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Unit 3

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  1. NADCA North American Die Casting Association Safety for Aluminum Processing and Finishing Operations Involving Combustible Dustin theDie Casting Industry Unit 3

  2. Enabling Objectives After completing this section of the course students should be able to: Discuss aluminum dust producing operations and the precaution for carrying out these operations safely Explain procedures for housekeeping, dust collection, fire prevention, prevention of accumulation of fugitive dusts, proper storage, and safety procedures for aluminum and magnesium. Metal Dust collector Exploded and Collapsed

  3. Dust Producing Operations • Two recognized methods to capture aluminum dust: • Wet collectors located near the point of generation • Dry collectors located outdoors as near as possible to the point of generation • Machines fitted with hoods and capture devices able to capture and transport all the dust that is produced

  4. Dust Producing Operations • Design system so all dust moves into the hoods, into the ducts and is collected • Connecting ducts must be kept as straight and short as possible

  5. Ductwork • Duct runs as short & straight as possible!

  6. Dust Producing Operations • Metal dust-air suspension can pass into the explosive range in the collector!

  7. CAUTION: This dust collector can contain explosible dust. Keep outside the marked area while equipment is operating. CAUTION • Dry-type provided with barriers or other protection • Area around collector posted with Caution Sign • Personnel outside of marked area when operating CAUTION: This dust collector can c

  8. ! Warning: Aluminum Metal Only – Fire or Explosion Can Result with Other Metals. • Dedicated equipment not to be used with other types of metals • Grinders, buffers posted with warning sign! Warning: Aluminum Metal Only – Fire or Explosion Can Result with Other Metals. Kaboom! Hi Aluminum! I’m another type of metal!

  9. Dust Producing Operations • Practice Quiz • 1. Duct runs for dust collectors should be: • A. As far away from the machine feeding into it as possible. • B. Build with curves and turns to slow down the movement of dust. • C. As short and straight as possible. • 2. When dry-type dust collectors are operating: • A. They should be indoors near the point of generation. • B. Barriers should be established and personnel should stay away. • C. Maintenance personnel should open them up to ensure they are working properly.

  10. Dust Producing Operations • Practice Quiz • 3. Grinders and buffers used for aluminum must be: • A. Dedicated equipment. • B. Used for all types of metal including stainless steel • C. Disconnected from dust collection units when used for other metals.

  11. Dust Producing Operations • Practice Quiz • 1. Duct runs for dust collectors should be: • A. As far away from the machine feeding into it as possible. • B. Build with curves and turns to slow down the movement of dust. • C. As short and straight as possible. • 2. When dry-type dust collectors are operating: • A. They should be indoors near the point of generation. • B. Barriers should be established and personnel should stay away. • C. Maintenance personnel should open them up to ensure they are working properly.

  12. Dust Producing Operations • Practice Quiz • 3. Grinders and buffers used for aluminum must be: • A. Dedicated equipment. • B. Used for all types of metal including stainless steel. • C. Disconnected from dust collection units when used for other metals.

  13. Individual Machines with Portable Dust Collection • Permitted to be used indoors when moving work piece is infeasible • Perform hazard analysis to minimize risk from fire & shrapnel • Limit collector capacity to < 1 lb • Empty daily Filtering Media Material Discharge Portable Media-Type Dust Collector

  14. Portable Dust Collectors • Cyclone’s are less hazardous than bag-or media-type • Exhaust discharge to atmosphere away from other operations!

  15. Dust Producing Operations • Dry collectors required to be located outdoors • (exception: small portable units • Dry collectors provided with barriers Filtration Media Material Discharge Build a barrier around the equipment! Fixed Media Type Dust Collector NOT the best choice!

  16. This dust collector can contain explosive dust, keep outside the marked area while equipment is running Dust Collection, Ducts and Ductwork • Collector area is to be marked and a sign posted • NFPA 68: length of a fireball from a vented collector • Collection system dedicated to aluminum only! 20'

  17. Experts indicate an eventual explosion can be expected from bag collectors use for aluminum fines! • Multiple-series cyclone with final liquid stage is a better choice Not so good… I’m a better choice Can lead to

  18. Dust Collection, Ducts and Ductwork If the collection system used for combustible aluminum dust is used for other materials it should be disassembled and cleaned before and after.

  19. Dust Collection, Ducts and Ductwork • Use separate collection systems for grinding and buffing operations • The dust collector should dissipate static electricity

  20. Dust Collection, Ducts and Ductwork • For bag-house shake-out design to minimize sparking • Pulse-types less likely to create a spark because there are no moving parts • Attach ground wires to bags and securely ground Mechanical Shaker Baghouse

  21. Dust Collection, Ducts and Ductwork • For baghouse an alarm sounds for pressure drop across bags • Locate baghouse or media type collector > 50 feet from other operations and buildings! • Keep personal > 50 feet away when shaking! At least I’m outside!

  22. Thermite Reaction • Avoid letting aluminum impact oxidized iron! • Thermite reaction possible for impact with aluminum & rusted iron or steel • Enough heat to produce molten iron! Laboratory created thermite reaction

  23. Dust Collection, Ducts and Ductwork • Practice Quiz • 1. Baghouse collectors for aluminum: • A. Are both economical and efficient. • B. Are considered better than cyclone collectors. • C. Have been associated with fires when used for aluminum. • 2. If aluminum impacts iron oxide: • The material produced is inert. • A dangerous thermite reaction can be initiated. • It makes a valuable by-product that is a commodity.

  24. Dust Collection, Ducts and Ductwork • Practice Quiz • 3. If a baghouse type collector is used: • A. A pulse-type is better than a mechanical shaker. • B. The collector should be located outdoors at least 50 feet away from buildings and other equipment. • C. Barriers and warning signs should be posted around the equipment. • D. All of the above • 4. Dust collection for grinding and buffing operations should be: • A. A single unit with adequate capacity for the amount of dust generated. • B. Located between the grinder and buffer. • Served by separate dust collection systems.

  25. Dust Collection, Ducts and Ductwork • Practice Quiz • 1. Baghouse collectors for aluminum: • A. Are both economical and efficient. • B. Are considered better than cyclone collectors. • C. Have been associated with fires when used for aluminum. • 2. If aluminum impacts iron oxide: • The material produced is inert. • A dangerous thermite reaction can be initiated. • It makes a valuable by-product that is a commodity.

  26. Dust Collection, Ducts and Ductwork • Practice Quiz • 3. If a baghouse type collector is used: • A. A pulse-type is better than a mechanical shaker. • B. The collector should be located outdoors at least 50 feet away from buildings and other equipment. • C. Barriers and warning signs should be posted around the equipment. • D. All of the above • 4. Dust collection for grinding and buffing operations should be: • A. A single unit with adequate capacity for the amount of dust generated. • B. Located between the grinder and buffer. • Served by separate dust collection systems.

  27. It’s a good thing! Explosion vents for dust collectors • Explosion vents are usually built into the system • If not a retrofit is a good idea! • Locate Explosion Vents away from personnel! Explosion Venting located away from personnel

  28. Ductwork • Ducts short and straight to maximize free airflow • No dead ends or unused caps in ducts that could trap accumulations of dust • Ducts grounded & bonded to dissipate static electricity

  29. Particles are suspended Air velocity at least 4500 ft/min Entrainment! is what you need! Air velocity less than 3500 ft/min Bad! Build-up of dust particles

  30. Duct Construction Smells like something’s burning! • Ducts made of conductive material • Lap joints face airflow direction • No unused or capped outlets • Duct seams away from personnel!

  31. Duct Construction Prevents buildup of static charges! • No add-ons without engineering redesign of system and the impact the add-ons will have • Collectors and machines that generate combustible dust properly bonded & grounded Copper wire is securely fastened to the equipment and then grounded to earth, for example by attaching it to a metallic water pipe or other object connected with earth.

  32. Dust Collection & Ductwork • Practice Quiz • 1. Explosion vents: • A. Should be built into collectors for combustible aluminum dust. • B. Located away from personnel. • C. Not necessary under normal circumstances. • D. Both A & B. • 2. Ducts for dust collectors should have: • A. Dead end sections to help collect dust at the point of generation. • B. Unused caps to maintain duct velocity pressure. • C. No dead ends or unused caps.

  33. Dust Collection & Ductwork • Practice Quiz • 3. Dust collectors and machines: • A. Isolated from ground to prevent conducting electricity. • B. Properly grounded and bonded. • C. Designed and installed to dissipate static electricity. • D. Both B & C.

  34. Dust Collection & Ductwork • Practice Quiz • 1. Explosion vents: • A. Should be built into collectors for combustible aluminum dust. • B. Located away from personnel. • C. Not necessary under normal circumstances. • D. Both A & B. • 2. Ducts for dust collectors should have: • A. Dead end sections to help collect dust at the point of generation. • B. Unused caps to maintain duct velocity pressure. • C. No dead ends or unused caps.

  35. Dust Collection & Ductwork • Practice Quiz • 3. Dust collectors and machines: • A. Isolated from ground to prevent conducting electricity. • B. Properly grounded and bonded. • C. Designed and installed to dissipate static electricity. • D. Both B & C.

  36. Wet-Type Dust Collector • Exhaust to the outside of building • Exhaust duct as short & straight as possible • Ducts designed to withstand same explosion pressure as wet-type collector

  37. Wet-Type Dust Collector • Aluminum and water can produce hydrogen gas • Extremely flammable and easy to ignite • Don’t trap in unventilated areas of the building or equipment!

  38. Wet-Type Dust Collector • Return air tested and approved for recirculation • Exhaust vent inspected and cleaned frequently • Particles can collect on the walls of the exhaust duct and can be highly combustible I’m forming a highly combustible cake! Particles Collecting on exhaust duct

  39. Mist eliminator packs Non-sparking work surface Expanded metal aluminum mesh Water level Liquid level control w/ interlock sludge Liquid Precipitator Collector For Portable Dust Collector Wet-Type Dust Collector

  40. H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 Sludge & Collector Sump Venting • Wetted dust is highly flammable! • Sludge removed regularly • Collector sump vented!

  41. Mist Eliminator Packs Liquid level control w/ interlock To dust producing equipment Power to dust- producing eq. motor cutoff by low liquid level or low airflow Inspection/ Cleanout door Water level Overflow/ Drain Piping Sludge in tank Power Supply • Interlocked with the exhaust blower and the liquid-level controller • Time delay on dust producing equipment prevents motor starting until collector is operating My power supply is dependent on my proper functioning

  42. Sludge Removal • Sludge removed daily • Covered vented containers for transport • Containers filled to < 50 lbs

  43. Sludge Removal • NO SMOKING ALLOWED! • Mix with inert at 5:1 ratio & dispose of properly • Hot Work requires a Permit use one!

  44. Wet-Type Collectors • Practice Quiz • 1. Wet aluminum dust: • A. Is inert • B. Is easily removed with steel shovels • C. Can generate explosive hydrogen gas • 2. Exhaust air: • A. Should be vented to the outside • B. Should be tested if it is to be returned to the building. • B. Both A & B.

  45. Wet-Type Collectors • Practice Quiz • 3. Sludge from wet-type dust collectors for combustible aluminum dust should be: • A. Emptied daily. • B. In containers of less than 50 lbs. • C. Covered in vented containers for disposal transport. • D. All of the above.

  46. Wet-Type Collectors • Practice Quiz • 1. Wet aluminum dust: • A. Is inert • B. Is easily removed with steel shovels • C. Can generate explosive hydrogen gas • 2. Exhaust air: • A. Should be vented to the outside • B. Should be tested if it is to be returned to the building. • B. Both A & B

  47. Wet-Type Collectors • Practice Quiz • 3. Sludge from wet-type dust collectors for combustible aluminum dust should be: • A. Emptied daily. • B. In containers of less than 50 lbs. • C. Covered in vented containers for disposal transport. • D. All of the above.

  48. Dry-Type Dust Collectors • Use only where permitted • Collection containers covered to prevent airborne fugitive dust • Collector designed and maintained to ensure internal cleanliness! • No accumulation of material allowed except discharge container

  49. Dry-Type Dust Collectors • Dust-collecting filter medium conductive with enmeshed noninsulated wire woven or fastened to it • Not fool proof: • No force passes charge across nonconductive areas of the fabric • Broken wires can hold or build-up a charge!

  50. Dry-Type Dust Collectors • Hoods regularly cleaned • Dry collectors for aluminum dust provided with deflagration vents • Air from dry dust collectors is not to be recycled back into the building Courtesy of Fenwal Safety Systems