Detection

Risk mitigation related to fire protection begins with a facility's detection systems. Without a meticulously planned detection scheme, it is impossible to provide the level of protection that high-risk power generation and chemical plants need. Implementing the correct detection system for high-risk areas requires extensive knowledge about the most current technology available as well as the environmental factors of each application.

Spot-Type Heat-Sensing Fire Detectors

These systems are a good choice for detecting robust fires in confined spaces. Detection rate can be stalled comparatively but the incidence of false alarms is very minimal. Alarms are actuated by devices attached to the ceiling or above the hazard and gauge temperature by a number of different methods:

  • Rate-of-rise - an alarm is actuated when the rate in which the temperature rises exceeds a predetermined rate
  • Fixed temperature - an element responds to a precise temperature, triggering an event that initiates an alarm
  • Rate-compensated - often utilized outdoors or in applications with fluctuating temperatures, an alarm is actuated when an element responds to a rapid rise in temperature or a fixed elevated temperature.
  • Combination heat detectors - possess characteristics of both rate of rise detectors and fixed temperature detectors
  • Line-type heat sensing devices - ideal for extended applications such as conveyors and electric cable trays, parallel conductors are separated by a material which melts under heat and subsequently causes the conductors to trigger an alarm

Smoke Particle-Sensing Fire Detectors

Ideal for applications where smoldering fires are likely to occur, these types of devices can quickly detect a fire:

  • Ionization smoke detectors - measures the conductance between electrodes, making it possible to detect ionized smoke particles and subsequently send a signal to the FACP
  • Photoelectric light scattering smoke detectors - a good option for remote areas, these devices function by transmitting and measuring light with sensors, detecting high density smoke particles
  • Photoelectric light obscuration smoke detectors - smoke particles interrupt light transmission, consequently sending a signal to the FACP
  • Air aspirated sampling smoke detectors - air is extracted from the area through an aspirating fan into a sampling chamber where it is then analyzed for indications of combustion
  • Linear beam smoke detectors - a transmitter and receiver are strategically placed in applications where smoke is susceptible to stratification and a ceiling spot detector may not be reliable
  • Duct smoke detectors - air in the HVAC ducts are sampled and a signal is sent to the FACP if smoke is detected within the sample

Flame-Sensing Radiant Energy Fire Detectors

Areas that encompass high-value hazards or flaming fires can benefit from this type of detection. In applications that demand the fastest detection and are at risk for deflagration the following options can help safeguard facilities:

  • Ultraviolet (UV) flame detectors -ultraviolet wavelengths detect the radiation emitted by a flame, these devices may not be effective in dusty environments
  • Infrared (IR) flame detectors - these devices use a photocell to seek out radiation, they are most effective for distances up to 50'
  • Ultraviolet/infrared (UV/IR) flame detectors - for use in indoor and outdoor applications, it is critical to consider the ambient variables that could set off false alarms and it is advantageous to utilize a detector that seeks out hazards specific to the environment
  • Spark/ember detectors - small amounts of radiant energy that are emitted before a fire fully ignites can be detected with these specialized flame detectors


Gas-Sensing Detectors

Hazardous gas releases can be detected with gas-sensing detectors before a dangerous concentration is reached.

Pressure Detectors 

When an increase in pressure is detected due to ignition, the contacts on a depression plate close and a signal is sent to the FACP.

 

 

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