The roof of one of the biggest liquid natural gas tanks in the world, which is being constructed in a remote area of India by Kvaerner, has been blown 40 metres into position by two massive electric fans.
In an unusual operation in the isolated west coast region of Dabhol, over six hours driving time south of Mumbai, Kvaerner has just completed lifting into place a 770-tonne steel roof for the tank. Because of its immense size cranes could not be used, so Kvaerner simplified the whole process by bringing in two giant fans to blow it into position. This took seven hours, with each fan producing 900 cubic feet of air per minute.
Ensuring the tank’s outer shell was completed before the start of the monsoon season, Kvaerner has set a new construction record for the international LNG market by building the tank roof inside the tank base while its walls were being simultaneously constructed. The domed roof is 80 metres in diameter, stands 14 metres high and was built from 600 separate steel sections.
The £175 million (US$278 million) turnkey project is the first fully integrated partnership between Kvaerner Construction and Kvaerner E&C. They are responsible to ENRON affiliates which is managing the construction of the LNG facilities for the Dabhol Power Company. Project director is Roy Isden who has just been appointed the first general manager of Kvaerner’s LNG business stream. Working alongside him is Paul Emson, Kvaerner E&C project manager for processing.
Mr Isden commented: “The Dabhol project, which introduces natural gas to the west coast of India, combines our broad technical and managerial abilities together with our long experience of the Indian construction market.”
Kvaerner’s contract is to supply, construct and equip facilities to offload LNG from ships in minus 160 degrees Celsius liquid form, pipe it to a storage centre where it is vaporised into gas and then pumped into the power station.
Kvaerner’s task involves
? fitting out a new LNG offloading jetty with mechanised LNG unloading arms;
? installing insulated supply pipelines running two kilometres from the jetty-head to a storage and processing area closer to the power station; and
? building an LNG storage and processing area, consisting of three concrete and steel insulated storage tanks each with a 160,000 cubic metre capacity as well as vaporisation and pumping process facilities to feed the new power station.
It is the towering scale of the storage tanks which dominates the site. They are built at three levels into a hillside in a narrow, rocky valley surrounded by 100-metre high cliffs. Kvaerner is constructing the first three of six planned LNG tanks that are believed to be the world’s biggest.
The design of the tanks is based on proven technology from Whessoe LGA. The outer shell of the first tank is now complete with the roof of the second also due to be blown into position before the monsoon season.
Internal workings for the tanks will follow during the rainy season including a metre-wide layer of expanded perlite insulation sandwiched between the outer wall and an inner steel casing. A suspended deck under the roof of each tank will contain a metre-thick blanket of fibreglass insulation. A layer of foam glass is already installed beneath the base, with tank-base heating to prevent the surrounding earth from freezing.
In Dabhol the schedule for completing a tank – fully closed off and insulated – is targeted to be accomplished within 30 months, against an industry norm of between 33 and 36 months. “If we meet programme – and I think we should – it will be the fastest construction time anywhere for this kind of structure,” said Roy Isden.
The desolate nature of the remote fishing region on the south western side of India’s Maharashtra state is such that just about every single item needed to serve the project and its workforce – apart from local aggregate – has to be imported.
The site is more than six hours driving time from Mumbai, so Kvaerner��s main mode of transport for personnel is by helicopter which makes three 70-minute round trips a week from Mumbai.
Mr Isden added: “The construction and process engineering is straightforward – it is the logistics that is the key to the success of the job.”
In procurement terms the project has been a global challenge, combining the technologies of four continents to achieve co-ordinated and timely support to meet a tight programme. About 80 per cent of the materials and equipment has been shipped in from Europe, the USA and Japan. This includes highly-specialised LNG plant such as pumps, pipe supports, bellows, vaporisers and boil-off gas condensers.
The project’s main focus until recently has been in London where procurement and engineering has originated. It is now moving to Dabhol where the emphasis is on process installation. Some 15 kilometres of stainless steel pipework has to be cut and prepared in a fabrication yard set up on site. Integrated working with suppliers is especially important as everything connected to the LNG pipe-runs must be designed to be thermally insulated, including cold supports fixed into the ground.
Kvaerner E&C’s Paul Emson explains: “It’s difficult to get it right because qualities of sturdiness and good insulation don’t go easily together. Supports have to be a complex combination of steel and resin-based insulation barriers that have sufficient strength and rigidity.”
With work progressing well at the moment and with two years still to run on the contract, what could be the greatest challenge for the project team is yet to come.
Each storage tank must be hydro-tested, requiring at least 100,000 cubic metres of water. Capturing sufficient fresh supplies to test a huge water-tight structure could present a difficulty as, despite the annual deluge of rainwater, there is nowhere locally that holds such large reserves.
Mr Isden said: “The original plan was to draw off from the firefighting system, but this is now not possible. At this moment we have no way to draw off and store this amount of water…it’s simply one more logistical problem we have to solve.”
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