CCPS Process Safety Glossary

Refers to PES equipment status. After successful operations as plant approved equipment, the plant wants to elevate the PES to "plant approved safety." This is desired so the plant may utilize its PESs in critical applications where appropriate. The plant meets with the PES producer and jointly develops the following strategy; the producer agrees to provide a plant approved safety controller "spin off" from the plant approved PES, the producer "freezes" the "spin off" PES from any changes without the mutual consent of the plant, All problems with the commercial PES are jointly reviewed (e.g., producer and plant) for impact on the "spin off" PES design, The producer provides all unsafe failure modes of the plant, The producer quantifies each unsafe failure mode for the plant, The plant develops a program to continuously qualify the PES. With the proper development of the above data, the PES is classified "plant approved safety."

A comparison of values for process variables that allows faults in the measurement channels of the safety system to be recognized while the process is still in its normal operating range.

A tubular reactor where the feed is continuously introduced at one end and the products continuously removed from the other end. The concentration / temperature in the reactor is not uniform.

See Equipment, On-Line Pluggage

Rise of plume in elevation above source due to buoyancy or momentum.

A DOT term for liquid, solid, paste, or semisolid substances-other than Class A poisons or irritating materials-which are known (or presumed on the basis of animal tests) to be so toxic to man as to afford a hazard to health during transportation. Importance: If a substance is known to be a poison, health and safety hazards exist and special protection and precaution sections should be checked on the MSDS.

The process by which charges are moved to new locations on a conductor by the creation of an electric field acting on the conductor or the movement of the conductor into the influence of an existing electric field. Electron redistribution occurs instantly in metals because owing to their infinite dielectric constants, internal electric fields cannot exist. The term is also used to describe the response of polar molecules to an electric field.

A chemical reaction in which one or more small molecules combine to form larger molecules. A hazardous polymerization is such a reaction which takes place at a rate which releases large amount of energy.

Any solid material through which gas can flow, and that affords some measure of heat extractive capability and flame quenching by cooling.

The determination of the materials of construction of an equipment item or component (e.g., piping).

The potential (f) any point is measured by the work required to bring unit positive charge from an infinite distance. Potential difference (V) between two points is measured by the work required to carry unit positive charge from one to the other. If the work is expressed in Joules and charge in Coulombs the potential difference is expressed in Volts. In practice, potentials are expressed relative to the earth which by convention is assigned a potential of zero volts. The potential difference between two points is commonly expressed as the difference in their potentials (volts) relative to that of the earth.

The temperature that a parcel of air at height z at temperature T would have if it were brought adiabatically to mean sea level. The gradient, dΘ/dz, is defined such that it equals the vertical gradient of actual temperature, dT/dz, plus 1 C/100 m. Therefore, in a neutral atmosphere, the vertical gradient of potential temperature is 0.0 C/100 m.

Vertical lines bounding and connected to Ladder Diagrams on the left and, optionally, on the right.

A screening tool to collect information that potential clients need to begin the selection processes.

Constant k* in the Arrhenius equation (also called frequency factor). The pre-exponential factor is associated with the frequency of collisions between molecules (entropy) and with the probability that these collisions result in a reaction. (See also Arrhenius equation and Activation energy.)

A systematic and thorough check of a process prior to the introduction of a highly hazardous chemical to a process. The PSSR must confirm the following: Construction and equipment are in accordance with design specifications; Safety, operating, maintenance, and emergency procedures are in place and are adequate; A process hazard analysis has been performed for new facilities and recommendations have been resolved or implemented before startup, and modified facilities meet the management of change requirements; and training of each employee involved in operating a process has been completed.

A process vessel or piping system (length to diameter ratio of less than 5) in which a confined deflagration occurs (as defined in CEN Standard EN 12874).

An equipment maintenance strategy based on measuring the condition of equipment in order to assess whether it will fail during some future period, and then taking appropriate action to avoid the consequences of that failure.

A requirement that explicitly states both "what to do" and "how to do it." For example, the specifications for a full body harness and the requirement that it be used when working at a certain height or within a specified distance from the edge of a roof are prescriptive requirements. (See also Performance-based requirement, which differs from a prescriptive requirement in that a performance-based requirement does not state how the activity should be performed.)

A pressure relief device which is designed to reclose and prevent the further flow of fluid after normal conditions have been restored.

The process of eliminating or preventing the hazards or risks associated with a particular activity. Prevention is sometimes used to describe actions taken in advance to reduce the likelihood of an undesired event.

Maintenance that seeks to reduce the frequency and severity of unplanned shutdowns by establishing a fixed schedule of routine inspection and repairs.

A tank, vessel, pipe, transport vessel or equipment intended to serve as the primary container for, or used for the transfer of, a material. Primary containers may be designed with secondary containment systems to contain or control a release from the primary containment. Secondary containment systems include, but are not limited to, tank dikes, curbing around process equipment, drainage collection systems into segregated oily drain systems, the outer wall of double-walled tanks, etc.

The primary management elements for transportation of hazardous materials, including regulatory compliance, standards and guidelines, operational management, emergency preparedness and response, incident reporting, management of change, and auditing.