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Glossary Term: Safety ground
1. A connection between metal structures, cabinets, cases, etc. which is required to prevent electrical shock hazard to personnel. 2. Safety ground is not a signal reference point.
Glossary Term: Safe state
The state of the process after acting to remove the hazard resulting in no significant harm.
Glossary Term: Safe area
1. Nonhazardous (unclassified) location. 2. An area in which explosive gas/air mixture are not expected to be present so that special precautions for the construction and use of electrical apparatus are not required.
Glossary Term: Safe failure
Failure that does not have the potential to put the safety instrumented system in a dangerous or fail-to-function state. The situation when a safety related system or component fails to perform properly in such a way that it calls for the system to be shut down or the safety instrumented…
Glossary Term: Rupture disc
A diaphragm designed to burst at a predetermined pressure differential. Symbol rupture disc device A nonreclosing pressure relief device that relieves excessive static inlet pressure via a rupture disc.
Glossary Term: RRF
Risk Reduction Factor - The inverse of PFDavg
Glossary Term: RMP
Risk management plan. Part of the US requirement under the Occupational Safety and Health Administration (OSHA) guidelines for managing risk when dealing with large quantities of certain materials.
Glossary Term: Risk integral
A summation of risk as expressed by the product of consequence and frequency. The integral is summed over all of the potential unwanted events that can occur. If calculating the risk integral for loss of life, the consequence of concern and thus the units of the integral are fatalities. It…
Glossary Term: Risk graph
A qualitative and category-based method of safety integrity level (SIL) assignment. Risk graph analysis uses four parameters to make a SIL selection: consequence, occupancy, probability of avoiding the hazard, and demand rate. Each of these parameters is assigned a category and a SIL is associated with each combination of categories.…
Glossary Term: Risk (Unmitigated)
The level of risk that is present in a process before any safety instrumented systems are considered. This level helps identify how much risk reduction is required to be provided by any safety instrumented system installed as part of a process. This unmitigated risk level must be defined in terms…
Glossary Term: Risk (Inherent)
The risk from a completed process design that contains a given amount of process materials at given process parameters (i.e. temperature, pressure, etc.) Can usually be managed by good process engineering.
Glossary Term: Risk
Risk is a measure of the likelihood (frequency) and consequence (severity) of an adverse effect. (i.e., How often can harm happen and what will be the effects if it does?)
Glossary Term: Response
1. The change in output of a device in relation to a change of input. 2. Defined output for a given input under explicitly stated conditions.
Glossary Term: Resealing pressure
The inlet pressure at which fluid no longer leaks past a relief valve after it is closed.
Glossary Term: Repeater
1. Device used to extend the range over which signals can be correctly transmitted and received for a given medium. 2. A device that amplifies or regenerates data signals in order to extend the distance between data stations.
Glossary Term: Repeatability
The ability of a transducer to reproduce output readings when the same input value is applied to it consecutively under the same conditions, and in the same direction. NOTE(S): Repeatability is expressed as the maximum difference between output readings; it is expressed as “within percent of full- scale output.” Two…
Glossary Term: Relief valve
An automatic pressure relieving device actuated by the pressure upstream of the valve and characterized by opening pop action with further increase in lift with an increase in pressure over popping pressure. See pressure relief device.
Glossary Term: Reliability block diagram
Probability combination method for estimating complex probabilities. Since it generally takes the “success” view of a system, it can be confusing when used in multiple failure mode modeling.
Glossary Term: Reliability
1. The probability that a device will perform its objective adequately, for the period of time specified, under the operating conditions specified. 2. The probability that a component, piece of equipment or system will perform its intended function for a specified period of time, usually operating hours, without requiring corrective…
Glossary Term: Redundancy
Use of multiple elements or systems to perform the same function. Redundancy can be implemented by identical elements (identical redundancy) or by diverse elements (diverse redundancy). Redundancy of primarily used to improve reliability or availability.
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