Learn from Experience
CCPS RBPS Pillar IV: Its four Elements are used to identify and correct incident and audit deficiencies, and share lessons learned and best practices with other organizations.
Lessons Learned
Applying knowledge gained from past incidents in current practices.
Lethal Concentration (LC )
A concentration of a substance being tested which will kill a test animal.
Lethal Concentration 50 (LC50)
The concentration of a material in air which, on the basis of laboratory tests, is expected to kill 50% of a group of test animals when administered as a single exposure (usually 1 or 4 hours). The LC50 is expressed as parts of material per million parts of air, by volume (ppm) for gases and vapors, or as micrograms of material per liter of air (micro-g/L) or milligrams of material per cubic meter of air (mg/m3) for dusts and mists, as well as for gases and vapors. Importance: Both are measures of the toxicity of a substance.
Lethal Dose (LD)
A concentration of a substance being tested which will kill a test animal.
Lethal Dose 50 (LD50 )
A single dose of a material which on the basis of laboratory tests is expected to kill 50% of a group of test animals. The LD50 dose is usually expressed as milligrams or grams of material per kilogram of animal body weight (mg/kg or g/kg). Importance: Both are measures of the toxicity of a substance.
Level of Acceptable Practice
Good, successful, common, or best practices in PSM that have evolved, either through common and successful usage, interpretation by regulators, or in clear and measurable reductions in process safety risk, into informal criteria that are used by industry and by regulators to define acceptable practices in PSM.
Level of Concern
The concentration of an airborne chemical above which there may be adverse human health effects experience as a result of a short-term exposure during an episodic release.
Life Cycle
The stages that a physical process or a management system goes through as it proceeds from birth to death. These stages include conception, design, deployment, acquisition, operation, maintenance, decommissioning, and disposal.
Likelihood
A measure of the expected probability or frequency of occurrence of an event. This may be expressed as an event frequency (e.g., events per year), a probability of occurrence during a time interval (e.g., annual probability) or a conditional probability (e.g., probability of occurrence, given that a precursor event has occurred).
Limit Dose
The upper limit dose used in testing (2000 5000 mg/kg)
Limiting Conditions for Operation
Specifications for critical systems that must be operational and critical resources that must be available to start a process or continue normal operation. Critical systems often include fire protection, flares, scrubbers, emergency cooling, and thermal oxidizers; critical resources normally involve staffing levels for operations and other critical functions.
Limiting Oxidant Concentration (LOC)
The concentration of oxidant, in a fuel-oxidant-diluent mixture below which a deflagration cannot occur under specified conditions. The LOC is synonymous with the term Minimum Oxygen Concentration (MOC).
Liquefied Flammable Gas (LFG)
Any flammable gaseous material or mixture of materials that is in liquid form under pressure.
Liquefied Natural Gas (LNG)
A fluid in the liquid state composed predominantly of methane and that can contain minor quantities of ethane, propane, nitrogen, or other components normally found in natural gas. (NFPA 59A)
Liquefied Petroleum Gas (LPG)
Any material having a vapor pressure not exceeding that allowed for commercial propane composed predominantly of the following hydrocarbons, either by themselves or as mixtures: propane, propylene, butane (normal butane or isobutane), and butylenes. (NFPA 58)
Liquid Seal
A device for preventing the passage of flame by passing the gas mixture through a suitable liquid. See Hydraulic Flame Arrester.
Local Exhaust
A system for capturing and exhausting contaminants from the air at the point where the contaminants are produced (welding, grinding, sanding, dispersion operations). See also, "General Exhaust". Importance: Adequate ventilation is necessary to prevent adverse health effects from exposures to hazardous materials and prevent vapor accumulations that cen be a fire hazard.
Localized Incident
An incident whose effect zone is limited to a plant area (e.g., pump fire, small toxic release), and does not extend into the off-site surrounding community.
Location Risk
Individual risk calculated for a particular geographical location, independent of the nature of the population, or whether anyone is likely to be present at a particular location. The calculation assumes a receptor present 24 hours per day, 365 days per year, out of doors, with no protection.
Loop Reactors
Continuous flow reactors that are characterized by the fact that part of the effluent stream is re-supplied to the reactor, either directly or mixed with a reactant supply stream.
Loss Event
Point in time in an abnormal situation when an irreversible physical event occurs that has the potential for loss and harm impacts.
Note: Examples include release of a hazardous material, ignition of flammable vapors or ignitable dust cloud, and overpressurization rupture of a tank or vessel. An incident might involve more than one loss event, such as a flammable liquid spill (first loss event) followed by ignition of a flash fire and pool fire (second loss event) that heats up an adjacent vessel and its contents to the point of rupture (third loss event). Generally synonymous with hazardous event.
Loss of Primary Containment (LOPC)
An unplanned or uncontrolled release of material from primary containment, including non-toxic and non-flammable materials (e.g., steam, hot condensate, nitrogen, compressed CO2 or compressed air).
Low Pressure Tank
A storage tank designed to withstand an internal pressure above 0.5 psig but not more than 15 psig measured at the top of the tank.
Lower Flammable Limit (LFL)
That concentration of a combustible material in air below which ignition will not occur. It is often, interchangeably called Lower Explosive Limit (LEL) and for dusts, the Minimum Explosible Concentration (MEC).
Mach Number, Mw
The ratio of the speed of a flame or blast wave to the speed of sound at ambient temperature and pressure.
Major Incident
An incident whose effect zone, while significant, is still limited to site boundaries (e.g., major fire, spill).
Man Machine Interface (MMI)
The means by which human interaction with the control system is accomplished.
Manage Risk
CCPS RBPS Pillar III: Its nine Elements are used to operate and maintain the facility's process risks, to manage changes to its processes, and to prepare for and safely respond to incidents.
Management of Change
A management system to identify, review, and approve all modifications to equipment, procedures, raw materials, and processing conditions, other than replacement in kind, prior to implementation to help ensure that changes to processes are properly analyzed (for example, for potential adverse impacts), documented, and communicated to employees affected.
Management of Change (MOC)
CCPS RBPS Element 13: This Element is used to verify that changes to the equipment and processes do not increase the risks and that changes in staffing do not reduce company competencies.
Management Review
A PSM program element that provides for the routine evaluation of other PSM program management systems/elements with the objective of determining if the element under review is performing as intended and producing the desired results as efficiently as possible. It is an ongoing due diligence review by management that fills the gap between day-to-day work activities and periodic formal audits.
Management Review and Continuous Improvement
CCPS RBPS Element 20: This Element is used to evaluate whether the process safety program's management systems are performing and producing the results as intended.
Management System
A formally established set of activities designed to produce specific results in a consistent manner on a sustainable basis.
Material Choke
A mass of bulk solids or powders in a rotary valve or screw feeder that prevents a flame from being transmitted.
Material Identification
The name of a chemical. It may be a trade name, chemical name or any other name a chemical is known by. On a MSDS this section also includes the name, address, and emergency telephone number of the distributing chemical company. Importance: Proper identification of a chemical allows an employee to get additional health hazard and safety information.
Maximum Allowable Concentration (MAC)
The maximum concentration in air of a toxic material that the facility and the public authorities having jurisdiction are willing to tolerate at a populated downwind location in the event of a major accident.
Maximum Credible Event (MCE)
A hypothetical explosion, fire or toxic event that has the potential maximum consequence to the occupants of the building under consideration from among the major scenarios evaluated. The major scenarios are realistic and have a reasonable probability of occurrence considering the chemicals, inventories, equipment and piping design, operating conditions, fuel reactivity, process unit geometry, industry incident history, and other factors. Each building may have its own set of MCEs for potential explosion, fire or toxic material release impacts.
Maximum Experimental Safe Gap (MESG):
The maximum gap of the joint between the two parts of the interior chamber of a test apparatus which, when the internal gas mixture is ignited and under specified conditions, prevents ignition of the internal gas mixture through a 25- mm-long joint, for all concentrations of the tested gas or vapor in air. The MESG is a property of the respective gas mixture, but can vary depending on the test apparatus.
Maximum Explosion Pressure, Pmax
The maximum pressure occurring in a closed vessel during the explosion of an explosible dust atmosphere determined under specific test conditions.
Maximum Potential Quantity
The maximum amount of a chemical that can be released from a process containment system. Such a system may be an isolated pressure vessel and associated piping or two or more interconnected and communicating vessels without isolation capability. This quantity is different from and often much greater than both the typical chemical inventory and design maximum inventory for a containment system.
Maximum Pressure After Decomposition
The maximum pressure which is obtained in a closed vessel. This pressure depends on the adiabatic temperature rise and the specific gas production.
Maximum Rate of Explosion Pressure Rise
The maximum value of the pressure rise, dp/dtmax, per unit time during explosions of all explosive atmospheres in the explosible range of a combustible particulate solid in a close vessel under specified test conditions.
Mean Time To Repair (MTTR)
The statistical average of time taken to identify and repair a fault. Normally expressed as t. Dimension (Time).
Measurement and Metrics
CCPS RBPS Element 18: This Element is used to identify process safety metrics based on leading and lagging indicators of the facility's process safety performance.
Mechanical Integrity
An management system focused on ensuring that equipment is designed, installed, and maintained to perform the desired function.
Mechanical Integrity Program
A program to ensure that process equipment and systems are and remain mechanically suitable for operation. It involves inspection, testing, upgrading and repairs of equipment, as well as written procedures to maintain on-going integrity of equipment
Median Lethal Concentration/Dose
Concentration or dose levels, respectively, that kill 50% of exposed laboratory animals in controlled experiments.
Median Lethal Dose , LD50
A statistically derived single dose of a chemical that is expected to cause death in 50% of tested animals.
Methodology
The use of a combination of two or more incident investigation tools to analyze the evidence and determine the root causes of the incident.