Glossary
Acceptance criterias: Criterias based on regulations, standards and/or theoretic knowledge that are basis for decisions on acceptable risk. Acceptence criterias can be expressed by words or be quantified.
AIT: Auto Ignition Temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark.
ALARP: As Low As Reasonably Practicable is a term often used in the milieu of safety-critical and high-integrity systems. The ALARP principle is that the residual risk shall be as low as reasonably practicable.
ATEX: Atmosphere Explosive, Abbreviation that is used in connection with two European directives concerning production of equipment and safety systems for use in potentially explosive atmospheres and safety for personell working in potentially explosive atmospheres.
Biomass: Biomass is material derived from recently living organisms. This includes plants, animals and their by-products. For example, manure, garden waste and crop residues are all sources of biomass.
Blast: A blast is an explosion.
Blast Prediction and Blast Modeling: Methods to quantify the effects and consequence of an explosion blast.
Chemical Reaction: A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants. Chemical reactions are usually characterized by a chemical change, and they yield one or more products which are, in general, different from the reactants.
Dust Explosion: A dust explosion refers to the explosive combustion of a dust suspended in air in an enclosed location.
DESC: DESC is a CFD code by GexCon for simulating the course of industrial dust explosions in complex geometries.
DSEAR: Dangerous Substances and Explosive Atmospheres Regulations 2002, The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) require employers to control the risks to safety from fire and explosions.
Explosion: Abrupt oxidation or decomposition reaction producing an increase in temperature, pressure or in both simultaneously.
Explosion pressure relief, pressure relief or Venting: In connection with explosions these expressions mean equipment or methods where one under a given explosion generated over pressure creates a relatively large opening where the over pressure is let out. In other connections the term depressurization is used in connection with valves (safety valves) which opens manually or automatically when the pressure exceeds certain limits. To remove an over pressure from a gas plant (pipes and tanks) to a safe area, is also expressed as depressurization.
Explosion Protection: Explosion protection is utilized to protect industrial assets against explosions or deflagrations.
Explosion Suppression: A method to suppress an explosion in it’s early stages thus limiting the pressure development of the incipient explosion.
Explosion Protection Document: In accordance with DSEAR and ATEX an explosion protection document has to be drawn up by the operator prior to the commencement of work in potentially explosive atmospheres. It must be reviewed when the workplace, work equipment or organization of work undergoes any significant changes,extensions or conversions.
Fire: It is here ment a combustion of hydrocarbons in air compounds caused by an ignition of natural gas mixed with air. In connection with explosions we distinguish between diffusion burning and combustion of premixed gas/air. The last one gives explosion. Burning by diffusion is what is normally understood as a fire. Both liquids and gases can be fuel. It is called diffusion burning because oxygen from the surroundings normally diffuse in to a limited combustion zone where the fuel is released.
FLACS: FLame ACceleration Simulator is an advanced tool for the modeling of ventilation, gas dispersion, vapour cloud explosions and blast in complex process areas. FLACS is used for the quantification and management of explosion risks in the offshore petroleum industry and onshore chemical industries.
HAZOP: Hazard and Operability Analysis (HAZOP) is a systematic method for examining complex facilities or processes to find actual or potentially hazardous procedures and operations so that they may be eliminated or mitigated.
IP: Ingress Protection, Enclosure rating/protection. Norm for resistibility/ingress of current and water. Standardized description for enclosure ratings for encapsulation of electrical equipment and instruments.
Kg: Explosion Constant for Gas. The maximum pressure and rate of pressure rise are measured and used to determine the Kg value. These data can be used for the purpose of designing dust explosion protection measures and equipment.
Kst: Explosion Constant for Dust The maximum pressure and rate of pressure rise are measured and used to determine the Kst value and St hazard class of the material. These data can be used for the purpose of designing dust explosion protection measures and equipment.
Kmax: Maximum Explosion constant for Kst and Kg.
Inerting: The effect of inerting is either to eliminate the oxygen completely, or to reduce it to a negligible level. Without sufficient oxygen, the fuel cannot ignite, and explosions cannot occur.
LEL: Lower Explosion Limit, The lower limit of the explosion range.
LFL: Lower Flammability Limit.
MIE: Minimum Ignition Energy, Lowest electrical energy stored in a capacitor which upon discharge is sufficient to ignite the most ignitable atmosphere under specified test conditions.
MEC: The minimum explosible concentration (MEC) test determines the smallest concentration of material in air that can give rise to flame propagation upon ignition when in the form of a dust cloud.
Primary incident: Usually a primary explosion, i.e. an explosive atmosphere is ignited by an ignition source.
Risk: Expression for the risk of an undesirable incident represents for humans and material goods. The risk is expressed by the probability and consequences of an incident.
Risk assessment or risk analysis: Systematic method to describe and/or estimate risk related to persons and material goods. The risk assessment is carried out by identification of undesirable incidents, estimation of the probability for the unwanted incidents to arise and the consequences of the undesirable incidents.
Secondary incident: An incident as a consequence of a primary incident. A secondary incident is for instance an explosion or a fire arising as a consequence of a primary incident. Secondary incidents may sometimes be far more dramatic than the primary incident.
Safety system: According to the ATEX product directive [1] this is a system who’s task is to reduce the probability of an explosion to occur or to reduce the consequences of an explosion. Safety systems must be “ATEX certified”.
Stoichiometric mixture: A mixture of a combustible gas and air where the fuel concentration is high enough to consume all the oxygen in the air. For Hydrogen the “stoichiometric mixture” is 30%.
UEL: Upper Explosion Limit, The upper limit of the explosion range.
UFL: Upper Flammability Limit.
VPE: A Vapour Cloud Explosion originates when a large cloud of flammable vapour in air ignites and flame accelerates through semi-confined or congested structure or obstructions, near and far field pressure effects are significantly higher than a deflagration event.
Zone (area): Hazardous areas are classified into zones based upon the frequency of the occurrence and duration of an explosive atmosphere. The term zoning or area classification must not be mistaken for “risk assessment”.