Safety for Aluminum Processing and Finishing Operations Involving Combustible Dust in the Die Casting Industry Unit 3 NADCA North American Die Casting Association

Enabling Objectives Explain procedures for housekeeping, dust collection, fire prevention, prevention of accumulation of fugitive dusts, proper storage, and safety procedures for aluminum and magnesium. 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

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 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 Dust Producing Operations

Ductwork Duct runs as short & straight as possible!

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

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 contain explosible dust. Keep outside the marked area while equipment is operating. CAUTION CAUTI ON: This dust collec tor can c

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. ! Warning: Aluminum Metal Only – Fire or Explosion Can Result with Other Metals. Hi Aluminum! I’m another type of metal! Kaboom!

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. 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. 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. 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. Dust Producing Operations

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 Individual Machines with Portable Dust Collection Filtering Media Portable Media-Type Dust Collector Material Discharge

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

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

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! This dust collector can contain explosive dust, keep outside the marked area while equipment is running 20'

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… Can lead to I’m a better choice

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.

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

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 Dust Collection, Ducts and Ductwork Mechanical Shaker Baghouse

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! Dust Collection, Ducts and Ductwork At least I’m outside!

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

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. 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. 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. 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. Dust Collection, Ducts and Ductwork

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

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

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

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

Duct Construction 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. Prevents buildup of static charges!

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.

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.

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.

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.

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

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!

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 Particles Collecting on exhaust duct I’m forming a highly combustible cake!

Wet-Type Dust Collector

Sludge & Collector Sump Venting Wetted dust is highly flammable! Sludge removed regularly Collector sump vented! H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2 H2H2

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 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 Liquid level control w/ interlock Sludge in tank Mist Eliminator Packs My power supply is dependent on my proper functioning

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

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

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.

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.

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

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.

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

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!

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

Dry-Type Dust Collectors Selection of type and location of weak sections or vents designed to minimize injury to personnel and minimize damage to nearby equipment & structures Explosion venting is a very important consideration! Al: high explosion pressure Courtesy of Fenwal Safety Systems

Dry Type Dust Collectors Practice Quiz 1. Air from dry-type dust collectors: –A. Should be vented back into the plant to balance negative pressure. –B. Should be used to provide warmth around grinding operations. –Should not be recycled back into the building. 2. Grounding cartridge filters with wires built into the cartridge : –A. Is a fool proof way of ensuring static charges will be controlled. –B. Does not ensure that static charges will move across the filter. –C. Never done.

Dry Type Dust Collectors Practice Quiz 3. Dry type dust collectors should: –A. Have their hoods regularly cleaned. –B. Be fitted with deflagration vents. –C. Allow for no accumulation of dust except for in discharge containers. –D. All of the above.

Dry Type Dust Collectors Practice Quiz 1. Air from dry-type dust collectors: –A. Should be vented back into the plant to balance negative pressure. –B. Should be used to provide warmth around grinding operations. –Should not be recycled back into the building. 2. Grounding cartridge filters with wires built into the cartridge : –A. Is a fool proof way of ensuring static charges will be controlled. –B. Does not ensure that static charges will move across the filter. –C. Never done.

Dry Type Dust Collectors Practice Quiz 3. Dry type dust collectors should: –A. Have their hoods regularly cleaned. –B. Be fitted with deflagration vents. –C. Allow for no accumulation of dust except for in discharge containers. –D. All of the above.

Additional Considerations Cutting tools sharp & sufficient coolant flow to prevent ignition of turnings Cutting & grinding eq. grounded Chips, swarf, turnings, etc. collected in closed-top containers Removed daily to safe storage or disposal

Additional Considerations Coolant non-flammable & filtered Collected solids max accumulation 5 gallons

Additional Considerations All electrical wiring conforms to NEC Collection systems bonded & grounded Metallic jumpers installed when continuous contact is interrupted NEC NFPA 70

Housekeeping No accumulation of fugitive combustible dust Ignition of a dust cloud or layer will likely result in an explosion Often followed by a more violent explosion Good housekeeping is extremely important!

Housekeeping Regular cleanup using conductive non-sparking tools Soft brooms with natural bristles Bulk of cleanup done with scoops, shovels & brooms Vacuum only small residual amounts Non-sparking

Housekeeping Compressed air blow down is generally not to be permitted Only allowed in areas otherwise impossible to clean Only allowed under carefully controlled conditions All potential ignition sources eliminated All equipment shut down

Vacuum Cleaners Vacuums only for too small, dispersed or inaccessible dust Bonded & grounded Listed or approved for use with combustible dust Periodic continuity tests performed Dusts from fixed vacuums collected to outside of building

Fixed Vacuum Systems If possible locate vacuum collection outside facility 50 feet from building If closer enclose in open-top steel shield Fit suction lines with explosion vents and anti-flash back valves 50 ft.

Water Cleanup Considerations Wet aluminum fines can evolve hydrogen gas! Keep hydrogen at or below 1% concentration in air using ventilation (H 2 LEL = 4%) Inform management of risks Competent person has determined wet cleaning is safest method available Applies to Aluminum Dross: Wet or Hot

Cleaning Frequency Avoid excessive accumulation of dust on any portion of building that is not cleaned during regular daily operations Regular cleaning of buildings and machinery as needed Machines idle and power off

Housekeeping Practice Quiz 1. Cleanup of aluminum dust should be done with: –A. Non-combustible conductive tools. –B. Brooms with soft natural bristles. –C. Mostly scoops, shovels and brooms. –D. All of the above. 2. Compressed air blown for aluminum dust: –A. Is a fast and safe way to clean up. –B. Is a common practice. –C. Should only be done under controlled procedures when no other method is feasible.

Housekeeping Practice Quiz 1. Cleanup of aluminum dust should be done with: –A. Non-combustible conductive tools. –B. Brooms with soft natural bristles. –C. Mostly scoops, shovels and brooms. –D. All of the above. 2. Compressed air blown for aluminum dust: –A. Is a fast and safe way to clean up. –B. Is a common practice. –C. Should only be done under controlled procedures when no other method is feasible.

Housekeeping Practice Quiz 3. Cleaning dust from the facility should: –A. Include additional cleaning on all parts of the building where dust can accumulate that is not cleaned during normal operations. –B. Be done as often as necessary. –C. Be done with machines idle with the power off. –D. All of the above.

Fire Prevention & Protection Large scale fires in aluminum dust are very difficult to extinguish DO NOT create a dust cloud in an attempt to fight an aluminum dust fire! Attempt to control as quickly as possible with minimum disruption to the pile

Fire Extinguishers Ample Class ‘D’ fire extinguishers should be available to fight incipient stage fires Available within 75 feet of metalworking areas. Required where dust is generated at least once every two weeks

Fire Extinguishers Install signs so other types of extinguishers are not used by mistake!

Extinguishing Agent Ring incipient fires with dry sand, or a Class D powder Properly ringed will form a metal oxide crust Apply with non sparking utensils Eliminate drafts, etc.

Extinguishing Agent Dry sodium chloride is very effective Check for caking Flux made of potassium and magnesium chloride and calcium fluoride Avoid Class B agents for dry powder aluminum fires, they will accelerate fires or cause an explosion!

Aluminum Slurry Fires Incipient stage fires involving a slurry (wetted) of aluminum powder can be fought using a Class B type extinguisher as long as the agent is not halogenated.

Sprinkler Systems No automatic sprinklers where dry aluminum powder is produced or handled Consider the hazards associated with aluminum and water in considering sprinkler systems

Fire Prevention and Protection Practice Quiz 1. Large aluminum fires: –A. Can be easily controlled with class ‘D’ fire extinguishers. –B. Are extremely difficult to extinguish. –C. Are best handled with class ‘B’ fire extinguishers. 2. Incipient stage aluminum fires: –A. Should be ringed with a Class ‘D’ extinguishing agent. –B. Should have extinguishing material applied with non- sparking scoops. –C. Should be protected from drafts. –D. All of the above.

Fire Prevention and Protection Practice Quiz 3. Class ‘D’ fire extinguishers –A. Are optional for aluminum dust processing areas. –B. Only needed by the dust collector. –C. Are required where combustible dust is produced at least once every two weeks.

Fire Prevention and Protection Practice Quiz 1. Large aluminum fires: –A. Can be easily controlled with class ‘D’ fire extinguishers. –B. Are extremely difficult to extinguish. –C. Are best handled with class ‘B’ fire extinguishers. 2. Incipient stage aluminum fires: –A. Should be ringed with a Class ‘D’ extinguishing agent. –B. Should have extinguishing material applied with non- sparking scoops. –C. Should be protected from drafts. –D. All of the above.

Fire Prevention and Protection Practice Quiz 3. Class ‘D’ fire extinguishers –A. Are optional for aluminum dust processing areas. –B. Only needed by the dust collector. –C. Are required where combustible dust is produced at least once every two weeks.

Employee Training & Emergency Evacuation Train employees in evacuation procedures Only trained employees are allowed to attempt to fight fires All others must evacuate!

Fire Safety Training Familiarize fire departments with the special potential hazards present Plant safety officer to provide instruction or direct the efforts of fire personnel Scrap metal fire “Will burn until it runs out of fuel”

Fire Safety Training Job hazard analysis should be conducted and safe work practices developed Employees trained on hazard recognition, elimination and control Don’t let this happen to you!

Fire Prevention & Control Set up test fires for fire department training Cover foreseeable scenarios and plan and prepare accordingly Train employees for the different types of fires possible

Fire Prevention & Control Train employees on the hazards present Focus on proper actions, decisions & procedures Train on location of controls, emergency supplies and fire extinguishers The stuff you NEED!

Fire Prevention & Control Train on proper method for fighting incipient stage aluminum dust fires Warn employees regarding the creation of a dust cloud or using liquids on combustible metal fires

Fire Prevention & Control Practice Quiz 1. If you have not been trained you should: –A. Only fight a major fire with coworkers who have experience. –B. Only attempt to extinguish incipient fires. –C. Not attempt to put out combustible dust fires. 2. Your training should focus on hazard: –A. Recognition. –B. Elimination. –C. Control. –D. All of the above.

Fire Prevention & Control Practice Quiz 1. If you have not been trained you should: –A. Only fight a major fire with coworkers who have experience. –B. Only attempt to extinguish incipient fires. –C. Not attempt to put out combustible dust fires. 2. Your training should focus on hazard: –A. Recognition. –B. Elimination. –C. Control. –D. All of the above.

Fire Prevention & Control Practice Quiz 3. It is important not to: –A. Put liquids on aluminum dust fires. –B. Use a high pressure extinguisher that will create a dust cloud. –C. Use the wrong type of fire extinguisher. –D. All of the above. –E. None of the above.

Fire Prevention & Control Practice Quiz 3. It is important not to: –A. Put liquids on aluminum dust fires. –B. Use a high pressure extinguisher that will create a dust cloud. –C. Use the wrong type of fire extinguisher. –D. All of the above. –E. None of the above.

Controlling Ignition Sources No smoking, cutting or welding in areas where wet sludge is present Any area where hot work takes place must be free of all accumulations of dust Comply with NFPA 51B Employees and visitors should not carry smoking materials in any areas where combustible dust is present!

Controlling Ignition Sources No propellant-actuated tools unless machinery is shutdown and cleaned Only non-sparking tools used on machines where combustible dust is present

Do not dress grinding wheels when the collection ventilation is on! Controlling Ignition Sources

Cleaning Tools Brooms & brushes natural fiber bristles No synthetic bristles Scoops and dustpans, etc. to conductive & non- sparking Do not return dry sweepings to processing

Proper PPE around Combustible Metal Dust Except for working around electricity, safety shoes should be worn with –Soles and heels attached by sewing –No nails or metal plates –Safety toes composite or covered –Shoes static dissipating Special static dissipating shoe

Proper PPE around Combustible Metal Dust Clothing clean, flame retardant and non-static generating Tight fitting, smooth fabrics from which dust can easily be should be used No cuffs or other folds where aluminum could collect No wool or silk

Proper PPE around Combustible Metal Dust Emergency procedures for clothing fires need to be implemented Use fire blankets where water is not allowed! Safety showers well away from dry aluminum powder Emergency procedures developed & implemented

Compressed air & inert gas Don’t mistake plant air for inert gas! Fittings for both shall not be interchangeable!

Safety Inspections Inspection program for operations that produce dust! Performed on a regular interval Skilled inspectors Reports filed Deficiencies corrected!

Controlling Ignition Sources Practice Quiz 1. No smoking, cutting or welding in areas: –A. Accumulations of dust are present. –B. Where wet aluminum is present. –C. Where powder actuated tools are approved. –D. All of the above. –E. A & B only. 2. Do not dress grinding wheels if: –A. If the ventilation system is turned off. –B. If the ventilation system is still turned on. –C. Neither A nor B.

Controlling Ignition Sources Practice Quiz 1. No smoking, cutting or welding in areas: –A. Accumulations of dust are present. –B. Where wet aluminum is present. –C. Where powder actuated tools are approved. –D. All of the above. –E. A & B only. 2. Do not dress grinding wheels if: –A. If the ventilation system is turned off. –B. If the ventilation system is still turned on. –C. Neither A nor B.

Emergency Procedures Practice Quiz 3. Emergency procedures: –A. For clothing fires needs to be implemented –B. Include fire blankets and their use where water is not permitted. –C. Are often overrated and usually not necessary –D. A & B only.

Emergency Procedures Practice Quiz 3. Emergency procedures: –A. For clothing fires needs to be implemented –B. Include fire blankets and their use where water is not permitted. –C. Are often overrated and usually not necessary –D. A & B only.

PPE Practice Quiz 4. Clothing should be: –A. Clean. –B. Non-static generating. –C. Flame Retardant. –D. All of the above. –E. B & C only.

PPE Practice Quiz 4. Clothing should be: –A. Clean. –B. Non-static generating. –C. Flame Retardant. –D. All of the above. –E. B & C only.

Summary In this section we discussed safe practices for machining and finishing aluminum. We identified the importance of safe means of dust collection We looked at housekeeping issues Fire prevention and fire protection were also discussed We also examined proper cleaning tools and the correct PPE to wear when working around aluminum where combustible dust is present