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Steeling the tanks

CONCRETE

EVEN once the concrete walls of the tanks have been completed there is still work to do before the first shipment of Liquefied Natural Gas can be pumped in.

All of the tanks have to be lined with an insulated steel sandwich construction inner tank, which will help keep the freezing cold LNG away from the prestressed concrete. The lining will be capped by a concave domed steel roof before two layers of concrete are cast over the top.

The steel leaf of the tank lining is welded into place against the steel embedments formed during the wall slip-forming, insulating material is then blown into place before the steel roof is fabricated and placed.

But even the steel roof is a complicated issue. For each tank it will be delivered to site in a ser ies of petals and fabr icated over a 19-week period within the confines of the concrete tank. The finished roof will then be blown into posit ion by placing air pumps at the access points at the base of each tank.

These will increase the air pressure sufficiently to lift the roof to the full 31 m height, where it will be retained by the highest horizontal steel embedment.

'The air pressure increase that is needed to lif t the roof into posit ion is actually small, ' says CB&I John Brown project manager Ron Kooy. 'By passing a few blowers across the bottom we should get enough of a pressu re increase to lif t the roof within a couple of hours.'