Page 74 - Reliability and Maintainability of In service Pipelines

Pipeline Inspection and Maintenance 63

Ahrary et al. (2007) report on a novel KANTARO robotic system that is
designed to detect faulty areas in sewer pipes, based on image acquisition and 2D
laser readings. The robot uses a combined graphic user interface and intelligent
fault detection module to detect various sewer defect types automatically, which
can be reported to the user in real time. The machine is designed to inspect
200 300 mm pipes with 90 bends and maximum steps of 50 mm. The authors

reported an accuracy of 6 1 mm; however, no information is provided as to
whether the measurement accuracy is applicable to the lateral/circumferential dis-
tance of size/depth of defects.
The rotating optical geometry sensor (ROGS) was developed by IOSB,
Germany (Ritter and Frey, 2010) and was specifically designed to survey buried

pipes. The sensor consists of four straight laser beams arranged at 90 angular
displacements and an optical triangulation technique is adopted to perform the
wall scan. This technique allows for reconstruction of a pipe wall surface in 3D
or plain regimes. The laboratory and field experiments in clean water and sewer
pipes revealed that an accuracy of pipe wall discontinuity of 1 mm can be
achieved.
Stani´ c et al. (2013) investigated the means of egg-shaped concrete sewer pipe
interior and exterior scanning using a laser-based profiler. The obtained images
from inside and outside of the pipe were used to reconstruct a 3D model of the
pipe wall surface, with further ability to measure the wall thickness and thinning
rate. The code to perform the operation was developed in MATLAB which also
enabled measurement of the pipe wall roughness coefficient based on Darcy-
Weisbach and Chezy equations. The results revealed that with the laser profiler
there is an average measuring error of 0.33%, which was approximately 1 mm of
the pipe wall thickness. However, distance measurement could have an error of
3 mm. When combining the results, a common error of 4 mm may be present.
The technique offers good accuracy for overall pipe wall condition review,
although it would require improvement if it was to be used in the field to detect
corrosion rate.

2.3.3 ULTRASONIC INTELLIGENT PIGGING

Intelligent pigging allows for a pipeline to be inspected for faults such as cracks,
corrosion, rust, deformations, etc. The method uses a range of nondestructive
techniques such as ultrasonic and magnetic leakage testing and also allows the
pipeline to be cleaned.
The magnetic method utilizes applications of a magnetic field within the inte-
rior of the pipe wall using permanent magnets. An irregularity in the magnetic
field due to varying wall thickness will be detected by the sensors and therefore