Jacket Repair Programme Inside a Running Metro Tunnel

Client Background

A metro operator identified 47 positions of jacket damage on tunnel cable during a condition survey. All of it was installation era damage from cable pulling and none of it had reached the core insulation.

Project Challenge

Repair 47 positions inside night possession windows using halogen free materials, on cable that is terminated at both ends and cannot be cut.

Customer Pain Points

• Cable terminated at both ends so no tube could be threaded on
• Halogen free specification mandatory in a running tunnel
• Possession windows of four hours with no possibility of overrun
• Any repair requiring cure time was ruled out entirely

Our Solution

R1 wraparound sleeves on the regular cylindrical damage and T1 halogen free heat shrink tape on the positions near cleats and fixings where a sleeve would not fit. Both are energisable as soon as they cool.

Manufacturing Process

Sleeves and tape produced to standard specification. T1 supplied in the halogen free RoHS compliant formulation required by the project.

Supply Chain Coordination

Delivery to the depot store two weeks before the first possession so the maintenance team could brief and prepare without time pressure.

Quality Control

Per lot testing of tensile strength ultimate elongation heat aging and water absorption. Adhesive bond verified on a sample of the actual cable jacket material supplied by the operator.

Final Result

All 47 positions were repaired across nine possessions. The average repair took 22 minutes. No possession overran. A repair register was created so the network record shows every position and date.

Customer Benefit

Forty seven positions of jacket damage closed out without cutting a single cable, using materials the tunnel specification allows.