A dependable maintenance free pilot monitor is an important system component. If the flame pilot is out, hazardous gasses may be vented accidentally into the environment. Continuous operation of the flare stack is a critical EPA requirement for the proper operation of the system in order to prevent a major safety hazard. The EPA requirement 63.987 states: (c) “Where a flare is used, the following monitoring equipment is required: a device (including but not limited to a thermocouple, ultra-violet beam sensor, or infrared sensor) capable of continuously detecting that at least one pilot flame or the flare flame is present.” A complete description of requirements can be found on the official EPA website.
Flare Stack Where, How, and Why?
Where? Flare stacks or gas flares are large diameter, tall vertical vent pipes used for burning off flammable gas released by pressure safety relief valves. This occurs during unplanned over-pressuring of plant equipment. Flares are found in oil refineries, natural gas processing plants, petrochemical plants, steel mills, and landfills.
How? The released gases and liquids are routed through large piping systems called flare headers to a flare stack. The released gases are burned as they exit the flare stacks. In order to keep the flare system functional, a small amount of gas is continuously burned, like a pilot light, so that the system is always ready for its primary purpose as an over-pressure safety system. Flammable vent gasses are ignited by a pilot flame when released into the atmosphere by petrochemical plants vessels or pipes.
Why? The proper incineration of these gasses is a critical safety and environmental concern. Therefore it is essential to confirm that the pilot is lit at all times. In industrial plants, the main purpose of a flare stack is that of safety by protecting pressure vessels or pipes from over-pressuring due to unplanned operational upsets.
Information in this section provided by: Encyclopedia of Earth
Pilot Monitor Technologies
Thermocouples Currently many pilot flames are monitored using thermocouples that must be mounted at the flame. This system, though effective, proves to be cumbersome when a thermocouple failure occurs. Thermocouples are prone to failure especially for frequently used flares because they are used in corrosive atmospheres. Failures frequently occur and replacements can require costly process shutdowns due to the location where the device is mounted.
Ultraviolet Flame Detectors Detects the presence of a flame through emitted ultraviolet (UV) energy. UV detectors are often used for pilot flames or flame detectors inside furnaces. However, conditions for a pilot flame in a furnace and an outside top of the flare stack are very different. Therefore it works detecting the presence of a flame with a hot furnace wall. Any other application, such as detecting the presence of a flare pilot is inappropriate and they are significantly less effective. With a flare stack, the UV sensor needs to be mounted relatively close if not on the stack itself. This is necessary to ensure that that UV detector only detects UV energy from the flame rather than other sources like sun-light reflection. Close monitoring is required otherwise false alarms are frequent. Usually, for flare stacks close monitoring is neither possible nor practical.
Infrared Sensors A noncontact device that senses the presence of the pilot flame by monitoring infrared (IR) energy. Unlike UV detectors, the IR is sensitive enough to be mounted hundreds of feet away. This enables IR sensors to be ground mounted and easily accessible if maintenance is required. The IR sensor is set to a wavelength where IR energy from the flame is visible. If the sensor reaches the threshold of IR energy associated with a flame the pilot flare is lit. If the IR energy falls below this threshold the area may be hot but there is no flame present. This will trigger an alarm that the pilot flare is no longer lit.
Pilot Monitor Being an infrared technology company, Williamson has an IR sensor that helps companies comply with the EPA regulations ensuring safe operations. The Williamson Pilot Monitor (PM) fills in the gaps where thermocouples and UV detectors fall short. When a pilot flare is lit, it is emitting more IR energy than UV energy. This makes the Williamson PM far more sensitive and allows for it to be mounted at a much greater distance. The PM can be used in conjunction with a thermocouple. When the thermocouple fails, the Williamson PM can provide a back-up that can be easily maintained and eliminate costly shutdowns. The Williamson PM utilizes proven dual-wavelength technology to sense the presence of a small, distant pilot flame. This technology allows the pilot monitor to view through severe weather conditions caused by fog, wind, rain, snow, and sleet. For more information on the Williamson PM Click Here!
To learn more about the Williamson Pilot Monitor and other flare products offered please see our Flare Monitor Data Sheets.
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