Maintenance Technology July 2017 - 20

INSPECTION SOLUTIONS

feedback from the thermal
sensors can provide a warning
of extreme conditions onsite
throughout the survey. When
inspecting cold, venting smoke
stacks, where un-ignited
hydrocarbons can be present,
methane or various other gas
sensors might be used to provide
additional warning during the
inspection operation.
Flight plans: The best way to
mitigate risk when inspecting flammable and hazardous sites is through
comprehensive planning. The reason
that drone inspection is used at all is
because it enables visual and nondestructive inspection of a site without
requiring personnel to be on the structure itself. Pre-planned flight paths can
easily keep a drone 20 to 50 ft. from a
structure and high-resolution imaging
can easily be captured from 300 ft.
away. The exact distance will always be
defined by the UAV inspection-service
provider and the facilities manager at
the plant. Common sense also dictates
that flight plans keep the UAV at an
angular tangent away from the structure, rather than directly overhead,
should anything fall.
Deploying UAVs to flammable
sites: All operations around oil and
gas infrastructure need to be carefully
regulated and tightly controlled.
Policies such as those related to
intrinsic safety have long been in place
to protect people and the environment
on these types of sites. While intrinsic
safety describes a set of electrical
design principles, it also considers
deployment procedures.
UAV platforms are not intrinsically safe in their electrical design.
However, professional UAV inspection
operations can offer an inspection
procedure that minimizes health and
safety risk to plant staff and the public,
in addition to delivering significant
economic savings to the plant.

Acquiring data
Using professional UAV inspection
services, an asset manager can reduce

20 |

MAINTENANCE TECHNOLOGY

UAV inspection quickly
collects imagery data
for the entire building
envelope.
the time that inspection personnel
need to spend on the building itself.
Provided a mission's flight route has
been well planned, a drone can collect
imagery data that covers the entire
building envelope in a fraction of
the time that it takes for inspection
personnel to traverse it.
Typically, visual and thermal
imagery are collected. After applying
automated statistical processes to
convert the imagery into a 3D 'point
cloud,' it is straightforward for skilled
interpreters to identify locations and
areas of deterioration on the building
envelope. Since the data are being
viewed in 3D, the roof and facades can
be visually interpreted.
As the data in the point cloud
is geo-referenced with real-world
geographic coordinates, a plan or a
map can be provided to an inspection
and maintenance team to identify
areas of deterioration before anyone
needs to climb any ladders or scaffolding, undertake rope-access
procedures, or walk on a roof.

Longwave vs. handheld
mid-wave IR cameras
Typically, a roof-inspection company
might use a MWIR (mid-wave
infrared) handheld camera or a LWIR

(long-wave infrared) unit to collect
data using an airborne platform.
The advantages and disadvantages
to the agency undertaking the roof
inspection and the customer need
to be assessed in terms of the sensor
technical characteristics and the
implementation implications.
Handheld MWIR can increase
sensitivity among reflective/cool
roofs and increased scaling values
in output images can make results
easier to interpret. However, the
reduced dynamic range the cameras
have could mean reduced sensitivity
across all material types. On the other
hand, using drone-mounted longwave
IR provides a high dynamic range
that leads to increased sensitivity
across dark, cooled roof structures.
But, LWIR technology requires an
increased expertise to interpret subtle
differences in thermal capacitance
between different roof materials,
especially when highly reflective.
In terms of implementation,
drone-mounted LWIR doesn't require
inspection personnel to walk on a
roof. The entire building envelope,
including hard-to-reach areas can be
imaged. Thermal ghosting (or leakage)
is minimized by a high straighton view of a roof by a camera. A
complete, geo-referenced report can be
quickly provided to the client.
Drones, equipped with a combination of sensors, are revolutionizing oil
and gas inspections. At the moment,
drones with thermal imaging,
photo, and video cameras, as well as
gas sniffers and other sensors, are
performing a variety of inspection
functions. The mobility and sensors
allow the drones to analyze facilities
for existing and potential defects safely,
quickly, and efficiently. MT
Sean Woessner is an FAA licensed pilot
at Industrial SkyWorks (industrialskyworks.com), Houston. He holds IFR
and FAA Part 107 Remote Pilot sUAS
ratings. Woessner has conducted more
than 500 inspections and logged more
than 400 sUAS hours.
JULY 2017
http://www.industrialskyworks.com
Table of Contents for the Digital Edition of Maintenance Technology July 2017
