Glossary

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[ Last Updated 20 December 2005 ]

Acute Exposure: Exposure of short duration, usually in the order of hours or minutes.
Adverse Effect: Any biochemical change, functional impairment, or pathological lesion which impairs and reduces the ability of an organism to respond to additional change.
Alkanes: Also known as paraffins. Aliphatic hydrocarbons (i.e. compounds having carbon atoms in chains rather than closed rings) of the general formula C_nH_2n+2. C_1-4 (Methane, ethane, propane and butane) are gases at ambient temperatures and pressures; higher members are liquids (up to C₁₆); and those above C₁₆ are waxy solids.
Alkenes: Also known as olefins. Aliphatic hydrocarbons of the general formula C_nH_2ncontaining one double bond. They closely resemble alkanes in physical properties.
Alkylation: Alkylation is a refinery operation which takes smaller (more volatile) hydrocarbon molecules and converts them to larger (less volatile) ones. Specifically it reacts light olefins (alkenes) such as propane and butene with iso-butane to form iso-paraffins which are a good source of octane that does not contain olefins or aromatics. The Marsden Point Refinery does not have an alkylation plant but some Australian refineries do.
Ambient Air: The air outside buildings and structures. It does not refer to indoor air, air in the workplace, or contaminated air discharged from a source.
Aromatic: A hydrocarbon based on a six-membered benzene ring. Aromatic hydrocarbons were so called because some of these compounds have a pleasant "aromatic" odour. However, the term is now applied to those hydrocarbons based on a six-membered ring having three apparently conjugated double bonds. The simplest member is benzene. The aromatic rings can be fused together to give polynuclear aromatics (also called polyaromatic hydrocarbons) (PAHs).
Benzene: This is the basic aromatic hydrocarbon. It has a high chemical reactivity and is highly volatile and flammable. Its ability to dissolve some rubbers leads to problems with gaskets in pumps and fuel lines. Benzene causes a number of human health problems, most notably cancer, and is toxic when inhaled, swallowed or absorbed through skin. However, it has a high octane rating.
Carcinogenic Agent: Any substance that incites or produces cancer.
Catalytic cracker (cat cracker): A refinery processing unit. The most widely used method of producing gasoline from heavy petroleum distillates is to subject the heavy fractions to catalytic cracking. Fluidized bed catalytic cracking, where the powdered catalyst is moved through the system in a fluidized state, is now almost universally used.; Many catalysts have been used but the standard catalysts are generally mixtures of silica and alumina or natural or synthetic aluminium silicate zeolites.; The major product is gasoline but gases and light and heavy gas oils are produced in proportions depending on feedstocks and operational conditions. The gasoline obtained is usually of a fairly high octane number due to the high proportion of unsaturated hydrocarbons.
Cetane Index (CI): An approximation of Cetane Number based on an empirical relationship with API gravity and volatility parameters such as the mid-boiling point.
Cetane Number (CN): A measure of the fuel's ignition quality (suitability for spontaneous self-ignition in a diesel engine).; Because diesel engines dispense with an externally-generated ignition spark, the fuel must ignite spontaneously and with minimal delay (ignition lag) upon being injected into the hot, compressed air in the combustion chamber.). The higher the cetane number, the greater the fuel's tendency to support self-ignition. The cetane number 100 is assigned to n-hexadecane (cetane), which ignites very easily, while heptamethyl nonane, with a low ignition quality, carries the cetane number 15. Cetane number is determined using a test engine.
Chronic Exposure: Exposure which occurs over a long time, usually one or more years.
Cloud Point (CP) and Cold Filter Plugging Point (CFPP): CP is the temperature at which wax crystals start to precipitate out and the fuel becomes cloudy, according to the test method specified in ASTM D2500.; CFPP is the lowest temperature at which the fuel can pass through a standard test filter under standard test conditions.; The precipitation of paraffin crystals at low temperatures can result in fuel-filter blockages, ultimately leading to interruption of the fuel flow. Under unfavourable conditions paraffin particles can start to form at temperatures as high as 0°C. Special selection and manufacturing procedures are necessary for winter diesel fuels in order to ensure trouble-free operation in cold weather.
Density: Mass of substance per unit volume. Density can provide useful indications of the fuel's composition and performance related characteristics such as ignition quality, power economy, low temperature properties and smoking tendency.
Diesel: As defined in the Regulations: A refined petroleum distillate having a viscosity and distillation range intermediate between those of kerosene and light lubricating oil, whether or not it contains additives, intended for use as fuel in internal combustion engines ignited by compression.
Diurnal Loss: The loss of fuel vapour from vehicles that results from the daily ambient temperature increase. Increases in fuel tank temperature causes enhanced vaporisation of liquid fuel and expansion and expulsion of the vapour stored in the tank.
Dose Response Curve: A graphical representation of the quantitative relationship between the dose and a specific biological response.; Two approaches are followed in the dose-response evaluation: a threshold approach, and a non-threshold approach. In the threshold approach, it is assumed that a level exists below which no adverse effects are likely to occur (NOAEL), and above which the effect is related to dose. The aim of the dose-response evaluation is to identify the NOAEL for each health endpoint being considered.; The non-threshold approach assumes that there exists no threshold for adverse effects: there is a finite probability that some adverse effect will occur as a result of exposure at any level. This approach is usually applied to carcinogens. The aim of the dose-response evaluation is to determine a curve that relates the exposure dose or concentration to the probability of an effect occurring at that dose. The results of evaluation of carcinogenic risks are usually expressed as unit risk factors. The unit of risk is the additional risk of cancer incidence in a population from continuous lifetime exposure to a concentration of 1 µg/m³ in the air breathed.; Health data can come from animal studies, opportunistic data from accidental or occupational human exposures, controlled human exposure studies, or epidemiological studies.
Driveability Index (DI): A measure of cold weather performance which is based on distillation parameters.
Emission: The discharge of contaminants into air.
E70, E100 and E180: The volume percentage of a liquid which evaporates up to 70°C, 100°C and 180°C respectively (i.e. defines the evaporation characteristics of a liquid).; Highly volatile liquids boil at low temperatures and evaporate rapidly. Fuel must contain a large enough proportion of highly volatile components for good cold starts, but the volatility must not be so high as to impair operation (vapour lock) and starting when the engine is hot. In addition, environmental considerations demand that evaporative losses be held low.
Flexible Volatility Index (FVI): A measure of the likelihood of a gasoline to cause vapour lock in vehicles on the road (a combination of the Reid Vapour Pressure and the Percentage Evaporated at 70°C).; Vaporisation of the fuel in the supply line to the engine that prevents the fuel pump from delivering an adequate supply of fuel is known as vapour lock. Factors contributing to vapour lock are high ambient temperatures, low ambient pressure, volatile fuel and vehicle designs where heat from the engine can give high fuel line temperatures.
Fuel: Diesel or petrol, as defined in the Regulations.
Gasoline Direct Injection (GDI): A developing technology for petrol engines of direct injection of petrol in the combustion chamber. This improves fuel economy by cooling the air-fuel charge (caused by the vapourisation of the fuel) which allows increase in compression ratio without reaching the knock limit. A significant improvement in efficiency is gained through stratified charge operation which allows fast rates of combustion despite overall lean air fuel ratios. This technology is not expected to be in the market until 2005+.
Genotoxic Agent: Any substance that interferes with genes or gene structure.
Haemotoxic Agent: Any substance that effects the blood or blood-forming tissues.
Hot Soak Loss: The loss of fuel vapour immediately after the vehicle has been operated due to the input of residual pressure and heat into the fuel system. Hot soak emissions occur within one hour or less following vehicle shutdown.
Isomerate, Isomerism: Compounds possessing the same composition and the same molecular weight, but differing in their chemical structure, are said to be isomeric, and each is an isomer of each other. Isomerisation is the conversion of a compound to an isomer of that compound.
Lead: Added to petrol as a knock inhibitor and valve lubricant.; Organic lead compounds are the most cost effective knock inhibitors, particularly the lead-alkyl compounds tetraethylene lead (TEL) and tetramethylene lead (TML). These can raise the octane number by several points, with the exact amount of improvement depending upon the specific hydrocarbon combination.; Lead also serves as a valve lubricant in engines. There is a world-wide trend to eliminate lead from petroleum fuels because of the known adverse affects on general health.
Lean Burn: When applied to air-fuel ratio in petrol engines, means that combustion occurs in a regime of excess air, similar to a diesel engine.
LOAEL: Lowest Observed Adverse Effect Level: the lowest exposure level at which there are statistically or biologically significant increases in the frequency or severity of adverse effects between the exposed population and its appropriate control group.
Marine Use: As defined in the Regulations: The use or intended use of diesel on a boat or ship.
Motor Octane Number (MON): A measure of the antiknock quality of a fuel as measured by ASTM D 2700 or equivalent methods. It is a guide to the antiknock performance of a fuel under relatively severe driving conditions, such as can occur under full throttle, i.e. when the inlet mixture temperature and the engine speed are both relatively high.
Naphtha: A description of a light distillate feedstock for gas or petrochemical manufacture, boiling range generally about 40-150°C.
NOAEL: No Observed Adverse Effect Level: the exposure level at which there are no statistically or biologically significant increases in the frequency or severity of adverse effects between the exposed population and its appropriate control group. Some effects may be produced at the level but they are not considered as adverse nor precursors to the adverse effects.
Octane Number: A measure of petrol's antiknock quality, in other words its resistance to pre-ignition. The higher the octane number, the greater the fuel's resistance to knock.; When petrol vapour and air is compressed by the piston in the hot cylinder of an internal combustion engine, the hydrocarbons may be so easily oxidised that the mixture ignites before the spark is passed by the spark plug. This premature ignition is effectively a detonation which produces shock waves (a characteristic knocking or pinging sound), causing the engine to overheat and lose power.; Vehicles are designed for a certain octane value. Using a petrol with a lower octane rating than that required can cause damage to the engine. Using petrol with a higher octane rating than that required does not improve a vehicle's performance.; There are two main measures of octane number, the Research Octane Number (RON) and the Motor Octane Number (MON).; Colloquial use of the phrase octane number generally refers to the RON. In New Zealand, regular petrol is 91 RON; premium petrol is 95 RON. Higher octane fuels, such as 98 RON are available.
Olefins: See alkenes.
Oxygenates: As defined in the Regulations: Alcohols and ethers added to fuel.
PAH or PCA: Polyaromatic or polycyclic hydrocarbons. Hydrocarbons with more than one aromatic ring. These include compounds such as naphthalene and benzo(a)pyrene.
Paraffins: See alkanes.
Petrol: As defined in the Regulations: A refined petroleum distillate, normally boiling within the limits of 30°C to 220°C, whether or not it contains additives, intended for use in spark-ignition internal combustion engines.
Petroleum: As defined in section 2 (1) of the Crown Minerals Act 1991:; Any naturally occurring hydrocarbon (other than coal whether in a gaseous, liquid, or solid state; or; Any naturally occurring mixture of hydrocarbons (other than coal) whether in a gaseous, liquid, or solid state; or; Any naturally occurring mixture or one or more hydrocarbons (other than coal) whether is a gaseous, liquid, or solid state, and one or more of the following, namely hydrogen sulphide, nitrogen, helium, or carbon dioxide -; And, except in sections 10 and 11, includes any petroleum as so defined which has been mined or otherwise recovered from its natural condition, or which has been mined or otherwise recovered but which has been returned to a natural reservoir for storage purposes in the same or an adjacent area.
Platformate: A high octane petrol blend stock produced through a reforming process using a platinum catalyst. The Marsden Point Refinery has a catalyst of this type.
PM, PM₁₀,PM_2.5: Particulate matter (less than 10 or 2.5 microns; local air pollutant).
Reid Vapour Pressure: The pressure exerted by the vapours derived from a liquid at a given temperature and pressure
Research Octane Number (RON): A measure of the antiknock quality of a fuel as determined by ASTM D 2699 or equivalent methods. It is a guide to the antiknock performance of a fuel when vehicles are operated under mild conditions such as at low speeds and low loads.; When octane number is used colloquially, it is usually the RON which is being referred to (in NZ, 91 RON for regular petrol; 95 RON for premium petrol).
Resting Loss: The loss of vapour from the fuel system or the evaporative control system as a result of permeation through various non-metallic fuel system components (e.g. rubber vapour routing hoses), vapour migration allowed by design features such as open-bottom carbon canisters and evaporating liquid fuel leaks. Resting losses can be affected by ambient temperature changes but they are relatively constant in comparison with other types of vapour loss.
Retail Sale: As defined in the Regulations: A sale to an end user who has no written supply agreement or written contract with the supplier in respect of the sale.
Running Loss: The loss of fuel vapour while the engine is running. These losses occur when the rate of fuel vapour formation exceeds the capacity of the vapour storage and purge systems. The critical factors affecting running losses for vehicles with evaporative emission control systems based on carbon canisters, are fuel temperature and canister purging strategy. Typical sources of running losses include the vapour canister vent, the fuel cap and fuel tank pressure relief valves.
Stoichiometric Ratio: When applied to air-fuel ratio in petrol engines, means the amount of O₂ available is exactly equal to the amount required for complete combustion.
Sulphur: Sulphur is present to a greater or lesser extent in all crude oils and, consequently, sulphur compounds remain present in distillate streams used for petrol and diesel fuel blending.; Its presence in petrol and diesel is controlled for a number of reasons including its contributions to odour, its corrosivity, its antagonistic effect on lead based octane enhancers and the acidic by-products (i.e. sulphur dioxide and trioxide) formed during combustion. Sulphur significantly reduces the performance of most "tailpipe" emission control technologies, such as catalytic converters, and also affects heated exhaust gas oxygen sensors.; To reduce sulphur concentrations in fuels and emissions, sulphur must be removed from the source during the refining process.
Threshold: The dose or exposure below which an adverse effect is not expected.
Unit Risk: The upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent at a concentration of 1 µg/litre in water, or 1 µg/m³ in air.

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Printed: 25/11/2009