Oxbo was contracted to complete a multiple-phase project which included installation of four 1,100-ton tanks into corresponding modules for overseas transport.
The project was a complicated one, as both coffer dams were installed in each section to enclose the modules prior to the installation of the tanks. Due to this build strategy, the tanks had to be lifted nearly 53 feet off the ground and then precisely lowered to avoid damage to the modules and the tanks.
Oxbo’s in-house engineering team came up with the perfect solution by designing a self-climbing gantry to install the tanks. The design utilized a custom built system consisting of four 600 metric ton, diesel powered strand jacks to provide speed, reliability and safety while mounted 160 feet in the air.
Oxbo only had five months to design, build and erect the gantry from the time the contract was signed to the day of the first pick.
A dock crane was utilized to place each of the four 135-foot-tall, 55,000-pound legs. Oxbo engineers incorporated a hinge mechanism in two of the legs to absorb the deflection of the trusses while under load. This feature protected the welds and bolts from being overstressed during the 2.2 million pound tank picks.
After all four legs were installed, Oxbo used 24 lines of electronic-steered Goldhofers to move the gantry into the buildway. Then the team utilized two remote control hydraulic jacking systems to power the eight climbing jacks.
All controls were routed to a command center that was installed on the main base beam to allow the operators to travel with the load. All gantry movements and video monitoring were capable of being controlled by a single operator safely housed in the command center.
Oxbo also provided the design and engineering of the picking lugs, making it extremely simple to attach all four lugs to the strand jacks with a single pin for each one. Each tank was lifted the full 53 feet in approximately two hours.
The skidding system was also operated by remote control to allow the technicians full control of smooth, precise movements both forward and backwards. The skid system smoothly traveled at 80 feet per hour with the 3.2 million pound combined load of the tank and the gantry system. The system also allowed the loads to be spread over a wider footprint to overcome the reduced allowable ground pressure as low as 1,000 PSF in some locations on the dock.
When it came time to lower the tank, lasers were utilized to allow the operators to precisely align the tank without leaving the command center. The first tank was completely installed from start to finish within a single 10 hour shift.
Once all four tanks were installed, Oxbo was ready to tackle the next phase of the project - getting the barge ready for launch.