Hünnebeck formwork for offshore LNG plant
By Richard High04 September 2008
Formwork manufacturer Hünnebeck's Italian subsidiary has supplied a range of formwork, including its Manto large-frame panels, for construction of the world's first reinforced concrete offshore terminal for the storage and re-gasification of liquefied natural gas (LNG).
Situated 15 km offshore from Venice, Italy and invisible from land, the plant is being constructed for Terminale GNL Adriatico (Adriatic LNG), an Italian company owned by affiliates of ExxonMobil (45%), Qatar Terminals Ltd (45%) and Edison SpA (10%).
The 45 m high structure (30 m of which is submerged) is 180 m long and will contain two large storage tanks, each capable of holding 250000 m3 of gas. This gas is ship from the North Field in Qatar, the world's biggest natural gas reservoir.
The reinforced concrete tanks feature a multi-cell structure. The 53 cells in each tank can be separated by bulkheads to create five totally independent sections.
Two circular, 40 m tall reinforced concrete columns connect the centre of each tank with the above-water part of the installation. Construction of the 56 m long, 28 m wide and 7 m deep tanks used Manto large-frame formwork.
According to Hünnebeck, Adriatic LNG chose the Manto system because it had the strength and versatility required during the pouring of each of the 10000 tonne concrete boxes. About 4000 m2 of the Manto formwork was used on the site - mainly large, 3,3 x 2,7 m panels.
What makes the Manto panels special, said a Hünnebeck spokesman, is "their exceptional flexural strength and robustness due to their internal stiffening ribs and their 140 mm thick steel frames. The panels are able to cope with a hydrostatic pressure of 80 kN/m² and allow pouring at any desired rate.
Another feature is the Manto aligning clamp, which joins the panels flush. 40 m2 of joined panels can be set upright, shuttered and moved in a single crane lift without further stiffening.
Using the Manto panels, the various, 6,5 m tall wall sections can be poured in a single work cycle. The extensive panel range also permits the shuttering of the individual tank cells without expensive extra equipment.
Besides the Manto panels, Hünnebeck has also supplied 500 m2 of its adjustable Ronda circular formwork for the pouring of the reinforced concrete columns and wooden beams for the column heads.
LNG (liquefied natural gas) is a natural gas (methane) liquefied by cooling to -161°C. In its liquid state, it is reduced to 1/600th of its original volume, simplifying shipment by sea and in large quantities in LNG tankers.
It is then stored in terminals, regasified and fed by methane gas pipelines to its destination.
Statistics show that the demand for natural gas in Europe will grow by about +1,2% per year in the coming years. Production capacity in Europe, however, is declining.
In Italy, for example, only 12 billion m3 of gas was produced last year, which is down -9% on the previous year. This trend will result in a considerable increase in imports by the European Union from the producing countries - from 45% in 2000 to an expected share of over 80% in 2030.
This is equivalent to almost five times the total quantity of natural gas marketed in the year 2000.