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Special Precautions
Instructions that describe proper handling and storage procedures specific to that material. Importance: Following these procedures would prevent excessive employee exposure. These procedures tell you additional information needed to handle the material safely.
Specific Gravity
A dimensionless, temperature dependent ratio of the density of one substance with that of a reference substance. For solids and liquids the reference substance is water at 39 F (4 C). For gases and vapors, the reference substance is dry air at 60 F (15.6 C).
Specific Impulse
The area under the overpressure versus time curve.
Spill Prevention Control and Countermeasures Plan
The document prepared in compliance with U.S. regulation "Guidelines For The Preparation and Implementation of a Spill Prevention Control and Countermeasure Plan (SPCC)" (EPA 40 CFR part 112.7. 216)
Spontaneous Combustion (Heating) of Powders
Ignition of powders in bulk caused by the rate of heat generation from oxidation and/or exothermic decomposition reactions of the powders being greater than the rate of heat loss to the surroundings.
Spontaneously Combustible
Capable of igniting and burning in air without the presence of an ignition source. Pyrophoric materials are spontaneously combustible, although some pyrophorics require the presence of a minimum amount of moisture (humidity) to spontaneously ignite. Other spontaneously combustible substances and mixtures may require more time or an insulating environment to self-heat to the point of ignition.
Stability
Refers to the ratio of the suppression of turbulence by thermal effects to the generation of turbulence by mechanical effects such as wind shears. Transport and dispersion models characterize the effect of stability through use of one or more dimensionless stability parameters, such as the Richardson number, Ri, the Monin-Obukhov length, L, or the Pasquill stability class.
Stability Class
The Pasquill stability class scheme is based on time of day, wind speed, cloudiness, and sun's intensity. The six stability classes are denoted by the letters A through F, with A being very unstable, D being neutral, and F being very stable
Stabilized Burning
Steady burning of a flame, stabilized at, or close to the flame arrester element.
Stable Detonation
A detonation that progresses through a confined system without significant variation of velocity and pressure characteristics. For atmospheric conditions, typical velocities range between 1600 and 2200 m/s for standard test mixtures and test procedures.
Stable Materials
Those materials that normally have the capacity to resist changes in their chemical composition, despite exposure to air, water, and heat as encountered in fire emergencies. (NFPA 704 2001)
Stakeholder
Individuals or organizations that can (or believe they can) be affected by the facility's operations, or who are involved with assisting or monitoring facility operation.
Stakeholder Outreach
CCPS RBPS Element 05: This Element promotes interactions with the facility's neighbors, including communications of how the facility manages its process safety risks.
Stakeholder Outreach
A PSM program element associated with efforts to (1) seek out and engage stakeholders in a dialogue about process safety; (2) establish a relationship with community organizations, other companies and professional groups, and local, state, and federal authorities; and (3) provide accurate information about company/facility operations, products, plans, hazards, and risks.
Stand-Off Distance, R
Distance from the center of an explosion
Standard Deviation (cloud concentration), s
The square root of the sum of squared values of concentration minus centerline concentration. The cloud half-width can be defined as the distance corresponding to a concentration of two or three standard deviations from the centerline.
Standards
The PSM program element, Compliance with Standards, that helps identify, develop, acquire, evaluate, disseminate, and provide access to applicable standards, codes, regulations, and laws that affect a facility and/or the process safety requirements applicable to a facility. More generally, standards also refers to requirements promulgated by regulators, professional or industry-sponsored organizations, companies, or other groups that apply to the design and implementation of management systems, design and operation of process equipment, or similar activities.
Standby Mode
Hardware operation that is normally not running but must be ready run, e.g., an emergency diesel generator.
Statement
A programming language construct that represents a set of declarations or a step in a sequence of actions.
Static Activation Pressure
Pressure that actuated a vent closure when the pressure is increased slowly (with a rate of pressure rise less than 0.1 bar/min (0.15 psi/min).
Static Electricity
The class of phenomena recognized by the presence of electrical charges, either stationary or moving, and the interaction of these charges, this interaction being solely by reason of the charges themselves and their position, and not by reason of their motion.
Stoichiometric Concentration
A term used to describe a balanced ratio of chemical reactants that would result in all of the chemical reactants becoming products if a chemical reaction were to occur.
Stoichiometric Mixture
A balanced mixture of fuel and oxidizer such that no excess of either remains after combustion.
Stoichiometry
Calculations about masses or volumes of reactants and products involved in a chemical reaction.
Stratification
As used here, any concentration profile that develops in an enclosure. The flammable mass will be between the LFL and UFL concentrations along such a concentration profile.
Stray Capacitance
Capacitance unessential for the function of a circuit and of relatively small value that nevertheless may introduce errors if not eliminated or unaccounted for. Of particular importance in high voltage, low capacitance spark ignition tests and in the measurement of small charges and currents.
Subcontractor
A company or individual performing work at a PSM-covered facility whose business relationship is with a third party (i.e., a general or specialty contractor) and not with the host facility directly. Subcontractors are subject to the Contractor Management element of PSM programs.
Superheated Liquids
Liquids at a temperature above their normal boiling point.
Suppressant
A chemical agent used in a deflagration suppressant system to extinguish the deflagration.
Suppressant Barrier
An isolation system using a suppressant.
Sustainability
Meeting the needs of the present without compromising the ability of future generations to meet their own needs.
System
A collection of people, machines and methods organized to accomplish a set of specific functions.
Task analysis
A human error analysis method that requires breaking down a procedure or overall task into unit tasks and combining this information in the form of event trees. It involves determining the detailed performance required of people and equipment and determining the effects of environmental conditions, malfunctions, and other unexpected events on both.
Technology Package
Information typically provided to a toller by their client delineating specifications for the equipment, chemicals, processing and quality control for a toll. Process safety information is a subset of the technology package.
Technology Steward
A person who is formally appointed to be responsible for maintaining the collective knowledge regarding a process, including process safety-related knowledge.
Technology-driving Criteria
Risk criteria that represent aggressive goals, whether or not experience indicates that such goals are currently attainable. The implication is that the goals will drive the development of the means for meeting the criteria.
Temperature of no return
The temperature at which the rate of heat generation of a reaction or decomposition is equal to the maximum rate of cooling available. Barton and Rogers 1997
Tempered
A term that describes an exothermic reaction involving a volatile reaction mass where the heat losses due to the latent heat of vaporization balances the heat of reaction. In this situation, the temperature and reaction rates do not increase, and hence the reaction does not runaway.
Teratogen
A substance or agent to which exposure of a pregnant female can result in malformations in the fetus. Importance: If a substance is known to be a teratogen, a potential health hazard exists and special protection and precaution sections should be checked on a MSDS.
Thermally Unstable
A material that will undergo an exothermic, self-sustaining or accelerating self-reaction (decomposition, polymerization or rearrangement) when heated to a specific temperature for given conditions of pressure, volume, composition and containment. Thus, the self-reaction can be initiated by thermal energy alone. CCPS 1995b
Thermodynamic Data
Data associated with the aspects of a reaction that are based on the thermodynamic laws of energy, such as Gibb's free energy, and the enthalpy (heat) of reaction.
Threat
Any indication, circumstance, or event with the potential to cause the loss of, or damage to, an asset. Threat can also be defined as the intention and capability of an adversary to undertake actions that would be detrimental to critical assets.
Threshold Limit Value (TLV)
The maximum exposure concentration recommended by the American Conference of Government Industrial Hygienists (ACGIH) for long term exposures.
Threshold Limit Value (TLV)
A term used by ACGIH to express the airborne concentration of a material to which nearly all persons can be exposed day after day without adverse effect. ACGIH expresses TLV's in three ways; TLV-TWA, TLV-STEL, and TLV-CL. TLV's are reviewed and revised annually where necessary by the ACGIH. If a TLV is exceeded, a potential health hazard exists and corrective action is necessary. Also see "Skin" relative to TLV's.
Threshold Limit Value Ceiling (TLV-C)
The concentration in air that should not be exceeded during any part of the working exposure. Ceiling limits may supplement other limits or stand alone. Developed by the American Conference of Governmental Industrial Hygienists (ACGIH).
Threshold Limit Value-Short-Term Exposure Limit (TLV-STEL)
A 15-minute, time -weighted average concentration to which workers may be exposed up to four times per day with at least 60 minutes between successive exposures with no ill effect if the TLV-TWA (see below) is not exceeded. The limit supplements the TLV-TWA where there are recognized acute effects from a substance with toxic effects that result primarily from chronic exposures. Developed by the ACGIH.
Threshold Limit Value-Time-Weighted Average (TLV-TWA)
The time-weighted average concentration limit for a normal 8-hour workday and a 40-hour workweek to which nearly all workers may be repeatedly exposed, day after day, without adverse effect. Developed by the ACGIH.
Time Related Failure
A failure that is primarily due to the degradation over the time that a device or system is in service. For example, the failure of a pump after 2000 hours of continuous service due to wear on the bearings would be considered a time-related failure.
Time To Failure
The time period measured from the moment when equipment installation is complete to the equipment's inability to perform its duty or intended function.
Time to Thermal Runaway
An estimation of the time required for an exothermic reaction, in an adiabatic container, (that is, no heat gain or loss to the environment), to reach the point of thermal runaway. (ASTM E 1445)