Reversal
A situation in which a non-response occurs at one dose, and a positive response is observed at the next dose tested, or vice versa.
Review
To study critically an operation, procedure, condition, event, or series of transactions.
Richardson Number, Ri
Measure of atmospheric stability proportional to the vertical gradient of potential temperature, ¶Θ/¶z, divided by the square of the vertical gradient of wind speed, ¶u/¶z.
Rijnmond Study
An early (1982) quantitative risk assessment that evaluated the risks associated with an integrated chemical/petrochemical process complex in the Netherlands.
Risk
Risk Acceptance Criteria
See Risk tolerance criteria.
Risk Analysis
The estimation of scenario, process, facility and/or organizational risk by identifying potential incident scenarios, then evaluating and combining the expected frequency and impact of each scenario having a consequence of concern, then summing the scenario risks if necessary to obtain the total risk estimate for the level at which the risk analysis is being performed.
Risk Assessment
The process by which the results of a risk analysis (i.e., risk estimates) are used to make decisions, either through relative ranking of risk reduction strategies or through comparison with risk targets.
Risk Based Approach
A quantitative risk assessment methodology used for building siting evaluation that takes into consideration numerical values for both the consequences and frequencies of explosion, fire, or toxic material release.
Risk Based Inspection
A risk assessment and management process that is focused on loss of containment of pressurized equipment in processing facilities, due to material deterioration. These risks are managed primarily through equipment inspection.
Risk Based Process Safety (RBPS)
The Center for Chemical Process Safety's process safety management system approach that uses risk-based strategies and implementation tactics that are commensurate with the risk-based need for process safety activities, availability of resources, and existing process safety culture to design, correct, and improve process safety management activities.
Risk Contour
Lines that connect points of equal risk around the facility ("isorisk" lines).
Risk Control Measure
Characteristic associated with a process that is expected to reduce the likelihood and/or severity of a loss event.
Risk Escalation
A risk management system whereby an increasingly higher level of authorization is required to sanction the continued tolerance of increasingly higher levels of risk. Some organizations use the term risk elevation.
Risk Estimation
Combining the estimated consequences and likelihood of all incident outcomes from all selected incidents to provide a measure of risk.
Risk Evaluation
Comparison of results of a qualitative or quantitative risk analysis coupled with an appraisal of the significance of the results, both overall and from individual events.
Risk Evaluation Criteria
A qualitative or quantitative expression of the level of risk that an individual or organization is willing to assume in return for the benefits obtained from the associated activity.
Risk Factor
Along with the probability that an event will occur (risk) are those factors of behavior, lifestyle, environment, or heredity associated with increasing or decreasing that probability.
Risk Factor
Along with the probability that an event will occur (risk) are those factors of behavior, lifestyle, environment, or heredity associated with increasing or decreasing that probability.
Risk Management
The systematic application of management policies, procedures, and practices to the tasks of analyzing, assessing, and controlling risk in order to protect employees, the general public, the environment, and company assets, while avoiding business interruptions. Includes decisions to use suitable engineering and administrative controls for reducing risk.
Risk Management Program (RMP) Rule
EPA's accidental release prevention Rule, which requires covered facilities to prepare, submit, and implement a risk management plan.
Risk Matrix
A tabular approach for presenting risk tolerance criteria, typically involving graduated scales of incident likelihood on the Y-axis and incident consequences on the X-Axis. Each cell in the table (at intersecting values of incident likelihood and incident consequences) represents a particular level of risk.
Risk Measures
Ways of combining and expressing information on likelihood with the magnitude of loss or injury (e.g., risk indexes, individual risk measures, and societal risk measures).
Risk Reduction
Development, comparison, and selection of options to reduce risk to a target level, if needed, or as needed.
Risk Targets
Objective-based risk criteria established as goals or guidelines for performance.
Risk Tolerance
The maximum level of risk of a particular technical process or activity that an individual or organization accepts to acquire the benefits of the process or activity.
Risk Tolerance Criteria
A predetermined measure of risk used to aid decisions about whether further efforts to reduce the risk are warranted.
Risk-Based
The adjective, risk-based, is used to portray one or more risk attributes of a process, activity, or facility. In this context, considering any one of the three risk questions can be viewed as a risk-based activity. For example, when considering the hazards of a substance or a process in deciding how much rigor to build into an operating procedure, the term risk-based design is used rather than hazard-based design, even though understanding the hazard attributes was the primary determinant in the design of the procedure. So, for simplicity, rather than use the independent terms hazard-based, consequence-based, or frequency-based, the single term risk-based is used to mean any one or a combination of these terms.
Risk-Based Inspection (RBI)
A systematic approach for identifying credible failure mechanisms and using equipment failure consequences and likelihood to determine inspection strategies for equipment.
Riverine Flood
A flood resulting from an overflow of a river, stream or creek.
Roll Over
The spontaneous and sudden movement of a large mass of liquid from the bottom to the top surface of a refrigerated storage reservoir due to the instability caused by an adverse density gradient. Rollover can cause a sudden pressure increase and can affect vessel integrity.(API 2510)
Root (or Cubic) Law
See KSt Value
Root Cause Analysis (RCA)
A formal investigation method that attempts to identify and address the management system failures that led to an incident. These root causes often are the causes, or potential causes, of other seemingly unrelated incidents. Identifies the underlying reasons the event was allowed to occur so that workable corrective actions can be implemented to help prevent recurrence of the event (or occurrence of similar events).
Root Causes
A fundamental, underlying, system-related reason why an incident occurred that identifies a correctable failure(s) in management systems. There is typically more than one root cause for every process safety incident.
Roughness Sublayer
The lower part of the boundary layer, typically of depth a few Hr, where the flow depends explicitly on the presence of the obstacles, their size, and their geometry.
Round Robin
A process involving an exchange of samples intended to transfer analytical capabilities from the client to the toller to support the toll project.
Route Data
Information regarding the route, including conditions of the infrastructure (such as road and rail condition and speed restrictions), specific segments of the route identified for analysis (including meteorological conditions), and the location of sensitive receptors along the route (such as urban and rural population densities, environmental crossings).
Rule Based Action
Behavior in which a person follows remembered or written rules. Examples might be the use of a written checklist to calibrate an instrument or a maintenance manual to repair a pump.
Rule-based behavior
Behavior in which a person follows remembered or written rules. Examples might be the use of a written checklist to calibrate an instrument or the use of a maintenance manual to repair a pump.
Run-up Distance or Run-up Length
The distance in the direction of flame propagation from the point of ignition to any point in a pipe system. Deflagration flames accelerate over this distance due to turbulence and pre-compression effects. Depending on pipe diameter, surface roughness, and the presence of turbulence-producing obstacles (elbows, valves, etc.) this distance may be sufficient for Deflagration to Detonation Transition to occur
Runaway
A thermally unstable reaction system which exhibits an uncontrolled accelerating rate of reaction leading to rapid increases in temperature and pressure.
Runaway Reactions
A thermally unstable reaction system which exhibits an uncontrolled accelerating rate of reaction leading to rapid increases in temperature and pressure.
Rung
A network in a Ladder Diagram Program with its attached left Power Rail and optionally attached right Power Rail.
Running Mode
Normal hardware operation, e.g., an unspared compressor which must operate to run the process.
Sachs' Scaling
Dimensionless terms for TNT equivalence explosion modeling.
Safe Burning Time
The period of stabilized burning on a flame arrester without flame being transmitted through the arrester.
Safe Haven
A building or enclosure that is designed to provide protection to its occupants from exposure to outside hazards
Safe Operating Limits
Limits established for critical process parameters, such as temperature, pressure, level, flow, or concentration, based on a combination of equipment design limits and the dynamics of the process.
Safe Upper and Lower Limits
The safe upper and lower limits refer to equipment design limits, not quality-related operating limits. Sometimes these values are referred to as design limits (e.g., design pressure, design temperature).
Safe Work Practices
An integrated set of policies, procedures, permits, and other systems that are designed to manage risks associated with non-routine activities such as performing hot work, opening process vessels or lines, or entering a confined space.