capture and system intelligence such as pitch, roll,
and system pressurization levels.
Crawler bodies are often modular in nature and
may be configured to accommodate a wide range
of assets (Figure 2). Wheeled or tracked units can
both be effective depending on the area to be tra-
versed. Access to the asset to be inspected should
also be considered, as confined launch areas, piping
geometry, or other obstacles may impact the ideal
wheel size, camera selection, or tooling configu-
ration. Vertical travel may be achieved utilizing
variable-geometry crawlers that leverage opposing
force on pipe walls, or by using vacuum-based,
magnetic-based, or magnetic-wheeled crawlers.
Each maintain certain advantages in specific appli-
cations depending on access, geometry, cleanliness,
material, contents, and line features.
Cameras and accompanying lighting are
utilized for both navigation and inspection. Ideally,
inspection cameras will offer PTZ features to
enhance data capture efforts. Advanced camera
features such as variable lighting control, aperture
manipulation, and automated weld, joint, or
feature scanning are invaluable to quality inspec-
tion efforts.
The cable reel functions as a means of com-
munication between the CCU and crawler, and
in case of an unplanned event such as a loss of
power or change in atmospheric conditions, the
safe removal of the tool. While some units may be
operated without tethers, deployment in industrial
applications typically requires a positive means of
extraction. Automated cable reels can advance and
retract the cable with the crawler movement to ease
operation and lessen the burden on the inspec-
tion team. Care should be taken with cable tending
when the crawler is navigating around obstacles
so as not to destabilize the unit. Excessive slack or
tension may inadvertently overturn the crawler.
Sensor payloads for inspection crawlers can be
extensive. Tremendous industry investment has
accelerated the advancement of remote operation
tooling. Common accoutrements include lidar or
laser scanning, ultrasonics, eddy current, radiogra-
phy, and cleaning apparatuses or nozzles to facili-
tate hydrolazing (high-pressure water jetting) or CO2
cleaning. Deployment of these tools and the asso-
ciated cables and/or hoses may constrain crawler
functionality, travel distance, and agility.
Deployment Considerations
Crawler selection should be suited for the mission
objectives, inspection specifications, and line/
asset features. Mission objectives should define the
purpose and work scope. Key mission parameters
may include distance to be traveled, what data is
to be collected, and what method of testing is to be
completed. Inspection specifications will under-
score the applicable codes and standards to be
utilized. Collectively, this information shapes equip-
ment selection, technician suitability based on nec-
essary experience or certifications, and inspection
team makeup.
Operators should use care in evaluating the
access point location, orientation, and obstacles
for insertion. Common line feature considerations
include pipe geometry such as the number of
bends, bend radius, slope, and/or vertical sections
of piping system design features such as valves and
their number, location, type, and orientation and
instrumentation such as thermowells. Additionally,
obstacles such as vertical tees or downcomers to be
traversed should also be evaluated. Fabrication and
service-induced anomalies (including backing or
chill rings) and excessive line exfoliation should also
be considered. Atmospheric testing, temperature,
and cleanliness will also impact crawler selection
and mission planning.
Figure 2. Modular
robotic crawler.
J U L Y 2 0 2 4 • M A T E R I A L S E V A L U A T I O N 37
CREDIT:
ENVIROSIGHT

While evacuated lines are more conducive to
RVI, inspections can also occur with the line full or
partially full. Clarity, turbidity, and flow rate may
negatively impact inspection effectiveness. Care
should be exercised as not to exceed the maximum
depth rating or head pressure for the crawler. If the
crawler is to be introduced to other compounds,
the Safety Data Sheets (SDSs) should be thoroughly
reviewed for possible hazards. This effort should
go beyond the typical job safety analysis (JSA) and
should evaluate hazards and chemical compatibil-
ity with the inspection crawler bill of materials. For
example, the crawler and camera O-rings, crawler
wheels or tracks, and the cable may all be suscepti-
ble to chemical-induced degradation.
Use Case
As a service provider, our RVI team experi-
ences a broad spectrum of applications across a
myriad of industries. The expansive nature of our
work necessitates a mastery of RVI equipment
deployment, utility, and manipulation. And while
some exams can be rather mundane, we are often
sought after for unique applications that challenge
current technology limitations. These difficult
inspections that challenge convention and tech-
nology limitations are often the most rewarding in
terms of provoking thought and advancing inspec-
tion capabilities.
We recently devoted our efforts to assist a
pipeline operator requesting assistance in validat-
ing several anomalies noted during a pipe pigging
effort. The results of the pipe pigging inspection
indicated that there were indentations in the line.
Our inspection tasks were to conduct a general
remote visual inspection, locate and identify the
anomalies, and measure the relevant indications to
support further engineering analysis.
The inspection presented a laundry list of
formidable challenges for our team. Beyond
the access point, the pipe was buried and
inaccessible. The line geometry was not
inspection-friendly, containing a tee joint at
the access, several bends, and an elevation
change. Furthermore, the line also changed in
diameter. These obstacles made it difficult for an
inspection crawler equipped with measurement
tools to travel to the areas of interest, some at
distances of more than 800 ft (243 m).
Crawlers that can accomplish this type of
inspection are not readily available, so customiza-
tion was necessary for a successful deployment.
Our team liaised with several equipment manufac-
turers and technology providers to understand how
we might “stack” various technologies for mission
success. After a bit of research, we fitted, tested, and
commissioned a remotely operated crawler coupled
with a terrestrial 3D laser scanner. This package
was able to fit in the smaller of the two pipe diam-
eters, navigate around multiple bends, and capture
high-fidelity measurements at great distances
(Figure 3).
The data capture effort included complete video
of the line, still image capture of points of interest
(Figure 5), and 3D laser scanning of indentations
and anomalies (Figures 4 and 6). Utilizing a terres-
trial laser scanning provided 1 mm accuracy, which
enabled enhanced engineering modeling and
analysis. Perhaps most importantly, this data was
captured without confined space entry and elimi-
nated the time and cost of excavations and external
data collection.
FEATURE
|
ROBOTICCRAWLERS
Figure 3. Crawler
equipped with a 3D
laser scanner. Also
note the “bridge”
utilized to drive over
the exposed tee
connection at the
bottom of the line.
38
M A T E R I A L S E V A L U A T I O N • J U L Y 2 0 2 4