Heavy-lift specialist Mammoet recently executed the first phase of a critical crane girder beam replacement project at thyssenkrupp Steel’s oxygen steel plant in Duisburg, navigating significant spatial constraints and tight deadlines. The project, part of a broader modernisation effort by the leading steel producer, necessitated meticulous planning and innovative engineering solutions to minimise production downtime.
Mammoet began planning several months before execution to address the complex sequence of lifts within the confined casting hall. The company utilised its Move3D engineering platform to precisely analyse obstacles, assess height conditions, and visualise all operations and crane positions. This proactive approach eliminated the need for time-consuming on-site modifications.
The project involves replacing 19 crane girder beams, each measuring between 30 and 45 meters in length, 5 meters in height, and weighing up to 160 tonnes. The initial phase saw the replacement of seven of these massive structures.
Mobile cranes handle initial lifts
Mammoet determined the appropriate crane sizes based on various load cases defined during the detailed planning phase. Two Liebherr mobile cranes, an LTM 1750-9.1 and an LTM 1650-8.1, performed most of the heavy lifting for the first five crane girder beams. These beams were carefully manoeuvred and transported upright on two units of six-axle SPMTs due to the limited space within the casting hall.
Custom gantry solution for challenging access
However, not all crane girder beams were accessible using the mobile cranes. For these difficult-to-reach sections, Mammoet engineers designed and implemented a unique gantry system. This bespoke solution featured two towers supporting skid tracks running transversely across the hall. A longitudinal beam, equipped with two movable strand jacks, was then installed on these tracks.
The installation of this gantry system itself presented further challenges. Mammoet had to erect the structure over existing plant components that could not be dismantled, carefully considering any interfering edges. Three mobile cranes – a Grove GMK 6450-1, a Grove GMK 5250L, and a Liebherr LTM 1095-5.1 – were employed for this task. A basement beneath one of the crane positions required an innovative load-bearing solution; Mammoet utilized extra-long load distribution mats to transfer the Grove GMK 6450-1’s operational loads to the building’s side walls, ensuring structural integrity.
Precision maneuvering under load
The two crane girder beams handled by the gantry system demanded a complex series of work steps and load transfers. Initially, two strand jacks lifted each beam from its position and moved it across the skid tracks toward the centre of the hall. The strand jacks and skid track then pushed the beam towards the Liebherr LTM 1750-9.1, which accepted the load at the first lifting point.
Subsequently, the beam, supported by the second strand jack, was moved until the load could be transferred from the LTM 1750-9.1 to the LTM 1650-8.1. The 750-tonne LTM 1750-9.1 then repositioned to pick up the beam’s other end from the second strand jack. The second beam underwent the same precise procedure. The confined space necessitated that both mobile cranes telescope in and out multiple times while under load, working in precise synchronization with the strand jacks and skid track – a testament to the team’s experience and communication.
René Xyländer, Director Operations at Mammoet in Germany, commented, “The cooperation between all parties involved and the Mammoet teams in Europe and Germany was crucial to the success of this project. The 3D engineering and the unique technical solution with several mobile cranes and a customised gantry system helped to meet the tight schedule.”
The first construction phase concluded safely and on schedule. The second phase of the crane girder replacement is set to follow
.jpg&w=256&q=75)
.jpg&w=256&q=75)
.png&w=256&q=75)
