Firstflex Project Brief

Project: Tunnel Boring Machine
Electrician: KDE Electrical Ltd and Control Techniques
Engineer: Belcher Industries
Product: Firstflex Power Complete with Device Net Custom Cable

The project involved the engineering of a Roadheader type tunnel boring machine, complete with jacking rig, soil removal and automatic bentonite system. Built by Belcher Industries and used in the construction of a 600 metre long tunnel on Auckland’s North Shore.

An important aspect of the project was to ensure power and control to 72 motorised ball valves. These valves control the flow of bentonite (a slippery clay like substance) to ports in the concrete pipes, filling the void between the cut soil and the pipes, acting as a lubricant when the concrete pipes are jacked through the ground.

Karl Douglas from KDE Electrical together with Eric Blaney from Control Techniques were contracted to design and construct the electrical component of this project. “We wanted to keep the system in one cable and standalone from the other services running up the tunnel,” said Karl “making life easier for the guy’s onsite to connect and usable in other applications once the project had finished.”

“One of our biggest challenges was finding a cable that would contain both the power supply (24VDC) and Device Net communication the full 600 metre length of the tunnel. Ensuring that we had control and feedback from all 72 motorised valves without the addition of extenders.”

Karl and the team from Firstflex Cables worked together to design a custom cable to meet those specific requirements while ensuring it was manufactured to a high quality and delivered within the time critical deadlines of the project.

The end result was a Power Complete with Device Net Custom Cable which was installed and used during the project, successfully meeting the demands required from it.