AP Sensing’s fiber optic Linear Heat Detection Series (N4387B) is one of several advanced technologies included in the tunnel in order to ensure its safety. Utilizing a passive fiber optic cable as a distributed temperature sensor, thousands of temperatures along the tunnel are measured in real-time, with hotspots or fires pinpointed with complete accuracy. AP Sensing’s N4387B is a system that is often deployed in traffic tunnels, as the system is particularly advantageous over long distances and in harsh environments. The fiber optic sensor cable can withstand temperatures up to 750 °C for two hours without losing monitoring capabilities (tested according to IEC60331-25), and can track fire size and spread, unaffected by air currents.
In this particular project, we are monitoring the entire tunnel utilizing three N4387B interrogator units, with all data managed by our SmartVision acquisition software and visualized on our SmartVision asset viewer platform for a better overview at all locations. The configuration of the system is redundant, with two different fibers connected to different LHD units at opposite ends of the same fiber optic cable. This eliminates system downtime in the case of a fiber break.
Following the configuration, an integrated alarm test took place to ensure that the SCADA system was receiving alarm outputs via Modbus. Despite the challenges of the current COVID-19 situation causing the need to commission the LHD system remotely, AP Sensing managed to meet Roxel Infra’s tight deadline to finish the project by the end of 2020.