Development, Validation and Execution of the Automated Ultrasonic Testing of a Subsea Pipeline Hot Tap Weld

摘要

As part of a project to supply gas to Britain from Norway in 2007, there was a requirement to build a new gas export pipeline and connect it into an existing high-pressure gas transportation pipeline. This connection was made by means of a 16-inch hot-tap into a 36-inch line i.e. welding a 16-inch stub on to a 36-inch pipe while the pipe is live carrying gas. The additional challenge was that the location of this work was 400km offshore in the North Sea and at 140m water depth. Due to the nature of the work, there was a major risk to safety and the environment; therefore it was vital that the connection was welded and tested to extremely high standards. The ENIQ methodology (European Network for Inspection and Qualification) was used to enable a rigorous and structured approach to be adopted. A high sensitivity automated ultrasonic inspection was developed and qualified such that there was extreme confidence that a reliable test could be performed. Following this exercise the hot tap weld was satisfactorily inspected and the whole project completed without concern.