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Glossary Term: FAT
Factory acceptance test. A test performed before shipment to site, usually at the vendor or integrator premises, often witnessed by the end user. Not a mandatory step in IEC61511, but very common to avoid problems during site acceptance testing (SAT) and site integration testing (SIT).
Glossary Term: Failure modes
The way that a device fails. These ways are generally grouped into one of four failure modes: Safe Detected (SD), Dangerous Detected (DD), Safe Undetected (SU), and Dangerous Undetected (DU) per ISA TR84.0.02.
Glossary Term: Failure rate
The number of failures per unit time for a piece of equipment. Usually assumed to be a constant value. It can be broken down into several categories such as safe and dangerous, detected and undetected, and independent/normal and common cause. Care must be taken to ensure that burn in and…
Glossary Term: Fail safe
(or preferably de-energize to trip) A characteristic of a particular device which causes that device to move to a safe state when it loses electrical or pneumatic energy.
Glossary Term: Fail open
A condition wherein the valve closing component moves to an open position when the actuating energy source fails.
Glossary Term: Fail close
A condition wherein the valve closing component moves to a closed position when the actuating energy source fails.
Glossary Term: Fail in place/last
A condition wherein the valve closing component stays in its last position when the actuating energy source fails
Glossary Term: Explosion proof enclosure
An enclosure that is 1) capable of withstanding an explosion of a gas or vapor within it, 2) able to prevent the ignition of an explosive gas or vapor that may surround it and 3) that operates with an external temperature that a surrounding explosive gas or vapor will not…
Glossary Term: Explosion door
A door in a furnace or boiler setting designed to be opened by a predetermined gas pressure.
Glossary Term: Explosion (Vapor Cloud)
The result of ignition of a cloud of flammable vapor, when the flame velocity is high enough (turbulent and supersonic) to produce an explosive shock wave. The effect zone is determined by the quantity of energy released and the blast shock wave overpressure resulting from the explosion.
Glossary Term: Explosion
Combustion which proceeds so rapidly that a high pressure is generated suddenly. This high pressure or shock wave is the result of a turbulent flame boundary and is very difficult to predict relative to a flash fire which propagates through laminar boundary flow.
Glossary Term: Explosion (Physical)
The result of sudden catastrophic rupture of a high-pressure vessel. The blast wave is caused when the potential energy stored in the high-pressure vessel is transferred to kinetic energy when that material is released. The effect zone is determined by the quantity of energy released and the blast shock wave…
Glossary Term: Exception reporting
An information system which reports on situations only when actual results differ from planned results. When results occur within a normal range they are not reported.
Glossary Term: Event tree analysis
A method of fault propagation modeling. The analysis constructs a tree- shaped picture of the chains of events leading from an initiating event to various potential outcomes. The tree expands from the initiating event in branches of intermediate propagating events. Each branch represents a situation where a different outcome is…
Glossary Term: Event (Intermediate)
An event that propagates or mitigates the initiating event during an event sequence (e.g., improper operator action fails to stop the initial ammonia leak and causes propagation of the intermediate event to an incident; in this case the intermediate event outcome is a toxic release)
Glossary Term: Event (Initiating)
The first event in an event sequence (e.g., the stress corrosion resulting in leak/rupture of the connecting pipeline to the ammonia tank)
Glossary Term: Event (Independent)
Events that do not affect each other (can be series or parallel).Tossing two coins (parallel) or one coin twice (series) are generally considered to be independent events.
Glossary Term: Elevation error
A type of error in temperature or pressure sensors that incorporate capillary tubes partly filled with liquid; the error is introduced when the liquid filled portion of the system is at a different level than the instrument case, the amount of error varying with distance of elevation or depression.
Glossary Term: EMI
Electromagnetic Interference: Any spurious effect produced in the circuits or elements of a device by external electromagnetic fields. NOTE: A special case of interference from radio transmitters is known as “radio frequency interference (RFI)”
Glossary Term: Effect Zone
The physical area in which a harmful effect is felt by a receptor. For a toxic release, the area over which the airborne concentration exceeds some level of concern. For a physical energy release, the area over which a specified overpressure criterion is exceeded. For thermal radiation effects, the area…
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