ALE on gantry for gas
28 June 2012
International heavy lift and transport specialist ALE has started work on one of the world's largest natural gas projects using a large gantry system to rotate major structures.
The Chevron-operated Gorgon Project in Henderson, Western Australia is also the biggest single-resource natural gas project in the country. As part of a team ALE is helping construct a 2.1 km jetty on Barrow Island from where the liquefied natural gas (LNG) will be distributed worldwide.
The structural steel top platforms, each weighing between 150 and 490 tonnes, are delivered to the Henderson site by barge. ALE used self propelled modular transporter (SPMT) for offloading after which they were temporarily stored on site.
Star of the equipment show, however, was an ALE-designed 50 metre high lifting gantry which rotates these top platforms through 180 degrees.
The caisson type jetty foundations were constructed on site by main contractor, Saipem-Leighton Consortium. Each one weighed 2,500 tonnes. ALE elevated the caissons by jacking to allow the positioning of its SPMTs underneath followed by transportation to the gantry. The caisson is then carefully positioned under the gantry using survey control. The top platforms are lowered using the gantry into the pre-formed voids in the caissons, creating a single structure weighing up to 3,760 tonnes.
ALE transported the combined structures post fit-out to the Henderson wharf for loading on to a semi-submersible barge. Ballast calculations performed by ALE, and close liaison between ALE's SPMT crew and the barge crew, achieved safe, co-ordinated loading onto the barge prior to its journey to Barrow Island.
Equipment used by ALE on the project includes six 650 tonne hydraulic jacks with stroke meters to allow computerised automatic jacking. Also used was SPMT in a range of configurations up to 128 axles. The lifting gantry was built from four A-frame support legs; two 46 m span main beams; three skidded bridge beams of 19.5 m span; four 200 tonne strand jacks; and a pair of 500 tonne strand jacks.
Mike Ward, ALE Australia regional project manager, says, "ALE is proud to be associated with this world-class gas processing facility at Barrow Island. ALE has successfully implemented solutions to the logistical and technical challenges of this project. The success of this project was, in part, due to the excellent working relationship with our client, working together to ensure the best solution was provided."
The Gorgon Project is a joint venture of the Australian subsidiaries of Chevron (with around 47%), ExxonMobil (25%), Shell (25%), Osaka Gas (1.25%), Tokyo Gas (1%) and Chubu Electric Power (0.417%). Centred 130 km north west coast of western Australia, it is a development of the Greater Gorgon gas fields, subsea gas-gathering infrastructure, and a liquefied natural gas (LNG) plant on Barrow Island. Production will start in 2014 with a forecast scope of 15 million tonnes of LNG a year.
