Common cause failure
The occurrence of two or more failures that result from a single event or circumstance.
Common Cause Failure (CCF)
The failure of more than one component, item, or system due to the same cause.
Common Cause or Common Mode Failure
Failure, which is the result of one or more events, causing coincident failures in multiple systems or on two or more separate channels in a multiple channel system, leading to system failure. The source of the common cause failure may be either internal or external to the systems affected. Common cause failure can involve the initiating event and one or more safeguards, or the interaction of several safeguards.
Common Mode Failure
Concurrent failures of different devices characterized by the same failure mode (i.e., identical faults).
Compatibility
The ability of materials to exist in contact without specified (usually hazardous) consequences under a defined scenario. (ASTM E 1445)
Competency
A PSM program element associated with efforts to maintain, improve, and broaden knowledge and expertise.
Component
An equipment part.
Component Boundary
See Equipment boundary.
Component Technique
One member of the roster of methods that collectively form the complete CPQRA procedure.
Computational Fluid Dynamics (CFD)
A class of models that can simulate very highly resolved three-dimensional time-dependent distributions of wind flows and material concentrations. These models generally solve the basic equations of motion and conservation using very small grid spacings and time steps and are computer intensive.
Computational Fluid Dynamics Models
Dispersion models that treat the partial differential Navier-Stokes equations describing fluid flow by numerically solving them using a grid of nodes or finite elements.
Computer
Equipment composed of hardware (H/W) and software (S/W) that performs basic control functions or process control optimization.
Computer-Type Equipment (CTE)
Includes various types of computers (e.g., mini and micro), programmable controllers, peripherals, interconnect systems, personal computers, instrument distributed control system controllers (including single and multi-loop controllers), and other associated equipment.
Computerized Aggregation of Reliability Parameters (CARP)
A computer code developed by SAIC to: aggregate data sets into a single generic set; determine uncertainty bounds (5th and 95th percentiles); fit raw data to statistical distribution; and print reports documenting determinations made.
Computerized maintenance management system (CMMS)
Computer software for planning, scheduling, and documenting maintenance activities. A typical CMMS includes work order generation, work instructions, parts and labor expenditure tracking, parts inventories, and equipment histories.
Concentration
The relative amount of a substance when combined or mixed with other substances. Concentration can be expressed as mole fraction, mass fraction, or component mole or mass density. Examples: yi = 2 ppm mole fraction; wi = 0.50 mass fraction; ci = 0.03 kmole/m3.
Conceptual design
The initial design of a project when basic parameters are known but design details have yet to be developed.
Condensed Phase Explosion
An explosion that occurs when the material is present in the form of a liquid or solid.
Condition Monitoring (CM)
Observing, measuring, and/or trending of indicators with respect to some independent parameter (usually time or cycles) to indicate the current and future ability of a structure, system, or component to function within acceptance criteria.
Conditional Modifier
One of several possible probabilities included in scenario risk calculations, generally when risk criteria endpoints are expressed in impact terms (e.g., fatalities) instead of in primary loss event terms (e.g., release, vessel rupture). Conditional modifiers include, but are not limited to: probability of a hazardous atmosphere, probability of ignition, probability of explosion, probability of personnel presence, probability of injury or fatality, and probability of equipment damage or other financial impact.
Conditional Probability
Probability of occurrence given that a precursor even has occurred.
Conduct of Operations (COO)
The embodiment of an organization's values and principles in management systems that are developed, implemented, and maintained to (1) structure operational tasks in a manner consistent with the organization's risk tolerance, (2) ensure that every task is performed deliberately and correctly, and (3) minimize variations in performance.
Conductive
Having a conductivity greater than 104 pS/m or a resistivity less than 108 W-m.
Conductive Floor
Having an average resistance between 2.5x103 W and 1x106 W as measured using specified electrodes placed a specified distance apart (Method: NFPA 99).
Conductive Hose
A hose having an electrical resistance less than 103 Ohms per meter of hose length, based on measurement between the end connectors.
Conductivity
The reciprocal of resistivity as Siemens per meter or more usually as picosiemens per meter, where 1 picosiemen (pS) = 1x1012 Siemen.
Cone (or Conical Pile) Discharge
See Bulking Brush Discharge.
Confidence
A statistical measure of uncertainty.
Confidence Bounds or Limits
The end points of a confidence interval.
Confidence Interval
That portion of a distribution which is expected to contain the mean value a certain percentage of the time.
Confidence Level
The probability that an assertion made about a statistical property of a population on the basis of a sample is true.
Confidence Limits
The upper and lower endpoints of a confidence interval.
Confidentiality agreement
A written agreement between a toller and their client to outline the extent of security required in the handling of the information, equipment or product.
Confidentiality Disclosure Agreement
An agreement that allows a toller to release information to a third party that would ordinarily be considered proprietary.
Configuration
A set of interconnected equipment forming a system.
Configuration Management
the systematic application of management policies, procedures, and practices to assess and control changes to the hardware and software of a system and to maintain traceability of the configuration to the design basis throughout the system life. Configuration management is a specialized form of management of change.
Confined Explosion
An explosion of fuel-oxidant mixture inside a closed system (e.g. vessel or building).
Confined Volume Deflagration
A deflagration occurring in an enclosed volume such as a pipe or pressure vessel.
Confinement
Obstacles such as walls and ceilings of a building, vessel, pipe, etc. that serve to limit the expansion of a dispersing or exploding vapor cloud.
Congestion
Obstacles in the path of the flame that generate turbulence.
Connect/Disconnect
Make/break a logical link (e.g., as between a MMI and a MPU, eventually through communication devices). See Plug/Unplug for physical connection/disconnection.
Consequence
The undesirable result of a loss event, usually measured in health and safety effects, environmental impacts, loss of property, and business interruption costs.
Consequence Analysis
The analysis of the expected effects of incident outcome cases, independent of frequency or probability.
Consequence Based Approach
The methodology used for building siting evaluation that is based on consideration of the impact of explosion, fire and toxic material release which does not consider the frequency of events.
Consequence Modeling
Development of numerical estimates of the expected effects of incident outcome cases independent of frequency or probability.
Conservation Vent Valve
A device designed to maintain pressure within preset limits in a liquid-containing vessel for the purpose of emissions reduction. It also provides protection against excessive pressure or vacuum.
Consistency
Continued uniformity, during a period or from one period to another.
Constant Stress Layer
The layer near the ground (about 50 m to 100 m deep) where the stress decreases by only about 10%, leading to the assumption of a constant u* layer near the ground
Contain and control measures
Primary containment system, basic process control system, operating procedures and training, and other measures to keep process materials and energies confined within the primary containment system and to keep the process within safe design and operating limits, thus avoiding abnormal situations and loss-of-containment events that could lead to loss, damage and injury impacts.
Containment
A system condition in which under no condition reactants or products are exchanged between the chemical system and its environment.