Guided wave ultrasonic (GWUT) technology has been used for more than 20 years to assess the integrity condition of aboveground and underground piping. An integrity verification of underground piping was conducted using two (2) technologies to generate guided waves. The first technology uses a belt of piezoelectric sensors in direct contact with the piping surface. The second technology uses a magnetostrictive sensor (MsS) to couple the waves into piping by a cobalt alloy-steel ribbon.
The piezoelectric technology was used to inspect a combined 2.2 km of (nominal pipe size) NPS 3, NPS 6, NPS 8, NPS10, NPS 12, and NPS 20 underground piping in 46 segments. The MsS technology was used to inspect a combined 1.025 km of NPS 4, NPS 6, and NPS 8 underground piping in 34 segments.
While GWUT has been used by the industry for many years, there is still a lack of information related to its performance when inspecting underground piping. This paper documents the results of using both technologies for integrity verification of underground piping while at the same time providing information regarding the effect of field-related variables such as coating type, coating condition, presence of bends, pipe contents and soil cover among others.
Ultrasonic guided wave technology has been frequently used for inspection of a variety of structures such as bridges, aircraft wings, and it has also been used for inspection of piping and pressure vessels.1-3 This technology has attracted a great deal of interest because of its long-range monitoring, cost-effectiveness, simplicity, and its applications as an inspection screening tool. GWUT technology is particularly useful for inspecting of difficult-to-access piping and pipelines, such as buried, insulated, high temperature, and underwater piping.
This paper documents the inspection methods and results of an integrity verification of approximately 3.225 km of underground piping carried out using piezoelectric and magnetostrictive sensors to generate and receive guided waves.
