The FIREYE UV Flame Scanner from HMA INSTRUMENTATION is ideal for gaseous fuels such as natural gas and propane. However, it can also be used to detect flames from standard fuel gases, some waste gases, and light oil fuels such as No. 2 oil. Flames from heavier oils can be detected with UV scanners, but the unburned fuel shroud and/or atomisation shroud can block passage of the UV from the flame zone to the UV tube, causing nuisance burner/boiler trips. Infrared detection is recommended for fuel oil heavier than No. 2, and some installations where waste gases are burned together with natural gas as a main flame.
The UV tube is made from quartz, and is filled with a gas that ionises when struck by UV radiation from the flame. In the absence of UV radiation, the gas acts as an insulator between two electrodes mounted inside the tube. These electrodes are energised continuously by a high voltage. During combustion, UV radiation ionises the gas, causing current pulses to flow between the electrodes. These current pulses result in a flame signal transmitted to the control amplifier, where it is processed to energise or hold in the flame relay.