Innovative jacking techniques produce safer tank jack-down in Sweden
Oil and Gas
Using innovative jacking techniques, ALE has performed the safe jack-down of a gas tank, weighing 1,500t, while minimising noise disruptions in a residential area of Stockholm, Sweden.
As the tank, measuring 96m high with a 56m diameter, was situated so close to the surrounding residential buildings, ALE needed to design a bespoke solution to assist with the demolition of the tank. The usual methods involved imploding the tank and cutting sections out from above. This requires large cranes and is therefore time consuming. The solution also needed to be safer and be viable with the location’s restricted space.
ALE produced an innovative plan that used climbing jacks to jack-up the tank, enabling the client to work at ground level to cut and remove a section. ALE then jacked-down the tank, ready to repeat the process.
The solution required a lot of advanced preparations. Holes were cut into the tank to install 20 climbing jacks, each with a capacity of 150t. They were positioned on top of concrete supports, at numerous points below the main steel construction pillars of the tank. Hydraulic hoses connected the jacks together, with a central contact point in the middle of the tank.
“Although there was ventilation, we constructed a wooden building with plexiglass to further protect the jacking operator from the toxic gasses created by the cutting process,” said Paul Walters, Manager Projects Department.
“This jacking technique was safer overall as it meant the client didn’t need to work at height. We also positioned the manifold inside the tank, reducing the noise level outside. This was important as the site was so close to the local residents and it was important to avoid any disruptions.”
The jacking was carried out in stages of 1.6m at a time. ALE initially completed each stage in a day and a half, but this was reduced to one day. Once in a routine, the preparation carried out beforehand enabled ALE to work swiftly and complete the entire jack-down safely in approximately 11 weeks.