Autoxidation
Also autooxidation or auto-oxidation. A slow, easily initiated, self-catalyzed reaction, generally by a free radical mechanism, between a substance and atmospheric oxygen. Initiators of autoxidation include heat, light, catalysts such as metals, and free radical generators. Davies (1961) defines autoxidation as interaction of a substance with molecular oxygen below 120 degrees C without flame. Possible consequences of autoxidation include pressure buildup by gas evolution, autoignition by heat generation with inadequate heat dissipation, and the formation of peroxides. CCPS 1995b
Availability
The fraction of time that the system is capable of performing its required functions. The fraction of time a system is fully operational.
Average Concentration
The concentration averaged over time and/or space.
Average Individual Risk
There are three Average Individual Risks; 1) Average Individual Risk (exposed population) is the individual risk averaged over the population which is exposed to risk from the facility, 2) Average Individual Risk (total population) is the individual risk averaged over a predetermined population, without regard to whether or not all people in that population are actually exposed to the risk, and 3) Average Individual Risk (Exposed hours/worked hours). The individual risk for an activity may be calculated for the duration of the activity or may be averaged over the working day.
Averaging Time
The length of time in atmospheric dispersion testing over which concentration data are averaged to produce the concentration-time series.
Balanced scorecard
A management system that provides feedback on both internal business processes and external outcomes to continuously improve strategic performance and results.
Barrier
A control measure or grouping of control elements that on its own can prevent a threat developing into a top event (prevention barrier) or can mitigate the consequences of a top event once it has occurred (mitigation barrier). A barrier must be effective, independent, and auditable.
Baseline Risk Assessment
a process to characterize the current and potential threats to human health and the environment that may be posed by contaminants migrating to groundwater or surface water; releasing to air; leaching through soil; remaining in the soil and bio-accumulating in the food chain. The primary purpose of the baseline risk assessment is to provide risk managers with an understanding of the actual and potential risks to human health and the environment posed by the site and any uncertainties associated with the assessment. This information may be useful in determining whether a current or potential threat to human health or the environment warrants remedial action.
Basic Event
An event in a fault tree that represents the lowest level of resolution in the model such that no further development is necessary (e.g., equipment item failure, human failure, or external event).
Basic Process Control System (BPCS)
A system that responds to input signals from the process and its associated equipment, other programmable systems, and/or from an operator, and generates output signals causing the process and its associated equipment to operate in the desired manner and within normal production limits.
Batch Reactor
Reactor in which all reactants and solvents are introduced prior to setting the reaction conditions (temperature, pressure). Products are only taken from the reactor upon conclusion of the reaction process. Both heat generation and concentrations in the batch reactor vary during the reaction process.
Batch Sheet
Sometimes called batch instruction. The operating procedure for making a batch product. Primarily focuses on material quantities, as well as instructions for any mixing, reaction, heating, cooling, drying required for the process.
Battery Limit
The perimeter of a specific manufacturing process area. It is often defined by the roads around the perimeter. This area will include process equipment, and may include in-process tankage.
Behavior-based safety program
A program designed to provide frequent feedback to personnel regarding their safety behaviors in the workplace.
Bench Scale
Technical laboratory scale (typically between 0.1 and 5 dm3), more specifically directed to process simulation and determination of technical plant facilities (cooling/heating capacities, temperature constraints, charging requirements, etc.)
Benchmark
A point of reference from which measurements may be made or from which other things can be measured. A program that is used to compare the operation of two or more systems is called a benchmark program.
Biological Oxygen Demand
The amount of dissolved oxygen in water, given in lbs. (kgs) or % that is consumed by biological oxidation of a chemical
Biosafety level
A specific combination of work practices, safety equipment, and facilities designed to minimize the exposure of workers and the environment to infectious agents.
Blanketing
The technique of maintaining an atmosphere that is either inert or fuel-enriched in the vapor space of a container or vessel. Also called Padding.
Blast
A transient change in the gas density, pressure, and velocity of the air surrounding an explosion point. The initial change can be either discontinuous or gradual. A discontinuous change is referred to as a shock wave, and a gradual change is known as a pressure wave.
Blast Load
The load applied to a structure or object from a blast wave, which is described by the combination of overpressure and either impulse or duration.
Blast resistant buildings
Buildings that are structurally designed to withstand an explosion generated load (pressure and impulse) while sustaining a predetermined amount of damage.
Blast Wave
The overpressure wave traveling outward from an explosion point. (CCPS, 1996, no. 22)
Block Flow Diagram
A simplified drawing representing a process. It typically shows major equipment and piping and can include major valves.
Blowdown Drum
Separators or accumulators used to separate liquids and vapors in pressure-relieving and emergency systems.
Boil-over
A violent expulsion of contents caused by a heat wave from the surface burning at the top of the tank reaching the water stratum at the bottom of the tank. Oils subject to boilover contain components having a wide range of boiling points, including both light ends and viscous residues. These characteristics are present in most crude oils. (Draft NFPA Understanding Fire Protection for Flammable Liquids)
Boiling-Liquid-Expanding-Vapor Explosion (BLEVE)
A type of rapid phase transition in which a liquid contained above its atmospheric boiling point is rapidly depressurized, causing a nearly instantaneous transition from liquid to vapor with a corresponding energy release. A BLEVE of flammable material is often accompanied by a large aerosol fireball, since an external fire impinging on the vapor space of a pressure vessel is a common cause. However, it is not necessary for the liquid to be flammable to have a BLEVE occur.
Bonding
The process of connecting two or more conductive objects together by means of a conductor so that they are at the same potential as each other but not necessarily at the same potential as the earth. 261
Bow Tie Model
A risk diagram showing how various threats can lead to a loss of control of a hazard and allow this unsafe condition to develop into a number of undesired consequences. The diagram can also show all the barriers and degradation controls deployed.
Branch point
A node with two paths in an event tree or cause-consequence diagram. One path represents success of a safeguard and the other path represents failure of the safeguard.
Brownfield
An industrial or commercial property that is abandoned or underused and being considered as a potential site for redevelopment.
Building
A rigid, enclosed structure.
Building Downwash Models
Models used for estimating the flow and dispersion in and near the recirculating cavity behind buildings, where plumes may downwash to the ground.
Building Siting Evaluation
The procedures used to evaluate the hazards and establish the design criteria for new buildings and the suitability of existing buildings at their specific locations.
Bulking Brush Discharge
A partial surface discharge created during bulking of powder in containers, appearing as a luminous, branched channel flashing radially from the wall toward the center of the container. Its maximum effective energy with respect to dust ignition is believed to be 10 - 20 mJ (less than the MIE of Lycopodium). May ignite flammable gas, hybrid mixtures and some fine dusts in air. Owing to large size of phenomenon the effective energy cannot be measured directly but instead must be inferred from accident case histories where dust of known spark MIE was ignited with proper grounding in place.
Buoyant Cloud
The in-cloud density is less than the ambient density, due to the emissions of hot gases or materials with low molecular weight. Buoyant cloud and light cloud are synonymous.
Burnback Resistance
The ability of a flame arrester to maintain its mechanical integrity and prevent flame breakthrough when the flame arrester is subjected to a standing flame. See also Endurance Burn(ing).
Burning Velocity
Burning velocity is the speed at which a flame front propagates relative to the unburned gas. This differs from flame speed. The laminar burning velocity (SL) is the speed at which a laminar (planar) combustion wave propagates relative to the unburned gas mixture ahead of it. The fundamental burning velocity (Su) is similar, but generally not identical to, the observed laminar burning velocity. This is because Su is a characteristic parameter referring to standardized unburned gas conditions (normally 760 mm Hg and 25 degrees C), and which has been corrected for nonidealities in the measurement. The turbulent burning velocity (St) exceeds the burning velocity measured under laminar conditions to a degree depending on the scale and intensity of turbulence in the unburned gas.
By Exception
A form of documentation where only information that fits a certain definition is documented and not all of the information that was generated by the activity. For example, in a HIRA, this most commonly happens when only those hazard scenarios that resulted in a recommendation(s) are documented and no others. In Asset Integrity, only those ITPM tasks that result in an out-of-specification result are documented.
C or Ceiling
The letter "C" or the word "ceiling" on the TLV or PEL shows the highest airborne concentration of a specific chemical that is allowed in the workplace. This concentration should never be exceeded, even for short periods of time. See also, "PEL" and "TLV". Importance: Chemicals that react rapidly in the body, causing ill health effects carry this value.
Calculated Adiabatic Reaction Temperature (CART)
See Flame Temperature
Capability Assessment
A systematic review of a system's ability to perform to meet system requirements under abnormal and perturbed dynamic conditions.
Car Seal
A metal or plastic cable used to fix a valve in the open position (car seal open) or closed position (car seal closed). Proper authorization, controlled via administrative procedures, must be obtained before operating the valve. The physical seal should have suitable mechanical strength to prevent unauthorized valve operation.
Carcinogen
A material that has been found by the International Agency for Research on Cancer or the National Toxicology Program to produce or potentially produce some type of cancer
CAS Registry Number
A unique number having up to nine digits that is assigned to a chemical by the Chemical Abstracts Service of the American Chemical Society. With the exception of aqueous solutions, mixtures are not covered under this registry.
Catalyst
A chemical substance that accelerates the rate of a chemical reaction by lowering the energy of activation required for the chemical reaction to occur.
Catastrophic
A loss with major consequences and unacceptable lasting effects, usually involving significant harm to humans, substantial damage to the environment, and/or loss of community trust with possible loss of franchise to operate.
Catastrophic Failure
A failure which is both sudden and causes termination of one or more fundamental functions.
Catastrophic Incident
An incident involving a major uncontrolled emission, fire or explosion that causes significant damage, injuries and/or fatalities onsite and have an outcome effect zone that extends into the surrounding community.
Catastrophic Release
An uncontrolled loss of containment of toxic, reactive, or flammable materials from a process that has the potential for causing onsite or offsite acute health effects, significant environmental effects (e.g., compromise of a public drinking water supply), or significant on-site or off-site property damage.