Due to the steep drop in the production of natural gas in older UK North Sea gas fields, energy companies have been forced to finance considerable decommissioning works. British and Norwegian law mandate the complete removal of platforms and all the gas processing equipment in them following the shutdown right down to the seabed.
Jet Edge abrasive waterjets are ideally suitable for steel-cutting in volatile gas-laden environments. A growing number of offshore operators have been opting for spark-free “cold cutting” to safely remove redundant oil and gas production hardware.
Cutting Obsolete Contactor Towers
Recently, Aquablast, the UK distributor for Jet Edge, cut up obsolete contactor towers on a live gas platform. Operated by Perenco, the French oil company in the four-decades-old Indefatigable Gas Field off the Norfolk coast of England, the towers were built using a 70 mm heavy steel plate that had a thickness of 2¾ inches and weighed more than 300 tons. Perenco commissioned Aquablast to cut the towers into smaller cylindrical sections to enable the crane of the platform to lift the towers by itself.
Aquablast cut 70 mm heavy plate steel contactor towers into smaller cylindrical sections.
Power of Jet Edge Spyder Abrasive Waterjet Unit
Before using a Jet Edge Spyder abrasive waterjet unit to make the deep circular cuts, a “mailbox” cut was made to enable an internal inspection to determine the precise position to make the tower separations. A Jet Edge 55-260DXS diesel-driven mobile hydraulic intensifier pump that included engines specifically adapted for operations in hazardous environments provided the abrasive waterjet power.
The pressure-compensated hydraulic intensifier, which is the crux of the Jet Edge system with the ability to produce up to 55,000 psi operating pressures, has a significant benefit over other systems in hazardous areas since it avoids the need for water dump systems and safety relief valves. Even in the case of an untoward event of a blockage, the Jet Edge intensifier just holds its pressure until the cause of the stoppage is rectified or the pressure is safely exuded.
A number of Jet Edge mobile intensifier pumps have been modified by Aquablast to comply with offshore oil and gas platform regulations. These modifications involved installing inlet air overspeed shutdown valves and other emergency shutdown provisions.
Jet Edge UHP intensifiers are extremely reliable. This is critical because equipment cannot be quickly replaced in the middle of the North Sea, for logistical and often weather-related reasons. Our reputation for dependability and minimal downtime is therefore vital to our customer relationships.
Donald Blair, Aquablast’s Managing Director and longtime Jet Edge support partner in Europe
Roughly 23 lbs per foot (29 kg/m) of almandine garnet abrasive was consumed for making the 2¾ inch-thick cuts at an average cutting speed of more than 1¾ inches per minute. Blair stated that Perenco (UK) Ltd. declared themselves “very impressed” with the super-thick cut and the way in which the operation was performed in a safe manner with only negligible interference to other works on a live North Sea gas installation.
The Spyder system can be rapidly installed and is highly portable. Flexible or straight track sections are secured to vertical or curved surfaces with the help of magnets, suction cups, or ratchet straps. Since the cutting nozzle transport unit is pneumatically driven, it avoids any chances of ignition in a volatile environment. The tower sections were safely shipped to shore in England for scrapping; however, the three-ton cap of one of the towers was contributed to Aquablast by Perenco to allow more trials and development to be performed in anticipation of future cold-cutting tasks for the Jet Edge Spyder abrasive waterjet system.
This information has been sourced, reviewed and adapted from materials provided by Jet Edge.
For more information on this source, please visit Jet Edge.