Underground piping inside plant boundaries is frequently out-of-sight, out-of-mind. While there exists a wide body of knowledge, mature technology, and established techniques for inspection of cross-country underground pipelines, and even above-ground in-plant piping, the converse is true for underground in-plant piping. Most in-plant piping was not built to be internally inspected, and there is most often a dearth of knowledge in regards to how much underground piping exists in the plant and where it is located. The attributes of in-plant piping, and the conditions of the environment above and below ground, are so different from the cross-country case, that the application of cross-country techniques to in-plant piping is difficult and costly to implement and sometimes ineffective.
This paper explores the conditions of the plant environment that impact underground piping and the challenges to implementing an effective inspection program. It draws from several years of inspection experience of in-plant piping at a large chemical plant complex in the U.S. and cites examples of lessons learned the hard way. It proposes some methodologies and techniques for successful inspection, and recommends where more research and development is needed.