osha respirable crystalline silica standard update... castingconnection.afsinc.org @amerfoundrysoc...
Post on 22-Jul-2020
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www.afsinc.org │ CastingConnection.afsinc.org │ @AmerFoundrySoc
OSHA Respirable Crystalline Silica Standard Update
Source and Control:
3A Identify Sources3B Investigate and Evaluate Control Options and Develop Engineering Plans3C Implement the Control Plan
www.afsinc.org │ CastingConnection.afsinc.org │ @AmerFoundrySoc
Exposure Control Error #1“Out of sight out of mind” • Visible dust is an imperfect surrogate for
respirable dust.• For reference
• Visible >80 microns• Human hair (>50)• Fine sand grain (~100)
Respirable particles(PM4) are not visible
PM4= sample device collects 50% of 4 micron diameter particles
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Out of sight, out of mind…
• Just because you don’t see dust doesn’t mean it’s not there!
• Respirable particles are not visible• “Floaters” are a clue!
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• Finding dust sources takes time• Process knowledge• Look• Instrumentation• Engineering
3A- Identify Sources
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Process Knowledge• Common Sources of Respirable Dust
• Shakeout (vibration and turbulence)• Knockoff/sorting• Vibrating conveyors• Conveyor transitions• Grinding• Leaks in sand systems / abrasive blast systems• Leaks in dust collection systems• Compressed air• Sand spillage• Crane bays handling sprue returns• Foot and vehicle traffic• Refractory repair• Floor sweepers• Housekeeping activities
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Process Knowledge
Shakeout
Grinding
Refractory Repair
Knock-off/sorting
Based on industry experience, these are all known sources of respirable silica
www.afsinc.org │ CastingConnection.afsinc.org │ @AmerFoundrySoc
Look
• Where is visible dust generated?• A fraction may be respirable• Strong light can help to see floaters
• Where is fine dust accumulating?• Do existing systems need maintenance?
• Curtains, duct leaks, plugged ducts, ventilation balance
• Where are housekeeping activities stirring dust?
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Look For Potential Sources
Basements
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Look For Potential Sources
Sand spillage and build-up
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Look For Potential Sources
Leaks in ventilation systems
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Look For Potential Sources
Leaks in ventilation systems
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Look For Potential Sources
Leaks in ventilation systemsMaintain your existing systems
Torn/missing curtainsDamaged enclosures
Fans disrupting airflow
www.afsinc.org │ CastingConnection.afsinc.org │ @AmerFoundrySoc
Instrumentation
• Real time respirable silica measurement is NOT currently available
• Real time respirable particulate monitors are available that measure total respirable particulate, but only part of that may be silica
• Respirable dust monitoring can, however, help provide clues as to sources
• More respirable dust may mean more silica
www.afsinc.org │ CastingConnection.afsinc.org │ @AmerFoundrySoc
Engineering
• Engineering firms are beginning to offer analysis and control help
• Dust mapping• Maps produced from real time measurements of respirable
particulate matter (RPM) with concurrent background samples for respirable silica to correlate RPM concentrations with silica content of the dust.
• Root cause analysis involving personal real time sampling to identify task-related components of the silica exposure.
• This RPM sampling is correlated with the silica content estimated using the foundry’s TWA compliance sampling results.
• Ventilation analysis• Ventilation upgrades
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