Britomart Rail Tunnel
Sandblast and Intumescent Fire-Proofing
LOCATION
SERVICE
The Challenge
The structural steel inside the operating rail tunnel required intumescent fire protection installed to specification, but the work had to proceed inside a live rail corridor rather than a closed site. Meeting the specified fire performance in this environment meant the coating process and its verification needed to hold up under the tunnel’s ongoing operational conditions.
Our Approach
BlastOff blast cleaned the structural steel to prepare it for coating before applying intumescent paint to specification within the tunnel. Dry film thickness was measured and recorded throughout the project, section by section, so the applied coating could be verified against the required build as work moved along the live corridor. Sequencing the blast cleaning and coating stages this way kept the fire protection system consistent across the full length of tunnel steel treated.
The Outcome
The tunnel’s structural steel received certified intumescent fire protection with dry film thickness verified throughout, giving KiwiRail a documented fire protection outcome delivered inside an operating rail corridor. The measured records confirm the coating was applied to specification across the treated steel members.
Fire-Proofing Structural Steel Inside a Live Rail Corridor at Britomart
Most intumescent fire-proofing projects happen inside a closed site. The work KiwiRail needed inside the Britomart rail tunnel did not have that luxury, since the structural steel requiring protection sat within a live rail corridor that continued operating around the project.
BlastOff blast cleaned the steel members to prepare them for coating, then applied intumescent paint to specification within the tunnel, with dry film thickness measured and recorded throughout as the work moved along the corridor section by section. That sequencing detail is really the story of this project. Blasting and coating inside an operating tunnel means every stage has to be planned around access windows, adjacent rail activity and the practical limits of working in a confined underground space, rather than around convenience. Verification could not simply happen once the whole run was finished, since sections of steel were completed and needed confirming as the crew progressed through the tunnel rather than waiting for a single end of job check.
For rail operators, transport authorities or any organisation managing steel infrastructure inside an operational corridor, the lesson from Britomart is less about the coating system itself and more about how a scope of work gets sequenced when a site cannot be shut down. Access, containment and verification all need to be built into the programme from the outset, not worked out on site once blasting has started.
The result was structural steel across the tunnel with certified intumescent fire protection and thickness verified throughout, giving KiwiRail a documented outcome achieved without interrupting the corridor’s operation. Anyone assessing similar steel infrastructure inside a live operational environment should raise sequencing and access constraints early in the scoping conversation, well before product selection. BlastOff carries out intumescent fire-proofing in demanding site conditions of this kind, alongside the structural steel blasting that prepares the surface beforehand.
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