Carrying the load - Part Two

This is the final part of a two part Special Report. To read part one of this article, click here: 'Carrying the load - Part One'

The Dockwise team had to wait for the right high tide and the right environmental conditions. The wind needed to be less than 15 knots, or Beaufort scale 4, while the water depth needed to be sufficient for long enough.

In Rotterdam, the Netherlands, the tide ebbs and flows every 12 hr, with high tide, at this time of year, providing water deep enough (at 24m) for 5 - 5.5 hr to carry out the operation.

On 8 May, the right weather window was identified and the action started early in the morning. The Armada Intrepid was taken from its dry dock by four tugs to the Caland Canal and, by 11 am, it was in position, ready for the high tide.

A few hours before the team had the right water depth, Dockwise ballasted the vessel so it had a free board of 1 m. Following the final go-ahead, the team continued to ballast the Dockwise Vanguard while the four harbour tugs brought the FPSO to its stern. At 4:30 pm, the float-on operation started, with the first tugger lines (from the Dockwise Vanguard to the Armada Intrepid) slowly pulling the vessel in between the two aft casings. This is a slow and careful process, with the Dockwise Vanguard crew taking over the handling for the final positioning onto guide posts on the heavy transport vessel’s deck.

By 7:30 pm, the vessel was in place. However, even once in place, the position had to be monitored to make sure it was correct, before the Dockwise Vanguard was slowly de-ballasted, finally lifting the Armada Intrepid out of the water. Once the Armada Intrepid was fully out of the water, further inspections were carried out and, finally, deballasting was completed and the load successfully executed. The final task before sailing saw 54 sea fastenings (each comprising approximately 2.5 m x 3m brackets) welded into place, to ensure the FPSO would remain secure during the transit.

The operation was executed under ideal circumstances. The weather was perfect, with no wind and clear skies, resulting in good sight, which is essential for the operation. The operation went as per schedule, and no unforeseen circumstances were experienced.

Preparation

However, loading an FPSO, or any major load, onto the Dockwise Vanguard’s deck requires preparation work in addition to careful loading and sea fastening.

First, the Dockwise Vanguard had to be cleaned following its transport of the Goliat FPSO. Then, the vessel had to be fitted with cribbing material, a 600 mm high wooden layer fixed with angle bars bolted to the deck, on which the Armada Intrepid or any other load would rest. In addition, the guide posts, against which the FPSO is positioned, had to be installed. This work was all completed before 8 May.

Moreover, the work does not stop until the FPSO is safely delivered, even though it has been safely loaded and secured. During the voyage, the FPSO, sea fastenings and cribbing are regularly inspected.

For this transport, Dockwise is also using permanent, real-time pressure monitoring on the cribbing, an operation which has yet to be tried.

The Dockwise Vanguard’s crew was increased for the loading operation, from the usual 25/26 to 33, due to the amount of line handling involved. With Dockwise as the main contractor, the project also employed other Boskalis companies, including SMIT Towage Northwest Europe tugs.

The biggest achievement of the project was proving the FPSO transport concept. Dockwise has been able to prove to the market that this is a fast and efficient solution to transport ship-shaped FPSOs from one side of the world to another, whether for refitting or newbuilds. The alternative is a wet tow, at half the speed. The company expects the Dockwise Vanguard to cruise at speeds of up to 12.5 knots, whereas wet tow speed is approximately 6 - 8 knots.

Insurance premiums for wet tows are also more expensive than the dry tow alternative.

The Dockwise Vanguard, with the Armada Intrepid on board, arrived in Southeast Asia in early July, having sailed via the Cape of Good Hope, without the need for tugs.

Conclusion

With 64% year-on-year growth expected in the FLNG market, according to analysts Douglas-Westwood, the ability to safely and efficiently transport both FPSOs and the emerging FLNG vessel fleet is set to be a welcome asset to the industry.

By proving the ship-shaped FPSO transport concept, Dockwise has also helped unlock opportunities for the FLNG market.

The first part of this article is available here: 'Carrying the load - Part One'.

Written by Taco Terpstra and Hans C. Leerdam, Boskalis, the Netherlands. Edited from various sources by Callum O'Reilly

Read the article online at: https://www.lngindustry.com/special-reports/24082015/carrying-the-load-part-two-1186/