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Anomaly.
Any kind of imperfection, defect, or critical defect that
may be present in the wall of the pipe.
Applied
Magnetic Field.
The strength of the magnetization field that is produced in
a pipe wall by a magnetizing system in an in-line inspection
tool.
Batching
Pig.
A utility pig that forms a moving seal in a pipeline to separate
liquid from gas media or to separate two different products
being transported in the pipeline. The most common configurations
of batching pigs are cup pigs and sphere pigs.
Bellhole.
An excavation in a local area to permit a survey, inspection,
maintenance, repair, or replacement of pipe sections.
Buckle. A partial
collapse of the pipe due to excessive bending associated with
soil instability, land slides, washouts, frost heaves, earthquakes,
etc.
Calibration
Digs.
Exploratory excavations, or bellholes, of portions of the pipeline
in which an in-line inspection tool has recorded an indication.
Camera
Pig.
A configuration pig that carries a video or film camera and
light sources for photographing the inside surface of a pipeline
on an intermittent or continuous basis.
Characterize.
To quantify the type, size, shape, orientation, and location
of an anomaly, defect, or critical defect.
Characterization.
The process of quantifying the size, shape, orientation, and
location of an anomaly, defect, or critical defect after it
has been detected. There are many degrees to which characterization
can be successful. For example, one type of characterization
of a mechanical-damage defect may be to determine whether
the defect contains a cold worked region (severe) or not (less
severe).
Class
Location.
A criterion for pipeline design set by the Code of Federal
Regulations. Class 1 is rural and Class 4 is heavily populated.
A class location is based on the number and type of buildings
situated in an area that extends 220 yards on either side
of the centerline of any continuous 1-mile length of a pipeline.
Classify.
To separate the cause of indications into one of three categories,
namely, anomalies, non-relevant conditions, or pipeline components.
Cleaning
Pig. A utility pig that uses cups, scrapers, or
brushes to remove dirt, rust, mill scale, or other foreign
matter from the pipeline. Cleaning pigs are run to increase
the operating efficiency of a pipeline or to facilitate inspection
of the pipeline.
Cold
working.
Distortion of the grains in the vicinity of a gouge. Cold
working often occurs immediately under the visible gouge and
can significantly reduce the mechanical properties of a pipe
steel.
Compression.
(1) The process of increasing the pressure of gas to maintain
its flow in a pipeline system. Compressing gas is analogous
to pumping liquids, such as water or oil. (2) The process
of reducing the amount of data to be stored in an in-line
inspection tool.
Configuration
Pig. An instrumented pig that collects data relating
to the inner contour of a pipe wall or of the pipeline. geometry
pigs, camera pigs, and mapping pigs are types of configuration
pigs.
Corrosion.
- General
External - Metal loss due to electrochemical, galvanic,
microbiological, or other attack on the pipe due to environmental
conditions surrounding the pipe.
- General
Internal - Metal loss due to chemical or other attack on
the steel from liquids on the inside of the pipe. Electrochemical
attack can also occur in local cells, but this condition
is less frequent.
- Pit
- Local concentrated-cell corrosion on the external or internal
surfaces that results from the generation of a potential
(voltage) difference set up by variations in oxygen concentrations
within and outside the pit. The oxygen-starved pit acts
as the anode and the pipe surface acts as the cathode.
- Stress
Corrosion Cracking - A progressive intergranular and/or
transgranular cracking that results from a combination of
applied tensile stress, cathodic protection currents, and
a suitable corrosive environment.
Cracks.
- Fatigue
- Progressive cracking in the base material, weld, or weld
zone that is caused by pressure cycling or oscillatory stresses
associated with the operation of the system.
- Girth
Weld - Cracks in the weld or weld zone of the butt welds
that connect sections of pipe.
- Seam
Weld - Cracks in the weld or weld zone of the longitudinal
seam weld of the pipe.
- Selective
Corrosion - A localized corrosion attack along the bond
line of electric resistance welds (ERW) and flash welds
(FW), that leads to the development of a wedge shaped groove
that is often filled with corrosion products.
Critical
Defect. As used in this text, a subset of defect,
for which an analysis, such as ASME B31G, would indicate that
the pipe is approaching failure at pressures equal to maximum
operating pressure or the maximum allowable operating pressure
for the pipe.
Cup
Pig.
A utility pig that is supported and driven by cups made of
a resilient material such as neoprene or polyurethane. At
least one of the cups forms a piston-like seal inside the
pipeline.
Defect.
As used in this text, an anomaly for which an analysis, such
as ASME B31G, would indicate that the pipe is approaching failure
as the nominal hoop stress approaches the specified minimum
yield stress of the pipe material.
Dent. A local
depression in the pipe surface caused by mechanical damage
that produces a gross disturbance in the curvature of the
pipe without reducing the pipe wall thickness.
Detect.
To sense or obtain a measurable indication from an anomaly
in a pipeline.
Detection.
The process of obtaining an inspection signal that
is recognized as coming from a defect or anomaly. An in-line
inspection tool can detect only those defects that produce
signals that are both measurable and recognizable. Not all
defects are detectable with all inspection systems.
Detection
Limit. The largest anomaly that could be missed
(not the smallest anomaly that could be found) by an in-line
inspection tool.
Disbonded Coating.
Any loss of bond between the protective coating and the steel
pipe as a result of adhesive failure, chemical attack, mechanical
damage, hydrogen concentrations, etc.
Dummy
Run.
A preliminary run of a utility pig to verify safe passage
of a fully instrumented tool through a section of pipeline.
Dummy runs may also be used to remove debris from inside the
pipeline.
Erosion.
Destruction or removal of material by abrasive action of moving
fluids (or gases) usually accelerated by the presence of solid
particles or matter in suspension.
Evaluation.
A review, following the identification of an anomaly, to determine
whether the anomaly meets specified acceptance criteria.
False
Call.
An indication from an inspection that is classified as an anomaly
where no imperfection, defect, or critical defect exists.
Flux.
The (scalar) number of flux lines crossing a unit area at
right angles to the unit area. See magnetic flux.
Flux
Density.
(1) A measure of the intensity of magnetization produced by
a magnetic field. (2) A vector quantity representing the number
of flux lines crossing a unit area at right angles.
Flux
Leakage.
The flow of flux out of a magnetic material, such as the wall
of a pipe, into a medium with lower permeability, such as
gas or air.
Gauging
Pig.
A utility pig that is permanently deformable by obstructions
in the pipeline and thus, upon retrieval from the line, provides
evidence of the worst-case obstruction in a given pipeline segment.
Gel
Pig.
A utility pig that is composed of a highly viscous gelled
liquid. These pigs are often used for pipeline cleaning and
are sometimes called gelly pigs.
Geometry
Pig.
A configuration pig designed to record conditions, such as
dents, wrinkles, ovality, bend radius and angle, and occasionally
indications of significant internal corrosion, by making measurements
of the inside surface of the pipeline.
Gouge. Local
damage caused by mechanical or forceful removal of metal from
a local area on the surface of the pipe that may work harden
the pipe and make it more susceptible to cracking.
Gouging.
The process of creating a zone of mechanical damage that includes
cold working, residual stresses, plastic distortion, and (generally)
moved or removed metal.
Hard
Spots. Local changes in hardness of the steel in
the pipe resulting from nonuniform quenching procedures during
the manufacture or changes in chemistry of the steel. Hard spots,
when stressed, are subject to failure from mechanisms, such
as hydrogen-stress cracking.
Holidays. Discontinuities
in a coating, such as pinholes, cracks, gaps, or other flaws,
that allow areas of the base metal to be exposed to any corrosive
environment that contacts the coating surface.
Hydrostatic
Retesting.
Proof testing of sections of a pipeline by filling the line
with water and pressurizing it until the nominal hoop stresses
in the pipe reach a specified value.
Identification.
The process of differentiating a signal caused by one type of
defect from signals caused by other types of defects or pipeline
features. Identification is particularly important for mechanical
damage defects because their signals are so small that they
can be mistaken as due to benign conditions. Mechanical-damage
signals are also small compared to signals from metal loss and
features such as valves.
Imperfection.
An anomaly in the pipe that will not result in pipe failure
at pressures below those that produce nominal hoop stresses
equal to the specified minimum yield stress of the pipe material.
Incident.
An event that is reported to U.S. Department of Transportation
Office of Pipeline Safety that involves fatalities, injuries,
property damage in excess of $50,000, unintentional release
of natural gas, customer outages, or other conditions that,
in the opinion of the pipeline operator, are significant enough
that they should be reported.
Inclusions. Foreign
material or particles in a metal matrix. These are usually
compounds, such as oxides, sulfides, or silicates, but may
be any substance that is foreign to the matrix whether it
is soluble or insoluble.
Indication.
(1) Any measured signal or response from an inspection of
a pipe above the normal baseline signal. (2) Measurements
made during monitoring of cathodic protection systems.
Induction
Coil Sensor.
A type of sensor that measures the time rate of change in
flux density. Induction coils do not require power to operate.
Inspection.
(1) The process of examining a pipe using a nondestructive
testing technique to look for anomalies or to evaluate the
nature or severity of an indication. (2) The process of running
a configuration tool or an in-line inspection tool through
a pipe to detect anomalies.
In-Line
Inspection (ILI).
The inspection of a pipeline from the interior of the pipe
using an in-line inspection tool.
In-Line
Inspection Tool (ILI Tool).
The device or vehicle, also known as an intelligent or smart
pig, that uses a nondestructive testing technique to inspect
the wall of a pipe. An in-line inspection tool is one type
of instrumented tool.
Intelligent
Tool.
See in-line inspection tool.
Instrumented
Tool or Pig.
A vehicle or device used for internal inspections of a pipe,
which contains sensors, electronics, and recording or output
functions integral to the system. Instrumented tools are divided
into two types: (a) configuration pigs, which measure the
pipeline geometry or the conditions of the inside surface
of the pipe, and (b) in-line inspection tools that use nondestructive
testing techniques to inspect the wall of the pipe for corrosion,
cracks, or other types of anomalies.
Joint.
A single section of pipe that is welded to others to make up
a pipeline. A joint of pipe is often 40-feet long.
Lack
of Fusion (LOF). In a weld, any area or zone that
lacks complete melting and coalescence (fusion) of a portion
of the weld. This may occur between weld passes or between weld
and base materials.
Lack of Penetration (LOP).
In the welding process, failure to achieve fusion of the base
metal to the desired or planned depth.
Lamination. A
type of imperfection or discontinuity with separation or weakness,
usually aligned parallel to the worked surface of a metal.
Launcher.
A pipeline facility used for inserting a pig into a pressurized
pipeline.
Magnetic
Flux.
A measure of the amount of magnetization carried by a material.
Magnetic
Flux Leakage.
An inspection technique in which a magnetic field is applied
to a pipe section and measurements are taken of the magnetic
flux density at the pipe surface. Changes in measured flux
density indicate the presence of a possible defect. Also called
MFL.
Mapping
Pig.
A configuration pig that uses inertial sensing or some other
technology to collect data that can be analyzed to produce
an elevation and plan view of the pipeline route.
Maximum
Allowable Operating Pressure (MAOP).
The maximum internal pressure permitted the operation of a
pipeline as defined by the Code of Federal Regulations.
Maximum
Operating Pressure (MOP).
The maximum internal pressure expected during the operation
of a pipeline, which cannot normally exceed the maximum allowable
operating pressure.
Measurable.
Producing an inspection signal that is above the noise level
inherently present in the pipe.
Mechanical
Damage.
Any of a number of types of anomalies in pipe caused by the
application of an external force. Can include dents, gouges,
and metal loss .
Mechanical
Distortion.
Changes in wall thickness or changes in the cylindrical shape
of a pipe. A gouge, because it includes cold working, residual
stresses, plastic strains, and moved or removed metal, contains
both mechanical and magnetic distortion.
Metal
Loss.
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.
MFL.
An inspection technique in which a magnetic field is applied
to a pipe section and measurements are taken of the magnetic
flux density at the pipe surface. Changes in measured flux
density indicate the presence of a possible defect. Also called
magnetic flux leakage.
Monitoring.
Measurements or periodic inspections made at selected locations
along the pipeline.
Nondestructive
Evaluation (NDE).
The evaluation of results from nondestructive testing methods
or nondestructive testing techniques in order to detect, locate,
measure, and evaluate anomalies.
Nondestructive
Testing (NDT).
The actual application of a nondestructive testing method
or a nondestructive testing technique.
Nondestructive
Testing Method (NDT Method).
A particular method of nondestructive testing, such as radiography,
ultrasonics, magnetic testing, liquid penetrants, visual,
leak testing, eddy current, and acoustic emission.
Nondestructive
Testing Technique (NDT Technique).
A specific way of utilizing a particular nondestructive testing
method that distinguishes it from other ways of applying the
same nondestructive testing method. For example, magnetic
testing is a nondestructive testing method while magnetic
flux leakage and magnetic particle inspection are nondestructive
testing techniques. Similarly ultrasonics is a nondestructive
testing method, while contact shear-wave ultrasonics and contact
compression-wave ultrasonics are nondestructive testing techniques.
Non-Relevant
Indication.
A response recorded on a chart, data display, or record that
comes from a source outside the pipeline, such as foreign
objects in the ditch.
Obstructions.
Any restriction or foreign object that reduces or modifies the
cross section of the pipe to the extent that gas flow is affected
or in-line inspection pigs can become stuck (ovality, collapse,
dents, undersized valves, wrinkles, bends, weld drop through).
Also any foreign object in the pipeline. (See pipe collapse)
Ovality. A condition
in which a circular pipe forms into an ellipse, usually as
the result of external forces.
Pig.
A generic term signifying any independent, self-contained device,
tool or vehicle that moves through the interior of the pipeline
for purposes of inspecting, dimensioning, or cleaning. All pigs
in this report are either utility pigs or instrumented tools.
Pipe. As used
in this text, the steel pipe exclusive of protective coatings
or attachments that is used to transport natural gas.
Pipeline.
That portion of the pipeline system between the compressor
stations including the pipe, protective coatings, cathodic
protection system, field connections, valves and other appurtenances
attached or connected to the pipe.
Pipeline
Component.
A feature, such as a valve, cathodic protection connection
or tee that is a normal part of the pipeline. The component
may produce an indication that is recorded as part of an inspection
by an in-line inspection tool or configuration pig.
Pipeline
System.
All portions of the physical facilities through which gas
moves during transportation including pipe, valves, and other
appurtenances attached to the pipe, such as compressor units,
metering stations, regulator stations, delivery stations,
holders and other fabricated assemblies. (See 49 Code of Federal
Regulations 192)
Plastic
Strains.
Strains beyond the elastic limit of a material due to mechanical
damage. Plastic strains and cold working are related, but
not the same.
Pole
Piece.
A magnetic material that channels a magnetic field from a
magnet into a pipe material.
Pole
Spacing.
The distance between pole pieces of a magnetizing assembly.
Porosity. Small
voids or pores, usually gas filled, in the weld metal.
Radius
Bends. The radius of the bend in the pipe as related
to the pipe diameter (D). Example: A 3D bend would have a radius
of three times the diameter of the pipe measured to the centerline
of the pipe.
Receiver.
A pipeline facility used for removing a pig from a pressurized
pipeline.
Recognizable.
Producing a signal that can be identified as coming from a
particular type of defect, e.g., mechanical damage.
Remanent
Magnetization.
The magnetization level left in a steel pipe after the passage
of a magnetic in-line inspection tool.
Remediation.
An operation or procedure that eliminates the factor or factors
causing an imperfection, defect, or critical defect.
Rerounding.
The process of changing the dent depth and shape by internal
pressure in the pipe. Generally, dents due to third-party
contact will reround, while dents due to rocks will not unless
the rock causing the dent is removed.
Residual
Stresses.
Elastic stresses that were not present within the pipe wall
before mechanical damage but that are present after the damage
has occurred.
Saturation.
The degree of magnetization where a further increase in magnetic
field strength produces a decrease in permeability of a material.
Scabs. See slivers
.
SCC.
Stress-corrosion cracking. 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 a susceptible line-pipe steel.
Shielded
Corrosion.
corrosion between the pipe and the protective coating, which
is not controlled by cathodic protection currents.
Sizing.
See characterization.
Slivers. A thin
elongated anomaly caused when a piece of metal is rolled into
the surface of the pipe. A sliver is usually metallurgically
attached at only one end. In MFL inspections, a sliver is
sometimes called a lamination.
Smart
Pig.
See in-line inspection tool.
Specified
Minimum Yield Strength or Stress (SMYS).
A required strength level that the measured yield stress of
a pipe material must exceed, which is a function of pipe grade.
The measured yield stress is the tensile stress required to
produce a total elongation of 0.5 percent of a gage length
as determine by an extensometer during a tensile test.
Sphere
Pig.
A spherical utility pig made of rubber or urethane. The sphere
may be solid or hollow, filled with air or liquid. The most
common use of sphere pigs is as a batching pig.
Stress.
Corrosion
Cracking. 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 a susceptible line-pipe steel. Also called SCC.
Survey.
Measurements, inspections, or observations intended to discover
and identify events or conditions that indicate a departure
from normal operation of the pipeline.
Tenting.
A tent-shaped void formed along a the longitudinal seam-weld
reinforcement in a pipe when the external coating is not in
continuous intimate contact with the pipe and weld surfaces.
Testing.
See hydrostatic retesting.
Tool.
A generic term signifying any type of instrumented tool or
pig.
Transducer.
A device for converting energy from one form to another; for
example, in ultrasonic testing, conversion of electrical pulses
to acoustic waves and vice-versa.
Transmission
Line.
A pipeline, other than a gathering or distribution line, that
transports gas from a gathering or storage facility to a distribution
center or storage operates at a hoop stress of 20 percent
or more of the specified minimum yield stress of the pipe,
or transports gas within a storage field. (See 49 Code of
Federal Regulations 192)
Trap.
pipeline facility for launching and receiving tools and pigs.
Utility
Pig.
A pig that performs relatively simple mechanical functions,
such as cleaning the pipeline.
Wrinkles.
Ripples that occur on the inner radius of a pipe when the pipe
is cold bent.
Yield
Pressure. The
pressure at which the nominal hoop stress in the wall of a pipe
equals the specified minimum yield stress of the pipe grade.
Source:
Battelle Memorial Institute
2002
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