Perfect. That was how both client Statoil and specialist contractor Fagioli summed up the 20-hour operation late last year to erect the final module to be put in place at the Hammerfest LNG plant – the imposing 609t flare tower which is scheduled to burn off gas from the Snøhvit processing facility from the summer of 2007.

A 24-hour weather window with wind speeds less than 10m/s (even though the lifting system is designed for 20m/s), and good visibility were needed for the lift. Any unforeseen hold-ups would probably have meant the operation being postponed until March this year to await better conditions, but in the event the job went without a hitch.

The stack was installed on Melkøya in November using a Towerlift and strand jacking system that Fagioli had persuaded Statoil to deploy instead of large cranes. The rationale for this was that the unguyed system would not only enable the stack to be erected as a piece, but also remove the need for risky, high-level crane work in this exposed Arctic Circle location. The flare could be brought to the island in just five preassembled sections, requiring only a few onsite man hours. And, since all the work could be done at ground level, without scaffolding, significant safety and cost advantages would accrue.

The flare stack was raised to the vertical by Fagioli’s two 80m high lifting towers, with two of the company’s SPMTs (multi-wheeled transporters) carrying the foot of the stack forward. At a speed of 10 vertical metres per hour, it took seven hours to bring the structure to an angle of 80 degrees from the horizontal. The transporters were then disconnected, and the stack placed vertically on a foundation attached to the bedrock at a height of 50m above sea level.

“Passing the centre of gravity was a crucial point in the operation,” says John Short, Statoil’s co-ordinator for the lifting operation. “So we attached three additional flare shoes totalling 23t to the foot of the stack to ensure that its centre of gravity was as low as possible.”

Nevertheless, 550t of the total weight rested on the lifting towers while the remainder was carried by the transporters. The flare stack lift took 20 hours and involved 50 people.

“Weather and light conditions at Melkøya during November are not ideal for this type of operation, but everything was perfect on the day,” reports Short.

A fitting conclusion

For Fagioli executive director Fabio Belli, the operation could not have gone better. “It went perfectly,” he says, “and provided a fitting conclusion to a big contract that has been very successful for us. Working in harsh conditions we have moved more than 40,000t of modules and equipment for the Snøhvit project.”

Officially, the flare stack constituted the last heavy lift on the island, with Fagioli now demobilising most of the 168 SPMT axles it had deployed there at peak last year. But it will leave a small amount of equipment on site to deal with lifting requirements that may arise during the remainder of the winter.

Looking back over the company’s 18 months on the island, Belli recalls how the location’s “interesting” environmental conditions presented an almost constant challenge for his team. “Snow, rain, and strong winds constituted a permanent and hazardous element, especially during load-out and lifting activities,” he says.

“Despite careful preparation and advanced planning, wind speed and swell restrictions often required activities to be modified and tailored in accordance with sudden changes in the weather. February 2005, for instance, was an extremely tough period for maritime activities, with total darkness, -10 deg C average temperature, and biting winds of up to 36m/s often obliging Statoil and Fagioli to wait on weather before barges could be safely unloaded.”

Fagioli won the heavy transport and lifting contract in open tender, and this was later expanded to cover lifting and transport of items on the Snøhvit process barge following its arrival incomplete on the island and activities related to the four tanks built for LNG and LPG storage. Belli is in no doubt that his company’s bid attracted Statoil’s attention because of its “innovative and creative approach, commitment to safety, co-ordinating skills and willingness to be flexible in fitting in with the continuous evolutions of a typical long-duration project”.

The Towerlift solution was a case in point. Although not new (the system was pioneered by Fagioli’s lifting arm – Fagioli PSC – in the UK some 20 years ago), this is its first application for flare stack construction.

The company is now working on a self-erecting version of the Towerlift, and sees further potential for it in the petrochemical plant and offshore fabrication sectors.

Fagioli’s recommended alternative approach to handling the LNG plant’s 2,635t ‘cold box’ also appealed to Statoil, resonating as it did with widespread industry learnings in the area of offshore platform hook-up and commissioning over the years. The contractor’s solution was to bring offshore practice onshore.

The tender documents for this module – the largest of the 180 units that Fagioli was required to transport, lift, and install for Snøhvit – originally called for it to be built on-site. In its bid, however, Fagioli envisaged this key module being built off-site at a specialist facility to avoid weather and other risks, and then loaded out and delivered complete to Melkøya.

In April last year, Fagioli successfully completed the load-out of the 68m high cold box assembly, with its specially designed support frame providing stability during the move, from the Fabricom yard in Antwerp, Belgium.

Weighed and transported

The structure was first weighed using hydraulics fitted with calibrated manometer pressure gauges, and its centre of gravity calculated from the reactions to within an accuracy of +/-3%. It was then transported 500m along a specially constructed roadway to the load-out jetty where it was transferred to an ocean barge. The barge and cold box were then floated onto a Dockwise semi-submersible heavy lift ship for the 1,700-mile voyage to Melkøya. After refloating and positioning the barge alongside the foundations at Melkøya, Fagioli then performed the load-in operations at site and placed the structure directly on its foundation.

This is an edited version of an article that first appeared in the December 2005 issue of Offshore Engineer magazine.