OSHA Respirable Crystalline Silica Standard Update... CastingConnection.afsinc.org @AmerFoundrySoc OSHA Respirable Crystalline Silica Standard Update Source and Control: 3A Identify

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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

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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



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!



• Finding dust sources takes time• Process knowledge• Look• Instrumentation• Engineering

3A- Identify Sources



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



Process Knowledge

Shakeout

Grinding

Refractory Repair

Knock-off/sorting

Based on industry experience, these are all known sources of respirable silica



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?



Look For Potential Sources

Basements




Sand spillage and build-up




Leaks in ventilation systems




Leaks in ventilation systems




Leaks in ventilation systemsMaintain your existing systems

Torn/missing curtainsDamaged enclosures

Fans disrupting airflow



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



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


Documents

OSHA Respirable Crystalline Silica Standard Update... CastingConnection.afsinc.org @AmerFoundrySoc OSHA Respirable Crystalline Silica Standard Update Source and Control: 3A Identify