Raising the roof

ALE was commissioned to erect a stockpile building roof for a mining company, at a site 4,000m above sea level. The normal method would be to install the roof one steel girder at a time.

The high altitude, combined with high wind speeds, temperatures ranging from - 30°C to +20°C, air pressure as little as 0.6 bar, and earthquake risks made this approach impossible. Instead, the a plan was developed to build the roof at lower altitudes, truck the roof modules to the site, and then raise them using the Mega Jack in three 1,500t pieces.

ALE used four towers of the Mega Jack system, with a total capacity of 20,000t and ten 90t capacity hydraulic skid shoes. With possible wind speeds of up to 150km/hr ALE took additional precautions by installing a guy wire system consisting of four 200t strand jacks at each end of the building to withstand high winds.

The roof of the building was positioned in three sections above the ground on temporary stands. ALE positioned the skid systems at each end of the building to enable the side sections of the roof to be skidded inward while the main inner section of the building was lifted 18m to the final position by the Mega Jack. Once complete the three sections created an A-frame shaped building.

Ronald Hoefmans, group technical director at ALE, said: "This project shows not only the capabilities and reliability of our equipment but also that of our highly trained personnel on site who overcame extreme conditions to ensure the project was a success. We are also pleased that the Mega Jack has completed its first project and as such has illustrated its versatility in conditions and also market sectors."

The Mega Jack System was launched in 2011 to meet growing needs within the offshore industry, primarily for the jacking of oil and gas platform modules and other large structures. The system, which is currently designed to lift up to 60,000t to a height of 50m, is the first of its kind and was designed and built by ALE's engineers at the Research and Development facility in Breda, The Netherlands.

The system comprises of jacking towers, each jacking tower has a jacking capacity of 5,200t and each tower consists of four jacking bases that contain a hydraulic jack with a stroke of 1,250mm. A temporary support is situated on top of each jacking base, which is also a hydraulic turntable. With the starter beams in position above the jacking bases and the jacks fully retracted, the system is ready to make its first stroke. In this position the starter height is just below 3.5m. After that two of four integral feed-in systems automatically insert the first set of jacking beams through the temporary supports.

Once in place, the jacks extend and raise the beams above the temporary supports, which rotate to hold the load while aligning their open sides with the other two feed-in systems, ready to repeat the process. This simple but incredibly powerful self-erecting tower continues for each 5m x 5m tower until they have reached the required height.

The jacking down process can start after the load-out support frame is put in place and as the starter beam is not welded to the deck, the tower can be lowered instantly. The stability of a tower is created by a very accurate hydraulic stroke controlled system, rather than being fixed to the deck.

Totally scalable, the number of towers can be adapted and increased according to the size, weight and balance of the structure, opening up new possibilities for an offshore sector increasingly under pressure to build ever bigger rigs.

Basic tower footprints consists of 2.5m x 2.5m, 2.5m x 5m and 5m x 5m jacking base centre distances, enabling ALE to create tailor made solutions for each client. By combining jacking bases in different configurations.