LNG Production: Cryogenic Strand Tendons Stabilize new LNG Tank
The sultanate Brunei in the South China Sea is very wealthy thanks to its revenues from its abundant oil and gas resources. In the coastal town of Lumut on the island of Borneo, Brunei LNG company produces liquid gas in a plant covering 130ha. 50% of the company’s shares are owned by the government of Brunei, and 25% each are held by Shell Overseas Trading Limited and by Mitsubishi Corporation.
At the time of its completion in 1973, the facility was the first LNG producing plant in the western Pacific region. After a comprehensive rehabilitation and renovation in 1993, the plant now produces approx. 7.2 million tons of liquefied natural gas per year. Within the scope of the rehabilitation work carried out 20 years ago, the former Dyckerhoff & Widmann AG built two large LNG tanks with a volume of 65,000m³ each and with outer shells consisting of post-tensioned reinforced concrete.
A short while ago, the company now known as STRABAG International GmbH – DYWIDAG LNG was awarded a contract to build an additional LNG tank nearly twice as large with a capacity of 120,000m³. The tank has an outer diameter of 75.9m and reaches a height of 46.15m at its highest point.
The tank’s foundation includes 1,328 vibro displacement columns, and the floor slab has a diameter of 77.9m. The 14,000m³ of concrete for the exterior tank required 800t of cryogenic reinforcing steel in addition to 4,200t of conventional reinforcing steel.
The concrete wall has a thickness of 120cm at the bottom and narrows to 60cm at the ring beam underneath the roof. The 1,700t steel roof will be brought into its final position using air pressure once the post-tensioned exterior tank is complete.
DSI supplied cryogenic DYWIDAG Strand Tendons for post-tensioning the exterior reinforced concrete tank. In total, 316 Type 6819 DYWIDAG Strand Tendons with MA Anchorages were installed in the exterior walls. The strand tendons are inserted into approx. 20,000m of PP ducts. In addition, 18t of Ø 28 and 32 GEWI® Bars and 5t of cryogenic GEWI® Bars with accessories were required to build the tank.