NFPA 480-1998 Standard for the Storage, Handling, and Processing of Magnesium Solids and Powders. 42.4.8* Each wet-type dust collector shall be dedicated to the collection of magnesium or magnesium alloy only. 4-2.5 Cyclone Dust Collectors. 4-2.5.1 Hoods and enclosures shall be connected to a high- efficiency cyclone(s) and blower ‘ocated outdoors. 4-2.5.2 The cyclone exhaust shall terminate in a safe, outdoor location, Recycling of air from any dust collector into buildings shall be prohibited. 42.5.3 All components of a dust collection system shall be made of conductive materials and shall be watertight. 42.5.4 The minimum length of duct from the dust-produc ing operation(s) to the cydone shall be 1511 (4.6 m). 42.5.5 Explosion venting shall be permitted to be installed on dry-type dust collection systems. 4-2.6 Ductwork. 42.6.1 The discharge duct for wet-type dust collection equipment shall terminate at a safe, outdoor location. Recycling of air from any dust collector into buildings shall be prohibited 4-2.6.2 The ductwork and fan system shall be designed such that the concentration of magnesium dust in the system is less than 25 percent of the minimum explosible concentration (MEC). In systems that involve multiple machines connected to one dust collector, the concentration limit and velocity requirement shall be met throughout the entire system. 42.6.3 All components of the dust collection system shall be of conductive material. Connecting ducts or suction tubes between points of collection and separators shall be completely bonded and grounded. Ducts and tubes shall be as short as possible, with no unnecessary bends. Ducts shall be fabricated and installed in accordance with NFPA 91, Standard Jr Ezhnur Svrk”is for ,41r Con’ning of.t4unik,. Ducts shall have no unused capped connections to the main trunk line where magnesium dust can accumulate. 4-2.6.4 The power supply to the dust-producing equipment shall be interlocked with the airflow from the exhaust blower and the liquid level controller of the wet-type dust collector so that improper functioning of the dust collection system will shut down the equipment it seives. A time-delay switch or equivalent device shall be provided on the dust-producing equipment to prevent staiting of its motor drive until the separator is in complete operation. 4-3 Cleaning. 4-3.1 Systematic cleaning of the entire grinding area, induding roof members, pipes, conduits, et cetera, shall be carried out daily or as often as conditions warrant. 4-3.2 Cleaning shall be done using soft brushes and conductive nonsparking scoops and...
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