Lu Feng 7-2 Topside Installation Project, China
ALE completed the offshore lifting and levelling operation of the 13,000t Lu Feng topside in the South China Sea. The extensive scope of work included the onshore lift, load-out and float-over. This multiple phase project combined all of ALE‘s expertise, from bespoke engineering to operational optimisation.
ALE supplied the engineering, equipment and personnel to perform all aspects of the project. Firstly, ALE performed an on-shore lift of the topside prior to the load out operation to enable the timber skid shoes to be installed and the lifeboats to be positioned beneath the cellar deck.
To install the Lu Feng 7-2 platform, weighing 13,000t, a bespoke installation method had to be designed around the low centre of gravity float-over to combat the constraints dictated by the width of the pre-installed jacket.
To complete the on-shore lift, twenty four 850t capacity strand jacks were installed to the four topside legs. A bespoke spreading mat was designed and positioned beneath each leg to support the load of the topside during the lift. The loads within the jacks were monitored throughout by the strand jack control system to ensure that neither the ground nor structure became overstressed.
The topside was then lifted 2m whilst the skid shoe and lifeboat installation works were completed. The topside was then lowered onto the skid track ready for the load-out. ALE’s engineering design ensured that the equipment was installed quickly and efficiently in the confined and congested platform environment by the ALE site team.
The load-out of the topside onto the transportation and float-over barge was performed at Shekou. The topside was pulled 140m from the build location to the float-over location on the barge using four 850t strand jacks installed in the cellar deck skid beams of the topside. The load-out was monitored using ALE ballast and barge level monitoring systems, allowing the ballast operator to observe real time information against local tide predictions and understand the positioning of the barge in relation to the quayside, as well as providing trim and heel data of the barge in real time.
The ballast system and layout were designed specifically for this project, with bespoke protection frames on the outer edges of the barge to avoid damage during sea-tow. The ballast control system enabled the ballast operator to control the passage of water from inlet to outlet through remotely operated hydraulic valves. Like the rest of the ballast system, the HPU was controlled remotely which allowed the flow rates to be varied as required. Once the topside had been manoeuvred into the jacket slot, the ballast operation was continuous through to the final separation and barge removal. The legs were then welded ready for the lifting operation to commence.
The platform was then lifted 10m using twenty four 850t strand jacks and in a synchronised manner by the ALE tem to ensure the loads of each leg were maintained with the design limits. The topside was then levelled within 5mm and locked in a safe position using a jacking system, comprised of sixteen 500t capacity screw locking collar jacks, to carry out leg welding work. The lift was monitored to limit the out of stroke tolerance of each individual strand jack to 5mm. The whole operation was safely completed within three months ; it achieved all of the client’s project milestones, most notably that the operation was complete prior to the typhoon season.