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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 Reactions
A thermally unstable reaction system which exhibits an uncontrolled accelerating rate of reaction leading to rapid increases in temperature and pressure.
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.
Safe Work Practices (SWP)
CCPS RBPS Element 09: This Element addresses the gap between operating and maintenance procedures, helping control special tasks performed at a facility through a permit system.
Safeguard
Any device, system, or action that interrupts the chain of events following an initiating event or that mitigates the consequences.
Safety
The expectation that a system does not, under defined conditions, lead to a state in which human life, economics or environment are endangered.
Safety Instrumented Functions (SIF)
A system composed of servers, logic servers, and final control elements for the purpose of taking the process to a safe state when predetermined conditions are violated.
Safety Instrumented System (SIS)
A separate and independent combination of sensors, logic solvers, final elements, and support systems that are designed and managed to achieve a specified safety integrity level. A SIS may implement one or more Safety Instrumented Functions (SIFs).
Safety Integrity
(there is no definition for this CPQRA) is defined as the likelihood that a safety-related system will achieve its required safety functions under all the stated conditions within a specified period of time.
Safety integrity level (SIL)
Discrete level (one out of four) allocated to the SIF for specifying the safety integrity requirements to be achieved by the SIS.
Safety Interlocking
Same as interlocking except a failure to control out-of-limit conditions can cause injury or unacceptable environmental contamination.
Safety Layer
A system or subsystem that is considered adequate to protect against a specific hazard. The safety layer; Cannot be compromised by the failure of another safety layer, is totally independent of any other protective layers, may be a non-control alternative (e.g., chemical, mechanical), may be an administrative procedure, may require diverse hardware and software packages, must be approved according to company policy and procedures, must have acceptable reliability, and must meet proper equipment classification.
Safety Review
An inspection of a plant or process unit, drawings, procedures, emergency plans, and/or management systems, etc., usually by a team and usually problem-solving in nature. (See Audit for contrast.)
Safety System
Equipment and/or procedures designed to limit or terminate an incident sequence, thus avoiding a loss event or mitigating its consequences.
Sampling
Selecting a portion of a large population of data or information to determine the accuracy, representativeness, or characteristics of the entire population.
Scale-up
The steps involved in transferring a manufacturing process or section of a process from laboratory scale to the level of commercial production.
Scenario
A detailed description of an unplanned event or incident sequence that results in a loss event and its associated impacts, including the success or failure of safeguards involved in the incident sequence.
Screening Tool
A simplified dispersion model with limited capabilities, suitable for screening-level studies.
Security Plan
A document that describes a plan to address security issues and related events including security assessment and mitigation options. This includes security alert levels and response measures to security threats.
Security Risk
The potential for damage to, or loss of, an asset. Risk, in the context of chemical process security, is the potential for the intentional event outcome to be realized. Typical examples include an intentional release of hazardous materials from containment, the theft of chemicals that could later be used as weapons, the contamination of chemicals that may later harm the public, the economic costs of the damage, or disruption of the chemical process or other nearby critical infrastructure. Therefore, risk is an expression of the likelihood (LAS) that a specific vulnerability (V) of a particular attractive target (AT) will be exploited by a defined threat (T) to cause a given consequence (C).
Security Vulnerability Analysis (SVA)
The process of determining the likelihood of an adversary successfully exploiting a weakness and the resulting degree of damage or impact. A SVA is not a quantitative risk analysis, but is performed qualitatively using a structured and repeatable method and the best judgment of safety, security, and transportation personnel. A qualitative determination of risk is the desired outcome of a SVA in order to provide the basis for ranking the security-related risks and thus to establish priorities for the application of countermeasures.
Self-Heating of Powders
See Spontaneous Combustion (Heating) of Powders.
Self-Igniting
The ignition and sustained combustion of a substance without introduction of any ignition source besides thermal energy or heat of reaction resulting when combined with other substances in the surrounding environment. Self-igniting materials include materials above their autoignition temperature, chemicals that ignite due to heat of reaction with oxygen in air, and chemicals that are unstable and spontaneously combust when released.
Self-reactive
Capable of polymerization, decomposition or rearrangement. Initiation of the reaction can be spontaneous, by energy input such as thermal or mechanical energy, or by catalytic action increasing the reaction rate.
Semi-Batch Reactor
A reactor in which some reactants are added to the reactor at the start of the batch, while others are fed intermittently or continuously during the course of the reaction.
Semi-Batch Reactor
In a semi-batch reactor, some reactants are added to the reactor at the start of the batch, while others are fed continuously during the course of the reaction.
Semi-Quantitative
Risk analysis methodology that includes some degree of quantification of consequence, likelihood, and/or risk level.
Semi-Quantitative Risk Analysis
Risk analysis methodology that includes some degree of quantification of consequence, likelihood, and/or risk level.
Sensitizer
A substance which on first exposure causes little or no reaction in man or test animals, but which on repeated exposure may cause a marked response not necessarily limited to the contact site. Skin sensitization is the most common form of sensitization in the industrial setting, although respiratory sensitization to a few chemicals is also know to occur. Importance: Knowing that a substance is a sensitizer allows you to be aware of the signs and symptoms of overexposure.
Sensitizer
A chemical that causes a substantial proportion of exposed people or animals to develop an allergic reaction in normal tissue after repeated exposure to the chemical.
Serious Injury
The classification for an occupational injury which includes: (a) all disabling work injuries and (b) non-disabling work injuries as follows: (1) eye injuries requiring treatment by a physician, (2) fractures, (3) injuries requiring hospitalization, (4) loss of consciousness, (5) injuries requiring treatment by a doctor and (6) injuries requiring restriction of motion or work, or assignment to another job.
Severity
The maximum credible consequences or effects, assuming no safeguards are in place.
Shelter-in-Place
A process for taking immediate shelter in a location readily accessible to the affected individual by sealing a single area (an example being a room) from outside contaminants and shutting off all HVAC systems.
Sheltering
Physical protection (such as an enclosed building) against the outcome of an incident.
Shock Sensitive
A relatively unstable material, the energetic decomposition of which can be initiated by merely the input of mechanical energy at normal ambient conditions. Materials are considered as shock sensitive if they are more easily initiated than dinitrobenzene in a standard drop-weight test.
Shock Wave
A transient change in the gas density, pressure, and velocity of the air surrounding an explosion point. The initial change can be either discontinuous or gradual. A discontinuous change is referred to as a shock wave, and a gradual change is known as a pressure wave.
Short Term Exposure Limit (STEL)
Is the limiting exposure concentration for exposure durations up to 15 minutes, as developed by the ACGIH.
Short-Stop Agent
A material added to a reaction mixture to stop or greatly reduce the reaction rate. This is usually done to prevent a runaway reaction.
Short-term Public Emergency Guidance Levels (SPEGLs)
For exposures whose occurrence is expected to be rare in the lifetime of any one individual, the 60-minute exposure concentration that reflects an acceptance of the statistical likelihood of a non-incapacitating reversible effect in an exposed population, while avoiding significant decrements in performance. Developed by the National Academy of Science (NAS).
Shutdown (S/D)
A process by which an operating plant or system is brought to a safe and non-operating mode.
Side-On Pressure
The impulse or pressure experienced by an object as a blast wave passes by it.
Siting
The process of locating a complex, site, plant, or unit.
Skill Based Action
The performance of more or less subconscious routines governed by stored patterns of behavior. Examples might be the use of a hand tool by an experienced mechanic or the initiation of an emergency procedure by a trained and experienced operator.
Skill-Based Behavior
The performance of routine actions governed by stored patterns of behavior. Examples might be the use of a hand tool by an experienced mechanic or the initiation of an emergency procedure by a trained and experienced operator.
Slip Flange
Loose ring flange for connecting flared or stub end pipe. Continuity may be lost across connection due to insulation by nonconductive gasket plus painted surfaces on the slip flange and/or pipe. A conductive gasket (such as flexible graphite filled spiral wound metal type) or jumper cable may be required.