ISO 16826 (2025): NON-DESTRUCTIVE TESTING —
ULTRASONIC TESTING — TESTING FOR
DISCONTINUITIES PERPENDICULAR TO THE SURFACE
The latest edition of ISO 16826 (2025),
published in March 2025 by the ISO/
TC 135/SC 3 committee, establishes a
structured framework for the tandem
technique and the longitudinal-
longitudinal-transverse wave (LLT) tech-
nique in ultrasonic testing. Designed
to enhance the detection of planar
discontinuities perpendicular or nearly
perpendicular to a material’s surface, this
standard refines nondestructive testing
(NDT) methodologies for improved flaw
characterization in critical applications.
Planar discontinuities, such as lack of
fusion in welded joints, fatigue cracks,
or delaminations in multilayer structures,
pose significant risks to structural integ-
rity, as they can serve as initiation points
for catastrophic failure under mechanical
stress. Detecting these defects is partic-
ularly important in industries where load-
bearing components and safety-critical
structures must meet stringent reliability
standards. For example, in aerospace
applications, pi-joint connections used
in aircraft fuselage assemblies rely on
flawless bonding, as any embedded
cracks could compromise airframe
strength. Similarly, in oil and gas pipe-
lines, perpendicular discontinuities in
girth welds could lead to stress corro-
sion cracking, increasing the risk of
leaks or ruptures under high-pressure
conditions. These discontinuities are also
critical concerns in nuclear power plant
components, shipbuilding, and heavy
industrial machinery, where failure could
have severe safety and environmental
consequences.
ISO 16826 (2025) provides specific
guidelines for inspecting metallic mate-
rials with thicknesses between 40 mm
and 500 mm, ensuring consistent
detection and evaluation of embedded
defects. While primarily developed
for industrial metallic components, the
standard allows for its application to
other materials and smaller thicknesses,
provided specialized testing proce-
dures are followed. The inclusion of
phased array ultrasonic testing (PAUT)
as a complement to tandem and LLT
techniques further enhances defect
detection and evaluation capabilities,
though additional verification steps may
be necessary.
By incorporating the principles
outlined in ISO 16810, this standard
strengthens quality control, structural
integrity assessment, and safety assur-
ance across industries such as oil and
gas, power generation, aerospace,
and heavy manufacturing. It ensures
that ultrasonic inspections maintain a
high degree of accuracy, particularly in
detecting internal planar defects that
might be missed by conventional testing
methods.
ISO 16826 (2025) underscores the
evolving landscape of ultrasonic testing,
offering a precise, standardized, and
adaptable approach for industries
that demand superior reliability in flaw
detection. As a key resource for NDT
professionals, this standard supports the
continued advancement of ultrasonic
inspection technology, enabling safer
and more efficient asset management
worldwide.
STANDARDS EDITOR
Hossein Taheri, PhD: Georgia
Southern University, Statesboro, GA
htaheri@georgiasouthern.edu
IN DEVELOPMENT
The following section provides a summary of new standards, drafts, and revisions that may be of interest to the nondestructive testing and evaluation
(NDT/E) community. This summary is provided in Materials Evaluation on a quarterly basis in January, April, July, and October. For the latest information,
please visit the website of the standards provider.
PROJECT INITIATION
ANSI procedures require notification by ANSI-
accredited standards developers of the initiation
and scope of activities expected to result in
new or revised American National Standards.
The following is a list of proposed actions and
new standards that have been received recently
from accredited standards developers. To view
information about additional standards for
which a project initiation notification has been
submitted, and to search approved American
National Standards, please visit ansi.org, which
is a database of standards information. Note that
this database is not exhaustive.
Ñ BSR S2.1/ISO 2041-202x, Mechanical
Vibration, Shock, and Condition Monitoring
Vocabulary. This is an identical national
adoption of ISO 2041:2018 and revision of
ANSI/ASA S2.1-2009 (R2020), ISO 2041-2009
(R2020). It contains a collection of terms, expres-
sions, definitions unique to the specialized areas
of mechanical vibration, shock, and condition
monitoring, and gives specific recommen-
dations for use in national and international
standards pertaining to those areas.
STANDARDSUPDATE
|
SCANNER
A P R I L 2 0 2 5 • M AT E R I A L S E V A L U AT I O N 19
ULTRASONIC TESTING — TESTING FOR
DISCONTINUITIES PERPENDICULAR TO THE SURFACE
The latest edition of ISO 16826 (2025),
published in March 2025 by the ISO/
TC 135/SC 3 committee, establishes a
structured framework for the tandem
technique and the longitudinal-
longitudinal-transverse wave (LLT) tech-
nique in ultrasonic testing. Designed
to enhance the detection of planar
discontinuities perpendicular or nearly
perpendicular to a material’s surface, this
standard refines nondestructive testing
(NDT) methodologies for improved flaw
characterization in critical applications.
Planar discontinuities, such as lack of
fusion in welded joints, fatigue cracks,
or delaminations in multilayer structures,
pose significant risks to structural integ-
rity, as they can serve as initiation points
for catastrophic failure under mechanical
stress. Detecting these defects is partic-
ularly important in industries where load-
bearing components and safety-critical
structures must meet stringent reliability
standards. For example, in aerospace
applications, pi-joint connections used
in aircraft fuselage assemblies rely on
flawless bonding, as any embedded
cracks could compromise airframe
strength. Similarly, in oil and gas pipe-
lines, perpendicular discontinuities in
girth welds could lead to stress corro-
sion cracking, increasing the risk of
leaks or ruptures under high-pressure
conditions. These discontinuities are also
critical concerns in nuclear power plant
components, shipbuilding, and heavy
industrial machinery, where failure could
have severe safety and environmental
consequences.
ISO 16826 (2025) provides specific
guidelines for inspecting metallic mate-
rials with thicknesses between 40 mm
and 500 mm, ensuring consistent
detection and evaluation of embedded
defects. While primarily developed
for industrial metallic components, the
standard allows for its application to
other materials and smaller thicknesses,
provided specialized testing proce-
dures are followed. The inclusion of
phased array ultrasonic testing (PAUT)
as a complement to tandem and LLT
techniques further enhances defect
detection and evaluation capabilities,
though additional verification steps may
be necessary.
By incorporating the principles
outlined in ISO 16810, this standard
strengthens quality control, structural
integrity assessment, and safety assur-
ance across industries such as oil and
gas, power generation, aerospace,
and heavy manufacturing. It ensures
that ultrasonic inspections maintain a
high degree of accuracy, particularly in
detecting internal planar defects that
might be missed by conventional testing
methods.
ISO 16826 (2025) underscores the
evolving landscape of ultrasonic testing,
offering a precise, standardized, and
adaptable approach for industries
that demand superior reliability in flaw
detection. As a key resource for NDT
professionals, this standard supports the
continued advancement of ultrasonic
inspection technology, enabling safer
and more efficient asset management
worldwide.
STANDARDS EDITOR
Hossein Taheri, PhD: Georgia
Southern University, Statesboro, GA
htaheri@georgiasouthern.edu
IN DEVELOPMENT
The following section provides a summary of new standards, drafts, and revisions that may be of interest to the nondestructive testing and evaluation
(NDT/E) community. This summary is provided in Materials Evaluation on a quarterly basis in January, April, July, and October. For the latest information,
please visit the website of the standards provider.
PROJECT INITIATION
ANSI procedures require notification by ANSI-
accredited standards developers of the initiation
and scope of activities expected to result in
new or revised American National Standards.
The following is a list of proposed actions and
new standards that have been received recently
from accredited standards developers. To view
information about additional standards for
which a project initiation notification has been
submitted, and to search approved American
National Standards, please visit ansi.org, which
is a database of standards information. Note that
this database is not exhaustive.
Ñ BSR S2.1/ISO 2041-202x, Mechanical
Vibration, Shock, and Condition Monitoring
Vocabulary. This is an identical national
adoption of ISO 2041:2018 and revision of
ANSI/ASA S2.1-2009 (R2020), ISO 2041-2009
(R2020). It contains a collection of terms, expres-
sions, definitions unique to the specialized areas
of mechanical vibration, shock, and condition
monitoring, and gives specific recommen-
dations for use in national and international
standards pertaining to those areas.
STANDARDSUPDATE
|
SCANNER
A P R I L 2 0 2 5 • M AT E R I A L S E V A L U AT I O N 19
