Testing of Buried Pipelines Using Guided Waves

Introduction The inspection requirements of pipes that have an operational history of many tens of years have lead to the adoption of new maintenance practices and safety standards. The solution currently considered as best maintenance practice is the direct assessment of 100% of the pipelines with the minimum possible economical impact. The use of RBI (Risk Based Inspection) methods and the introduction of new safety rules have also contributed to concentrate the inspection efforts onto the most critical parts of a given pipeline network. The cost of the inspection is in several cases a fraction of the cost for removal of the in service pipes and/or fittings. However when the pipe is buried the costs associated with NDT testing or substitution of the pipe substantially increase with respect to the same type of operation on an above ground exposed pipe. Buried pipelines can be tested using intelligent pigging methods. While this technology is generally accepted as providing excellent inspection data it is relatively expensive and it may also require significant operational disruption. As opposed to standard UT inspection methods the use of guided waves enable sections of piping to be tested from a single convenient to access location. Testing buried pipes can be performed by opening dig locations at appropriate positions and performing the test on the buried portion of pipe without direct access. This is particularly effective when testing crossings where the section of pipe under the road can be inspected from positions either side of the road.