Fire Detection At Nanticoke
Nadine International of Mississauga, Ontario was retained to upgrade the fire protection systems at Ontario Power Generation's Nanticoke Generating Station, one of the largest coal generating stations...
Nadine International of Mississauga, Ontario was retained to upgrade the fire protection systems at Ontario Power Generation’s Nanticoke Generating Station, one of the largest coal generating stations in North America.
Located in Haldimand County on the shores of Lake Erie, Nanticoke has 30 kilometres of conveyor belts, each travelling at 600 feet (183 metres) per minute. The existing fire protection for the conveyers consisted of closed-head, pre-action sprinklers that were activated by a pilot line system. While this system met National Fire Protection Association (NFPA) standards, it could not detect moving fires or provide fire protection under the carrier or return belts. As a result a fire might not be extinguished before extensive damage occurred.
Asked to develop a system that would detect both moving and stationary fires along the conveyors and chutes, Nadine International evaluated traditional spot type heat detection, infra-red/flame detection, gas/smoke analysis and various types of linear heat detection. All these systems can detect stationary fires, but none will detect fast-moving fires.
After research and testing, the engineers recommended an advanced fibre optic linear heat detector cable called a “Fibro-Laser.” The technology has been used in Europe to detect stationary fires in highway tunnels and in special industrial and power hazardous applications. However, this was the first time it had been installed to detect a fast moving fire anywhere in the world. At Nanticoke the fibre optic laser heat detection system is combined with a deluge water suppression system. By providing an early warning of any temperature rise along the conveyor, the fibre optic laser cables notifies the station’s staff to take action before a fire becomes large enough to activate the sprinkler system.
When OPG decided to upgrade the fire detection system, having a reliable and early fire detection system was critical. In addition, the fibro-laser system was found to be the lowest cost-effective alternative.
Fibre-optic heat detection cable
Effectively one sensor with thousands of measurement points, the Fibro-Laser technology system monitors conditions along the entire span of the cable simultaneously.
Within one metre accuracy, the system can measure:
• absolute temperature anywhere along the cable;
• rate-of-rise temperature in degrees, per minute, anywhere along the cable;
• degrees over ambient temperature anywhere along the cable.
The cable contains no electronics, and is immune to electromagnetic interference.
Fibre-optic temperature sensors work according to the Raman effect, which involves an interaction between the light particles (photons) and electrons of molecules, and the emission of light of new wavelengths.
Designing and calibrating the system
Because the product had not previously been used in this type of application and had never been tested to detect a rapidly moving fire, Nadine performed exhaustive tests and models. These included staging a mock-up and simulating an extensive fire condition using 2000-W electric heaters at various points along the conveyor.
The engineers also had to find the optimal location for the detector cable within the conveyor. It had to be placed where it could detect overheated bearings on both the upper carrier belt and on the return belt, which are separated by the sheet metal frame. The cable also could not be in a location where it would hinder maintenance operations. Ultimately a location alongside the conveyer bed was selected.
Also complicating the system design was the fact that the parts of the conveyor are located outdoors and exposed to the elements. So the cable detector had to be calibrated to account for varying ambient temperatures over a wide range of conditions including rain, snow, sun, shade and even wind direction.
Making the system code compliant was a challenge as the product was not recognized by Underwriters Laboratories Canada at the time, nor was there any standard for measuring its adequacy for detecting moving fires.
The cable was run for a six month trial run to monitor its performance parameters and did not generate any false alarms.
The project won an award of excellence from Consulting Engineers of Ontario in 2008.
Client: Ontario Power Generation
Prime consultant, research and design: Nadine International (Ajwad Gebara, P. Eng., Ashar Kahn, Paul Tomlinson, P. Eng., Ashraf Elhanafey, CET)
Other key players: Siemens Building Technologies (FibroLaser cable); Aker Kvaerner Songer Canada (cable installation)