Inspection Robots
Introduction
The harsh environment of a boiler in a coal-fired powerplant stresses and wears
out the constituent water walls which then must be repaired. It is a continual
struggle between a large fire ball, cinder stalactites, and steam or water
cannons to break down the build-up.  When
an actual hole develops in the water wall, there is severe inefficiencies which
tend to cause the plant to be shut down for repair. Since every hour of
shutdown represents large potential losses in the vicinity of $20,000 to
$100,000 per hour, minimizing downtime is imperative.
TTU researchers have been developing inspection robots which can crawl
vertically up the water pipes in boiler carrying inspection sensors to measure
tube wall thickness. These robots can work on walls too hot for human workers,
and can begin long before scaffolding to hold human workers can be built. The
quicker the "bad" sections can be identified for replacement, the better.
Design
Several different prototypes have been build over the course of the research
program, but a common design characteristic is a dual tank track design with
"magnetic feet". 
A dedicated robotics labratory with its own lathe and mill, combined with
off-the-shelf parts and talented researchers, makes robot fabrication at TTU a
reality.
Designs have varied from a large 50 pound version which can easily lift a
graduate student off the ground, to a compact 20 pound version which can be
lifted onto a water-wall via small access panels.
Typically power for the robot is via a power "tether" which is dragged behind
the robot. A telerobotic operator is currently required, but more and more
autonomy is being added. Video and sensor feedback is via wireless
communication and the robot can be "driven" via the video information sent to
an operator monitor.
Instrumentation
Any commercial sensor can be outfitted for use with the inspection robot. At
this time, TTU researchers are not designing their own sensors, but instead are
utilizing 3rd party transducers.
 Various mechanisms for
following the irregular surface of the water-wall have been developed as well
as tube-to-tube positioning mechanisms, and tube following mechanisms.
Further advancements in spatial indexing for thickness measurements, and
autonomy of inspections are being developed in this ongoing research effort.
Also good for Tank Inspection
The same basic concept employed in the water-wall robot has been extended to any
steel tank inspection. This simpler task does not require the robot to navigate
over layers of built up fly-ash, old welds, and rust accumulation as typical
tanks are kept in better condition than the inside of a boiler. Tank owners did
request at least one modification to the design, and that was a "shoe" to
protect the paint on the tank. A thin layer of plastic was added to the design
of each "boot" to prevent scuffing of paint.
A sample output screen of a wall thickness transducer is shown in Figure 6.
Reitterating any instrument could be used, and a custom interface could be
designed to meet a companies data requirements.
The Future
This is an ongoing research program which has lots of potential to help the
Electric Power Industry. Other inspection mechanisms are also being planned an
may get reported here in the future.
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