Mechanistic Understanding of Aerosol Emissions from a Brazing Operation

Details

• Personal Author:
  Biswas P ; Zimmer, Anthony T.
• Description:
  Welding operations produce gaseous and aerosol by-products that can have adverse health effects. A laboratory furnace study was conducted to aid understanding of the chemical and aerosol behavior of a widely used, self-fluxing brazing alloy (89% Cu, 6% Ag, 5% P) that is also used with a supplemental fluxing compound to prevent oxidation at the molten metal surface. The results indicate that the aerosols generated by the alloy are transient (produced over a short duration of time) and are associated with mass transfer of phosphorus species from the molten metal surface to the surrounding gas. In contrast, when the alloy was used in conjunction with the supplemental fluxing compound, a relatively nontransient, submicron-size aerosol was generated that was several orders of magnitude higher in concentration. Thermodynamic equilibrium analysis suggests that fluoride (a major constituent in the fluxing compound) played a significant role in reacting with the brazing alloy metals to form gas phase metal fluoride compounds that had high vapor pressures when compared with their elemental or oxide forms. As these metal-fluoride vapors cooled, submicron-size particles were formed mainly through nucleation and condensation growth processes. In addition, the equilibrium results revealed the potential formation of severe pulmonary irritants (HF and BF3) from heating the supplemental fluxing compound. These results demonstrated the importance of fluxing compounds in the formation of brazing fumes, and suggest that fluxing compounds could be selected that serve their metallurgical intention and suppress the formation of aerosols. [Description provided by NIOSH]
• Subjects:
  Aerosols Fluorides Laboratories Lung Diseases Metals Occupational Health Respiratory Tract Diseases Safety Welding
• Keywords:
  Author Keywords: Aerosols Brazing Chemical Equilibrium Analysis Fumes Gases Laboratory Testing Pulmonary System Disorders Respiratory System Disorders Welders Welding Industry
• ISSN:
  0002-8894
• Document Type:
  Text
• Genre:
  Journal Article
• Place as Subject:
  Ohio ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DART - Division of Applied Research and Technology
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  351-361
• Volume:
  61
• Issue:
  3
• NIOSHTIC Number:
  nn:20020873
• Citation:
  Am Ind Hyg Assoc J 2000 May/Jun; 61(3):351-361
• Contact Point Address:
  National Institute for Occupational Safety and Health, Division of Physical Sciences and Engineering, 4676 Columbia Parkway, R5, Cincinnati, Ohio 45226
• CAS Registry Number:
  Boron trifluoride (CAS RN 7637-07-2) ; Hydrofluoric acid (CAS RN 7664-39-3)
• Federal Fiscal Year:
  2000
• Peer Reviewed:
  True
• Source Full Name:
  American Industrial Hygiene Association Journal
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:ade714a665d82c1f39e230db48922aa5ab5403c024e83780710d288474e798938e989810f354cb5040fbc8850ce7082b0941b339f8d153f75c7d8ae5ca220851
• Download URL:
  https://stacks.cdc.gov/view/cdc/198530/cdc_198530_DS1.pdf
• File Type:
  [PDF - 468.50 KB ]