Replacement of crane girder beams underway at the oxygen steel plant

As part of the renewal and modernization of central production units of leading steel producer thyssenkrupp Steel, Mammoet was contracted to replace and transport crane girder beams in the casting hall of the oxygen steel plant in Duisburg, Germany.

In order to minimize production downtime, this highly complex sequence of lifts had to be planned early - and accurately, with regard to the limited space available. This meant the planning phase began several months in advance of execution.  

Mammoet used its Move3D engineering platform to precisely analyze obstacles and height conditions and to visualize all operations and crane positions. This avoided the need for additional and time-consuming modifications. 

The 19 crane girder beams are between 30 and 45m long, 5m high and weigh up to 160t. The execution was split into two construction phases, with seven crane girder beams to be replaced in the first phase.

After defining the individual work steps, the crane sizes were determined based on the various load cases. Two Liebherr mobile cranes, an LTM 1750-9.1 and an LTM 1650-8.1, were used for most of the heavy lifting work. However, not all crane girder beams could be replaced in this way.

Unique gantry solution

Mammoet's engineers developed a customized solution for the crane girder beams that were difficult to access, which involved the use of a gantry system.

The gantry system consisted of two towers on which skid tracks were placed in the transverse direction of the hall. A longitudinal beam was then installed on these two skid tracks, on which two strand jacks could be moved.

The structure of this unique lifting system presented further challenges to the engineers and the team on site. As some parts of the plant could not be dismantled, the equipment had to be installed over these parts, taking into account any interfering edges.

A total of three mobile cranes were used to install the gantry system: a Grove GMK 6450-1, a Grove GMK 5250L and a Liebherr LTM 1095-5.1. However, one of the crane positions had a basement, which meant that the load-bearing capacity of the floor was insufficient. The Mammoet team provided a quick and safe solution here, too.  The loads of the Grove GMK 6450-1 were transferred to the side walls of the building via extra-long load distribution mats, thus creating the necessary load-bearing capacity.

Precision at every step

The removal, reinstallation and transport of the first five crane girder beams was performed quickly using the two Liebherr mobile cranes and two units of six axle lines of SPMT. Due to the limited space available, the crane girder beams could only be placed upright on the SPMTs for transport in the casting hall.

This was followed by the two crane girder beams, which could only be reached via the gantry system. These required a large number of work steps and load transfers.

First, two strand jacks were attached to the crane girder beam to lift it out of position and move it across the skid tracks towards the center of the hall.

Then the crane girder beam was pushed using the strand jacks and the skid track in the direction of the Liebherr LTM 1750-9.1, which took over the load at the first lifting point.

The crane girder beam was then moved together with the second strand jack until the load could be transferred from the LTM 1750-9.1 to the LTM 1650-8.1. The 750-ton crane was then able to swing back and pick up the beam at the other end from the second strand jack. The second beam followed in the same procedure.

Due to the confined space, both mobile cranes had to telescope in and out several times under load and work in sync with the strand jacks and skid track. These demanding maneuvers could only be performed safely and successfully by a practiced and experienced team and very good communication skills.

“The cooperation between all parties involved and the Mammoet teams in Europe and Germany was crucial to the success of this project,” says René Xyländer, Director Operations at Mammoet in Germany.

”The 3D engineering and the unique technical solution with several mobile cranes and a customized gantry system helped to meet the tight schedule.”

The first construction phase was completed safely and on schedule. The second phase will follow.

Copyright hero image: thyssenkrupp Steel