DYWIDAG Post-Tensioning Systems used for Modern Ethylene Tank in Singapore

In the fourth quarter of 2006, Shell Eastern Petroleum Ltd (SEPL) broke ground for the construction of a petrochemical complex on the island of Pulau Bukom in Singapore. The Shell Eastern Petrochemical Complex includes an ethylene cracker in Pulau Ular (extension of Pulau Bukom) which will produce 800,000t of ethylene per year after its completion.

Ethylene is one of the most important basic chemicals in petrochemistry and is mainly used to produce plastics. Ethylene also serves as a fuel gas and can be used to ripen fruit.

Utracon Structural Systems Pte Ltd (USS), DSI’s licensee in Singapore, was awarded the subcontract to construct an 18,000m³ capacity post-tensioned concrete tank for the ethylene cracker complex. The tank measures 33.8m at its outer diameter. Its wall is 28.6m tall and has a varying thickness of 550mm to 650mm. There are a total of 3 prestressing buttresses in which type MA 6819 Tendons are anchored for stressing purposes.

The tank’s dome roof is cast on a shell steel roof which was constructed at ground level.

Once completed, this steel roof was air lifted and floated to its final position using two specially designed air compressors. Well-known throughout the world for its cryogenic post-tensioning systems, DSI was able to provide invaluable advice to USS on the post-tensioning system that was used for the tank. The system had to fulfill special cryogenic requirements due to the tank’s very low operating temperature.

Apart from providing specialist advice on post-tensioning matters, USS was also responsible for the construction of the tank superstructure. Wall construction was carried out using the special USS jump form system and was cast in 11 lifts of 2.75m height each.

Thanks to the experienced specialists on site, the post-tensioning systems were installed quickly and efficiently.