Appendix C: Glossary

AC: alternating current, a type of electricity whose voltage varies at a constant sinusoidal rate
administrative controls: controls placed on activities through the use of permits, standard operating procedures, standard maintenance procedures or practices, supervision, etc. to insure safe operation and maintenance of the facility as well as maintain normal operations
analytical: the use of logic or other methodologies to analyze
approved: 1) acceptable to the authority having jurisdiction (AHJ); 2) tested and certified by a national testing laboratory such as Underwriter Laboratories (UL) or Factory Mutual (FM); UL "lists" while FM "approves" equipment
authority having jurisdiction (AHJ): 1) organization, office, or individual responsible for approving equipment, an installation, or procedure (NFPA); 2) acceptable to the Occupational Safety and Health Administration (OSHA)
autoignition temperature (AIT): the temperature at which a hot component or surface can ignite a flammable mixture
availability: the fractional uptime of a system or process, expressed as a percentage, i.e., a system is 90% available

bathtub curve: a reliability curve shaped like a bathtub that plots failure rate ( ?) on the y-axis against operating time on the x-axis; commonly applies to electronic and electrical instruments and equipment
blowdown: the process of venting process material from a primary element, impulse lines, or an instrument; because of the hazards involved, most facilities have safety procedures governing how to do this
board: slang for a control panel; in distributed control systems it means control room display instrumentation
board operator: control room operator

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