Multi Spectrum Approach Reduces False Alarms
Vol 21 No 4
Hydrocarbon fires are the number one concern in any petrochemical facility. Mist flame detectors using infrared technology utilize nar-row band filters that look for a wavelength of 4.3 microns that indicates hot carbon dioxide produced by hydrocarbon burning.
However, what if something beside hydrocarbon is burning? Or, instead of producing CO2, the oxygen starved hydrocarbon fire emits carbon monoxide?
"Our primary interest is in using technologies that address all fire types," said Dr. Ted Lapp, engineering vice president of Fire Sentry Corp. "Many of our competitors address hydrocarbon fires and that's all."
Fire Sentry is the leader in wideband IR technology for electro-optical fire detectors with thousands operating worldwide. This patented multi-spectrum technology senses radiant energy in the near-IR, visible and wide band infrared spectrum. Radiant energy produced by fire and flame alerts the detector to the presence of fire.
"Even though we address the 4.3 micron wavelength, we also incorporate nearby wavelengths as well," Lapp said. "Using our wide band technology we detect all fire types -- burning metals, hydrogen and others."
Sophisticated software algorithms and microprocessors ensure that Fire Sentry detectors combine high fire protection performance with optimal false alarm rejection. A continuous stream of information is analyzed by the microprocessor. When the alarm activates, the detector stores all of the pre-fire data from its sensors in memory for later retrieval and evaluation.
Performance is not affected by high IR background radiation. It is immune to common UV sources such as arc welding and corona discharge is achieved.
"We have a flexible arrangement as to alternative digital and analog interface techniques," Lapp said. "We provide a means for connecting to these digital interfaces to download an event log to a PC. We also download another batch of digital data we call FirePic that can be used to postulate the cause of the fire."
Fire Sentry is moving ahead in other areas of detection technology as well. Fire Sentry Corporation also supplies a unique product, Visual Smoke Detection (VSD), for the very early detection of smoke in traditionally difficult applications. VSD utilizes video cameras to view large areas where detection is required. Detection time is significantly faster than traditional smoke and heat detectors, especially where it is difficult to locate detectors close to the fire source.
VSD system provides very early warning of fire at the incipient stage, using state of the art image processing technology. This technology has been subjected to rigorous scrutiny by many industries including the Nuclear Power Industry. VSD uses standard CCTV equipment linked to a self-contained central processing system, which is capable of recognizing small amounts of smoke within the video image.
Highly complex algorithms process video information for up to eight cameras simultaneously. The system can be configured to vary the quantity of smoke and the length of time that the smoke exists before an alarm condition is enabled. This allows for conditions where background smoke or steam may be present. A single system can be configured for up to 80 zones of detection.
By using cameras, which can see through glass or be fitted into intrinsically safe camera housings, VSD can safely detect fires in hazardous areas such as radioactive, explosive, corrosive and extreme weather environments.
VSD employs the ultimate in false alarm rejection -- an alerted human operator viewing the highlighted source of alarm on a monitor screen.