Occupational Incident
An incident involving injury to workers.
Off-Site exposure
People, property, or the environment located outside of the site property line that may be impacted by an on-site incident.
Off-Site population
Persons located outside of the site property line that may be impacted by an on-site incident.
Ohm (W)
See Resistance.
Ohm's Law
The Current Density (Amperes per square meter) divided by Electric Field Intensity (volts per meter) is a constant known as Conductivity (Siemens per meter). For small conductors such as wires, the voltage between two points (volts) divided by the current (Amperes) is a constant known as Resistance (Ohm).
Olfactory
Relating to the sense of smell. Importance: The olfactory organ in the nasal cavity is the sensing element that detects odors and transmits information to the brain through the olfactory nerves. This sense of smell is a "built in" vapor detector.
On-Line
A PES is said to be On-Line when it is in active control of a machine or process.
On-Site Personnel
Employees, contractors, visitors, service providers, and others present at the facility.
On-Stream Factor
The fraction of the time that a process unit is operating
Oncogene
an oncogene is a gene that, when mutated or expressed at high levels, helps turn a normal cell into a tumor cell.
Onset Temperature
Defined to be the temperature at which the heat that is released by a reaction can no longer be completely removed from the reaction vessel, and consequently, results in a detectable temperature increase. The onset temperature depends on detection sensitivity, reaction kinetics, on vessel size and on cooling, flow and agitation characteristics. Scaling of onset temperatures and application of "rules of thumb" concerning onset temperatures must be regarded as highly unreliable.
Open Loop Control
A method of control by which signals are transmitted by one or more forward paths, exclusive of any monitoring feedback.
Operating Instructions
A series of sequential written details describing how to operate equipment.
Operating Limits
The values or ranges of values within which the process parameters normally should be maintained when operating. These values are usually associated with preserving product quality or operating the process efficiently; however, they may also incorporate the safe upper and lower limits of the process, or other important limits.
Operating Mode
A phase of operation during the operation and maintenance stages of the life cycle of a facility. Operating modes include start-up, normal operation, shutdown, product transitions, equipment cleaning and decontamination, maintenance, and similar activities.
Operating Pressure
The maximum pressure at which a flame arrester can be used according to its certification.
Operating Procedures
Written, step by step instructions and information necessary to operate equipment, compiled in one document including operating instructions, process descriptions, operating limits, chemical hazards, and safety equipment requirements.
Operating System
Manufacturer's provided functions intended to management of Internal PES interdependent functions.
Operating Time
The amount of time an equipment is in its operating mode.
Operating Window
The parameters (i.e., safe upper and lower limits, run time) under which equipment can function without failure.
Operation
A defined action, namely the act of obtaining a result from one or more operands in accordance with a rule that completely specifies the result for any permissible combination of operands. See instructions.
Operational Discipline (OD)
The performance of all tasks correctly every time.
Individuals demonstrate their commitment to process safety through OD, executing the organization's Conduct of Operation (COO) RBPS Element each and every day.
Operational Interruption
An event in which production rates or product quality is seriously impacted.
Operational Readiness
A PSM program element associated with efforts to ensure that a process is ready for start-up/restart. This element applies to a variety of restart situations, ranging from restart after a brief maintenance outage to restart of a process that has been mothballed for several years.
Operational Reliability
Also known as equipment reliability. The probability that, when operating under stated design conditions, process equipment will perform its intended function adequately for a specified exposure period.
Operator
An individual responsible for monitoring, controlling, and performing tasks as necessary to accomplish the productive activities of a system. Operator is also used in a generic sense to include people who perform a wide range of tasks (e.g., readings, calibration, incidental maintenance, manage loading/unloading, and storage of hazardous materials).
Optimum Mixture
A specific mixture of fuel and oxidant that yields the most rapid combustion at a specific measured quantity or that yields the lowest value of the minimum ignition energy or that produces the maximum deflagration pressure. The optimum mixture is not always the same for each combustion property that is measured.
Oral
Used in or taken into the body through the mouth. Importance: A route of exposure to a hazardous material.
Oral Toxicity
Adverse effects resulting from taking a substance into the body via the mouth. Importance: Ordinarily used to denote effects in experimental animals.
Ordinary Commodity
A term used to describe a material not having special properties or hazards and is categorized by its relative fire hazard.
Organic Peroxide
Any organic compound having a double oxygen or peroxy (O-O) group in its chemical structure. (NFPA 43B)
Organic Peroxide Formulation
A pure organic peroxide or a mixture of one or more organic peroxides with one or more other materials in various combinations and concentrations. Organic Peroxide Formulations can be further classified as follows; Class I - Those formulations that are capable of deflagration but not detonation, Class II - Those formulations that burn very rapidly and that present a severe reactivity hazard, Class III - Those formulations that burn very rapidly and that present a moderate reactivity hazard, Class IV - Those formulations that burn in the same manner as ordinary combustibles and that present a minimal reactivity hazard, and Class V - Those formulations that burn with less intensity than ordinary combustibles or do not sustain combustion and that present no reactivity hazard. (NFPA 43B)
Organizational Culture
The common set of values, behaviors, and norms at all levels in a facility or in the wider organization that affect the operation of the facility.
Organizational Error
A latent management system problem that can result in human error.
Outbreak
The spread of a disease over a short period in a limited geographic area.
Output
The current, voltage, power or driving force delivered by a circuit or Device. Also call Output Value. The terminals or other places where current, voltage, power or driving force may be delivered by a circuit of Device, also called Output Terminals. Data which can be written the Application Program to an Interface between the user program execution function and another functional unit of the PES, also called Program Output.
Output Device
Converts a computer level signal into an industrial level signal. A device that acts to change a physical condition as a result of a (logic) decision (i.e., fuel shutoff valve, steam turbine governor valves, etc.). In computers, a unit which delivers information from the computer to an external device or from internal storage to external storage. The part of a machine which translates the electrical impulses representing data processed by the machine into permanent results such as printed forms, punched cards, magnetic writing on tape or, into control signals for a process. Used to turn real-world devices on and off. Typical output devices are pilot lights, solenoid valves, and motor starters, actuated either electrically or pneumatically.
Outsourced Manufacturing
Providing manufacturing services for a fee by a contractor to a company issuing a contract for those services. Services can include reaction processes, formulation, blending, mixing or size reduction, separation, agglomeration, packaging, repackaging, and others, or a combination of the above.
Over-Adiabatic mode
A quasi-adiabatic mode in which the (small) energy leaks to the environment are overcompensated by input of supplementary energy.
Overdriven Detonation
The unstable condition that exists during a deflagration-to-detonation transition (DDT) before a state of stable detonation is reached. Transition occurs over the length of a few pipe diameters and propagation velocities of up to 2000 m/s have been measured for hydrocarbons in air. This is greater than the speed of sound as measured at the flame front. Overdriven detonations are typically accompanied by side-on pressure ratios (at the pipe wall) in the range 50-100. A severe test for detonation flame arresters is to adjust the run-up distance so the DDT occurs at the flame arrester, subjecting the device to the overdriven detonation impulse.
Overpressure
Any pressure above atmospheric caused by a blast.
Override
A control action which overrides the normal control action to prevent exceeding a process limit. Overrides normally are part of the POCS rather than the ESD. To manually or otherwise deliberately overrule an automatic control system or circuit and thereby render it ineffective. To cancel the influence of an automatic control by means of a manual control.
Override Control
Generally, two control loops connected to a common final control element; one control loop being normally in control, with the second being switched in by some logic element when an abnormal condition occurs so that constant control is maintained. A technique in which more than one controller manipulates a final control element. The technique is used when constraint control is important.
Overriding Process Control
Process control in which any one of several controllers associated with one control valve can be made to override another in accordance with a priority requirement of the process.
Overt Fault
Fault that can be classified as announced, detected, revealed, etc
Owner-user
Person, plant, or corporation legally responsible for the safe operation of a pressure-retaining item (e.g., a pressure vessel).
Oxidant
Any gaseous material that can react with a fuel (either gas, dust, or mist) to produce combustion. Oxygen in air is the most common oxidant.
Oxidant Concentration Reduction
The technique of maintaining the concentration of the oxidant in a closed space below the concentration required for combustion to occur. This is commonly called inerting.
Oxidation
Depending on the context, oxidation can either refer to; a) a reaction in which oxygen combines chemically with another substance, or b) any reaction in which electrons are transferred. For the latter definition, oxidation and reduction always occur simultaneously (redox reactions), and the substance that gains electrons is termed the oxidizing agent. Electrons might also be displaced within a molecule without being completely transferred away from it.
Oxidizer
Any material that readily yields oxygen or other oxidizing gas, or that readily reacts to promote or initiate combustion of combustible materials. Examples of other oxidizing gases include Bromine, Chlorine, and Fluorine. Oxidizers can be further classified as follows; Class 1 - An oxidizer whose primary hazard is that it slightly increases the burning rate but does not cause spontaneous ignition when it comes in contact with combustible materials, Class 2 - An oxidizer that will cause a moderate increase in the burning rate or that causes spontaneous ignition of combustible materials with which it comes in contact, Class 3 - An oxidizer that will cause a severe increase in the burning rate of combustible materials with which it comes in contact or that will undergo vigorous self-sustained decomposition due to contamination or exposure to heat, Class 4 - An oxidizer that can undergo an explosive reaction due to contamination or exposure to thermal or physical shock. In addition, the oxidizer will enhance the burning rate and may cause spontaneous ignition of combustibles. (NFPA 430)