Radar Level Application for Coal Silo

The  usage of coal silos is to store coal, the primary fuel for firing the kiln and the preheater in a cement plant. Coal Silos are usually constructed of steel, but concrete is also used. silos are circular, square, or rectanglar in cross section and generally designed for a three- or four-day capacity. The hoppers should be designed for mass flow to eliminate static coal deposits. The bin outlet should be large enough to prevent arching or plugging. All bins should be self-cleaning, and internal surfaces should be kept free of stiffeners, weld strips, or flange surfaces. For explosion venting design, many factors must be considered. The National Fire Protection Association (NFPA) Guide for Explosion Venting  should be used in evaluating each installation. Explosion venting provides relief for explosion force build-up inside the bin and limits the damage should an explosion ever occur.




Level monitoring inside a coal bunker is the most challenging of level applications. The occasional fires inside the silo cause most transmitter electronics to fail. Western coal is more friable than eastern coal. It fractures more easily in handling, conveying, and stockpiling and produces a higher percentage of fines which contribute to the dust accumulation. Dust accumulations increase the risk of fire and explosion. However, western coals have a higher moisture content, but they tend to dehydrate which causes fissures and subsequent degradation of lump size. Also, western coal has a higher tendency for spontaneous combustion. Volatile gases resulting from thermal decomposition when the coal is heated can cause a serious explosion in a confined area such as a silo or surge bin.


The TIPL LevelExpert LTR58 Pulse Radar Level transmitter is designed specially to prevent damage to the electronics under low to medium level explosions in the coal silo. The special process seals and high temperature electronics are tested to operate under temperatures upto 400°C. Mounted over the silo, the high directivity Radar sensor continuously measures coal level and transmits either as 4-20 mA analog signal or via HART to a communicator device. The  LevelExpert transmitter is available with both  Intrinsically Safe (Exia IIC T6 Ga) and Intrinsically Safe+Flameproof Approval (Exdia [ia Ga] IIC T6 Gb) certifications  for minimising the risk of explosions due to electronics.


Self-Ignition Risk (Coal)

Characterstics Temperature (°C)

Very High

≤ 250








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