We were brought in by the client to manufacture a shield for a tunnel boring machine to be used in the creation of a new baggage tunnel, connecting Heathrow Airport Terminal 5 with Terminals 1 and 3.
Our team was awarded this lucrative contract on the basis of previous impressive work completed for the client, who trusted us to replicate this quality on a very high-profile job.
We adhered to a complex brief, which required the shield to be 5.5 metres in diameter and 4.4 metres in length, with a total weight of 76 tonnes. In addition, under no circumstances was the shield allowed to be smaller in diameter at the front than the back. Furthermore, allowances needed to be made for welding shrinkage.
Using the client’s basic drawings, we were able to get the plates cut, prepped and rolled while the main drawings were completed. This approach resulted in saving crucial time, guaranteeing that all deadlines were met.
The shield was manufactured in eight segments. With tight time constraints in mind, we fed each component through in the order required, to maintain continuous production.
Our meticulous approach involved manufacturing the bottom segment, before fabricating the adjoining segment with the outer skin plate. At this stage, we did as much welding as possible.
After this, precise measurements were taken of each segment to monitor any shrinkage noted. This segment was then put into the main assembly to assess the adjustments needed to overcome this shrinkage. The segment was then taken away for final welding, before being reinserted into the main assembly.
We repeated this process for each segment until the task was completed.
In addition, we manufactured two sledges to move concrete segments into position for assembly, and four sets of overcut beads to help gauge the diameter of the tunnel.
Our approach paid off, as the shield was completed within the client’s time and budget requirements, greatly aiding the construction of a very complex machine. The largest segments manufactured weighed 10 tonnes. The completed tunnels made using the excavating machine contributed to a successful baggage network.