Peter Dixon is Regional Engineering Manager for Europe, Africa, Russia and Caspian, based in the UK. He has since spent 17 years working in various engineering functions to support the deep-water pipeline pre-commissioning sector. His primary involvement has been with the development and sustaining of the Denizen™ deep-water pipeline flooding and hydro-testing systems. He led much of the conceptual and detailed engineering for the first Denizen system. His current role entails developing engineering methodologies, policies and competency standards across the region’s engineering team. He also works with the engineering teams to develop the unique solutions required to evolve the pre-commissioning service, offering and deliver competitive solutions for operations projects. Peter holds an MSc in Mechanical Engineering from the University of Edinburgh, Scotland and is a Chartered Engineer.
Virtual Pipeline Summit 15 Dec
Highlights and challenges of dry pre-commissioning
Newly installed gas export pipelines have traditionally been flooded, hydrotested, dewatered and air dried before finally being nitrogen inerted, prior to commissioning gas-up. For long export pipelines, typically of high diameter, this process is both time and resource intensive. A large volume of water is pulled from the sea, via a filtration and chemical dosing processes before being pumped into the pipeline. This water is then pressurized to provide a strength test of the pipeline and establish its leak-tightness. The subsequent dewatering and drying phases, particularly for deepwater pipelines, require enormous horsepower from air compression units that will run for weeks.
However, in conjunction with pipeline operators and DNV GL, Baker Hughes PPS has pioneered a new way to pre-commission these massive export lines, where the disadvantages with the system pressure test are extraordinary. Instead, the strength assessment of the pipeline is made under the DNV waiver via stringent requirements of the mill pressure tests, rigorous inspection and test of joints made during construction, higher design factors of safety and an installation track-record.
The term “dry pre-commissioning” refers to the removal of the flood and hydrotest operations. Consequently, the air-drying phase is also either eliminated or significantly condensed. Pipeline cleaning, conditioning, gauging and caliper inspection remain likely project requirements. Performing these operations without the traditional flooding of the pipeline is challenging, particularly where the pipeline profile has significant elevation changes. Prediction and control of the pig speed, ensuring consistent MEG swabbing, sufficient cleaning with minimum fluid and minimizing the diesel-powered air-spread are all competing factors.
This presentation details several of those technical challenges that were overcome in the development of a successful and innovative “dry pre-commissioning” methodology that demonstrates the viability of the no-hydrotest approach for major export pipelines.