FOSA Installation Considerations
Distributed fiber optic sensing techniques such as Distributed Temperature Sensing (DTS) are powerful tools for monitoring long linear or other large assets. Consequently, these techniques fit perfectly with specific requirements of fire detection in tunnels, large buildings, industrial sites and large equipment. In fire detection applications fiber optic DTS systems are also referred to as a Fiber-Optic Linear Heat Detection (FO-LHD) systems; in contrast to conventional LHD systems that are based on electrical sensing. Some common fire detection applications are:
- Road and railway tunnels
- Railway and metro line stations
- Cable trays, shafts and ducts
- Parking lots
- Industrial sites such as refineries or steel plants
- Hazardous areas
- Floating roof tanks
- Conveyor belts
- Nuclear power facilities (requiring special fiber)
In each of these applications, distributed fiber optic sensing offers the clear benefit in the ability to cover a wide area from a central monitoring point. There are numerous additional benefits: the passive fiber-optic cable is lightweight, small and easy to install. In addition, the insensitivity to electromagnetic interference, moisture and dust is a clear advantage in comparison to electrical heat and smoke detectors.
FO-LHD systems measure temperature profiles over location and time and use this information as the base for sophisticated alarming. FO-LHD systems use maximum temperature, several rate-of-rise and difference-to-ambient algorithms in order to maximize detection sensitivity and diminish false alarms. If required, all alarm parameters can be set individually for each alarm zone, which makes the system very adaptable to any environmental challenges.
In explosive environments, the absence of electrical energy is of clear benefit for explosion safety when a fiber-optic cable is routed through classified areas. Nevertheless, a potential release of optical energy in case of a cable break as well as potential dangers arising from fire propagation, electrostatic discharge or transmission of lightning energy by the cable itself have to be taken into account when evaluating explosion safety. Users are advised to compare the ATEX / IECEX certification of the FO-LHD system with the requirements of the project before deploying it in explosive environments.
Optimum performance for any particular application is dependent on the system configuration, cable type, installation method, cable position and the environmental conditions of the site.
This document provides guidance on best practice for the selection and installation of cables for distributed temperature sensing (DTS) in the fire detection domain.