of a vapour stream. For example, partial condensers are used to condense the reflux liquid stream and

liquid top product from the overhead vapours of a fractionation column.

PARTIAL PRESSUREPartial pressure of a component of a mixture in vapour-liquid equilibrium is that part of the pressure which is contributed by that component.

PENETRATIONConsistency, expressed as the distance that a standard needle or cone penetrates vertically into a sample of the material under known conditions

of loading, time and temperature. A measure of the hardness and consistency of asphaltic bitumen by which a weighted special coneor needle will penetrate the sample in five seconds, the temperature, unless otherwise stated, being 25

PETROLTerm commonly used for motor spirit or gasoline.

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PETROLEUMA material occurring naturally in the earth, predominantly composed of mixtures of chemical compounds of carbon and hydrogen with or

without other nonmetallic elements such as sulphur, oxygen, nitrogen, etc. Petroleum may contain, or be composed of, suchcompounds in the gaseous, liquid, and/or solid state, depending on the nature of these compounds and the existing conditions oftemperature and pressure.

PHENOLHydroxyl derivative of aromatic hydrocarbons. Found in effluent water - occurs from contact with certain crudes.

PHOSPHATE1. A salt of phosphoric acid.

2. At NZRC - generally used to refer to TRISODIUM PHOSPHATE, an alkaline water treatment chemical. Na3Po4

pH VALUEThe logarithm of the reciprocal of the hydrogen ion concentration. This indicates the acid or alkaline condition of a substance, pure water and

neutral solutions having a pH of 7. Acid solutions have a pH less than 7; alkaline solutions, a pH greater than 7.

PILOT PLANTA small version of the full-scale plant in which a laboratory pursues development work, after bench-scale investigation of a new process has

shown promise.

POLYMERA substance produced from another by polymerisation, i.e. the combination of a number of identical molecules to form a larger one.

POUR POINTThe lowest temperature at which an oil will flow in a laboratory test, measured under specified conditions.

PREHEATTo heat, previous to some treatment; as an oil to be subsequently distilled, or as a body of gas or oil to be used as fuel.

PREHEATERAny form of apparatus in which heat is applied to a material prior to its introduction into the main heating apparatus. The application of heat is

usually accomplished by means of hot streams which have to be cooled and whose heat would otherwise be wasted. (See also HEATEXCHANGER).

PRESSUREThe force or thrust exerted on a surface, normally expressed as force per unit area. Pressure is exerted in all directions in a system. Common

examples; air pressure in a tyre, or water pressure at some depth in the ocean.

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PRESSURE DROPThe decrease in pressure due to friction, which occurs when a liquid or gas passes through a pipe, vessel, or other piece of equipment.

PRESULPHIDETo add sulphur (as DMDS or CS2) in order to initially activate a catalyst by changing the oxide sites to sulphides.

PURGINGThe removal of one fluid from a vessel or plant by introduction and subsequent evacuation of a second fluid. A common usage of this operation

is in the removal of hydrocarbon vapours or air from a plant by flushing with nitrogen.

QUENCHTo suddenly cool hot material discharging e.g. into a vacuum column, by injecting cool oil into the base; its purpose is to check the cracking

reaction quickly to avoid coking

RADIANT ENERGYEnergy sent out or emitted by rays or waves.

RADIANT ENERGYEnergy sent out or emitted by rays or waves.

REACTIONAny chemical change; the transformation of one or more molecules into other molecules.

REACTION TIMEThe interval during which the material being processed experiences chemical change.

REACTORTerm applied to the part of a plant where a chemical reaction takes place.

REBOILERA special type of heat exchanger for the supply of heat to the bottom of fractionating columns.

RECIPROCATING COMPRESSORA displacement compressor relying on forward and backward piston movement.

RECIPROCATING PUMPA positive displacement pump consisting of a plunger or a piston moving back and forth within a cylinder(s). With each stroke of the plunger or

piston, a definite volume of liquid is drawn in through the suction valve(s) and subsequently pushed out through the dischargevalves(s).

RECYCLE GASGas fed back from a later stage of process (usually from the separators) to the early stage. Usually impure and heavy.

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REFLUXA part (if the top product is in the liquid state) or all (if the top product is the vapour phase) of the condensed top vapour of a fractionating

column, which is returned to the top of the column. The purpose is to create an extra downward flow of liquid; if properly applied thisliquid acts as an absorbing agent for the relatively heavy components which are thus rejected from the top product.

REGENERATION1. The process of restoring a material to its original strength or properties.

2. In a catalytic process, the reactivation of the catalyst, usually done by burning off the coke deposits under carefully controlledconditions of temperature and oxygen content of the regeneration gas stream. May be done in situ or ex situ.

REGENERATORTerm applied to the part of a catalytic cracking unit or continuously regenerable platformer (CCR) where the spent catalyst is regenerated by

burning off the coke.

REID VAPOUR PRESSURE (RVP)The pressure caused by the vapourised part of a liquid and the enclosed air and water vapour, as measured under standardised conditions in

standardised apparatus: the result is given in Kilo pascals at 37.8oC, although normally reported simply as "RVP in kPa". There is nosimple relation between the RVP and the true vapour pressure of the liquid. RVP gives some indication of the volatility of a liquid,e.g. gasoline. Lower in summer & higher in winter.

RESIDENCE TIMEThe average length of time a quantity of reactant spends in contact with catalyst, or within a particular part of the process.

RESIDUEThe heavy residual liquid from the atmospheric distillation of crude oil is called long residue. If such residue if further distilled under vacuum a

still heavier residual liquid results, which is called short residue.

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RESINOrganic compounds produced by polymerisation.

1. Water treatment resins are used for water softening. With a very large surface area, liken to a sponge.

2. Epoxy and polyester resins of various types are used as fillers, adhesives and coatings.

ROTAMETERSimple flow gauge utilising a ball or float in a tapered graduated tube. The greater the flow, the more it raises the ball up the tube.

ROTARY PUMPA positive displacement pump used mainly to pump liquids which are either too viscous or too difficult to obtain suction with a centrifugal pump.

There are many types of rotary pump designs. One of the most common is the gear type, in which two gears mesh and rotate towardeach other within a very close-fitting casing. The liquid is trapped between the gear teeth and the casing and is carried around to thedischarge side of the pump. The meshing gear teeth prevent the liquid from returning to the suction side.

RUNDOWN TANKOne of the tanks in which are received the condensates from the stills, agitators, or other refinery equipment, and from which the distillates are

pumped to larger tanks known as work tanks or storage tanks. Rundown tanks are also known as "pans" or receiving tanks. If thecondensates were received directly into the large storage tanks, possible puking of a still could unnecessarily contaminate a largequantity of distillate.

ROTAMETERSimple flow gauge utilising a ball or float in a tapered graduated tube. The greater the flow, the more it raises the ball up the tube.

ROTARY PUMPA positive displacement pump used mainly to pump liquids which are either too viscous or too difficult to obtain suction with a centrifugal pump.

There are many types of rotary pump designs. One of the most common is the gear type, in which two gears mesh and rotate towardeach other within a very close-fitting casing. The liquid is trapped between the gear teeth and the casing and is carried around to thedischarge side of the pump. The meshing gear teeth prevent the liquid from returning to the suction side.

RUNDOWN TANKOne of the tanks in which are received the condensates from the stills, agitators, or other refinery equipment, and from which the distillates are

pumped to larger tanks known as work tanks or storage tanks. Rundown tanks are also known as "pans" or receiving tanks. If thecondensates were received directly into the large storage tanks, possible puking of a still could unnecessarily contaminate a largequantity of distillate.

SETTLERA separator, a tub, pan, vat, or tank in which the partial separation of a mixture is made due to difference in density. The operation may be

continuous or batch. The separation may be solids from liquid or gas; liquid from gas.

SETTLING POINTLaboratory test determining the temperature at which solidification of a molten wax begins.

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SETTLING TANKA tank employed for separating two liquids which are not miscible. If the liquids do not form an emulsion they separate into layers according to

their specific gravities, and these layers can be drawn off from different levels in the tank.

SOLUTIONA homogenous mixture of two or more chemically un-reacted fluids.

SOLVENTA substance, usually liquid, capable of dissolving another liquid, gas or solid to form a homogenous mixture.

SOLVENT EXTRACTIONSee Extraction.

SPECIFIC GRAVITYThe ratio of the weight of a volume of a body to the weight of an equal volume of some standard substance. In the case of liquids and solids, the

standard is water, in the case of gases, the standard is hydrogen or air.

SPECIFIC HEATThe ratio of the quantity of heat required to raise the temperature of a body by one degree to that required to raise the temperature of an equal

mass of water by one degree.

STABILISATIONThe process of separating light gases from petroleum or gasoline, thus leaving the liquid stable in the sense that it can be handled or stored with

less liability to change in composition.

STABILITYResistance of petroleum products to chemical change. Gum stability means the resistance of a gasoline to gum forming while in storage.

Oxidation stability means that the product is stable to oxidation, i.e resists the action of oxidation which forms gums, sludges etc.

STABILISERA fractionating column designed to make a sharp separation between very volatile components and gasoline ex crude oil, casing head gasoline or

pressure distillate, thus controlling the gasolines Reid vapour pressure

STANDARD PRESSUREPressure under which the mercury barometer stands at 760mm, or 30in. (Equivalent to approximately 14.7 psia).

STRIPPINGRemoval of the lightest fractions from a mixture. The process is usually carried out by passing the hot liquid from a flash drum or tower into a

stripping vessel or stripping section of a column, through which open steam or inert gas is passed to remove the more volatilecomponents of the cut. A fractionating process, closely related to distillation by which undesired volatile components are separatedfrom a liquid mixture by fractional evaporation. The desired fraction is thus purified from lower boiling components. Stripping is

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generally effected by the introduction of steam, by the reduction of pressure, by the vapour generated in a reboiler or a combination ofthese. In the laboratory nitrogen is often used as a stripping agent.

SULFOLANETetrahydro - Thiophene - Dioxide - A component of sulfinol solution.

SULPHATEA salt of sulphuric acid, e.g. sodium sulphate, Na2SO4, or ethylsulphate (C2H5)2SO4.

SULPHIDEAny of the compounds resulting from the combination of sulphur ions (S==) with metallic or other positive ions, or organic radicals.

SULPHURAt NZRC, the final product from H2S removal. A non-metallic element of lemon-yellow colour, sometimes known as brimstone. Sold in liquid

form to fertilizer works.

SULPHUR DIOXIDEA colourless gas, SO2, a by product of combustion of sulphurous fuels.

SULPHURIC ACIDTraditionally known as Oil of Vitrol. A combination of sulphur trioxide with water (SO3+H20=H2SO4). it is a eavy, strongly oily liquid, an

important water treating agent.

SURFACE AREAThe sum of the outer and inner surfaces. A porous solid may be said to have two different types of area - one made up of the external, the

geometric, or the outer surface of the particle; the other, called the inner, made up of the walls of capillaries, crevices, and cracks in theparticle. The sum of these is the total surface area. The ratio of total to outer area is sometimes known as the roughness factor.

SURFACE TENSIONThe force exerted by the particles of a liquid at its surface which maintains a continuous surface. The surface tension is determined by measuring

the energy required to increase the surface by the unit of area. That property, due to molecular attractive forces and existing in thesurface film of all liquids, which tends to bring the volume contained in the liquid surface film into a form having the least surface area.

SURFACRANTS(Surface active agents) ie trace chemical species which can adversely affect the water shedding properties of fuel.

SURGE1. An upheaval of fluid in a system frequently causing a carryover of liquid through the vapour lines (see also PUKING).

2. An undesirable condition of unstable flow occurring within centrifugal compressors when the surge parameter drops below a criticalvalue. A very dangerous condition for the compressor, hence the need for surge protection (anti-surge line).

SURGE DRUMVessel used to even out the flow into a unit, as the unit throughput and the feed rate may vary. See also buffer.

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SUSPENSIONA heterogeneous mixture of one or more materials - distinct from a solution. The state of a solid or liquid when its particles are mixed with and

buoyed in another liquid but are not dissolved by it. A suspension of a liquid in a liquid is called an emulsion.

TEMPERATUREAn arbitrary measurement of the degree of heat possessed by a body. It should be distinguished from heat itself. Heat is a form of energy;

temperature is a measurement of its intensity.

TEMPERATURE GRADIENTThe difference in temperature between two locations, e.g. between the top and bottom of a distillation column. Often expressed as temperature

difference per unit length.

THERMAL CRACKINGProcess of breaking down the larger molecules of heavy oils into smaller ones by the action of heat. In this way heavy oils can be converted into

lighter and more valuable products.

THERMOCOUPLE.The junction of two wires of dissimilar metals, which develops an electrical potential that is a function of the temperature. An instrument for

measuring temperature by means of the electrical potential produced at a heated junction of two dissimilar metals.

THERMOSTATAn automatic device for regulating temperature.

TOLUENE C6H5CH3An aromatic hydrocarbon, used in the manufacture of the explosive TNT (trinitrotoluene) and in the production of dyestuffs and pharmaceuticals.

TORQUEAn engineering term defined as the product of force times the length of the lever arm. It is a measure of the ability to produce rotation.

TRIP SYSTEMA system of fail safe partial and total shutdown mechanisms to protect the plants safety under extreme operating conditions.

TURBINEA rotating prime mover actuated by either the reaction or the impulse, or both, of a current of water, steam or gas, usually on a series of curved

vanes attached to a central shaft. (Steam turbines only used at NZRC).

UNSATURATED.A term applied to organic compounds in which some carbon atoms are held together by double or triple bonds, so that these compounds are

under favourable conditions, capable of combining with other elements or compounds.

VACUUMA space entirely devoid of matter (called specifically absolute vacuum); a space, such as the interior of a closed vessel,

exhausted to some degree by a steam ejector set or other artificial means. (Any vacuum less than absolute is a partial vacuum).

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VACUUM DISTILLATIONDistillation of a liquid under reduced pressure, aimed at keeping the temperature level so low as to prevent appreciable cracking. For example

used to distill vacuum gas oil and waxy distillate feedstock from long residue, leaving the short residue as remainder, also used formanufacture of bitumen.

VALENCEThe combining power of an element, as exhibited by the number of atomic weights of hydrogen with which one atomic weight of the element

will combine. Certain atoms are capable of combining with others in different proportions; they are said to have a number of valencesor are multi valent.

VAPOURGaseous substance which can be at least partly condensed by cooling or compression.

VAPOUR DENSITYThe weight per unit volume of gas e.g. grams per litre or pounds per cubmic foot.

VAPOUR LINEThe pipe through which vapours are led from a column to a condenser.

VAPOUR LOCKA condition which arises when a gas or vapour is present in the fuel line or fuel pump in sufficient volume to interfere with or prevent the flow of

fuel to the carburettor of an engine.

VAPOUR PHASEThe term describing a substance in the gaseous state, under conditions in which it is capable of being liquefied either by pressure or cooling or a

combination of both.

VAPOUR PRESSURE (AT GIVEN TEMPERATURE)The pressure exerted by the vapours released from any material, at a given temperature, when enclosed in a vapour-tight container. The lower

pressure at which a liquid, contained in a closed vessel at the given temperature, can remain in the liquid state without evaporation.Lowering the vessel pressure below the vapour pressure results in evaporation of part or all of the liquid. A compound or fraction witha high vapour pressure requires a high pressure to be kept as a liquid, thus it is volatile.

VAPORISATIONThe conversion of a liquid to its vapour, such as the changing of water into steam.

VENTURI METERA specially designed tube for measuring the rates of flow of gases or liquids, having a constriction or throat with convergent upstream and

divergent downstream walls, the angles of which are such that streamline or almost streamline flow through the tube is achieved. Therate of flow is measured by the pressure drop across the throat.

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1.1 VISCOSITYThe dynamic viscosity of a liquid is a measure of its resistance to flow. It is defined as the force per unit surface required to shear a layer of unit

thickness at unit velocity. The kinetic viscosity is equal to the dynamic viscosity divided by the density of the liquid. If no distinctionis made the dynamic viscosity is usually meant.

1.2 VISCOSITY INDEXA method of indicating the viscosity/temperature of an oil. Oils are generally classed as high, medium and low viscosity index oils (HVI, MVI,

LVI).

1.3 VOLATILETerm applied to materials which have a sufficiently high vapour pressure at normal temperature to evaporate readily at normal atmospheric

pressure and temperature. It implies a high degree of volatility.

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