Page 173 - CW E-Magazine (29-7-2025)

Special Report

collect detailed data regardless of
crack orientation(6).

When used in conjunction with
other integrity management program
components, technologies like the
Eclipse UCx, can be used as a safer
and more economical replacement for
post-construction hydrostatic testing.

Long Range Ultrasonic Testing
(LRUT)
Guided waves are used in long
range ultrasonic testing (LRUT) to
scan pipelines that are otherwise in-
accessible for inspection. Guided
waves are propagated in a pipe wall
from a ring of equally spaced ultra-
sound probes supported by a collar
wrapped around the pipe. The ultra-
sonic waves are refl ected by disconti-
nuities such as girth welds, branches
in pipeline circuit, and reductions
in wall thickness (an indication of
corrosion). These refl ected waves are Fig. 9: LRUT setup used for buried coated pipelines and insulated pipelines
detected and then analysed with the sion above 3% of the cross-sectional of pipelines passing under non-acces-
help of computers. area. Figure-9 shows an LRUT setup sible culverts, buried piping and at
used for buried coated pipelines and road crossings.
LRUT can typically scan a length insulated pipelines.
of 60-120 m if the line is straight. If Benefi ts of using ultrasonic crack
the line is insulated, the length will be The velocity of the guided wave inspections for pipes
reduced, since absorption is greater is a function of the thickness of the One of the main benefi ts of ultra-
with some kinds of insulation. Sup- medium and frequency (mode) of wave. sonic inspections is the speed and
port locations, connections, and bends CUI will lead to changes in thickness versatility over other inspection tech-
in pipelines further reduce the span of in the medium (pipe wall) locally. In niques. Some other advantages include:
inspection. Even so, LRUT is consi- addition to scatter and refl ection, this  Sensitivities to surface and subsur-

dered one of the most eff ective tools will lead to mode conversion of the face discontinuities allow the ins-
in identifying CUI in pipelines where incident waves. Therefore, refl ected pections to detect the early onset
removal of insulation is diffi cult. LRUT waves will contain both incident wave of more signifi cant structural issues.
can be done on two-inch diameter mode, plus mode-converted waves.  The depth of penetration of ultra-

pipes or greater. It requires a portion Detection of these mode-converted sonic sound waves surpasses that of
of the insulation to be removed for waves in a refl ected signal is a strong other NDT methods, such as mag-
the instrument’s collar to attach to the indicator of discontinuities such as netic fl ux inspection.
pipeline. The ultrasonic waves can CUI in an insulated pipeline.  Some ultrasonic testing techniques
detect corrosion in the piping from require only single-side access,
approximately 5-200 m from the col- The interpretation of LRUT is diffi - making the method ideal for pipe-
lar, which depends on factors such cult compared to tools such as an IR lines that may be diffi cult to access.
as the coating, type of corrosion, and survey and often require a specialist.  Minimal part preparation is re-

whether the pipe is buried. LRUT can But it is the most reliable tool to quired; therefore, ultrasonic testing
be used for buried coated pipelines and inspect insulated pipelines at non- units can be quickly mobilised and
insulated pipelines. It can detect corro- accessible locations, such as portions deployed.

Chemical Weekly July 29, 2025 173

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