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Glossary Term: Fixed program language (FPL)
This type of language limits the user to adjusting a few parameters (for example, range of the pressure transmitter, alarm levels, network addresses). Typical examples of devices with FPL are: smart sensors (for example, pressure transmitter), smart valves, sequence of events controllers, dedicated smart alarm boxes, and small data logging…
Glossary Term: Fireball
Result of a sudden and widespread release of a flammable gas or volatile liquid that is stored under pressure, coupled with immediate ignition. This is distinguished from a jet fire by the shorter duration of the event and the difference in the geometry and shape of the flame. When a…
Glossary Term: Fire (Pool)
Results when spilled flammable liquids are ignited. The magnitude of the effect zone created by a pool fire will depend on the size of the flame that is generated, which in turn depends on the size of the spill surface and the properties of the spilled fluid. The flame’s footprint…
Glossary Term: Fire (Jet)
Results when high-pressure flammable material is ignited as it is being released from containment. The effect zone of a jet fire is proportional to the size of the flame generated. As a high-pressure material is released from a hole, the material will exit with a velocity that is mainly a…
Glossary Term: Fire (Flash)
The result of ignition of a cloud of flammable vapor, when the flame velocity is too slow (laminar and subsonic) to produce an explosive shock wave. When a gas phase mixture of fuel an air is ignited, a flame front travels from the point of ignition in all directions where…
Glossary Term: Final element
Component of a safety function (such as a valve) which directly prevents the harmful event and brings the process to a safe state.
Glossary Term: Fault tree diagram
Probability combination method for estimating complex probabilities. Since it generally takes the failure view of a system, it is useful in multiple failure mode modeling. Care must be taken when using it to calculate integrated average probabilities.
Glossary Term: Fieldbus
A Fieldbus is a digital, two-way, multi-drop communication link between intelligent measurement and control devices. It serves as a Local Area Network (LAN) for advanced process control, remote input/output and high speed factory automation applications.
Glossary Term: Fault propagation modeling
The analysis of the chain of events that leads to an accident. By analyzing what events initiate that chain, which events contribute to, or allow the accident to propagate, and establishing how they are logically related, the event frequency can be determined. Fault propagation modeling techniques use the failure rates…
Glossary Term: Fault tolerance
Ability of a functional unit to continue to perform a required function in the presence of random faults or errors. For example a 1oo2 voting system can tolerate one random component failure and still perform its function. Fault tolerance is one of the specific requirements for safety integrity level (SIL)…
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.
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