PHMSA Pipeline Glossary

Abandoned Pipeline. An abandoned pipeline is one that is no longer being used by any pipeline operating company to transport natural gas or oil. Abandoned pipelines are usually left in the ground but are no longer used or maintained in a usable condition. They are emptied of oil or gas and filled with nitrogen, water, or some other non-flammable filler. Technically speaking: An abandoned pipeline is a pipeline that has been physically separated from its source of gas or hazardous liquid and is no longer maintained under federal regulations. Abandoned pipelines are usually purged of the gas or liquid they transported and refilled with nitrogen, water, or a non-flammable slurry mixture. (Reference 49CFR 192.727 and 49CFR 195.59).#

Abandonment. (1) Abandonment indicates that a company has received approval from the regulator to cease providing a particular service (e.g., to permanently shut down operation of a particular pipeline or facility) under that regulatory agency’s jurisdiction. (2) Abandonment also refers to the process and actions taken by a Company at the end of the useful life of a pipeline or pipeline facility to gain approval from the regulator. This process requires that the Company follow strict guidelines regarding how to prepare the pipeline or facility for permanent cessation of operation. The process often requires that the Company contact the landowners where the pipeline or facility is located and inform them of the planned actions.#

Ability. The capacity to do or act, physically and/or mentally.#

Alternating Current (AC). Alternating current is the common form of electricity that we get in the United States when we plug an appliance into the wall. The form of electricity we get from flashlight batteries is known as direct current. Technically speaking: Alternating current is an electrical current for which the current direction, or positive to negative flow (known as polarity), changes back and forth over a specified period of time. The frequency with which the current direction alternates is measured in cycles per second and is referred to as ‘hertz.’ In North America, the common frequency is 60 hertz, which indicates that the current direction or polarity changes back and forth 60 times per second.#

Accident. An accident is an unplanned occurrence that results in a release of oil or natural gas from the pipeline. Accidents can be expensive and can sometimes result in extensive property loss, environmental insult, injury and, sometimes, even death. Accidents can result from a lot of reasons, but the biggest reason is from damage to the pipeline resulting from digging. Technically speaking: As used in pipeline safety regulations, accidents are failures occurring in liquid pipeline systems for which the pipeline operator must make a report to the Office of Pipeline Safety. Specific criteria defining events that are considered accidents are contained in 49CFR 195.50. Events or failures of similar magnitude related to gas pipelines are considered incidents and are defined in 49CFR 191.3.#

Active Corrosion. Active corrosion is a term that indicates that pipeline corrosion is occurring now and is deteriorating the pipe. Technically speaking: Active corrosion describes an ongoing electro-chemical process in which microscopic metal particles are removed from iron-based materials. Corrosion can occur in moist, aboveground atmospheric conditions but is more prevalent in underground environments. Active corrosion within the pipeline industry is a serious threat to pressure containing structures (i.e., steel pipelines) that, unless controlled, could result in leaks or failures. See Also: Corrosion#

Activity. A specific deed, action, function, or sphere of action.#

Actuator. An actuator is a device that causes a valve to move from the open to the closed position or vice versa. Technically speaking: A component designed to provide the mechanical energy to physically move a connected device. Actuators are used extensively to move valves to their open and closed positions. Valve actuators can be pneumatic, hydraulic, or electric motor driven and can be automated to respond to a remote control signal.#

Aerial River Crossing. An aerial river crossing is a location where a pipeline is suspended to cross a waterway, either by cables over the waterway or attached to the girders of a bridge designed to normally carry vehicle traffic.#

Affects the Operation or Integrity of the Pipeline. Any activity, or omission of an activity, that could directly or indirectly result in a hazard to persons, property or the environment. As used in the safety context of the OQ rule, the phrase indicates activities that could result in an abnormal operating condition that in turn could result in an unsafe operating condition.#

American Gas Association (AGA). From the web site of the American Gas Association: The American Gas Association represents 200 local energy utility companies that deliver natural gas to more than 64 million homes, businesses and industries throughout the United States. AGA’s members' deliver 92 percent of all natural gas provided by the nation’s natural gas utilities. AGA is an advocate for natural gas utility companies and their customers and provides a broad range of programs and services for member natural gas pipelines, marketers, gatherers, international natural gas companies and industry associates. AGA can be contacted at or for more information see www.aga.org.#

Anode. An anode is the pole or terminal from which current flows in a direct current electrical circuit. In an electrical cell or battery(such as a flashlight battery), the anode is recognized as the negative terminal. When a completed circuit exists (as when you turn on the flashlight), electrical current flows from the negative terminal (the anode) through the circuit to the positive terminal (the cathode). Along the way, the current lights the flashlight bulb. As the anode gives up electrons it deteriorates, or corrodes. Technically speaking: An anode is the electrode in an electrochemical corrosion cell where oxidation or corrosion occurs and from which current flows. In a pipeline-related cathodic protection system, the anode is the sacrificial material or electrode having low electrolytic potential. Current flows away from the anode, causing it to corrode.#

Anomaly. An anomaly is something that is identified that normally should not be there. For example, a hole in your sock could be considered an anomaly. A pipeline anomaly is generally thought of as an imperfection in the wall of the pipe. Many pipeline anomalies result during the pipe manufacturing process and don’t affect the performance of the pipeline or its ability to function in a safe manner. Other pipeline anomalies are caused by corrosion or damage to the pipe from outside forces like digging equipment. Some of these can be detrimental to the integrity of the pipeline if not repaired. Technically speaking: An anomaly is a possible deviation from otherwise sound material in a pipe or weld. Indication of an anomaly may be determined by nondestructive examination, such as inline inspection.#

American National Standards Institute (ANSI). From the web site of the American National Standards Institute: The American National Standards Institute (ANSI) is a private, non-profit organization (501(c)3) that administers and coordinates the U.S. voluntary standardization and conformity assessment system. The Institute’s mission is to enhance both the global competitiveness of U.S. business and the U.S. quality of life by promoting and facilitating voluntary consensus standards and conformity assessment systems, and safeguarding their integrity. ANSI can be contacted at or for more information see www.ansi.org.#

Abnormal Operating Conditions (AOC). As defined in §§ 192.803 and 195.503. Note: To be qualified, an individual must be able to properly perform assigned covered task(s) and be able to recognize and react appropriately to any AOC that may (reasonably be expected to) be encountered while performing the covered task – whether the condition arises as a direct result of his/her work performance (e.g., be specific to the covered task being performed) or not (e.g., be generic in nature, but still observable because the individual is present on site).#

Association of Oil Pipelines (AOPL). From the web site of the Association of Oil Pipelines: The Association of Oil Pipe Lines (AOPL) is an unincorporated nonprofit organization started in 1947. As a trade association, the AOPL: - Acts as an information clearinghouse for the public, the media and the pipeline industry. - Provides coordination and leadership for the industry’s ongoing Joint Environmental Safety Initiative. - Represents common carrier crude and product petroleum pipelines in Congress, before regulatory agencies, and in the federal courts. The AOPL can be contacted at or for more information see www.aopl.org.#

American Petroleum Institute (API). From the web site of the American Petroleum Institute: The American Petroleum Institute (API) is the major national trade association representing the entire petroleum industry: exploration and production, transportation, refining, and marketing. With headquarters in Washington, D.C., and petroleum councils in 33 states, it is a forum for all parts of the oil and natural gas industry to pursue priority public policy objectives and advance the interests of the industry in a legally appropriate manner. API can be contacted at or for more information see www.api.org.#

Accountable Pipeline Safety and Partnership Act (APSPA). The Accountable Pipeline Safety and Partnership Act of 1996 (APSPA) was to reduce risk to public safety and the environment associated with pipeline transportation of natural gas and hazardous liquids, and for other purposes. In part, the APSPA required the U.S. Department of Transportation to conduct a four-year Risk Management Demonstration Program (RMDP) in which pipeline operating companies were selected to demonstrate pipeline risk management processes.#

American Society of Mechanical Engineers (ASME). From the web site of the American Society of Mechanical Engineers: The American Society of Mechanical Engineers (ASME) conducts one of the world’s largest technical publishing operations, holds some 30 technical conferences and 200 professional development courses each year, and sets many industrial and manufacturing standards. Founded in 1880 as the American Society of Mechanical Engineers, today ASME International is a nonprofit educational and technical organization serving a worldwide membership. ASME can be contacted at 1- or for more information see www.asme.org.#

ASTM International. From the web site of the ASTM International: Founded in 1898, ASTM International is a not-for-profit organization that provides a global forum for the development and publication of voluntary consensus standards for materials, products, systems, and services. Formerly known as the American Society for Testing and Materials, ASTM International provides standards that are accepted and used in research and development, product testing, quality systems, and commercial transactions around the globe. ASTM International can be reached at or for more information see www.astm.org.#

Atmospheric Corrosion. Atmospheric corrosion is a chemical attack on exposed metal surfaces by elements in the air. A common form of atmospheric corrosion is known as rust. Rust commonly occurs when a ferrous metal (iron), such as a nail, is exposed to moist air. Technically speaking: Atmospheric corrosion affects aboveground pipeline or components that are exposed to the atmosphere and is a chemical change in the pipe or component material resulting from the material’s interaction with the atmosphere. Most commonly this interaction causes the oxidation of metal. See Also: Corrosion#

Automatic Control Valve. An automatic control valve is a valve that controls the flow of oil or natural gas in a pipeline and that opens or closes automatically in response to some signal. Technically speaking: An automatic control valve is one that closes automatically in response to a pressure loss or a flow rate increase, either of which exceeds a predetermined set point.#

Backfilling. Backfilling means filling the dirt back into a ditch or hole you previously dug. Technically speaking: Backfilling is the process of filling the trench where a newly constructed or recently unearthed pipeline is installed. Adequate fill material is provided and compacted around the pipe to completely fill the excavation and to ensure that the pipe is properly supported and not subjected to added stresses due to soil subsidence or movement.#

Barrel. (1) A barrel is a standard measure of a volume of oil and is equal to 42 gallons. (2) A beginning point or end point of a pipeline is sometimes referred to as a barrel. Barrels are designed with opening closures similar to doors that allow the pipeline operator to insert inline inspection tools into the pipelines. Barrels where pigs are inserted into the pipeline are called launchers and barrels where pigs are retrieved and taken out of the pipeline are called receivers. Reference 49CFR 194.5 and 49CFR 195.2#

Baseline Assessment Plan. A baseline assessment plan (BAP) is the plan a pipeline operator must develop to assess the integrity of all of the lines included in its integrity management program. The BAP must show when each line is to be assessed and the assessment method the operator will use. Technically speaking: The baseline assessment plan is an integral part of an operator’s pipeline integrity management program. The BAP must, as a minimum: 1) identify all segments of a pipeline system that could impact a High Consequence Area (HCA); 2) identify the specific integrity assessment method(s) to be conducted on those segments; 3) specify the schedule by which those integrity assessments will be performed; and 4) provide the technical justification for the selection of the integrity assessment method(s) and the risk basis for establishing the assessment schedule. (Reference 49CFR 195.452).#

Bell Hole. A bell hole is a hole dug into the ground over or alongside a pipeline to allow the line to be examined and to provide room for workmen to perform maintenance on the pipeline. In a broader sense it is any hole, other than a ditch, that is opened for pipeline work. Technically speaking: A bell hole is an excavation made to permit a survey, inspection, maintenance, repair, or replacement of pipe sections. It is so called because of its upside-down bell shape, wide at the top and narrowing to a smaller diameter around the pipeline to be examined. The walls of the hole are angled according to OSHA rules to prevent cave-ins and risks to worker safety.#

Bend Radius. Bend radius is the measurement of the radius of a bend in a pipeline. Bends can be included in the manufacture of the pipe or created in the field during construction and installation of a pipeline.#

Bureau of Land Management (BLM). From the web site of the Bureau of Land Management: The Bureau of Land Management (BLM) is an agency in the Department of Interior, in the US Government. The BLM manages 264 million acres of surface acres of public lands located primarily in the 12 Western States, including Alaska. The agency manages an additional 300 million acres of below ground mineral estate located throughout the country. The BLM administers public lands within a framework of numerous laws. The most comprehensive of these is the Federal Land Policy and Management Act of 1976 (FLPMA). All Bureau policies, procedures and management actions must be consistent with FLPMA and the other laws that govern use of the public lands. It is the mission of the Bureau of Land Management to sustain the health, diversity and productivity of the public lands for the use and enjoyment of present and future generations.#

Block Valve. A block valve is a mechanical device (valve) installed in a pipeline that can be closed to block the flow of oil or gas through the line. Technically speaking: A block valve is a valve used to stop the flow of product through a pipeline and isolate a segment of the pipeline system or a component of the system.#

Branch Service Line. A branch service line is a service line in a natural gas distribution system that branches off of a main line or another service line. Technically speaking: In natural gas distribution systems, branch service line is a line that branches off of another service line; thereby changing the classification upstream of the branch point from a service line to a main.#

Breakout Tank. A breakout tank is a tank used to temporarily store oil in a pipeline system. Technically speaking: A breakout tank is a tank used to relieve surges in a hazardous liquid pipeline system or to receive and store hazardous liquids transported by the pipeline for later re-injection and continued transportation by the pipeline. Reference 49CFR 194.5 and 49CFR 195.2#

Buckle. A buckle is an anomaly that represents a partial collapse of the pipe wall and is usually caused by excessive bending or curvature being applied to the pipe. Depending on the severity of the buckle, it may represent an undesirable anomaly that can cause localized stress concentrations and must be repaired. Technically speaking: A buckle is a partial collapse of the pipe wall due to excessive bending associated with soil instability, landslides, washouts, frost heaves, earthquakes, etc. Buckles can also occur in pipeline construction during a field bending operation using a side boom. Buckles cause localized stress concentrations and must not be installed in new construction or, if found, must be removed from existing systems. See also: Wrinkle#

Bulkhead. A bulkhead is a wall built or installed along a coastline or waterway to protect an adjacent pipeline from washout or soil erosion.#

Caliper Tool. A caliper tool is an adjustable measuring tool that can be used to measure the thickness of an object, the diameter of a circle, or the distance between two surfaces. Hi-tech variations of these tools are used to measure the inside diameter of a pipe and record variations in that diameter. Technically speaking: A caliper tool is an inline inspection device that measures deviations in the geometry of a pipeline’s internal surface. A caliper tool uses a set of mechanical fingers that ride against the inside diameter of the pipe and record deviations caused by the relative movement of these fingers as the tool passes through the pipe#

Corrective Action Order (CAO). PHMSA may issue a Corrective Action Order if it determines that a particular pipeline represents a serious hazard to life, property, or the environment. They usually address urgent situations arising out of an accident, spill, or other significant, immediate, or imminent safety or environmental concern. In a Corrective Action Order, PHMSA identifies actions that must be taken by the operator to assure safe operation. These actions may include the shutdown of a pipeline or operation at reduced pressure, physical inspection or testing of the pipeline, repair or replacement of defective pipeline segments, and similar measures. Corrective Action Orders are described in 49 CFR 190.233.#

Carbon Steel. All steel is formed as an alloy of iron and carbon and may contain small quantities of other elements. However, ‘carbon steel’ is steel for which the content of elements other than iron is not specified and the content of manganese or copper does not exceed specified amounts. Technically speaking: All steel is formed by alloying iron with carbon. Steel is commonly considered to be carbon steel when: (1) no minimum content is specified or required for aluminum, boron, chromium, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium, or any other element added to obtain a desired alloying effect; (2) the specified minimum content does not exceed 1.65% for manganese or 0.60% for copper. All carbon steels may contain small quantities of unspecified residual elements unavoidably retained from raw materials. These elements (copper, nickel, molybdenum, chromium, etc.#

Cast Iron. Cast iron is iron that is cast (heated to melting and poured into molds) and in which the carbon molecules in the metal are not bonded with the iron molecules. Cast iron is brittle and can crack. It is not suitable for high-pressure applications. Technically speaking: Cast iron applies to gray cast iron, which is a cast ferrous material in which a major part of the carbon content occurs as free carbon in the form of flakes interspersed through the metal. Because the carbon flakes do not bond with the ferrous material on the molecular level, the metal is brittle and susceptible to stress cracking under high-pressure situations. Many older, low-pressure gas systems were constructed with cast iron pipe. In 2011 PHMSA appealed to all pipeline safety stakeholders for help to increase pipeline safety awareness and repair, rehabilitate, and replace aging infrastructure.#

Cathode. Simply speaking, a cathode is the pole or terminal to which current flows in a direct current electrical circuit. In an electrical cell or battery (such as a flashlight battery), the cathode is recognized as the positive terminal. When a completed circuit exists (as when you turn on the flashlight), electrical current flows from the negative terminal (the anode) through the circuit to the positive terminal (the cathode). Along the way, the current lights the flashlight bulb. Technically speaking: A cathode is a component of an electrochemical corrosion cell. It is the metal that attracts ions and gains mass through the corrosion process. In a cathodic protection system, the pipeline acts as the cathode and is protected from corrosion by the sacrificial activity of the anode.#

Cathodic Protection Monitoring or Survey. Monitoring cathodic protection systems is an activity performed by pipeline operators to assess the adequacy of cathodic protection on the pipeline.#

Centering. Centering is a method of determining the approximate location of a pipeline leak. Technically speaking: The process of approximating the location of a pipeline leak. Centering can be done manually using gas detection equipment, such as acoustical equipment, or through a more sophisticated SCADA-based leak detection system using mathematical modeling of critical pressures, temperatures, flow-rates, etc. to predict volume loss and location estimates.#

Centrifugal Compressor. Centrifugal compressors are pumps that are used to boost the internal pressure of gas pipelines. They are usually placed at key locations along the pipeline systems.#

Council on Environmental Quality (CEQ). From the web site of the Council On Environmental Quality: The Council on Environmental Quality (CEQ) coordinates federal environmental efforts and works closely with agencies and other White House offices in the development of environmental policies and initiatives. The Council’s Chair, who is appointed by the President with the advice and consent of the Senate, serves as the principal environmental policy adviser to the President and Vice President. In addition, CEQ reports annually to the President on the state of the environment; oversees federal agency implementation of the environmental impact assessment process; and acts as a referee when agencies disagree over the adequacy of such assessments. CEQ was established by Congress within the Executive Office of the President with passage of the National Environmental Policy Act of 1969.#

Code of Federal Regulations (CFR). Federal regulations are published systematically (codified) in the Code of Federal Regulations (CFR). The CFR is the official compilation of the federal regulations of general applicability and legal effect. The CFR is divided into 50 titles that represent broad topical areas that are subject to federal regulation. For example, Title 49 covers Transportation, Title 10 covers Energy, and Title 34 covers Education. Each title is divided into volumes, sections, parts, or chapters. Those may be further divided and grouped into subtitles, chapters, subchapters, parts, subparts, or divisions. Specific chapters or parts within each title are devoted to agencies having regulatory authority in that major area, in which all of that agency’s regulations are codified.#

Common Ground Alliance (CGA). From the web site of the Common Ground Alliance: The Common Ground Alliance (CGA) is a nonprofit organization dedicated to shared responsibility in damage prevention and promotion of the damage prevention Best Practices identified in the Common Ground Study Report. The purpose of the CGA is to ensure public safety, environmental protection, and the integrity of services by promoting effective damage prevention practices. The CGA can be reached at or for more information see www.commongroundalliance.com.#

Check Valve. A check valve is a valve that allows liquids or gases in a pipeline to flow in one direction but closes to prevent flow in the opposite direction. These types of valves are used extensively in the pipeline industry to prevent reverse-flow or back-flow in the event of a pipeline leak or abnormal operating occurrence.#

Close Interval Surveys (CIS). A close interval survey is a method of testing corrosion protection systems on pipelines. It involves inspection and electrical testing of the corrosion protection system every two to three feet along the pipeline to confirm the status of the protection system and to help identify mechanical damage to the pipeline.#

Class Location. Class location refers to a regulatory designation for natural gas transmission pipelines that indicates the level of human population within a certain distance on either side of the line. The class location of a pipeline is a factor in determining the maximum allowable operating pressure of the pipeline. Technically speaking: Class location is a criterion for gas pipeline design set by the U.S. Code of Federal Regulations, 49CFR 192.5. A class location is based on the number and type of buildings intended for human occupancy that are situated in an area that extends 220 yd (200 m) on either side of the centerline of any continuous 1.0-mile (1.6-km) length of a gas pipeline. Class locations are specified as Class 1, 2, 3 or 4.#

Cleaning Pig. A cleaning pig is a device that is placed inside a pipeline to remove unwanted debris from the inside of the pipeline. The pig can be drawn or pushed through a pipeline but often is moved through the line as a result of the flow of the product in the line. A type of utility pig, a cleaning pig uses cups, scrapers, or brushes to remove dirt, rust, mill scale, and other debris from the internal surface of a pipeline. Cleaning pigs are used periodically or as necessary to increase the operating efficiency of a pipeline or to facilitate inspection of the pipeline.#

Carbon Dioxide (CO2). Carbon dioxide is a naturally occurring gas that is transported and used in the petroleum industry. Carbon dioxide is a heavy gas that can displace breathing air and breathing carbon dioxide can be hazardous to your health. Technically speaking: Carbon dioxide is a naturally occurring gas consisting of molecules formed of one carbon and two oxygen atoms. Carbon dioxide is a heavy gas that is transported by pipeline as a compressed fluid consisting of more than 90% carbon dioxide molecules. If released into the atmosphere from a pipeline leak carbon dioxide is considered hazardous due to its ability to displace breathing air. (Reference 49CFR 195.2)#

Commercially Navigable Waterway. A commercially navigable waterway is a waterway where there is a substantial likelihood of commercial navigation. These waterways are identified in the National Waterways Network, a geographic database created by the National Waterways GIS Design Committee. The database is available from the U. S. Department of Transportation, Bureau of Transportation Statistics.#

Communicate. To convey information about; make known; to reveal clearly.#

Compliance. Activity(ies) in accordance with a rule.#

Component. A component in a pipeline system is any part of the system that is subject to the internal system pressure. System components must be designed to not leak; thereby assuring that the oil or gas is not released from the system and that the system operating pressure is maintained. Examples of components include the pipe, valves, flanges and other fittings.#

Compressor Stations. Compressor Stations are facilities located along a natural gas pipeline which house and protect compressors. Compressors are used to compress (or pump) the gas to move it through the system. Compressor stations are strategically placed along the pipeline to boost the system pressure to maintain required flow rates.#

Confirmation Digs. Confirmation digs are excavations performed at selected pipeline locations to expose the pipe to allow confirmation of the existence and characteristics of potential anomalies in the pipe wall that were identified by inline inspection techniques.#

Consensus Standards. Consensus standards are standards for performance that are established in open and voluntary forums by consensus of parties affected by the standards. These standards provide the best available professional guidance related to specific subjects. National consensus standards reflect the professional knowledge and judgment of people having appropriate experience, training, and education in the subjects to which the standards apply. The National Technology Transfer and Advancement Act (Public Law 104-113) mandates that Federal departments and agencies use voluntary consensus standards in place of Government standards wherever practical. There are consensus standards that apply to virtually all aspects of energy transportation pipeline design, construction, and operation.#

Consent Order. Once PHMSA has issued a Corrective Action Order or given notice to an operator of other proposed enforcement action, PHMSA and the operator may occasionally agree to the issuance of a Consent Order in lieu of a Compliance Order or the imposition of civil penalties. In a Consent Order, the operator agrees to the jurisdictional facts of the case and agrees to implement the specific actions in the Consent Order by the required deadlines. Should the operator not comply with the Consent Order terms, PHMSA can enforce its terms as the parties have agreed. Consent Orders can thus offer various advantages over more traditional enforcement remedies. They can expedite the resolution of cases, facilitate future enforcement action by PHMSA, and require operators to take additional measures beyond those required by regulation, thus achieving a greater level of safety.#

Consequence. A consequence is the result of some action or condition or series of events. A consequence may be observed directly, determined by investigation after an action or series of events has occurred, or determined by evaluation and analyses as the logical result of a postulated action or condition or series of events. Technically speaking: A consequence is often noted as the cumulative, undesirable result of an accident. Consequences are usually measured in health and safety effects, environmental impacts, loss of property and/or business costs. Consequence descriptions may be qualitative or quantitative estimates of the effects of an accident.#

Consequence Analysis. A consequence analysis is the evaluation or analyses of a postulated action or condition or series of events to determine the logical result. A consequence analysis may be performed to determine the expected effects of events leading to a pipeline accident, independent of the likelihood of such events occurring.#

Continual Evaluation of Pipeline Integrity. Under pipeline integrity management regulations, pipeline operators must develop programs for conducting periodic pipeline integrity assessments and evaluating the results of those assessments to understand current pipeline conditions and identify integrity issues. This periodic assessment and evaluation cycle is recognized as a continual evaluation of pipeline integrity.#

Contributed. Determined to be a factor.#

Contributed to. A judgment by designated operator personnel, that the action or inaction of an individual(s) was a factor in the occurrence of an incident/accident.#

Corrosion. Corrosion is the deterioration of a material, usually a metal, which results from a reaction with its environment. Common rust is an example of corrosion of iron. Steel pipe is subject to corrosion damage. See Also: Active Corrosion, Atmospheric Corrosion, Corrosion Fatigue, Non-active Corrosion, Pitting, Selective Corrosion, Stress Corrosion Cracking (SCC), Uniform Corrosion#

Corrosion Fatigue. Corrosion fatigue is a reduction of the durability of a pipe due to corrosion. Technically speaking: Fatigue is a weakening of a material caused by the repeated application and removal of stress. For example, if you bend a piece of metal back and forth repeatedly in the same spot, fatigue will result at the bend location and will weaken the metal until it eventually breaks. Pipelines experience fatigue as a result of periodic increases (application of stress) and decreases (removal of stress) in operating pressures. Because fatigue can cause a failure to occur at stress levels well below those that a material can withstand in a single, non-repetitive loading, materials that must resist repeated stress cycles must be specially designed for this service. Durability is the ability of the material to resist fatigue.#

Cost/Benefit Analysis. A cost/benefit analysis is an evaluation and comparison of an activity’s cost to its perceived benefits. Technically speaking: A cost benefit analysis a determination and comparison of the expected costs to implement a proposed activity and the expected safety, environmental, or other benefits resulting from the activity. Cost/benefit analysis can be used to establish priorities among various activities, to compare and select among alternate ways of accomplishing an objective, or to decide whether a proposed activity should be implemented. The various expected benefits of a proposed activity are often translated into dollar values (‘monetized’) to allow different types of benefits to be combined and then compared with the costs of achieving these benefits.#

Cost/Benefit Ratio. A cost/benefit ratio is the ratio of the cost of performing an activity compared to the perceived benefits of performing it. Technically speaking: The monetary costs required to complete a proposed activity (for example, replacing a section of pipe) divided by the monetized value of the benefits expected to be derived from that activity (for example, decreased pipe leak rate or likelihood of rupture). Cost/benefit ratios are usually used as an input to, but not sole determinate of, a decision to proceed with the proposed activity.#

Covered Task. As defined in § 192.801 and § 195.501.#

Cathodic Protection (CP). Cathodic protection is a method of protecting metallic pipelines from corrosion. Technically speaking: Cathodic protection is a method of corrosion prevention in which the pipeline is allowed or made to act as the cathode in an electrochemical corrosion cell. A sacrificial anode having a lower electrolytic potential than the pipe is provided to complete the cell. The same electrolytic action that causes the anode to corrode protects the cathode (the pipeline or other component) from corroding.#

Computational Pipeline Monitoring (CPM). Computational Pipeline Monitoring is a method of monitoring the operation of a pipeline system. It makes use of a software-based monitoring tool that alerts the pipeline dispatcher of possible pipeline operating abnormalities that could indicate a commodity release.#

Cracks. Cracks are undesired openings or separations in a normally rigid material, such as a pipe wall. Often cracks are found only on the surface and do not fully penetrate the pipe wall. Using specialized equipment, cracks that may not appear on the surface of the pipe can be found within the thickness of the pipe wall. Regardless, cracks that don’t fully penetrate the pipe wall and result in leaks are considered critical anomalies that could propagate into a leak or failure and must be repaired. Technically speaking: Cracks in line pipe are separations in the molecular structure of the base metal and form as a result of improper manufacturing or operational stresses. Cracks are detrimental to the pipe’s pressure restraining capabilities and can propagate into complete failure or rupture zones.#

Criterion. A standard upon which a judgment is based.#

Critical Bond. A critical bond is a wire connecting one pipeline to another, nearby pipeline to help prevent corrosion. Technically speaking: Buried pipelines in close proximity or crossing over/under one another will often have different levels of cathodic protection and thus a strong possibility of different electrical potentials (voltage differences). If the soil resistance path between the pipelines is low, electrical currents will flow from one pipeline to the other. The pipeline with the current leaving will experience metal loss or corrosion. To prevent this occurrence, pipeline companies electrically connect or bond their pipes to one another using a copper wire. The wire provides an electrical path for the current to flow through rather than allowing current to flow off the pipe and into the soil, thus eliminating corrosion. The connecting wire is referred to as an electrical bond.#

Critical Defect. A critical defect is an identified pipeline defect for which analysis indicates immediate attention is required.#

Crude Oil. Crude oil is oil that is extracted from the ground before it is refined into usable products, such as gasoline. Technically speaking: Crude oil is the raw liquid petroleum product extracted from oil wells. It is a mixture of thousands of chemicals and compounds, primarily hydrocarbons. Crude oil must be broken down into its various components by distillation before these chemicals and compounds can be used as fuels or converted to more valuable products. Crude oil is classified as either ‘sweet crude’ (sulfur content less than 0.5%) or ‘sour crude,’ (at least 2.5% sulfur).#

Curb Valve. A curb valve is a valve installed in a natural gas service line and is used to shut off the gas supply to a building. Curb valves are installed underground at or near the property line, normally with protective curb boxes or standpipes installed over or around the valve. They are operated by use of a removable key or specialized wrench.#

Current. (1) Current is the measure of the flow of electrons in an electrical circuit. Current is usually measured in engineering units called amperes, which indicate how much electrical energy is flowing through the circuit. (2) Belonging to the present time; now in progress.#

Damage Prevention Initiatives. In addition to enforcing Damage Prevention Regulations in the Code of Federal Regulations, the Office of Pipeline Safety has undertaken a variety of other initiatives to promote pipeline damage prevention. These initiatives, some of which involve collaboration with various stakeholder industry groups, promote public awareness of pipelines and other underground facilities; education of the public and emergency officials, excavators, emergency responders, legislators and other stakeholders on how to recognize and respond to pipeline leaks; and other aspects of pipeline safety. Some more notable recent efforts include: Dig Safely, Common Ground Alliance (CGA), and the One-Call Systems Study (OCSS).#

Damage Prevention Regulations. Damage prevention regulations for pipelines are found in the Code of Federal Regulations. They require pipeline operators to implement programs to prevent damage to buried pipelines from excavation activities. The regulations specify requirements for operators to interact with the public near pipelines and with companies/persons likely to perform excavation near pipelines. Pipeline operators may comply with some of the regulatory requirements for damage prevention by participating in public service programs such as a one-call system. However, such participation does not relieve the operator of the responsibility of compliance to the regulation.#

Direct Current (DC). Direct current refers to an electrical current that flows in only one direction. As an example, direct current is the form of electricity we get from flashlight batteries. Technically speaking: Direct current is a form of electricity in which the polarity or direction of the current stays constant with respect to time (as opposed to alternating current). Direct current is typically used in impressed current cathodic protection systems because of its ability to maintain a constant polarity for the pipe’s protection.#

Defect. A defect is an imperfection that can cause an inadequacy or failure. In pipelines, certain types of defects have been known to cause failures. When defects are found in a pipeline that are characteristic of problem defects, they must be evaluated and, if necessary, repaired or removed to prevent future failures. Technically speaking: A defect is an imperfection of sufficient magnitude in a pipeline that it should be analyzed using a recognized and approved engineering procedure, such as ASME B31G. Analysis determines if the defect is severe enough to require removal or repair, depending on prescribed operating requirements. Examples of defects include dents, corrosion pits, and cracks.#

Demonstrate. Provide tangible evidence.#

Dent. A dent is a depression in the pipeline surface caused by pressure or a blow. A dent does not reduce the thickness of the pipe wall. Dents are usually local depressions caused by outside mechanical force, such as the pipe resting on a rock or being hit by a backhoe. Pipeline repairs or replacement may be needed depending on the severity of the deformation.#

Destructive Testing. Destructive testing refers to testing of a specimen in which the specimen is rendered unusable (i.e., destroyed) for its intended or practical use. Destructive tests are typically conducted on representative specimens to prove the strength or chemical characteristics of the sample piece.#

Determine. Determine means to decide or settle conclusively and authoritatively. As used in pipeline safety regulations, determine means to establish that a condition actually or definitely exists, after evaluating by either investigation or calculation the potential for the condition to exist. There is a difference between identifying a potential condition and determining that the condition actually exists. See also Discovery of a Condition.#

Dig Safely. Dig Safely is the nationally recognized campaign to enhance safety, environmental protection, and service reliability by reducing underground facility damage. This damage prevention education and awareness program is used by pipeline companies, one-call centers, and others throughout the country. Dig Safely was developed through the joint efforts of the Office of Pipeline Safety and various damage prevention stakeholder organizations. Dig Safely is now within the purview of the Common Ground Alliance (CGA). The CGA can be reached at or for more information see www.commongroundalliance.com.#

Direct. To take authoritative charge of or supervise; to control, order or command.#

Direct Assessment. Direct assessment refers to a method of evaluating the integrity of a pipeline. Various indirect measurement tools are used to determine locations on the pipeline that may require direct examination to verify pipeline integrity. These locations are then excavated and examined to verify that the pipe is in good condition or to make necessary repairs.#

Direct Observation. Observation of an unqualified individual(s) during the performance of a covered task by an individual who is qualified to perform the task at hand. The observer must be in direct visual and verbal contact with the individual(s) and must be able to take immediate and effective corrective action if incorrect procedures or abnormal operating conditions are observed.#

Disbonded Coating. Disbonded coating refers to any loss of bond or adhesion between the protective coating applied to the outside of a steel pipe and the pipe itself. Disbondment can result from adhesive failure, chemical attack, mechanical damage, hydrogen concentrations or other causes.#

Discovery of a Condition. Discovery is the instance of discovering something or recognizing it for the first time. Technically speaking: Under the Pipeline Integrity Management requirements found in the Code of Federal Regulations, ‘discovery’ refers to the point in time at which an operator has adequate information about a defect, anomaly, or other pipeline feature to determine the need for repair. Depending on the circumstances, adequate information may be available when a preliminary inline inspection (ILI) report is completed, following an analytical evaluation that integrates information from other sources, following excavation of the pipeline and observation of a condition, or following receipt of the final ILI report.#

Distribution Line. A distribution line is a line used to supply natural gas to the consumer. A distribution line is located in a network of piping located downstream of a natural gas transmission line. As defined in natural gas pipeline safety regulations, a distribution line is a pipeline other than a gathering or transmission line.#

Document. Prepare a retrievable record.#

Department of Transportation (DOT). From the DOT web site: A cabinet-level department of the executive branch of the federal government. The DOT is headed by the Secretary of Transportation, who is appointed by the President and confirmed by the Senate. The DOT is responsible for government involvement in all types of transportation, including transportation of hazardous liquids and natural gas by pipeline. Within the DOT, the Office of Pipeline Safety, part of the Research and Development Administration, is responsible for regulating pipeline safety. The Department of Transportation can be contacted at or for more information see www.dot.gov. dot#

Double Submerged Arc Welded (DSAW) Pipe. Double-submerged arc-welded pipe is pipe produced from a flat piece of steel of which the edges are rolled together, to create a tube or pipe, and then connected or ‘fused’ together utilizing a specific process known as double-submerged arc-welding. Technically speaking: Double-submerged arc-welded pipe is pipe having a longitudinal or spiral seam produced by at least two weld passes, including at least one pass each on the inside and outside of the pipe. The molten weld metal is shielded by a blanket of granular, fusible material used to reduce the impurities (slag) introduced from the surrounding air. Mechanical pressure is not used and filler metal for the inside and outside welds is obtained from the electrode(s). Use of DSAW in pipe fabrication is required by some pipe design standards, e.g., ASTM A-381, API 5L.#

Durability. Durability refers to the ability of a material to resist wear and tear. Technically speaking: Durability is the ability of a material to resist fatigue, which is a weakening of the material resulting from the repeated application and removal of stress. Pipelines experience fatigue as a result of periodic increases (application of stress) and decreases (removal of stress) in operating pressures. Durability refers to the pipe’s ability to resist fatigue and continue to perform its required function.#

Environmental Assessment (EA). An environmental assessment is an evaluation required by the National Environmental Policy Act (NEPA) to determine whether a Federal action (major projects or legislative proposals) would significantly affect the environment. If the Environmental Assessment concludes that the Federal action could significantly affect the environment, a more detailed Environmental Impact Statement must be produced. If not, a Finding of No Significant Impact (FONSI) is filed.#

Easement. An easement is an acquired privilege or right, such as a right-of-way, afforded a person or company to make limited use of another person’s or company’s real property. For example, the municipal water company may have an easement across your property for the purpose of installing and maintaining a water line. Similarly, oil and natural gas pipeline companies acquire easements from property owners to establish rights-of-way for construction and operation of their pipelines.#

Emergency Flow Restricting Device (EFRD). An emergency flow restricting device is a device used to restrict or limit the amount of oil or gas that can release out of a leak or break in a pipeline. Check valves and remote control valves are types of EFRDs.#

Environmental Impact Statement (EIS). An Environmental Impact Statement is a document required of federal agencies, by the National Environmental Policy Act (NEPA), for major projects or legislative proposals significantly affecting the environment. A tool for decision making, it describes the positive and negative effects of the undertaking and cites alternative actions. Technically speaking: An Environmental Impact Statement is preceded and determined by an environmental assessment.#

Electric Resistance Weld (ERW) Pipe. Electric resistance weld (ERW) pipe is pipe produced from a flat piece of steel of which the edges are rolled together, to create a tube or pipe, and then connected or ‘fused’ together utilizing a specific process known as electric resistance welding. Technically speaking: Electric resistance welding is a method used for making pipe in which the two edges of a curved plate of metal are heated by passing an electric current through them and the edges are then forced together to create a solid longitudinal weld, thus turning the plate into a section of pipe. Prior to 1970, much ERW welded pipe was produced using low frequency welding technology that can be more prone to seam failure than the high frequency welding technology adopted by most pipe manufacturers by 1970.#

Emergency Response. Operator qualification requirements for emergency response are limited to that portion of the response performed on the pipeline facility, rather than at offsite locations remote from the facility (e.g., deploying booms miles away is not a “covered task”). Fire departments and other public responders are not required to be qualified and (if not qualified) must not perform covered operations or maintenance tasks on the pipeline facility. All other individuals employed by the operator shall be qualified to perform their assigned covered tasks or shall be under the direct observation of a qualified individual. Covered emergency response tasks are those tasks listed in § 192.615(a) and § 195.402(e) that meet the four part test specified in § 192.801 and § 195.501.#

Emergency Response Personnel. Emergency response personnel are persons engaged in the immediate response to accidents and emergencies. Emergency response personnel can include firefighters, police/sheriffs, medical personnel, civil defense and emergency management personnel, and, sometimes, military, manufacturing and transportation personnel. Emergency response personnel are sometimes referred to as ‘emergency responders’ and ‘first responders.’#

Encroachment. Encroachment refers to the unauthorized use of a right-of-way in violation of the terms by which the right-of-way was established (e.g., easement).#

Environmentally Sensitive Area (ESA). An environmentally sensitive area is an area of environmental importance that is sensitive to environmental damage from a liquid pipeline release. (Reference 49CFR 195.2).#

Evaluation. As defined in § 192.803 and § 195.503. Note: Any evaluation of an individual’s qualifications must follow an objective, consistent process that documents the individual’s ability to perform the covered task, including the ability to recognize and react to AOCs.#

Evaluator. Persons performing evaluations should possess the required knowledge (1) to ascertain an individual’s ability to perform the covered tasks and (2) to substantiate an individual’s ability to recognize and react to abnormal operating conditions that might surface while performing those activities. This does not necessarily mean that the person performing the evaluations should be physically able to perform the covered tasks themselves.#

Event. An event is a significant occurrence or happening. As applicable to pipeline safety, an event could be an accident, abnormal condition, incident, equipment failure, human failure, or release.#

Event Sequence. An event sequence is a specific, unplanned series of events composed of an initiating event and subsequent, intermediate events that lead to a result, such as a pipeline accident.#

Event Tree. An event tree is a logic diagram that is used to identify and analyze individual events and event sequences that can or did lead to a singular, usually larger, event of interest, such as an accident. It is called a tree because on the diagram each individual event is shown on a branch connected to a trunk that leads to the accident. Event trees are powerful analysis tools that can help determine the cause of an accident or anticipate and prevent failures.#

Excavation. Excavation refers to any operation involving movement of earth, rock or other materials below existing grade or surface level. Excavation can include digging, blasting, boring, tunneling, and backfilling.#

Excavation within a Pipeline Facility. Qualification for this covered task does not require the Operator’s employee or contractor employee to be proficient in the operation of excavation equipment. Covered task(s) requiring qualification shall address the following: Third party excavations that take place on the operator’s pipeline facility shall be handled in accordance with the operator’s damage prevention program requirements.#

Outside Force Damage (External Force Damage). Outside force damage is damage to an underground facility, such as a pipeline, resulting from some external force acting on the facility. Outside force damage to a pipeline or its protective coating is most often associated with damage from excavation activities around the buried pipe as a result of excavation equipment hitting the pipe, or from agricultural practices such as deep plowing or drainage tile installation. Outside force damage can usually be prevented by calling the one-call center before digging, waiting for the underground facility location to be marked, and excavating carefully while respecting the locate marks. Technically speaking: Ground movement from landslides, subsidence, or seismic activity can also exert damaging external loads on a pipeline. However, ground movement is not usually considered as outside force damage.#

Failure. Failure is a condition in which a human, structure, component, device, or system fails to adequately perform its intended purpose. Technically speaking: While a pipeline that is actually leaking product is the most obvious indication of failure, failure is often also defined as the point at which the pipe material is stressed beyond its elastic or yield point. At that point the material is deformed and does not return to its original shape. A pipeline rupture is an example of this type of failure.#

Failure Frequency. Failure frequency is the rate at which failures occur. Technically speaking: The number of failure events that occur divided by the total elapsed calendar time during which those events occur or by the total number of demands, as applicable. See also Failure Rate#

Failure Probablilty. Failure probability is the probability that a failure will occur. Technically speaking: Failure probability is the probability that a structure, device, equipment, system, etc. will fail on demand or will fail in a given time interval, expressed as a value from 0 to 1.#

Failure Rate. Failure rate is the rate at which failures occur. Technically speaking: Failure rate is the number of failure events that occur divided by the total elapsed operating time during which those events occur or by the total number of demands, as applicable. See also Failure Frequency#

Fatigue. Fatigue is the weakening of a material caused by the repeated application and removal of stress. For example, if you bend a piece of metal back and forth repeatedly in the same spot, fatigue will result at the bend location and will weaken the metal until it eventually breaks. Technically speaking: Pipelines experience fatigue as a result of periodic increases (application of stress) and decreases (removal of stress) in operating pressures. Because fatigue can cause a failure to occur at stress levels well below those that a material can withstand in a single, non-repetitive loading, materials that must resist repeated stress cycles must be specially designed for this service. Durability is the ability of the material to resist fatigue.#

Fault Tree. A fault tree is a logic diagram that is used to identify and analyze potential causes or failures that can or did lead to an event. It is called a tree because each possible fault or cause is shown as a branch on a trunk that leads to the accident. Technically speaking: A fault tree is a logic model that graphically portrays the combinations of conceivable human or mechanical failures (or faults) and events that can or did eventually lead to a specific result or consequence of interest. Fault trees are powerful analysis tools that can help determine the cause of an accident or anticipate and prevent failures.#

Fault Tree Analysis. Fault tree analysis is a logical, structured process using cause and effect or fault tree diagrams to determine the causes of an event. Fault tree analysis can help identify potential and contributing causes of failures before or after the failures actually occur.#

Federal Energy Regulatory Commission (FERC). From the web site of the Federal Energy Regulatory Commission: The Federal Energy Regulatory Commission is an independent regulatory agency within the Department of Energy that - regulates the transmission and sale for resale of natural gas in interstate commerce; - regulates the transmission of oil by pipeline in interstate commerce; - regulates the transmission and wholesale sales of electricity in interstate commerce; - licenses and inspects private, municipal, and state hydroelectric projects; - oversees related environmental matters; - administers accounting and financial reporting regulations and conducts of jurisdictional companies; and - approves siting and abandonment of interstate pipeline facilities. FERC can be contacted at 866-208-FERC (208-3372) or at www.ferc.gov.#

Final Order. After an operator has been given an opportunity to respond to a Notice of Probable Violation, the Associate Administrator for Pipeline Safety issues a Final Order, making findings of fact and ordering appropriate relief, if any. Civil penalties may be assessed and/or the operator may be required to comply with specified corrective actions. Only after PHMSA verifies that all corrective actions specified in Compliance Orders have been successfully completed and/or civil penalties paid are Final Orders considered “closed”. Final Orders are described in 49 CFR 190.213.#

Finding of No Significant Impact (FONSI). A Finding of No Significant Impact is a document prepared by a federal agency showing why a proposed action would not have a significant impact on the environment and thus would not require preparation of an environmental impact statement. An FONSI is based on the results of an environmental assessment.#

Fracture Toughness. Fracture toughness is the ability of a material (e.g., steel pipe) to resist stress and prevent cracks in the material from spreading. Technically speaking: Fracture toughness is the ability of a material to deform under increasing tensile stress in the presence of a defect or crack without exhibiting rapid and extensive fracture propagation. Materials that have high fracture toughness can absorb larger amounts of energy (i.e., can withstand higher pressures or levels of stress) before an existing crack spreads.#

Frequency. The number of events that are observed or are predicted to occur over a period of time.#

Gas. In general, gas is the vapor state of a substance. Gas is distinguished from the solid and liquid states by relatively low density and viscosity, relatively great expansion and contraction with changes in pressure and temperature, the ability to diffuse readily, and the spontaneous tendency to become distributed uniformly throughout any container. Technically speaking: As used in pipeline safety regulations (Reference 49CFR 192) gas is considered to be natural gas, flammable gas, or gas which is toxic or corrosive. Gases are normally compared to air in terms of its density. Since the specific gravity of air is 1.0, any gas with a specific gravity less than 1.0 will rise and usually disperse. Gas having a specific gravity greater than 1.0 will fall and collect near the ground or in low lying areas such as trenches, vaults, ditches, and bell holes.#

Gathering Line. Gathering lines are pipelines that transport oil or natural gas from the wellhead to a transmission line. Technically speaking: For gas pipelines, a gathering line is a pipeline that transports gas from a current production facility to a transmission line or main (49CFR 192.3). For hazardous liquid pipelines, a gathering line is a pipeline that is no more than 8 5/8 inches (219.1 mm) in diameter and transports petroleum from a production facility (49CFR 195.2).#

Geometry Tools. Geometry tools are inline inspection tools that are used to identify changes in the internal shape/diameter of a pipeline. Changes in the internal shape or diameter of pipe can be caused by dents, wrinkles, ovality, bend radius and angle, and occasionally indications of significant internal corrosion.#

Geographic Information System (GIS). A geographic information system is a combination of computer hardware, software, and data that is used to capture, maintain, analyze, and display information related to the geographic location of features and facilities. Geographic information systems are often used by pipeline operators to display information related to the location of their pipelines and the geographic features of the land surrounding their lines.#

Global Positioning System (GPS). Global Positioning System is a satellite navigation system funded and controlled by the U. S. Department of Defense (DOD). While there are many thousands of civil users of GPS world-wide, the system was designed for and is operated by the U. S. military. GPS provides specially coded satellite signals that can be processed in a GPS receiver, enabling the receiver to compute precise position, velocity and time. The space segment of GPS consists of the GPS satellites that send radio signals from space. The nominal GPS Operational Constellation consists of 24 satellites that orbit the earth in 12 hours. There are often more than 24 operational satellites as new ones are launched to replace older satellites. Four GPS satellite signals are used to compute the position of a receiver in three dimensions and the time offset (velocity) in the receiver clock.#

Gas Technology Institute (GTI). From the web site of the Gas Technology Institute: A membership organization that performs technical/research services for its members. GTI provides energy and environmental products and services with a focus on natural gas. Programs of this kind allow organizations to out-source all or part of their technology function and implement technology solutions to gain competitive advantage. GTI can be contacted at or for more information see www.gastechnology.org.#

Hazard. A hazard is a condition or substance that has the potential to produce harmful effects.#

Hazardous Liquid. A hazardous liquid is a liquid that is dangerous to human health or safety or the environment if used incorrectly or if not properly stored or contained. Pipeline safety regulations identify petroleum, petroleum products, or anhydrous ammonia as hazardous liquids. (Reference 49CFR 195.2).#

Hazardous Liquid Trunkline. A hazardous liquid trunkline is a main transmission pipeline that transports hazardous liquids. Technically speaking: A hazardous liquid trunkline is a hazardous liquid transmission pipeline other than a flow line, gathering line, or in-plant pipeline.#

Hazardous Material. A hazardous material is any substance or material that is dangerous to human health or safety or the environment if used incorrectly or if not properly stored or contained.#

Hazardous Site. A hazardous site is the location of a hazard. This includes locations where hazardous materials are used, stored, transported or produced. It could also include a location where a hazardous liquid has been accidentally released.#

Hazards Analysis. A hazards analysis is an analysis performed to identify hazardous conditions that could result in an accident. A hazards analysis is performed in a systematic fashion using procedures such as Hazard and Operability Analysis and Fault Tree Analysis.#

Hazard and Operability Analysis (HAZOP). A hazard and operability analysis is a systematic method for evaluating hazards. It often involves the review of detailed system drawings, specifications, and operating procedures. Process hazards and potential operating problems are identified through a qualitative investigation of deviations from normal process conditions.#

High Consequence Area (HCA). A high consequence area is a location that is specially defined in pipeline safety regulations as an area where pipeline releases could have greater consequences to health and safety or the environment. For oil pipelines, HCAs include high population areas, other population areas, commercially navigable waterways and areas unusually sensitive to environmental damage. Regulations require a pipeline operator to take specific steps to ensure the integrity of a pipeline for which a release could affect an HCA and, thereby, the protection of the HCA.#

High Population Area. A high population area is an urbanized area, as defined and delineated by the U.S. Census Bureau, which contains 50,000 or more people and has a population density of at least 1,000 people per square mile. High population areas are considered high consequence areas.#

High Pressure Distribution System. A high pressure distribution system is a natural gas distribution system in which the gas pressure in the main is higher than the pressure at which gas is provided to the customer. (Reference 49CFR 192.3).#

Holiday. A holiday is a discontinuity or break in the anti-corrosion coating on pipe or tubing that leaves the bare metal exposed to corrosive processes. Excavators that hit a pipeline might observe damage only to the coating on the pipe and, therefore assuming they’ve done no real damage, cover the line back up. However, this coating damage may lead to accelerated corrosion and subsequent failure of the pipe. Any time that a pipeline is hit during digging should be reported to the pipeline operator.#

Hoop Stress. Hoop stress is stress that acts around the circumference of a pipe (i.e., perpendicular to the pipe length) and is caused by the internal pressure pushing outward against the pipe wall. As pressure within the pipe increases, the stress in the pipe wall must be capable of acting against that pressure to contain it. Hoop stress is a critical factor in determining a pipe’s pressure holding capacity and thus in determining its appropriate application.#

Highly Volatile Liquid (HVL). A highly volatile liquid, as defined in pipeline safety regulations, is a hazardous liquid that will form a vapor cloud when released to the atmosphere and has a vapor pressure exceeding 276kPa (40 psia) at 37.8oC (100oF).#

Hydrogen Induced Damage. Hydrogen induced damage is a form of degradation of metals caused by exposure to environments that cause absorption of hydrogen into the material. Oil or natural gas within a pipeline can cause hydrogen induced damage to the pipe. Technically speaking: Examples of hydrogen induced damage are: (1) formation of internal cracks, blisters, or voids in steels; (2) embrittlement (i.e., loss of ductility); and (3) high temperature hydrogen attack (i.e., surface decarbonation and chemical reaction with hydrogen).#

Hydrostatic Pressure Testing. Hydrostatic pressure testing (or ‘hydro testing’) is a method of testing pipeline integrity in which the line is filled with a liquid, usually water, and then the pressure of the liquid is raised to a specified pressure that is maintained for a specified period of time. Any ruptures or leaks revealed during the test must be repaired and the test repeated until no problems are noted.#

Identify. To establish the identity of; to ascertain the origin, nature, or definitive characteristics of.#

Inline Inspection (ILI). Inline inspection is a method of inspecting a pipeline using an inline inspection tool or smart pig. ILI is also known as Internal Inspection or Smart Pigging. Different ILI techniques and tools are designed to detect defects in the pipe wall and on the internal and external surfaces of the pipe. Defects can include areas of corrosion, dents, metal loss, and the presence of cracks.#

Immediate Corrective Action. Taking steps to correct mistakes or abnormal or hazardous conditions without delay.#

Immediate Repair Condition. An immediate repair condition is a defect or anomaly in the condition of the pipe for which pipeline safety regulations require immediate action to repair the anomaly. (Reference 49CFR 195.452)#

In-Service Pipeline. An in-service pipeline is a pipeline that is being used to transport natural gas or hazardous liquid.#

Inactive Pipeline. An inactive pipeline is a pipeline that is not presently being used to transport oil or natural gas but that is being maintained in accordance with regulatory requirements so that it can be put back in to active use if needed.#

Incident. As used in pipeline safety regulations, an incident is an event occurring on a natural gas pipeline for which the operator must make a report to the Office of Pipeline Safety. Events of similar magnitude affecting hazardous liquid pipelines are considered accidents. (Reference 49CFR 191.3, 49CFR 195.50).#

Incident Command System. In widespread or major emergencies that could affect large populations or have significant environmental impacts an Incident Command System (ICS) is usually established to coordinate the combined actions of various emergency response personnel. Such emergencies could include natural disasters, such as tornados, train wrecks involving hazardous materials or major oil or natural gas pipeline releases. An ICS is an emergency management system that allows coordination and key decisions to be made by a unified command group consisting of representatives of involved government (Federal, state, and local), emergency response organizations (fire, police, medical, hazardous materials) and other responsible organizations such as, in pipeline related events, the pipeline operator.#

Individual. A person who, on behalf of the operator, performs one or more covered tasks on a pipeline facility operated by the operator. This includes contractors, subcontractors, and operator employees.#

Industrial User. An industrial user is a company that uses natural gas to produce process steam or heat for industrial purposes. For example, electric power generating utilities use natural gas to produce steam to turn turbines and generate electricity. Natural gas is also delivered to refineries and chemical plants to provide them with energy necessary to operate their facilities and carry out their production processes.#

Industry Cost of an Incident. The industry cost of an incident is defined as all costs to the operator and its contractors.#

Interstate Natural Gas Association of America (INGAA). From the web site of the Interstate Natural Gas Association of America: The Interstate Natural Gas Association of America (INGAA) is a trade organization that advocates regulatory and legislative positions of importance to the natural gas pipeline industry in North America. INGAA represents virtually all of the interstate natural gas transmission pipeline companies operating in the U.S., as well as comparable companies in Canada and Mexico. INGAA can be contacted at or for more information see www.ingaa.org.#

Initiating Event. An initiating event is the first event in a sequence of events that leads to, for example, a pipeline accident.#

Inline Inspection Tool (ILI Tool). An inline inspection tool is a device used to perform inline inspection. An ILI tool is inserted into a pipeline and, usually, is pushed through the line by the pressure of the fluid being transported. As the ILI tool travels through the pipeline it uses nondestructive testing techniques and technology to identify and record potential pipe defects or abnormalities. An ILI tool is also known as an Intelligent or Smart Pig.#

Integration of Data. As used in pipeline integrity management regulations, integration of data (or data integration) is the process of bringing together all available risk and integrity-related data and information. Data integration is necessary and useful in evaluating the combined impact of diverse factors on pipeline risk.#

Integrity. Integrity is being of sound and unimpaired condition. Pipeline integrity assures that the pipeline is in sound and unimpaired condition and can safely carry out its function under the conditions and parameters for which it was designed.#

Integrity Assessment. An integrity assessment is an evaluation to determine pipeline integrity. Acceptable assessment methods for pipelines include the use of internal inspection tools, hydrostatic pressure testing, or other technology that the operator demonstrates can provide an equivalent understanding of the pipe condition. (Reference 49CFR 195.452)#

Integrity Management Program. An integrity management program is a documented set of policies, processes, and procedures that are implemented to ensure the integrity of a pipeline.#

Integrity Management Program Framework. A documented description of how an operator intends to implement (or has implemented) each element of an integrity management program.#

Smart Pig (Intelligent Pigging). See Inline Inspection Tool.#

Inline Inspection (Internal Inspection). Inline inspection is a method of inspecting a pipeline using an inline inspection tool or smart pig. ILI is also known as Internal Inspection or Smart Pigging. Different ILI techniques and tools are designed to detect defects in the pipe wall and on the internal and external surfaces of the pipe. Defects can include areas of corrosion, dents, metal loss, and the presence of cracks.#

Interstate Pipeline. An interstate pipeline is a pipeline that extends beyond the boundaries of one state. Technically speaking: An interstate pipeline is a pipeline or that part of a pipeline that is used in transportation of hazardous liquids or natural gas in interstate or foreign commerce.#

Interval. The amount of time between two specified instants, events, or states.#

Intrastate Pipeline. An intrastate pipeline is a pipeline or that part of a pipeline that is entirely contained within one state’s borders. An intrastate pipeline system may be under a state’s regulatory jurisdiction as long as that state has a pipeline safety and inspection program that meets or exceeds the federal program. The state may opt to have its intrastate pipelines regulated by federal inspectors.#

International Organization for Standardization (ISO). From the web site of the International Organization for Standardization: The International Organization for Standardization (ISO) is a worldwide federation of national standards bodies from some 140 countries, one from each country. ISO is a non-governmental organization established in 1947. The mission of ISO is to promote the development of standardization and related activities in the world with a view to facilitating the international exchange of goods and services, and to developing cooperation in the spheres of intellectual, scientific, technological and economic activity. ISO’s work results in international agreements which are published as International Standards. The ISO can be contacted at + 41 22 749 01 11 or for more information see www.iso.org.#

Knowledge. Understanding gained through experience or study.#

Knowledge, Skills, and Abilities (KSAs). An appropriate combination of information (knowledge), craftsmanship (skills), and proficiency (ability or capability) that allows an individual to perform covered tasks in a competent manner.#

Lateral. A lateral is a segment of a pipeline that branches off of the main or transmission line to transport the product to a termination point, such as a tank farm or a metering station.#

Launcher. A launcher is a pipeline component that is used for inserting an inline inspection tool, cleaning pig, or other device into a pressurized pipeline. After performing its task, the tool or pig is removed via receiver.#

Local Distribution Company (LDC). A local distribution company is a pipeline operator responsible for distributing natural gas locally to its customers. An LDC purchases gas from gas pipeline transmission companies for resale to the consumer. LDC’s operate and maintain the underground network piping, regulators, and meters that connect to each residential and commercial customer.#

Leak. A leak is a small opening, crack, or hole in a pipeline allowing a release of oil or gas. Pipeline operators periodically perform leak surveys as leaks may not be readily or immediately detected.#

Leak History. The leak history is the record of leaks on a given pipeline over a period of time.#

Leak Survey. A leak survey is a systematic inspection for the purpose of finding leaks on a pipeline. The frequency and methods of performing leak surveys are regulated and may vary depending on several factors.#

LEPC. See Local Emergency Planning Committees.#

Likelihood. Likelihood refers to the probability that something possible may occur. The likelihood may be expressed as a 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).#

Line Markers. Line markers are signs or other markers installed above the pipeline to indicate the approximate pipeline route and provide emergency phone numbers. Requirements for line markers are specified in federal pipeline safety regulations. (Reference 49CFR 192.707 or 49CFR 195.410)#

Line Pipe. Line pipe is pipe that is part of a line section.#

Line Section. A line section is a designated section of a continuous run of pipeline. Line sections may designate sections that run, for example, between adjacent compressor stations or pump stations, between a compressor/pump station and a storage facility, between a compressor/pump station and a block valve, or between adjacent block valves. A line section can also be designated for testing purposes. For example, a line section may be a pipeline segment designated for hydrostatic testing that runs between two mainline valves.#

Liquefied Natural Gas (LNG) Facilities. A liquefied natural gas facility is a pipeline facility that is used for liquefying natural gas or synthetic gas or transferring, storing, or vaporizing liquefied natural gas.#

Liquefied Petroleum Gas. Liquefied petroleum gas is a gas containing certain specific hydrocarbons which are gaseous under normal atmospheric conditions, but can be liquefied under moderate pressure at normal temperatures. Propane and butane are principal examples.#

Liquefied Natural Gas (LNG). Liquefied natural gas is natural gas or synthetic gas having methane (CH 4) as its major constituent, which has been changed to a liquid.#

Local Emergency Planning Committees (LEPCs). LEPCs are committees appointed by the State Emergency Response Commissions (SERCs) and are composed of representatives of the following groups and organizations: elected officials, public safety and health personnel, local environment and transportation agencies, community groups and media, and representatives of affected facilities. LEPC’s are responsible for development and maintenance of emergency plans for response to chemical emergencies, including pipeline accidents.#

Locate. Locate refers to the process of determining the existence and location of an underground facility, such as an oil or gas pipeline, and indicating that location through the use of stakes, flags, paint or some other customary manner. Such markings identify the location of the underground facility so that excavators can avoid damage to the facility when digging.#

Low-pressure Distribution System. A low-pressure distribution system is a pipeline system designed and used for distributing natural gas, and is characterized by the gas pressure in the main being substantially the same as the pressure provided to the consumer.#

Main. A main is a natural gas distribution line that serves as a common source of supply for more than one service line.#

Mainline Valves. A mainline valve is a valve positioned at a location along the pipeline system that can be closed down to isolate a line section in an emergency. Mainline valves are especially important to minimize hazards and damage or pollution from an accidental release of oil or natural gas. Mainline valves may also be referred to as sectionalizing block valves for natural gas pipelines. (Reference 49CFR 192.179 and 49CFR 195.260)#

Maintain. To keep in a condition of good repair or efficiency.#

Maintenance. Maintenance is the process of maintaining property or equipment, including pipelines, to preserve it and prevent it from failure and ensure that it will continue to perform its intended function.#

Maximum Allowable Operating Pressure (MAOP). Maximum allowable operating pressure is the maximum internal pressure at which a natural gas pipeline or pipeline segment may be operated.#

Metal Loss. Metal loss refers to any of a number of types of anomalies in pipe in which metal has been removed from the pipe surface, usually due to corrosion or gouging.#

Metering and Regulating (M&R) Stations. Metering and regulating stations are installations containing equipment to measure the amount of gas entering or leaving a pipeline system and, sometimes, to regulate gas pressure.#

Magnetic Flux Leakage (MFL). Magnetic flux leakage is a inline inspection technology used to identify defects and anomalies in pipe. Technically speaking: Magnetic flux leakage refers to an inline inspection technology in which a magnetic field is induced along a pipe wall through the use of a smart pig. As the smart pig travels through the pipeline, measurements are taken of the magnetic flux density at the internal surface of the wall. Changes in measured flux density indicate the presence of potential defects. A number of different MFL tool designs are used for pipeline inspection. These tools are often categorized as standard resolution or high resolution devices. High resolution MFL tools contain a greater number of sensors and thus provide more accurate measurements of potential defects and anomalies.#

Maximum Operating Pressure (MOP). Maximum operating pressure is the maximum internal pressure at which a hazardous liquid pipeline may be operated.#

Multi-attribute Utility Decision Model. A multi-attribute utility decision model is a model that helps compare the relative value (or expected benefit) of various proposed actions by examining the impact of those actions on a set of attributes (such as safety, environmental impact, etc.), and assigning relative weights to each of the attributes. Such models are frequently used to prioritize safety-related activities and to optimally allocate resources among these activities.#

National Association of Corrosion Engineers (NACE). From the web site of NACE International - the Corrosion Society: The National Association of Corrosion Engineers was established in 1943 by eleven corrosion engineers in the pipeline industry. These founding members were involved in a regional cathodic protection group formed in the 1930s, when the study of cathodic protection was introduced. The NACE is a membership association focused on the study of corrosion and development of corrosion prevention and control standards. AMPP merged the NACE and SSPC standards programs into what is now the AMPP Standards Program.#

National Association of Pipeline Safety Representatives (NAPSR). From the web site of NAPSR: The National Association of Pipeline Safety Representatives (NAPSR) is a non-profit organization of state gas pipeline safety directors, managers, inspectors and technical personnel who serve to support, encourage, develop and enhance pipeline safety regulation. The Association was founded on December 2, 1982. For more information on NAPSR visit www.napsr.org#

National Association of Regulatory Utility Commissioners (NARUC). From the web site of NARUC: The National Association of Regulatory Utility Commissioners (NARUC) is a non-profit organization founded in 1889. Its members include the governmental agencies that are engaged in the regulation of utilities and carriers in the fifty States, the District of Columbia, Puerto Rico and the Virgin Islands. NARUC’s member agencies regulate the activities of telecommunications, energy, and water utilities. Under State law, NARUC’s members have the obligation to ensure the establishment and maintenance of such energy utility services as may be required by the public convenience and necessity, and to ensure that such services are provided at rates and conditions that are just, reasonable and nondiscriminatory for all consumers. NARUC can be contacted at or for more information see www.naruc.org.#

National Association of State Fire Marshals (NASFM). From the web site of NASFM: The National Association of State Fire Marshals (NASFM) represents the most senior fire official of each of the 50 United States and District of Columbia. State Fire Marshals’ responsibilities vary from state to state, but Marshals tend to be responsible for fire safety code adoption and enforcement, fire and arson investigation, fire incident data reporting and analysis, public education and advising Governors and State Legislatures on fire protection. Some State Fire Marshals are responsible for fire fighter training, hazardous materials incident responses, wildland fires and the regulation of natural gas and other pipelines. NASFM can be contacted at or for more information see www.firemarshals.org#

Natural Gas Transmission Pipeline. A natural gas transmission pipeline is a pipeline used to transport natural gas from a gathering, processing or storage facility to a processing or storage facility, large volume customer, or distribution system. A large volume customer may receive similar volumes of gas as a distribution center, and includes factories, power plants, and institutional users of gas. Technically speaking: A natural gas transmission pipeline is a pipeline, other than a gathering line, that 1) transports gas from a gathering line or storage facility to a distribution center, storage facility, or large-volume customer that is not downstream from a distribution center; 2) operates at a hoop stress of 20 percent or more of specified minimum yield strength (SMYS); or, 3) transports gas within a storage field.#

Nondestructive Testing (NDT). Nondestructive testing is material testing in which the part being tested is not destroyed or rendered unusable. Technically speaking: Pipeline NDT typically consists of: 1. Radiography (X-rays): identifies laminations and weld discontinuities. 2. Ultrasonics: locates lamination in the walls of pipe; determines wall thicknesses. 3. Magnetic particle inspection: tests for surface cracks in welds and component bodies. 4. Dye penetrant: locates surface cracks in welds or component bodies. 5. Ammonium persulfate: identifies hard spots in welds due to arc burns. See Also: Destructive Testing#

New Construction. New construction is the act of building a pipeline facility, or expanding an existing pipeline facility (as in looping a pipeline segment, which may also be done to meet increased load requirements or to enhance reliability of the system) in order to provide new service to a customer(s) or in order to meet increased demand.#

National Fire Protection Association (NFPA). From the web site of NFPA: NFPA is an international nonprofit membership organization founded in 1896 as the National Fire Protection Association. Today, with more than 75,000 members representing nearly 100 nations and 320 employees around the world, NFPA serves as the world’s leading advocate of fire prevention and is an authoritative source on public safety. In fact, NFPA’s 300 safety codes and standards influence every building, process, service, design, and installation in the United States, as well as many of those used in other countries. NFPA serves as an advocate of fire prevention, develops and advocates scientifically-based consensus codes and standards, research, training, and education. NFPA can be contacted at or for more information see www.nfpa.org#

Natural Gas Liquid (NGL). Natural gas liquids are associated hydrocarbons found in natural gas, including ethane, propane, butane, iso-butane, and natural gasoline. Before natural gas can be transported it must be processed and purified. NGLs are valuable by-products of natural gas processing. They are extracted or isolated, processed and sold separately. NGLs have a variety of different uses, including enhancing oil recovery in oil wells, providing raw materials for oil refineries or petrochemical plants, and as sources of energy.#

Notice of Amendment (NOA). PHMSA inspections, incident investigations, and other oversight activities routinely identify shortcomings in an operator’s plans and procedures under PHMSA regulations. In these situations, PHMSA issues a Notice of Amendment (NOA) letter alleging that the operator’s plans and procedures are inadequate and requiring that they be amended. The operator has a right to respond to the Notice and to request an administrative hearing. Notices of Amendment and the procedures for their issuance and enforcement are described in 49 CFR 190.237.#

Non-active Corrosion. Non-active corrosion is corrosion that has been discovered and treated (coated, chemically inhibited, or otherwise controlled) to stop the metal particle loss. Non-active corrosion areas are often monitored over time to verify the corrosion process is in fact halted. See also: Corrosion.#

Notice of Probable Violation (NOPV). Notices of Probable Violations (NOPVs) are commonly used as an enforcement tool. After routine inspections, incident investigations, or other oversight activity by authorized Federal or Interstate Agent pipeline inspectors, the PHMSA Regional Director will determine if probable violations have occurred, and, if appropriate, issue an NOPV to the operator. The NOPV alleges specific regulatory violations and, where applicable, proposes appropriate corrective action in a Compliance Order and/or civil penalties. The operator has a right to respond to the NOPV and to request an administrative hearing. The administrative enforcement procedures and other regulations governing the enforcement program are described in 49 CFR 190 Subpart B “Enforcement.”#

Noteworthy Industry Practices. In pipeline integrity management, noteworthy industry practices are unique methods or procedures found to be in use by one or more pipeline operators and deemed to be notable such that their adoption by other operators could significantly enhance the implementation of pipeline integrity management requirements by those other operators.#

National Propane Gas Association (NPGA). From the web site of NPGA: The National Propane Gas Association (NPGA) is the national trade association representing the propane industry. Its membership includes small businesses and large corporations engaged in the retail marketing of propane gas and appliances; producers and wholesalers of propane equipment; manufacturers and distributors of propane gas appliances and equipment; fabricators of propane gas cylinders and tanks; and propane transporters. NPGA can be contacted at or for more information see www.npga.org.#

National Pipeline Mapping System (NPMS). The National Pipeline Mapping System is a geographic information system (GIS) database that contains the locations and selected attributes of natural gas transmission lines, hazardous liquid trunklines, and liquefied natural gas (LNG) facilities operating in onshore and offshore territories of the United States. The NPMS is managed, operated, and maintained by the Office of Pipeline Safety (OPS) and is being developed under a joint government-industry effort involving OPS, other federal and state agencies, and the pipeline industry. OPS can be contacted at or for more information see www.npms.phmsa.dot.gov.#

Notice of Proposed Rulemaking (NPRM). A notice of proposed rulemaking is a formal notice by a federal agency of its intent to adopt specific proposed requirements into regulations. The NPRM is published in the Federal Register (unless all persons subject to the proposed requirements are personally served with copies), invites comments from the public on the proposed requirements, and specifies when, how, and to whom comments are to be submitted. Recent OPS NPRM’s can be seen at https://www.phmsa.dot.gov/regulations/federal-register-documents.#

National Response Center (NRC). The National Response Center is an entity within the U.S. Coast Guard that serves as the central point for reporting for all accidental discharges of hazardous materials into the environment of the United States and its territories. The NRC serves as the communications and operations center for the National Response Team and coordinates with other federal agencies having oversight responsibility for modes of transportation or that respond to hazardous material releases of specific kinds. NRC can be contacted at or for more information see https://www.epa.gov/emergency-response/national-response-center.#

National Transportation Safety Board (NTSB). The National Transportation Safety Board is an independent Federal agency charged by Congress with investigating significant accidents in all modes of transportation — pipeline, aviation, railroad, highway, and marine. NTSB issues safety recommendations aimed at preventing future accidents. NTSB can be contacted at or for more information see www.ntsb.gov.#

Observation of On-The-Job Performance. (1) Observation without interaction during on-the-job performance does not provide an adequate measurement of the knowledge and skills of the individual; (2) PHMSA has determined that there are no covered tasks to date where observation of on-the-job performance is an adequate, sole method for examining or testing qualification; and (3) Observation of on-the-job performance does not measure the individual’s ability to recognize and react to abnormal operation conditions (AOCs).#

Observe. The act of watching; to watch or perceive. For purposes of conducting qualification evaluations using on the job (OTJ) performance, observations must include the interaction of the evaluator and qualification candidate to ensure that the candidate’s knowledge of the specific task requirements and procedures (and the reasons for key task steps) is adequate to ensure the continued safe performance of the task.#

Offshore Pipeline. An offshore pipeline is a pipeline located off the coast of the United States. Large quantities of natural gas and crude oil are produced from beneath the ocean floor. Offshore pipelines transport these products from the offshore production areas to onshore processing plants and pipelines. Technically speaking: An offshore pipeline is a pipeline located beyond the line of ordinary low water along that portion of the coast of the United States that is in direct contact with the open seas or beyond the line marking the seaward limit of inland waters.#

Offshore Platforms. Offshore platforms are structures located in oil and natural gas production areas located off the coast of the United States. Offshore platforms are anchored to the ocean floor and provide stable working platforms for the production of oil and natural gas. Modern platforms are large structures engineered to accommodate the equipment necessary for gathering and processing the oil and natural gas that is produced. They can resemble small cities, with living, dining, and entertainment facilities, and even hospital facilities.#

One-Call Notification Center. A one-call notification center is an organization that houses and administers a one-call system.#

One-Call System. A one-call system is a system that allows excavators (individuals, professional contractors, and governmental organizations) to make one telephone call to provide notification of their intent to dig to underground facility operators. The one call center will then notify all underground facility operator members of the intended excavation along with the date and location of the excavation. The facility operators or, in some cases, the one-call center can then locate the facilities before the excavation begins so that extra care can be taken to avoid damaging the facilities. All 50 states within the U.S. are covered by one-call systems. Most states have laws requiring the use of the one-call system at least 48 hours before beginning an excavation. Local one-call center numbers can be determined by calling, toll-free, 1-.#

Operate. Starting, stopping and/or monitoring a device or system.#

Operating Stress. Operating stress is the stress imposed on a pipe or structural member under operating conditions. This term normally refers to stress resulting from the internal forces due to the pressure of the gas or liquid in the pipeline; however, other forces such as thermal growth, expansion, or contraction may impose stress as well.#

Operation. Actions taken to facilitate storage or movement of product through a regulated pipeline.#

Operations and Maintenance (O&M) Manual. Operations and maintenance manual is the common term for the set of comprehensive procedures that federal pipeline safety regulations require pipeline operators to develop and follow. Procedures in the O&M manual should cover pipeline operations, maintenance, and response to abnormal events and emergencies.#

Operations and Maintenance (O&M) Task. Activities performed by an individual, or group of individuals, (1) to perform a function on a pipeline facility, or (2) to provide upkeep of a pipeline facility. This includes in-kind replacement of an existing section of pipe necessitated by severe corrosion, where the capacity of the pipe segments is maintained and service is not expanded. It also includes maintenance and repair tasks performed on the right-of-way or within the confines of a “pipeline facility”, as defined. This would include ordinary repairs to a pipeline, including replacement of one or more pipe joints or segments that have been severely damaged by threats such as corrosion or third party damage. Tasks performed away from a “pipeline facility”, as at a vendor shop (such as rebuilding/refurbishment of meters and regulators, rebuilding of compressors or valves, etc.#

Operator. An operator is a person who engages in the transportation of gas (Reference 49CFR 192.3) or a person who owns or operates pipeline facilities (Reference 49CFR 195.2). ‘Person’ in this case means any individual, firm, joint venture, partnership, corporation, association, State, municipality, cooperative association, or joint stock association, and including any trustee, receiver, assignee, or personal representative thereof.#

Office of Pipeline Safety (OPS). OPS is the agency within the U. S. Department of Transportation, Pipeline and Hazardous Materials Safety Administration (PHMSA), that is responsible for regulating the safety of design, construction, testing, operation, maintenance, and emergency response of U.S. oil and natural gas pipeline facilities. OPS can be contacted at or for more information see http://phmsa.dot.gov/pipeline.#

Occupational Safety & Health Administration - US Dept. of Labor (OSHA). OSHA is the federal agency responsible for implementing the Occupational Safety and Health Act of 1970, regulating safety in U.S. workplaces. OSHA can be contacted at 800-321-OSHA (6742) or for more information see www.osha.gov.#

Other Populated Area. An other populated area is a place, as defined and delineated by the Census Bureau, that contains a concentrated population, such as an incorporated or unincorporated city, town, village, or other designated residential or commercial area.#

Outside Force Damage. Outside force damage is damage to an underground facility, such as a pipeline, resulting from some external force acting on the facility. Outside force damage to a pipeline or its protective coating is most often associated with damage from excavation activities around the buried pipe as a result of excavation equipment hitting the pipe, or from agricultural practices such as deep plowing or drainage tile installation. Outside force damage can usually be prevented by calling the one-call center before digging, waiting for the underground facility location to be marked, and excavating carefully while respecting the locate marks. Technically speaking: Ground movement from landslides, subsidence, or seismic activity can also exert damaging external loads on a pipeline. However, ground movement is not usually considered as outside force damage.#

Ovality. Ovality is a condition in which the internal diameter of the pipe is not consistent around the entire circumference of the pipe. This can be thought of as the internal diameter of the pipe being, to varying degrees, egg-shaped. Ovality can be measured by inline inspection tools known as caliper pigs or geometry pigs.#

Perform. To begin and carry through to completion; to demonstrate in accordance with the requirements of; to accomplish (a covered task) in the proper, customary or established manner.#

Performance Measures. Performance measures are parameters or information that can be collected and evaluated to determine if a program of action is accomplishing its intended purpose. Federal pipeline safety regulations require that pipeline operators establish performance measures as part of their integrity management programs.#

Person. As defined in § 192.3 and § 195.2.#

Petroleum. Petroleum is crude oil, condensate, natural gasoline, natural gas liquids, and liquefied petroleum gas. In prehistoric times, much of the Earth’s surface was covered by oceans. Plants and animals that lived in the seas and died sank into layers of mud and sand. Over long periods of time, movement in the Earth’s crust put those organic deposits under tremendous heat and pressure. In these conditions and over millions of years, those underground deposits were turned into chemicals called hydrocarbons. Different compounds of these hydrocarbons are the basic ingredients of petroleum. Technically speaking: Petroleum is an oily, flammable bituminous liquid that may vary from almost colorless to black and occurs in many places in the upper strata of the earth.#

Petroleum Gas. Petroleum gas refers to heavier gases of different hydrocarbons than natural gas, including propane, propylene, butane (normal butane or isobutanes), and butyline (including isomers) or mixtures composed predominantly of these gases, found naturally in petroleum well formations. Technically speaking: Petroleum gas means propane, propylene, butane (normal butane or isobutanes), and butyline (including isomers) or mixtures composed predominantly of these gases, having a vapor pressure not exceeding 208 psi (1434 kPa) gage at 100º F (38º C).#

Pipeline and Hazardous Materials Safety Administration (PHMSA). The Pipeline and Hazardous Materials Safety Administration (PHMSA) is one of ten agencies within the U.S. Department of Transportation (DOT). PHMSA works to protect the American public and the environment by ensuring the safe and secure movement of hazardous materials to industry and consumers by all transportation modes, including the nation’s pipelines. PHMSA was created under the Norman Y. Mineta Research and Special Programs Improvement Act (P.L. 108-426) of 2004. The creation of PHMSA provides DOT a modal administration focused solely on its pipeline and hazardous materials transportation programs. PHMSA’s Administrator is appointed by the President and confirmed by the United States Senate. PHMSA’s Administrator is the agency’s chief executive and provides direction to nearly 400 employees within the agency’s Washington, DC Headquarters and regional offices.#

Pig. Pig is a generic term signifying any independent, self-contained device, tool, or vehicle that is inserted into and moves through the interior of a pipeline for inspecting, dimensioning, or cleaning. These tools are commonly referred to as ‘pigs’ because of the occasional squealing noises that can be heard as they travel through the pipe. See Also: Inline Inspection Tool#

Pipeline. Used broadly, pipeline includes all parts of those physical facilities through which gas, hazardous liquid, or carbon dioxide moves in transportation. Pipeline includes but is not limited to: line pipe, valves and other appurtenances attached to the pipe, pumping/compressor units and associated fabricated units, metering, regulating, and delivery stations, and holders and fabricated assemblies located therein, and breakout tanks. Reference 49CFR 192.3 and 49CFR 195.2#

Pipeline Component. A pipeline component is some feature or part of a pipeline, such as pipe, valves, fittings, flanges, closures, tees or cathodic protection.#

Pipeline Corridor. A pipeline corridor is a linear area where two or more pipelines (either part of the same or different pipeline systems) are closely grouped in a single right-of-way.#

Pipeline Crossing. A pipeline crossing is a point where two or more pipelines cross without a physical connection existing between the pipelines.#

Pipeline Facility. From a regulatory perspective, a pipeline facility is: 1) New and existing pipelines, rights-of-way, and any equipment, facility, or building used in the transportation of gas or in the treatment of gas during the course of transportation (Reference 49CFR 192.3); and 2) New and existing pipe, rights-of-way and any equipment, facility, or building used in the transportation of hazardous liquids or carbon dioxide. (Reference 49CFR 195.2)#

Pipeline Intersection. A pipeline intersection is a point where a physical connection between two pipelines occurs.#

Pipeline (Pipeline System). Used broadly, pipeline includes all parts of those physical facilities through which gas, hazardous liquid, or carbon dioxide moves in transportation. Pipeline includes but is not limited to: line pipe, valves and other appurtenances attached to the pipe, pumping/compressor units and associated fabricated units, metering, regulating, and delivery stations, and holders and fabricated assemblies located therein, and breakout tanks. Reference 49CFR 192.3 and 49CFR 195.2#

Pitting. Pitting is Metal loss causing the formation of small depressions in a metallic surface. Pitting may be the result of sand blasting, mechanical gouging, acid etching or corrosion. See Also: Corrosion#

Pre-1970 Electric Resistance Welded (ERW) Pipe. Pre-1970 ERW pipe is pipe that was manufactured prior to 1970 with a low-resistance electric-weld longitudinal-seam that can be susceptible to certain types of seam failures. See Also: Electric Resistance Weld (ERW)#

Pressure. Pressure is the force exerted on a given area expressed in pounds per square inch (PSI) or its metric equivalent of kilo Pascals (kPa). Oil and natural gas transported within a pipeline exert pressure on the pipe wall.#

Pressure Relief Valve. A pressure relief valve is a mechanical safety device that provides protection to a pressurized container, such as a pipeline, by reducing the internal pressure by releasing it outside the container.#

Hydrostatic Pressure Testing (Pressure Testing). Hydrostatic pressure testing (or ‘hydro testing’) is a method of testing pipeline integrity in which the line is filled with a liquid, usually water, and then the pressure of the liquid is raised to a specified pressure that is maintained for a specified period of time. Any ruptures or leaks revealed during the test must be repaired and the test repeated until no problems are noted.#

Preventive and Mitigative Measures. Preventive and mitigative measures are activities designed to prevent or reduce the likelihood of a pipeline failure (preventive) and/or mitigate the consequences of a pipeline failure (mitigative). Examples of preventive measures include enhanced damage prevention practices, conducting periodic close interval surveys, or inspecting pressure relief devices more frequently. Examples of mitigative measures include the installation of emergency flow restricting devices, improving leak detection system capability, or conducting drills with local emergency responders.#

Prior. Preceding in time or order.#

Private Right-of-Way. A private right-of-way is a land use grant obtained through negotiations between the private landowner and the pipeline company that provides an easement for a specific purpose such as building and maintaining underground pipelines.#

Probability. Probability is a measure, either qualitative or quantitative, of the likelihood that an event will occur within some unit of time.#

Probability Analysis. Probability analysis is an evaluation of the probability of occurrence of specific events, such as an analysis of the probability of certain pipeline failures.#

Process. A systematic series of actions directed to some end.#

Product Transported. Product transported refers to the oil or natural gas transported by energy pipelines.#

Program. A written description of processes to be followed, a clear delineation of authorities and responsibilities there under and the specific results expected to be achieved for the implementing organization.#

Protective Coating. A protective coating is a substance or material applied to the exterior of the pipe or a pipeline component to prevent contact with the outside environment. Protective coating is generally applied to prevent corrosion. Many types of protective coatings are used on pipelines, including coal tar, tape wraps, and fusion bonded epoxy compounds.#

Protocol. A set of instructions which guides how an activity is performed. As used by OPS, it is a standard methodology used to conduct inspections of regulated entities to determine conformance with the operator qualification rule.#

Provision. The written description of the element(s) or approach employed by an operator to satisfy the requirements of the OQ Rule in § 192.805 and § 195.505.#

Public Cost of an Incident. The public cost of an incident is defined as public and private (non operator) costs for the incident.#

Pump. A pump is a mechanical device used to increase the pressure of the fluid in a container, such as oil in a pipeline. Increased pressure is used to move the oil along through the pipeline by pushing it towards an area of lower pressure.#

Pumping Station. A pumping station is a facility that houses the pumps used to move oil along through a pipeline.#

Pursuant. In accordance with (or) as a follow-up.#

Qualified. As defined in § 192.803 and § 195.503.#

Qualitative Risk Analysis. A qualitative risk analysis is an analysis of hazards to determine which ones should be of most concern to address in preventing an accident. Technically speaking: A qualitative risk analysis is a disciplined analysis of the event sequences that could transform a potential hazard into an accident. The process is used to identify and assess risks to determine which ones should be of most concern. The identified hazards can then be ranked according to risk, allowing preventive and mitigative measures to be prioritized and taken to prevent accidents.#

Quantitative Risk Analysis. A quantitative risk analysis is a numerical analysis of risks. Technially speaking: A quantitative risk analysis is a process of hazard identification, followed by numerical evaluation of incident consequences and frequencies, and their combination into an overall measure of risk. Often associated with expressions of absolute risk but can also include methods expressing risk in relative terms, such as indices or scores.#

Receivers. A pipeline component used for removing an inline inspection tool, cleaning pig, or other device from a pressurized pipeline. The device is inserted into the pipeline via a launcher.#

Records. Recorded information or data on a particular subject, collected and preserved to demonstrate compliance with a rule or process requirement.#

Rectifier. A rectifier is a device for converting alternating current to direct current. A rectifier is one component of a cathodic protection system used to protect pipelines from corrosion.#

Regulatory Construction. The regulatory structure consists, sequentially, of Title, Part, Subpart, Section, Paragraph, and Subparagraph.#

Relative Risk Index Model. A relative risk index model is an analytical model or tool that is used to calculate a numerical score, representing the relative risk of a pipeline segment. This score is calculated based on variables that represent characteristics of the pipeline segment and the perceived importance of these characteristics to the risk of the segment.#

Reliability. Reliability is the likelihood that a component or system will continue to perform its intended function.#

Reliability Analysis. A reliability analysis is the determination, through evaluation and analysis, of the probability or likelihood that a component will perform its required function in the desired manner under all relevant conditions. It includes the analysis of potential failures that could render the component unable to perform its normal required functions.#

Relief Valve. See: Pressure Relief Valve.#

Remote Control Valve. A remote control valve is a type of valve that can be operated from a location other than at the valve site.#

Repair. Repair is the act of returning a damaged or defective item to its original condition. Pipeline repairs address defects or anomalies that reduce the strength of a pipe in a manner that restores that strength. Repairs can include replacing sections of pipeline.#

Repair Conditions. Repair conditions are identified pipeline conditions (defects and anomalies) that require repair. Under pipeline safety regulations for integrity management programs, characteristics are defined to reflect the severity of a condition and determine the timeframe in which repairs must be made. (Reference 49CFR 195.452)#

Repair Criteria. Repair criteria are standards and requirements that govern the methods and timeframes to make pipeline repairs, based on the type, extent or configuration of identified anomalies, defects, or damages.#

Residential User. A residential user is a consumer using natural gas to provide heat and light for personal use to a private residence. Local distribution companies (LDCs) provide natural gas directly to residential users.#

Retain. To keep possession of, in a retrievable and useable condition.#

Risk. Risk is a measure of both the likelihood that an adverse event could occur and the magnitude of the expected consequences should it occur.#

Risk Assessment. A risk assessment is a comprehensive evaluation of the pipeline system to identify hazards and estimate the likelihood and consequences of potential pipeline incidents or accidents. A pipeline risk assessment should provide a significant understanding of pipeline risks and significant risk contributors. (Sometimes referred to as risk analysis or risk evaluation.)#

Risk Factors. Risk factors are contributing factors that can influence the likelihood and/or consequence of a pipeline accident.#

Risk Management. Risk management is the process by which an organization understands and makes decisions about its risks.#

Risk Reduction. Risk reduction is the act of making changes to controllable factors (e.g., operating pressure, patrol frequency) to reduce risk. Risk reduction can also refer to a quantitative measurement of the magnitude of a reduction in risk.#

Risk-Benefit. Risk-benefit is an integral part of Risk Management that simultaneously considers and compares risk and the financial costs/savings of risk reduction.#

Root Cause. Root cause is the basic, underlying causal factor in an accident or other event scenario which if removed would have prevented the accident or event from occurring.#

Root Cause Analysis. Root cause analysis is a problem solving process that focuses on the task of finding the root cause and determining the best prevention solutions to a problem.#

Rights-of-Way (ROW). A rights-of-way is a defined strip of land on which an operator has the rights to construct, operate, and/or maintain a pipeline. A ROW may be owned outright by the operator or an easement may be acquired for specific use of the ROW.#

Pipeline and Hazardous Materials Safety Administration (RSPA). The Pipeline and Hazardous Materials Safety Administration (PHMSA) is one of ten agencies within the U.S. Department of Transportation (DOT). PHMSA works to protect the American public and the environment by ensuring the safe and secure movement of hazardous materials to industry and consumers by all transportation modes, including the nation’s pipelines. PHMSA was created under the Norman Y. Mineta Research and Special Programs Improvement Act (P.L. 108-426) of 2004. The creation of PHMSA provides DOT a modal administration focused solely on its pipeline and hazardous materials transportation programs. PHMSA’s Administrator is appointed by the President and confirmed by the United States Senate. PHMSA’s Administrator is the agency’s chief executive and provides direction to nearly 400 employees within the agency’s Washington, DC Headquarters and regional offices.#

Rulemaking. Rulemaking is an administrative process, under the Administrative Procedures Act, by which federal agencies establish requirements. The process must involve an opportunity for affected members of the public to comment on proposed regulations, usually by publication of a Notice of Proposed Rulemaking in the Federal Register.#

Rupture. A rupture is the process or instance of breaking open or bursting, as in the rupture of a pipe. Technically speaking: A rupture is the propagation or growth of a defect to such an extent that the pipe becomes completely unserviceable.#

Supervisory Control and Data Acquisition System (SCADA). A SCADA is a pipeline control system designed to gather information such as pipeline pressures and flow rates from remote locations and regularly transmit this information to a central control facility where the data can be monitored and analyzed. Through this same system, the central control facility can often issue commands to the remote sites for actions such as opening and closing valves and starting and stopping pumps.#

Stress Corrosion Cracking (SCC). Stress corrosion cracking is cracking that occurs in the steel pipe material that is caused by a combination of stress, corrosive environment, and temperature. Technically speaking: SCC is environmentally-assisted cracking that can result when the combined action of stress, an electrochemical cracking environment, and temperature causes cracks to initiate and grow in susceptible line-pipe steel. See also: Corrosion#

Selective Corrosion. Selective corrosion is Corrosion that preferentially attacks one element of a material. Pipeline welds may experience selective corrosion because the corrosion resistance of the weld material is not fully equivalent to that of the base metal. Selective corrosion is sometimes referred to as preferred corrosion.#

Serious Incident. PHMSA defines a serious pipeline safety incident is an event involving a fatality or injury requiring in-patient hospitalization.#

Service Line. A service line is a distribution line that transports gas from a common source of supply to (1) a customer meter or the connection to a customer’s piping, whichever is farther downstream, or (2) the connection to a customer’s piping if there is no customer meter. (A customer meter is the meter that measures the transfer of gas from an operator to a consumer.)#

Ship Transportation. A portion of the oil and natural gas we use in the U. S. every day comes from foreign countries. Ship transportation refers to the transportation of oil and natural gas in ocean-going ships.#

Significant. As applicable to OQ program modifications, significant includes but is not limited to: increasing evaluation intervals, increasing span of control ratios, eliminating covered tasks, mergers and/or acquisition changes, evaluation method changes such as written vs. observation, and wholesale changes made to OQ plan.#

Significant Incident. Significant Incidents are those incidents reported by pipeline operators when any of the following conditions are met: (1) Fatality or injury requiring in-patient hospitalization. (2) $50,000 or more in total costs, measured in 1984 dollars. (3) Highly volatile liquid releases of 5 barrels or more or other liquid releases of 50 barrels or more. (4) Liquid releases resulting in an unintentional fire or explosion. Serious incidents, a subset of Significant Incidents, are incidents which involve a fatality or injury requiring in-patient hospitalization.#

Siting. Siting is the process of determining the location where a facility or structure, such as a pipeline, will be constructed.#

Skill. A demonstrable competency to perform a given task well, arising from talent, training or practice.#

Sleeve. A sleeve is a method used to repair a pipeline. Technically speaking: A sleeve is a full-encirclement of a pipeline with a reinforcing material at the location of a damage or defect to restore the strength of the pipe. Sleeves may be fabricated from steel or composite material. Sleeves may be for reinforcement only (Type A) or for reinforcement and pressure retention (Type B).#

Smart Pig. See Inline Inspection Tool.#

Subject Matter Expert (SME). An individual recognized as having a special skill or specialized knowledge of a process in a particular field, or of a piece of equipment.#

Specified Minimum Yield Strength (SMYS). SMYS is the minimum yield strength, expressed in pounds per square inch (psi) gage, prescribed by the specification under which pipe material is purchased from the manufacturer.#

Spill Response Plan. A spill response plan is a plan required of hazardous liquid pipeline operators for responding, to the maximum extent practicable, to a worst case discharge (spill) of oil, or the substantial threat of such a discharge.#

Standard. A written document which is commonly used and accepted as a basis for judging acceptability of performance in the areas addressed.#

Storage Facilities. Storage facilities are facilities designed and used for storage of oil or natural gas. Storage facilities vary greatly in size and design based on the product stored and the location and need within the pipeline system. Natural gas storage facilities typically operate so that large volumes of natural gas can be readily available for delivery to customers upon demand. The largest storage facilities are created in underground caverns, such as salt domes, or in porous rock formations.#

Stress. Stress is the resultant internal forces within a material that resist change in the size or shape of the material when the material is acted on by external forces. For example, as you blow into a balloon this causes stress in the material of the balloon that resists your efforts. Stress in the wall of a pipe resists the internal pressure exerted by the transported products. See Also: Hoop Stress.#

Surge Pressure. Surge pressure is internal Pressure produced in a pipeline by a change in velocity of the product stream flowing through the pipeline. Surge pressure can result from shutting down a pump, closure of a valve, or any other blockage of the flow.#

Survey. Survey refers to measurements, inspections, or observations performed to discover and identify events or conditions that indicate a departure from normal operation of the pipeline. One example is a leak survey.#

Tank Farm. A tank farm is a location of a group of large tanks maintained by a pipeline company and used to store crude oil and refined products. Tank farms normally store many different types of petroleum products, which are transported to and from the tank farm through pipelines.#

Task. A piece of work assigned to or expected of an individual(s).#

Outside Force Damage (Third Party Damage). Outside force damage is damage to an underground facility, such as a pipeline, resulting from some external force acting on the facility. Outside force damage to a pipeline or its protective coating is most often associated with damage from excavation activities around the buried pipe as a result of excavation equipment hitting the pipe, or from agricultural practices such as deep plowing or drainage tile installation. Outside force damage can usually be prevented by calling the one-call center before digging, waiting for the underground facility location to be marked, and excavating carefully while respecting the locate marks. Technically speaking: Ground movement from landslides, subsidence, or seismic activity can also exert damaging external loads on a pipeline. However, ground movement is not usually considered as outside force damage.#

Third Party Damage Prevention. Third-party damage prevention includes all efforts and programs designed to prevent outside force damage to underground facilities (e.g., pipelines) that can occur during excavation activities. Responsibility for preventing underground facility damage is shared by all stakeholders. Advanced planning, effective use of one-call systems, accurate locating and marking of underground facilities, and the use of safe-digging practices can all be very effective in reducing underground facility damage. See Also: Damage Prevention Initiatives, Damage Prevention Regulations, Outside Force Damage, External Force Damage#

Throughput. Throughput is a measurement of the amount of oil or gas product flowing through a pipeline.#

Total Cost of Incident. Total cost is defined as total property damage as reported on the operator-filed incident report.#

Training. An educational or instructional process (e.g., classroom, computer-based, or on-the-job) by which an individual’s knowledge and skill level is improved. While not currently required by the OQ rule, training is nonetheless fundamental to implementing many of the OQ rule’s requirements.#

Transmission Line. A transmission line is a pipeline used to transport natural gas from a gathering, processing or storage facility to a processing or storage facility, large volume customer, or distribution system. A large volume customer may receive similar volumes of gas as a distribution center, and includes factories, power plants, and institutional users of gas. Often used to describe hazardous liquid pipelines also, a transmission line is a pipeline used to transport crude oil from a gathering line to a refinery and refined products from a refinery to a distribution center.#

Trap. A trap is a pipeline component used to launch or receive inline inspection tools and pigs. See also: Launcher, Receiver#

Treatment Facilities (Natural Gas). Natural gas treatment facilities are facilities where natural gas is cleaned and conditioned to make it ready for transportation and use as an energy fuel. Natural gas extracted from wells often contains impurities, such as water, carbon dioxide and hydrogen sulfide, which could prevent use of the gas as an energy source or reduce its efficiency. Often too the natural gas is part of a mixture containing petroleum liquids. Removal of impurities allows for better transport and end usage of the gas. Treatment facilities contain equipment specifically designed to remove these impurities.#

Trench. A trench is a long narrow ditch dug into the ground and embanked with its own soil and used for concealment and protection of line pipe. Trenches are usually dug by a backhoe or by a specialized digging machine. See Also: Backfilling#

Uniform Corrosion. Uniform corrosion is corrosion occurring relatively evenly over a metal surface area. Rather than a few localized pits, uniform corrosion, sometimes referred to as ‘general corrosion’, is characterized by relatively uniform wall thinning over an area. It appears as a textured surface similar to that of an orange peel, where the affected surface area is deteriorating at an equal rate.#

Unusually Sensitive Areas (USAs). A USA is a drinking water or ecological resource area that is unusually sensitive to environmental damage from a hazardous liquid pipeline release, as defined in 49CFR 195.6.#

Uprating. Uprating is a process by which an existing pipeline is subjected to engineering evaluation to demonstrate its capability to operate at a pressure greater than that for which it was originally approved.#

Utility Pig. A utility pig is a pig that performs relatively simple mechanical functions, such as cleaning the pipeline.#

Valve. A valve is a mechanical device installed in a pipeline and used to control the flow of gas or liquid.#

Wall Loss. Wall loss is a term used to describe the thinning of a pipe wall, usually due to metal loss by corrosion.#

Wall Thickness. Wall thickness refers to the thickness of the pipe wall material. It is the dimensional measurement between a point on the inside surface of the pipe and the closest point on the outside surface of the pipe.#

Warning Letter. For some lower risk probable violations and program deficiencies, PHMSA has the option of issuing a Warning Letter notifying the operator of alleged violations and directing it to correct them or be subject to further enforcement action. PHMSA then follows up on these items during subsequent inspections or through other interactions with the operator. Warning Letters are described in 49 CFR 190.205.#

Wellhead. Wellhead refers to the point at which oil and natural gas is extracted from the ground.#

Work Performance History Review (WPHR). A process established by the Operator to ascertain the previously demonstrated competency of an individual to perform a covered task. Evaluation parameters should include:#

Wrinkles. Wrinkles are anomalies that are usually caused by excessive bending or curvature being applied to the pipe. Depending on the severity of the wrinkles, they may represent an undesirable anomaly that can cause localized stress concentrations and must be repaired. See also: Buckles#

Written. To set down in writing.#

Yield Strength. Yield strength is the stress level at which a material begins to deform permanently.#