Evaluation of Leakage from a Metal Machining Center Using Tracer Gas Methods: A Case Study

Details

• Personal Author:
  D'Arcy JB ; Earnest, Gary S. ; Heitbrink, William A. ; Mead, Kenneth R. ; Mickelsen, Ronald L.
• Description:
  To evaluate the efficacy of engineering controls in reducing worker exposure to metalworking fluids, an evaluation of an enclosure for a machining center during face milling was performed. The enclosure was built around a vertical metal machining center with an attached ventilation system consisting of a 25-cm diameter duct, a fan, and an air-cleaning filter. The evaluation method included using sulfur hexafluoride (SF6) tracer gas to determine the ventilation system's flow rate and capture efficiency, a respirable aerosol monitor (RAM) to identify aerosol leak locations around the enclosure, and smoke tubes and a velometer to evaluate air movement around the outside of the enclosure. Results of the tracer gas evaluation indicated that the control system was approximately 98% efficient at capturing tracer gas released near the spindle of the machining center. This result was not significantly different from 100% efficiency (p = 0.2). The measured SF6 concentration when released directly into the duct had a relative standard deviation of 2.2%; whereas, when releasing SF6 at the spindle, the concentration had a significantly higher relative standard deviation of 7.8% (p = 0.016). This increased variability could be due to a cyclic leakage at a small gap between the upper and lower portion of the enclosure or due to cyclic stagnation. Leakage also was observed with smoke tubes, a velometer, and an aerosol photometer. The tool and fluid motion combined to induce a periodic airflow in and out of the enclosure. These results suggest that tracer gas methods could be used to evaluate enclosure efficiency. However, smoke tubes and aerosol instrumentation such as optical particle counters or aerosol photometers also need to be used to locate leakage from enclosures. [Description provided by NIOSH]
• Subjects:
  Aerosols Air Movements Air Pollutants, Occupational Case Reports Engineering Metals Metal Workers Occupational Exposure Occupational Health Particulate Matter Safety Ventilation

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• Keywords:
  Air-filters Air-flow Case-studies Engineering-controls Metalworking Metalworking-fluids Metalworking-industry Occupational-exposure Oil-mists Ventilation-systems Workers

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• ISSN:
  0002-8894
• Document Type:
  Text
• Genre:
  Journal Article
• Place as Subject:
  Michigan ; Ohio ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DPSE - Division of Physical Sciences and Engineering
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  60
• Issue:
  6
• NIOSHTIC Number:
  nn:20025258
• Citation:
  Am Ind Hyg Assoc J 1999 Nov/Dec; 60(6):785-788
• Contact Point Address:
  U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 4676 Columbia Parkway--R5, Cincinnati, OH 45226
• 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-512:73bc5c1d95726ebd98c3170392cb27141285a5be6cb300aaa7c0f5a5696093dde00b29ce0e6d8e6b9325d9484bdf9409c7438b4f6d44d2863e83bcb04eb93cb0
• Download URL:
  https://stacks.cdc.gov/view/cdc/196712/cdc_196712_DS1.pdf
• File Type:
  [PDF - 296.53 KB ]