Challenge

Cyclone separators are used both as receiving vessels and for the collection of dust. They separate solids from the air stream by the centrifugal action of a vortex created as the inlet air tangentially enters the cyclone. The dust or granular material is thrown to the walls of the cyclone and then falls to the hopper section from which it discharges via a rotary gate valve. Meanwhile the cleaned air exhausts through an outlet.

The Hazard
If the material being handled by a process is combustible, then the dust it generates is likely to be explosive. When a cyclone is used as a primary separator, an explosible dust cloud may be present continuously during normal operation. Under these conditions, an ignition source is all that is required to trigger an explosion. This can be provided by static electricity or by incoming burning particles from upstream equipment such as mills or dryers.

Protection System Considerations
Protection systems for cyclones must accommodate the need to maintain a smooth inside vessel wall for efficient cyclone performance. IEP Technologies suppression systems achieve this by using flush spreader assemblies for suppressant dispersal.

Protection system description
Cyclones are frequently located inside the plant where explosion relief venting is impractical. Additionally their configuration makes explosion relief venting a challenge since a smooth inside wall and adequate vent area are required. An explosion suppression system provides the solution. In such a system, explosion pressure detectors, mounted on the cyclone, detect the pressure excursion from an impending explosion. The detectors transmit a signal to a control panel, which triggers high rate discharge extinguishers while simultaneously shutting down the process.

Extinguishers mounted on the cyclone are designed to rapidly discharge suppressant and quench the fireball before maximum pressures are reached. An isolation extinguisher mounted on the inlet duct mitigates flash-back to upstream process equipment. Additionally an explosion-proof rotary gate valve mounted on the hopper reduces the likelihood of burning materials passing downstream.


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