A novel approach to installation of a new flare line, flare access stairway and flare tips was adopted on Fairfield Energy's Dunlin Alpha platform last summer.
Aker Solutions, which carried out the job in collaboration with the operator and specialist offshore service company Vertech Offshore, is currently applying for a patent for the innovative hook-and-pin clamping method employed and see significant potential for future offshore use of the system in inaccessible places on the North Sea's ageing assets.
Using Vertech personnel and a Super Puma supplied by CHC Helicopters, Aker came up with a methodology by which an entire new stairway could be slotted into place secured by hook-and-pin clamping without the need for scaffolding.
The project started with a new high pressure line, then access to the flare-tip, then flare tip replacement. 'We ended up optimising three projects, each of which would have been very labour intensive, with a high impact on the platform and require a lot of planning and mobilisations cost,' says Aker Solutions' project manager Jim Thompson.
'We were able to absorb all that into one optimised scope,' he explains. 'From there we had quite a short duration to redesign our strategy and come up with these stairway sections that were able to be combined in a single lift by helicopter and hooked up with minimum manual intervention. The design that our guys came up with is just brilliant. It is so simple.' The scope included a 6in flare tip, a 16in flare tip replacement, a 6in flare line and header, a shared pilot system, a shared electrical ignition package plus access platform and stairs.
Aker PSV at Portlethen, seven miles south of Aberdeen, was the primary fabricator but as the installation date drew nearer Thompson says the project ended up using four fabricators around the Granite City and three different painters, with half a dozen trucks running 24-hour operations to make sure everything was ready in plenty of time. There were probably three key people – the structural designer, the project engineer and the fabrication co-ordinator, with a team of 12 to 15 in total. The gas import project is one of a number of scopes that Aker Solutions is completing through a frame agreement contract with Fairfield, now in its fifth and final year, following the taking up of two options.
After several months of planning, Aker PSV built a full-size scaffold replica section to contain the top stair section and the new main platform section. It then conducted a trial-fit of the connections by crane, to prove the methodology prior to the start of installation offshore. The replica took a week to construct. 'Each section had this simple, but brilliant design to lower two pins into existing hooks,' enthuses Thompson. One set of hooks was installed at the base of the platform, then a set of hooks for the next module at the top of each section.
Once trialled onshore, the replacement of a total of seven stair sections, three platform sections and two flare tips which could have taken as long as three months to complete using traditional methods, was completed in just six days. And offshore operations were reduced from five weeks to five days, reports Thompson.
Besides its speed, another major benefit claimed for this method is the reduced manpower required. Outwith the helicopter crew, just four mechanics and one supervisor were required to complete the work. 'Not only did the solution radically reduce the manhours required for construction and installation, it also reduced the volume of overboard working for prolonged periods of time, thus significantly reducing the risk of safety incidents,' says Thompson. He adds: 'There was a great buzz throughout the project, a real sense of achievement all the way through. It couldn't have been done without the attitude of the team that we had, the willingness to take responsibility for their work, to see it through and deliver an exceptional result without anyone getting hurt.' He is also full of praise for the skill of the Vertech team, describing them as 'a very professional outfit'.
'The ultimate test came when the ex-military man responsible for Vertech's helicopter pilot training stood in the middle of an open field and instructed the pilot to lower the hook on a 20-25m line into his hand,' recalls Thompson.
Vertech works in partnership with CHC and lays claim to being the only company globally certified for helicopter-conducted flare boom modification change-outs using long-line flying – sometimes referred to as vertical reference – techniques. OE