Page 80 - Reliability and Maintainability of In service Pipelines

Pipeline Inspection and Maintenance 69

2.3.7 GROUND PENETRATION RADAR

Ground Penetrating Radar (GPR) is a well-established method of monitoring civil
structures such as bridges, tunnels, and buildings. GPR is also used as part of a
nondestructive detection method to identify underlying features or buried services.
It is well known to be a reliable method of identifying the location and depth of
underground pipes of different materials and sizes.
Koo and Ariaratnam (2006) carried out field studies, using GPR to identify
internal sewer damage in concrete and clay test pipes of 5 50 cm in diameter,
followed by concrete and PVC field pipes of 75 90 cm in diameter. The method
reported to have a number of limitations due to its bulky size and the length of
antenna; however studies revealed that even small defects, such as material loss
due to deterioration and corrosion, can be identified (no quantitative figures were
provided). In general, compared to other techniques, GPR is capable of detecting
geometric discontinuities and changes in material properties that the human eye
would be unlikely to notice.
Digital scanning and evaluation technology (DSET) is a proven method to
provide a high definition quality of visual data. Koo and Ariaratnam (2006) com-
bined this technique with GRP to support the measurements. The results of the
merged techniques proved a great correlation between radar and visual data which
helps to classify defects in a consistent and error-free manner.

2.3.8 METHODS OVERVIEW

A number of inspection techniques which are specially designed to monitor the
pipeline condition or those that have a great potential to be further developed in
this context were reviewed in the previous sections. A summary of these techni-
ques including their advantages and disadvantages is presented in Table 2.1.

2.4 Pipeline Maintenance

A variety of preventative measures can be taken to reduce corrosion of pipelines.
Methods include implementing cathodic protection, regular cleanings, and pipe
coatings. The simplest and most effective way to prevent a pipeline from corrod-
ing is to keep it out of contact with the environment.
To ensure pipelines are operating at their highest functionality routine mainte-
nance must be undergone. Depending on the age and material of the pipes