CCPS Process Safety Glossary | AIChE

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CCPS Process Safety Glossary

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Fatal Accident Rate (FAR)

A measure of individual risk expressed as the estimated number of fatalities per 108 exposure hours (roughly 1000 employee working lifetimes).

Fault Avoidance

Use of component selection, conservative design, testing, and burn-in to achieve high reliability. Design assurance.

Fault Event

A failure event in a fault tree that requires further development.

Fault Tolerance

Ability to continue to perform a required function in the presence of faults or error.

Fault Tolerant

A system where some parts may fail but the system will still execute properly. A control system configuration that inherently provides auto selection of alternate or redundant signal paths to effect uninterrupted operations.

Fault tree

A logic model that graphically portrays the combinations of failures that can lead to a specific main failure or accident of interest.

Fault Tree Analysis

A method used to analyze graphically the failure logic of a given event, to identify various failure scenarios (called cut-sets), and to support the probabilistic estimation of the frequency of the event.

Feedback Control

A method by which one or more controlled variables (i.e., pressure, temperature, current, speed, power) are made to obey a common signal, whether constant or varying, according to a prescribed law, as a result of the measurement of the variable(s) in questions.

Final Control Element

A device that manipulates a process variable normally associated with the basic process control system. An instrument that takes action to adjust the manipulated variable in a process. This action moves the value of the controlled variable back towards the set point. The last system element that responds quantitatively to a control signal and performs the actual control action. Examples include valves, solenoids, and servometers.

Final Control Element (for an interlock system).

A field device used to drive the process to its lowest energy state, or a state away from its critical operating limit. A common final control element is a solenoid valve either directly applied to the process for control of fluid flow or to vent from or admit instrument air to an air-operated control valve. Motor control starter circuits also serve as final control elements to start or stop motors. Also, see "Output Devices".

Final Element

Process control or safety device that implements the physical action necessary to achieve or maintain a safe state; e.g., valves, switch gear, and motors, including their auxiliary elements (such as the solenoid valve used to operate a valve).

Finding

A conclusion reached by the audit team based on data collected and analyzed in response to a specific audit question which indicates a need for improvement in the PSM program design or implementation. Findings are sometimes also referred to exceptions. Although strictly speaking a finding can be a positive or negative conclusion, common custom and terminology in auditing is to refer to the deficiencies identified as the findings. Findings include both the basis for the conclusion, i.e., an audit question or criteria, as well as the explanatory conclusion and the evidence that substantiates the conclusion.

Fire

A combustion reaction accompanied by the evolution of heat, light, and flame.

Fire Point

The minimum temperature at which a flammable or combustible liquid, as herein defined, and some volatile combustible solids will evolve sufficient vapor to produce a mixture with air that will support sustained combustion when exposed to a source of ignition, such as a spark or flame.

Fire Protection

Methods of providing for fire control or fire extinguishment. (NFPA 850)

Fire Triangle

Three basic conditions are required for fire to take place. These are fuel, oxygen, and heat.

Fireball

The atmospheric burning of a fuel-air cloud in which the energy is mostly emitted in the form of radiant heat. The inner core of the fuel release consists of almost pure fuel whereas the outer layer in which ignition first occurs is a flammable fuel-air mixture. As buoyancy forces of the hot gases begin to dominate, the burning cloud rises and becomes more spherical in shape.

Firmware

Configurable digital programs, procedures, rules, and associated documentation contained in vendor supplied standard hardware required for the operation and/or maintenance of a digital system.

First Out

A term usually referring to an annunciator feature that indicates which interlock caused the trip.

Fitness for service (FFS)

A systematic approach for evaluating the current condition of a piece of equipment in order to determine if the equipment item is capable of operating at defined operating conditions (e.g., temperature, pressure).

Fixed facility

A portion of or a complete plant, unit, site, complex or any combination thereof that is generally not moveable. In contrast, mobile facilities, such as ships (e.g., transport vessels, floating platform storage and offloading vessels, drilling platforms), trucks, and trains, are designed to be movable.

Flame

A region in which chemical interaction between gases occurs, accompanied by the evolution of light and heat

Flame Arrester

A device fitted to the opening of an enclosure or to the connecting piping of a system of enclosures and whose intended function is to allow flow but prevent the transmission of flame from either a deflagration or detonation.

Flame Arrester Element (Matrix):

That portion of a flame arrester whose principal function is to prevent flame transmission, usually by quenching the flame front.

Flame Arrester Housing

That portion of flame arrester whose principal function is to provide a suitable enclosure for the flame arrester element, and to facilitate mechanical connection to other systems.

Flame Barrier

A device that prevents transmission of a flame from a source to a receptor.

Flame Expansion Dimensions

The dimensions in which a burning or exploding gas is free to expand, 1D, 2D, or 3D.

Flame Front

That portion of the flame reaction zone moving into the unburned gas where the bulk of the reaction occurs and the medium reaches its ignition temperature

Flame Front Diverter

A device that opens in response to the pressure wave preceding the flame front of the deflagration, venting the flame front and pressure wave.

Flame Propagation

The movement of a flame front in piping or equipment.

Flame Speed

The speed of a flame front relative to a fixed reference point. Flame speed is dependent on turbulence, the equipment geometry, and the fundamental burning velocity.

Flame Temperature

Theoretical temperature achieved based on chemical equilibrium with the assumption of Gibbs free energy minimization

Flame Trap

Another name for a flame arrester, commonly used in the United Kingdom.

Flame Velocity

See Flame Speed

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. Importance: The range represents an unsafe gas or vapor mixture with air that may ignite or explode. Generally, the wider the range the greater the fire potential. See also Lower Explosive Limit / Lower Flammable Limit and Upper Explosive Limit / Upper Flammable Limit.

Flammable

A gas that can burn with a flame if mixed with a gaseous oxidizer such as air or chlorine and then ignited. The term flammable gas includes vapors from flammable or combustible liquids above their flash points.

Flammable Gas (NFPA 55)

A gas that is flammable in a mixture of 13 percent or less (by volume) with air, or the flammable range with air is wider than 12 percent regardless of the lower limit, at atmospheric temperature and pressure.

Flammable Limits

The minimum and maximum concentration of fuel vapor or gas in a fuel vapor or gas/gaseous oxidant mixture (usually expressed in percent by volume) defining the concentration range (flammable or explosive range) over which propagation of flame will occur on contact with an ignition source. See also Lower Flammable Limit and Upper Flammable Limit.

Flammable Limits (Dusts)

The minimum and maximum concentration of a particulate solid (dust) in a dust/gaseous oxidant mixture (usually expressed in percent by volume) defining the concentration range (flammable or explosive range) over which propagation of flame will occur on contact with an ignition source. See also Lower Flammable Limit and Upper Flammable Limit.

Flammable Liquids

Any liquid that has a closed-cup flash point below 100 F (37.8 C), as determined by the test procedures described in NFPA 30 and a Reid vapor pressure not exceeding 40 psia (2068.6 mm Hg) at 100 F (37.8 C), as determined by ASTM D 323, Standard Method of Test for Vapor Pressure of Petroleum Products (Reid Method). Class IA liquids shall include those liquids that have flash points below 73 F (22.8 C) and boiling points below 100 F (37.8 C). Class IB liquids shall include those liquids that have flash points below 73 F (22.8 C) and boiling points at or above 100 F (37.8 C). Class IC liquids shall include those liquids that have flash points at or above 73 F (22.8 C), but below 100 F (37.8 C). (NFPA 30)

Flammable Mass

The mass of fuel in a vapor cloud that is in the flammable range, mf.

Flammable Range

The range of concentrations between the lower and upper flammability limits.

Flammable Vapor

A vapor that is above its lower flammable limit (LFL) concentration. A zone of flammable vapor will exist in equilibrium with a flammable or combustible liquid any time it is above its flash point.

Flash Fire

A fire that spreads by means of a flame front rapidly through a diffuse fuel, such as a dust, gas, or the vapors of an ignitable liquid, without the production of damaging pressure.

Flash Point

The minimum temperature at which a liquid gives off sufficient vapor to form an ignitable mixture with air within the test vessel used (Methods: ASTM 502). The flash point is less than the fire point at which the liquid evolves vapor at a sufficient rate for indefinite burning.

Flashback

Undesired flame propagation opposite to the direction of flow. It is also used to describe failure of a flame arrester element.

Flashback Arrester

A device to limit damage from a flashback by preventing propagation of the flame front beyond the location of the arrester.

Flashback Prevention

Prevention of a recession of the flame into or back of the mixing chamber.

Flashpoint

The temperature at which a liquid develops sufficient vapor pressure to form a vapor/air mixture capable of undergoing combustion after ignition from an external energy source. (Fire point is the temperature at which the reaction will be sustained).

Flow Controlled Aperture

An aperture designed to produce flow velocities which exceed the local flame speed of the flammable mixture, thus preventing flame transmission in the reverse direction.