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Risk Terminology
| Term | Definition |
|---|---|
| Administrative Controls | Procedural mechanisms, such as lockout/tagout procedures, used for directing and/or checking human performance on plant tasks. |
| Autoignition Temperature | whether solid, liquid or gaseous, the minimum temp required to initiate/cause self-sustained combustion in air without a specific source of ignition. (for paraffinic hydrocarbons, it decreases with increasing molecular weight). |
| BLEVE (boiling liquid expanding vapor explosion) | A type of rapid phase transition in which a liquid which is contained above its atmospheric boiling point is rapidly depressurized, causing a nearly instantaneous transition from liquid to vapor with a corresponding energy release. |
| Catastrophic incident | An incident involving a major uncontrolled toxic emission, fire or explosion with an outcome effect in which the zone extends offsite into the surrounding community. |
| Combustible | A term used to classify certain liquids that will burn on the basis of flash points. |
| Deflagration | The chemical reaction of a substance in which the reaction front advances into the unreacted substance at less than sonic velocity. Where a blast wave is produced that has the potential to cause damage, the term explosive --- may be used. |
| Detonation | A release of energy caused by the extremely rapid chemical reaction of a substance in which the reaction front advances into the unreacted substance at equal to or greater than sonic velocity. |
| DIERS (Design Institute for Emergency Relief Systems) | Institute under the auspices of the American Institute of Chemical Engineers founded to investigate design requirements for vent lines in case of two-phase venting. |
| DIPPR (Design Institute for Physical Property Data) | Institute under the auspices of the American Institute of Chemical Engineers, founded to compile a database of physical, thermodynamic, and transport property data for most common chemicals. |
| Dow's Fire and Explosion Index (F&EI) | A method (developed by Dow Chemical Company) for ranking the relative fire and explosion risk associated with a process. Analysts calculate various hazard and explosion indexes using material characteristics and process data. |
| Dow's Chemical Exposure Index (CEI) | Method for computing airborne releases from release scenarios, and distances pertaining to ERPG (Em. Response Planning Guidelines) and EEPG (Emergency Exposure Planning Guidelines) for a wide range of commonly manufactured industrial hazardous chemicals. |
| Emergency Response Planning Guidelines (ERPG) | Guidelines established by the American Industrial Hygiene Association (AIHA) which are intended to provide estimates of concentration ranges where one might reasonably anticipate observing adverse effects. |
| Explosion | A release of energy that causes a pressure discontinuity or a blast wave |
| Fire Point | The temperature at which a material continues to burn when the ignition source is removed. |
| Fireball | The atmospheric burning of a fuel-air in which the energy is mostly emitted in the form of radiant heat. |
| Flammability Limits | The range of gas or vapor amounts in air that will burn or explode if a flame or other ignition source is present. |
| Flammable | A "Flammable Liquid" is defined by NFPA as a liquid with a flash point below 100°F (37.8°C). |
| Flash Fire | The combustion of a flammable vapor and air mixture in which the flame passes through that mixture at less than sonic velocity, such that negligible damaging overpressure is generated. |
| Flash Point | The lowest temperature at which vapors above a liquid will ignite. |
| Hazards | An inherent chemical or physical characteristic that has the potential for causing damage to people, property, or the environment. |
| Hazard Identification | The process by which hazards are identified. Commonly known as Process Hazards Analysis (PHA). |
| Inert Gas | A noncombustible, nonreactive gas that renders the combustible material in a system incapable of supporting combustion. |
| Intrinsic and Extrinsic Safety | Safety features that protect by virtue of their intrinsic nature and do not require activation or human intervention to be effective. Intrinsic Risk Control features are passive rather than active. |
| LD50 and LC50 | Lethal dose of a chemical that will kill 50% of the an organism. LC means "lethal concentration." |
| Likelihood | A measure of the expected frequency with which an event or incident occurs. |
| Lower Explosive Limit (LEL)/ Lower Flammable Limit (LFL) | the lowest concentration of vapor in air that will burn |
| Oxidant | Any oxidizing agent that can react with a combustible material (either in the form of liquid, solid, gas, dust or mist) to produce combustion. Oxygen in air is the most common oxidant. |
| Pool Fire | The combustion of material evaporating from a layer of combustible liquid at the base of the fire. |
| Process Safety | A discipline that focuses on the prevention of fires, explosions, and accidental chemical releases at process plant facilities. It normally classic worker health and safety issues involving working surfaces, ladders, protective equipment, etc. |
| Purge Gas | A gas that is continuously or intermittently added to a system to render the atmosphere non-combustible by, typically, excluding air. The purge gas itself may be an inert gas (e.g., nitrogen) or a combustible gas (e.g., fuel gas). |
| QRA | QRA stands for Quantitative Risk Assessment, as opposed to Hazards Identification, which is qualitative in nature. Hazards Identification is a necessary prerequisite to QRA |
| Quenching | Rapid cooling from an elevated temperature such that the further decomposition is halted or severely reduced. |
| Risk Analysis | The process of evaluating the consequences and frequencies of occurrence of hazardous activities. |
| Risk Appraisal | Judging the acceptability of risks |
| Risk Assessment | Combination of Risk Analysis and Risk Appraisal |
| Risk Contour/Isopleth | Line drawn around a facility connecting all points having the same level of risk |
| Risk Mitigation | Method(s) existing or introduced for the express purpose of reducing the frequency or consequences of a hazardous event. Methods are often categorized as active or passive. |
| Risk Measurement | Usually measured in terms of: Death (Lethality) Property Damage ($) Lost Production ($) Environmental Damage |
| Risk Management | The process of acting upon information supplied on Hazards Identification, Risk Assessment and Risk Control for management decision-making purposes. |
| Runaway Reaction | A thermally unstable reaction system which shows a rapid escalation of temperature increase and reaction rate. |
| Safety | Risk posed to a societal group who are exposed to a hazardous activitA judgement of the acceptability of risky |
| Upper Explosive Limit (UEL)/ Upper Flammable Limit (UFL) | The highest concentration of a vapor or gas (the highest percentage of the substance in air) that will burn when an ignition source (heat, arc, or flame etc.) is present. |
| Vapor Cloud Explosion (VCE) | A vapor cloud explosion is the explosive oxidation of a vapor cloud. The flame speed may accelerate to high velocities and produce significant blast overpressure |
| Vapor Density | The weight of an airborne concentration (vapor or gas) as compared to an equal volume of dry air. |
| Vapor Pressure | the pressure exerted by a vapor over a liquid |
| Voluntary Risk | risk that is consciously tolerated by someone seeking to obtain the benefits of the activity that poses the risk |
| Involuntary Risk | Risk beyond one's control and not the result of a willful decision. |
| Worst Possible Scenario | Largest possible release and consequential damage (human, property, financial, environmental) without regard for its likelihood. May result in an overly pessimistic view. |
| Worst Credible Scenario | Largest credible release and consequential damage (human, etc.) taking into account its likelihood. |
| Availability | The percentage of the time that a protective system is available for operation (e.g., when a protective system is being tested it may cease to be available for that test period). |
| Common Mode Failure | An event having a single cause with multiple failure events |
| Demand Rate | The rate at which a protective system is called upon to act |
| Double Jeopardy | The chance that two (or more) unrelated events or incidents will occur at the same time. (It is important to note that two (or more) events or incidents arising from a common cause do not qualify). |
| Emergency Shut Down System (ESD) | A safety control system which is installed in a facility and is capable of shutting the facility or unit in the event of an emergency. It over-rides the action of the basic control system when predetermined conditions are violated. |
| Equipment Reliability | The probability that, when operating under stated environment conditions, process equipment will perform its intended function adequately for a specified exposure period. |
| Fail-Safe | Design features providing for the maintenance of safe operating conditions in the event of a malfunction of control devices or an interruption of an energy source (e.g., direction of failure of a pneumatically actuated valve on loss of instrument air). |
| Interlock System | A system that detects out-of-limits or abnormal conditions or improper sequences and either halts further action or starts corrective action. |
| Protective Device | Any device that alarms or trips a system, or part of a system, or relieves the condition in a safe manner (e.g., a pressure relief valve). |
| Programmable Electronic System (PES) | A system based on a computer connected to sensors and/or actuators in a plant for the purpose of control, protection or monitoring |
| Programmable Logic Controller (PLC) | A solid-state control system which receives inputs from user-supplied control devices (switches/sensors), implements them in a precise pattern via instructions in the PLC memory, & provides outputs for devices such as relays/motor starters. |
| Redundancy | Additional or spare protective devices that will operate in the event of first line devices failing. |
| Societal Risk | Risk posed to a societal group who are exposed to a hazardous activity |
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aquilina_lm
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