explosion isolation for interconnected ducts through which flame propagation may occur. The major advantages of explosion suppression are that no flame is ejected from the protected vessel, and the risk of a post-deflagration thermal event is greatly diminished. EXPLOSION ISOLATION Explosion isolation devices prevent a deflagration in a process vessel from propagating through a connection such as a duct, chute, or conveyor to other equipment, where it could cause subsequent explosions. The devices work by mitigating the flame propagation and pressure piling between connected equipment. An isolation device can be active or passive. An active device has detection components, including explosion pressure and/or flame detectors, and a control unit. The detectors detect explo-sion pressure or a flame and send a signal to the controls to rap-idly deploy the device. These active explosion isolation devices are either chemical or mechanical. A chemical isolation device works by rapidly discharging a chemical extinguishing agent, such as sodium bicarbonate, into connecting ductwork to miti-gate flame propagation. A mechanical isolation option includes a high-speed gate valve. Milliseconds after the active high-speed gate valve’s detectors sense explosion pressure or flame, the con-trols rapidly deploy a mechanical barrier --closing the valve’s gate across the connecting ductwork. In addition to the active isolation options, there are passive isolation means available to mitigate flame propagation. The pas-sive valve, which can have a flap or float, is self-actuated by the airflow from a deflagration so it requires no detectors or controls. This device is typically used to isolate dust-handling equipment with relatively low dust loads. Dust explosions at wood-handling facilities do not need to happen. Understanding where an explosion may happen in the facility, implementing ignition prevention systems, fol-lowing rigid housekeeping standards, and proper employee training should all be part of designing and operating a pro-cess to minimize the threat of an explosion starting. Employ-ing explosion protection measures such as explosion venting, suppression and isolation, will minimize the risk of an incip-ient explosion in process equipment from escalating into a catastrophic event in the facility. • Ed Chovanec C.E.T., C.S.P . is the Northeast Regional Manager of Fenwal – IEP Technologies and is located in Burlington, Ontario. David Grandaw is the Vice President of Sales for Fenwal – IEP Tech-nologies in Marlborough, Mass. For more information, go to www. ieptechnologies.com, or email the authors at [email protected] or [email protected]. For more articles on biomass handling, go to www.canadianbiomassmagazine.ca. Rotary Dryer System Heat Energy PelletPress Biomass Pelletizing & Energy Systems Pellet Plants | Dryers | Furnaces | Steam Boilers | Thermal Oil Heaters | Cogeneration Dieffenbacher USA, Inc. 2000 McFarland 400 Blvd. | Alpahretta, GA 30004 Phone: (770) 226-6394 | [email protected] www.dieffenbacher.com 24 Canadian BIOMASS Dieffenbacher Biomass marapr14.indd 1 MARCH/APRIL 2014 2014-03-11 9:48 AM
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