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Glossary Term: I/S barrier
Intrinsic safety barrier. Physical element that limits current and voltage into a hazardous area in order to satisfy Intrinsic Safety requirements.
Glossary Term: I/O
Input/Output. Refers to the electronic hardware where the field devices are wired. Discrete I/O would have switches for inputs and send signals to solenoid valves and pumps for outputs. Analog I/O would have continuously variable process values inputs, and controller outputs.
Glossary Term: Intrinsic safety
1. A type of protection in which a portion of the electrical system contains only intrinsically safe equipment (apparatus, circuits, and wiring) that is incapable of causing ignition in the surrounding atmosphere. No single device or wiring is intrinsically safe by itself (except for battery-operated self-contained apparatus such as portable…
Glossary Term: Interlock
1. Instrument which will not allow one part of a process to function unless another part is functioning. 2. A device such as a switch that prevents a piece of equipment from operating when a hazard exists. 3. To arrange the control of machines or devices so that their operation…
Glossary Term: Interference, normal-mode
A form of interference which appears between measuring circuit terminals. See also EMI.
Glossary Term: Interference, electromagnetic
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)” See also EMI.
Glossary Term: Interference, common mode
A form of interference which appears between measuring circuit terminals and ground. See also EMI.
Glossary Term: Inductance
1. In an electrical circuit, the property that tends to oppose changes in current magnitude or direction. 2. In electromagnetic devices, generating electromotive force in a conductor by means of relative motion between the conductor and a magnetic field such that the conductor cuts magnetic lines of force.
Glossary Term: Incident
The result of an initiating event that is not stopped from propagating. The incident is most basic description of an unwanted accident, and provides the least information. The term incident is simply used to convey the fact that the process has lost containment of the chemical, or other potential energy…
Glossary Term: Impedance
The complex ratio of a force-like parameter to a related velocity-like parameter - for instance, force to velocity, pressure to volume, electric voltage to current, temperature to heat flow, or electric field strength to magnetic field strength.
Glossary Term: IEC
International Electrotechnical Commission. A worldwide organization for standardization. The object of the IEC is to promote international cooperation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, the IEC publishes international standards. See 61508 and 61511.
Glossary Term: Impact analysis
activity of determining the effect that a change to a function or component will have to other functions or components in that system as well as to other systems
Glossary Term: IDLH
Immediately Dangerous to Life and Health. Use in consequence analysis to estimate toxic effects on people.
Glossary Term: Hydrogen damage
Any of several forms of metal failure caused by dissolved hydrogen, including blistering, internal void formation, and hydrogen induced delayed cracking.
Glossary Term: HSE
(UK) Health and Safety Executive
Glossary Term: HMI/MMI
Human or Man Machine Interface. Refers to the software that the process operator “sees” the process with. An example HMI/MMI screen may show a tank with levels and temperatures displayed with bar graphs and values. Valves and pumps are often shown and the operator can “click” on a device to…
Glossary Term: Heuristic
Pertaining to a method of problem solving in which solutions are discovered by evaluation of the progress made toward the final solution, such as a controlled trial and error method. An exploratory method of tackling a problem, or sequencing of investigation, experimentation, and trial solution in closed loops, gradually closing…
Glossary Term: H&MB
Heat and Material Balance. An accounting of the distribution of the heat and material input and output for a process. Usually prepared as part of the process flow sheet or diagram (PFD) development early in an engineering project. Usually part of the input to a HAZOP or other hazard identification…
Glossary Term: HAZOP
Hazards and operability study. A process hazards analysis procedure originally developed by ICI in the 1970s. The method is highly structured and divides the process into different operationally-based nodes and investigates the behavior of the different parts of each node based on an array of possible deviation conditions or guidewords.
Glossary Term: Hazardous material
Any substance that requires special handling to avoid endangering human life, health or well being. Such substances include poisons, corrosives, and flammable, explosive or radioactive chemicals.
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