MOOGs participation at the Queensferry Crossing, Scotland
Six under-bridge travelers and two deck shuttles for the „Queensferry Crossing” bridge were supplied to Scotland
Who has not heard of the construction of the Queensferry Crossing Bridge in Edinburgh/Scotland in the past two years? The world’s longest cable-stayed bridge with three towers (2.7 km) has now been completed and was officially opened to traffic on 30.08.2017. Reason enough to introduce our participation in this project:
As a manufacturer of under-bridge access solutions, it was a great pleasure for us to assert ourselves again in the tendering process and finally win the contract for this major project. Due to the high volume of traffic that the bridge was supposed to withstand and the specified bridge width, the access travelers (gantries) were already taken into consideration in the planning process, since inspection with a mobile under-bridge unit would not have been possible.
So we took on the challenge to design, build and finally install six under-bridge access travelers and two deck shuttles especially for the “Queensferry Crossing”. The dimensions of the permanently mounted under-bridge access travelers speak for themselves and have brought the size of our production halls to their limits several times:
4x MBU 220-3 (Gantry A/B)
These travelers make access possible from the first pier to the south of the South Tower (S1) and the first pier to the north of the North Tower (N1). The access platform is 3m wide and has a maximum horizontal reach of 22 m. The payload of up to 5,000 kg per unit allows up to 20 people to work on one access platform simultaneously with heavy equipment (about 3,000 kg of material).
The special construction was individually adapted to the design of the bridge, whereby several working platforms, arranged in line with the angle of the outer deck, were installed in different positions on the respective main platform. Each of the 4 devices runs on rails, which were installed on the bridge deck. The travelers can be moved along the bridge with a speed up to 20 m/min
Two MBU 220-3 were installed on the south and two on the north side to inspect and maintain the complete length of the bridge. The parking positions of the machines are located at the towers.
2x MBU 270-3 (Gantry C)
These travelers provide access to the bridge underside between the south tower and south abutment and north tower and north abutment and have a horizontal reach of up to 27 m each. In park position (telescopic inspection platforms are retracted), the access platforms can be driven through the V-shaped bridge piers in the approach area.
In addition to the main and telescopic platforms, service platforms made out of aluminum were installed to the left and right of the main platform. On one of the two lateral platforms is the control panel for controlling the access traveler, in the other one there are sanitary facilities for the workers.
The platform width and load-carrying capacity are the same as with the MBU 220-3, however, an additional integrated hydraulic lift was installed at each of these gantries, which allows access to hollow box girders. This can be positioned anywhere on both the main or telescopic platform. The maximum working height of the lift is 7.4 m.
One MBU 270-3 was installed on the south and one on the north side. The park positions of the machines are again at the towers of the bridge.
The Gantries A/B and C were not only designed to have access to any location in the huge steel hollow boxes, but were also adapted to the specific environmental conditions over the arm of the sea „Firth of Forth “. The units are designed to withstand violent storms; in addition the surfaces were hot-dip galvanized to prevent corrosion.
The gantries are each equipped with a drive system which is powered by an integrated diesel generator. This allows the travelers to be driven on their respective bridge section completely. The generator is not only designed to provide the driving force, but also to power electrical tools via the electrical outlets.
The control system designed to the customer’s requirements guarantees a continuous, adjustable travel speed for a maximum bridge slope of 3%. In addition, it also has a system that maintains the synchronization between the lower edge and the upper frame of the driving system (Anti-Crabbing System). It does not matter how the load is distributed across the platform. The system constantly checks the driving speed and adjusts the respective drive motor if necessary.
2x Deck Shuttles
In addition to the gantries, two transport shuttles were also manufactured and installed, which run inside the bridge deck and can thus carry 2 persons and up to 150 kg of equipment each, regardless of the traffic on the bridge deck. The driving speed is 4 m/s. The deck shuttle’s structure is a steel frame and is covered with aluminum plates and perspex.
It is powered by rechargeable gel-type batteries which have enough capacity for 3 round trips on the bridge (= 16 km).
The deck shuttles were installed by us in November 2016 before the bridge deck was closed.
The six gantries were produced in succession, hung on test rails in our production halls, dismantled in transportable components and shipped to Scotland on several trucks. On site, the components were reassembled by our mechanics and lifted on to large barges. After positioning these under the bridge, they were lifted by hoists under the bridge deck and installed by MOOG. Due to the size of the gantries, this millimeter-accurate positioning and installation was a challenging task, which the crane operators and our team on-site mastered with excellence in March and July 2017.
In addition to supplying the Gantries and Deck Shuttles for this bridge, MOOG is also very proud to report that its biggest German customer Wemo-tec GmbH from Eichenzell was working on the bridge for several months with several mobile MOOG under-bridge units as well:
In December 2016 Wemo-tec arrived on the site at the Queensferry Crossing after months of work behind the scenes and discussions with FCBC; the machine selections were made and works commenced. With a multitude of tasks to be completed and a very tight schedule for completion, this project has brought the machines and operators to their limits, without permitting any room for mistakes.
MOOG MBI 160 platform units and MBL 1200 bucket units were selected due to their individual merits:
The flexibility of the MBL 1200 units enabled steady access for completing the external drainage systems and also for small repair works on the bridge structure caused by the construction process before.
The MBI 160 units were chosen to carry out major works, where several workers needed to be on the platform at the same time. These works also included the installation and alignment of the rails for the under-bridge travelers MOOG designed, manufactured and installed as described above and for several painting works.
Additional work was also required in relation to the towers, which in particular could only be started once the tower cranes had been removed. This added extra pressure onto the already tight completion schedule. Once the wind barriers were installed completely, the only machine that had the working scope for both access requirements, vertically and horizontally, was the platform unit MBI 160. The only other option would have been to remove the top sections of the wind barrier again, which was no practical solution.
Wemo-tec sent its most experienced operators for these tasks as there were only a couple of centimeters space between the machine and the wind barriers during setup, which of course left no room for errors. The operators worked tirelessly and the co-operation between Wemo-tec staff from Germany and the UK was great. As the completion date got closer and closer, the personnel was planned in two shifts and thus the MOOG machines run twenty-two hours a day. The works were finally accomplished successfully with zero days of breakdown, neither of Wemo-tec personnel nor of the MOOG machines in operation, which is an excellent result!
Even if humans and machines came to their limits while this project, all the workers from the Wemo-tec and MOOG on-site team feel they were part of something special. Not only because of the numbers of works that had to be finished, but also because of the great hospitality on-site and the contacts that had been established there.
Photographs: Courtesy of Transport Scotland
