Operations & Maintenance Enforcement Guidance Part 192 Subparts L and M

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Compressed natural gas

Natural gas stored inside containers at a pressure greater than atmospheric air pressure. CNG is normally placed in pressure containing vessels (bottles) where it can be used as a portable fuel source (i.e., in CNG vehicles and other applications not attached to a pipeline).


Compressor station

Any combination of facilities which supplies the energy to move gas at increased pressure from production fields, in transmission lines, or into storage. Compressor stations are strategically placed along the pipeline to boost the pressure to maintain required pressures and flow rates. Typical components found at gas compressor stations include: piping manifolds, coolers, valves, reciprocating or centrifugal compressors, prime movers (electric motors, gas engines, gas turbines), and local controls and instrumentation, and may include liquid separation and collection facilities, as well as pigging facilities.



The ability of a substance (measured in ohm-cm) to conduct an electric charge or current due to the presence of positively or negatively charged ions.


Confirmatory direct assessment

An integrity assessment method using more focused application of the principles and techniques of direct assessment to identify internal and external corrosion in a covered transmission pipeline segment.


Control piping

Pipe, valves and fittings used to interconnect air, gas, or hydraulically operated control apparatus.


Control room

An operations center staffed by personnel charged with the responsibility for remotely monitoring and controlling a pipeline facility.



Control valve

A mechanical device used to vary flow rates and pressures on pipelines. Positioning signals are sent to the valve to achieve and maintain the desired set point. A control valve may be a globe, plug, or ball-type valve. Its actuator may be pneumatic, hydraulic or electrically driven.



A qualified individual who remotely monitors and controls the safety-related operations of a pipeline facility via a SCADA system from a control room, and who has operational authority and accountability for the remote operations functions of the pipeline facility.



Conversion of Service

A steel pipeline previously used in service not subject to this part




The deterioration of a material, usually a metal, that results from a reaction with its environment.


Corrosion rate

The rate at which corrosion proceeds.



A small, carefully weighed and measured specimen of metal that is used to determine metal loss caused by corrosion over a specified period of time.


Covered segment or covered pipeline segment

A segment of gas transmission pipeline located in a high consequence area


Covered task

An activity, identified by the operator, that: (1) Is performed on a pipeline facility; (2) Is an operations or maintenance task; (3) Is performed as a requirement of this part; and (4) Affects the operation or integrity of the pipeline.

192.801 195.501


Cracks in line pipe are separations in the molecular structure of the base metal and form as a result of improper manufacturing, construction, operational stresses, or mechanical damage. Cracks are detrimental to the pipe's pressure restraining capabilities and can propagate into complete failure or rupture zones.



Standards on which a judgment or decision is made. The standard is established by rule, test, standard, consensus, or other means.


Critical Interference bond

An interference bond whose failure would jeopardize structural protection. 'Critical bonds' are metallic connections between adjacent buried structures that, if not connected, would allow detrimental corrosion to occur on one facility. The bond is only critical to the more negative pipeline facility, or the one losing current to the other facility.


Curb valve

A valve installed for the purpose of shutting off the gas supply to a building. It is installed below grade in a service line at or near the property line and is operated by use of a removable key or specialized wrench. The valve is normally installed with a protective curb box or standpipe over or around it for quick subsurface access.



The flow of electrons in a circuit, measured in amperes (amps).


Customer meter

A device that measures gas delivered to a customer from consumption on its premises.


Customer regulator

A device that limits and maintains a set pressure to the customer. This pressure controlling device is normally installed just upstream of the customer meter.


Deep anode (ground) bed

A ground bed in which the anodes are placed far below the earth’s surface in a single vertical hole. Deep ground beds are typically considered 50 feet or deeper.



An imperfection in a pressure vessel or pipe that, depending on the type of defect, should be analyzed using a recognized and approved procedure, such as ASME B31G or RSTRENG. Defects may need to be repaired or removed, or the operating pressure lowered, depending on operating requirements of the facility.



A depression that produces a gross disturbance in the curvature of the pipe wall without reducing the pipe-wall thickness. The depth of a dent is measured as the gap between the lowest point of the dent and a prolongation of the original contour of the pipe.


Design formula - gas

Based on Barlow's Equation, the formula is used to calculate the maximum design pressure of new pipe, and is determined in accordance with the following formula. When used to calculate gas pipeline design pressures, additional factors of F(class design factor as found in §192.111), E (longitudinal joint factor as determined in §192.113) and T (temperature derating factor as found in §192.115) are used, which makes the final gas design formula P=(2St)/D) x F x E x T.

192.105 Interpretation 192.106(6), July 25, 1973

Destructive testing

A physical testing process (such as a burst or a tensile test) during which the specimen being tested is rendered unusable.



To establish or ascertain definitely after considering an investigation or calculation. This is critical in differentiating between "discovering" vs. "determining" with respect to required time frames with which to file a "safety-related condition" report to the Office of Pipeline Safety (191.25 and195.56(a)). However, for integrity Management (§§192.933 and 195.452) there is no distinction between discovery and determination.




Direct assessment (DA)

An integrity assessment method that utilizes a process to evaluate certain threats (i.e., external corrosion, internal corrosion and stress corrosion cracking) to a covered pipeline segment's integrity. The process includes the gathering and integration of risk factor data, indirect examination or analysis to identify areas of suspected corrosion, direct examination of the pipeline in these areas, and post assessment evaluation.

192.903 195.553

Direct current (DC)

An electrical current whose polarity or direction is constant with respect to time. DC current is typically used in impressed current cathodic protection systems. A rectifier is used to produce DC current.


Direct sales lateral

A pipeline that transports gas directly from a transmission line to a large volume customer such as a factory or power plant. This pipeline is connected upstream from a distribution center or directly off of a transmission line.

Interpretation PI 89-019


The loss of adhesion between a coating and the substrate (pipe surface).

NACE/ASTM G193 Corrosion Terms


To find, obtain knowledge or information, or become aware of a condition for the first time. For IM, discovery is when an operator has adequate information about the condition to determine a potential threat (FAQ-58).


Distributed anode bed

A ground bed where the anodes are spread over a wide geographical area. Usually employed to protect densely routed buried piping systems, such as in compressor station yards.


Distribution line

A pipeline other than a gathering or transmission line. A pipeline that carries or controls the supply of natural gas from a town border or city gate and moves the gas to the customer.


Double submerged arc weld (DSAW)

A pipe having longitudinal or spiral butt joints produced by at least two weld passes, including at least one each on the inside and outside of the pipe. Coalescence is produced by heating with an electric arc or arcs between the bare metal electrode or electrodes and the work. The welding molten metal is shielded by a blanket of granular, fusible material on the work that is used to reduce the impurities (slag) introduced from the surrounding air. Pressure is not used and filler metal for the inside and outside welds is obtained from the electrode(s).



The direction in which the fluid is going with regard to a reference point. With compressor and pump stations, downstream would be the discharge side of the facility.


Drip type odorizer

Equipment for introducing odorant from a storage tank directly into a gas stream through a gravity flow system. The odorant may be regulated by the orifice float valves or rotameters.


Ductile (nodular) iron

A cast ferrous material in which the free graphite (carbon) present is in a spherical form rather than a flake form as in cast iron. These round shaped carbon elements cause ductile iron to be more malleable than cast iron, yet retain its toughness. These desirable properties of ductile iron are achieved by means of chemistry and a specialized heat treatment of the castings.


Elbow (ELL)

A pipe fitting that makes an angle in a pipe run. Unless stated otherwise, the angle is usually assumed to be 90°. In larger pipelines, fitting type elbows may not be recommended due to their abrupt change in direction. Piggable lines should be equipped with bends of a minimum bend ratio of 1 1/2D, but the actual radius depends on the type of pig.


Electric flash welded pipe

Pipe having a longitudinal butt joint wherein coalescence is produced simultaneously over the entire area of butting surfaces by the heat obtained from resistance to the flow of electric current between the two surfaces, and by the application of pressure after heating is substantially completed. Flashing and upsetting are accompanied by the expulsion of metal from the joint.


Electric fusion welded pipe

Pipe having a longitudinal butt joint wherein coalescence is produced in the preformed tube by manual or automatic electric-arc welding. The weld may be single or double and may be made with or without the use of filler metal.


Electric resistance welded (ERW) pipe

Pipe which has a longitudinal butt joint wherein coalescence is produced by the application of pressure and by the heat obtained from the resistance of the pipe to the flow of an electric current in a circuit of which the pipe is a part.


Electrical isolation

The condition of being electrically separated from other metallic structures or the environment.


Electrical resistance probes

An electronic probe that can be used in systems where gas or liquids (including hydrocarbons) are present to determine metal loss over time by measuring the increase in the resistance of the electrode as its cross-sectional area is reduced by corrosion. The resistance of the electrode is then compared with the resistance of a reference electrode.


Electrical survey

A series of closely spaced pipe-to-soil readings over pipelines which are subsequently analyzed to identify locations where a corrosive current is leaving the pipe.

192.3 195.553


An electronic conductor used to establish electrical contact with an electrolyte as part of a cathodic protection circuit.



A chemical substance containing ions that migrate in an electric field. Electrolytes can play a role in external corrosion or internal corrosion of metallic pipelines.  For external corrosion, electrolyte refers to the soil or liquid adjacent to and in contact with a buried or submerged piping system, including the moisture and other chemicals contained therein. For internal corrosion, electrolyte refers to the chemicals contained in water on the inside the pipeline, including solutions of salts, acids and bases.


Electrolytically shorted/coupled casing

A casing with a low casing to pipe resistance due to the presence of an electrolyte in the casing/pipe annulus. Electrolytically shorted or coupled casings may be shorted periodically and not continuously. These casing are not considered to be metallically shorted.


Emergency response personnel

Any persons engaged in the response to an emergency, including firefighters, police, civil defense/emergency management officials, sheriffs, military, manufacturing and transportation personnel.


Emergency valve

For gas transmission operations, an emergency valve is any valve that might be required during any emergency. For gas distribution operations, an emergency valve is any valve which may be necessary for the safe operation of a distribution system.

192.745 192.747


The surroundings or conditions (physical, chemical, mechanical) in which a material exists.

NACE/ASTM G193 Corrosion Terms


Abrasive metal loss caused by high surface velocity of the transported media, particularly when entrained solids or particulates are present.


Evaluation (OQ)

A process, established and documented by the operator, to determine an individual's ability to perform a covered task by any of the following: (a) Written examination; (b) Oral examination; (c ) Work performance history review; (d) Observation during (1) performance on the job, (2) on the job training, or (3) simulations; or (e) Other forms of assessment

192.803 195.503

Excavation activities

Excavation, blasting, boring, tunneling, backfilling, the removal of above ground structures by either explosive or mechanical means, and other earth moving operations.



Excavation damage

Any impact that results in the need to repair or replace an underground facility due to a weakening, or the partial or complete destruction, of the facility, including, but not limited to, the protective coating, lateral support, cathodic protection, or the housing for the line device or facility.


Excess flow valve (EFV)

A device that is installed in a gas pipeline or service line to automatically restrict or shut off the gas flow through the line when the flow exceeds a predetermined limit.



To undergo a rapid chemical reaction with the production of noise, heat, and violent expansion of gases, or to burst violently as a result of pressure.

Exposed pipeline

Any part of a pipeline not completely buried, and partially exposed to the atmosphere.


Exposed underwater pipeline

An underwater pipeline where the top of the pipe protrudes above the underwater natural bottom (as determined by recognized and generally accepted practices) in waters less than 15 feet (4.6 meters) deep, as measured from mean low water.

192.3 195.2 195.413

External corrosion direct assessment (ECDA)

A four-step process that combines pre-assessment, indirect inspection, direct examination, and post-assessment to evaluate the threat of external corrosion to the integrity of a pipeline.




A design feature which will maintain or result in a safe condition in the event of malfunction or failure of a power supply, component, or control device. Fail-safe may occur by three methods: fail open, fail close, or fail at last position.


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