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Engineering Controls Database

Water Mist Control of Airborne Refractory Ceramic Fibers

The friction between the wheel of the disc sander/ belt of the belt sander and the ceramic workpiece results in the release of particles and fibers. Those particles are ejected at high speeds along a path tangential to the rotation of the wheel. The respirable particles, if not captured, can be carried into the breathing zone of the worker resulting in exposure to the refractory ceramic fibers and dust particles.
There are an estimated 30,000 workers who may be exposed to refractory ceramic fibers (RCFs) during the manufacture or use of products made from this material. A study of air samples collected in the manufacturing workplace indicated that some fiber dimensions were within the respirable size range. Results of inhalation tests with animals have shown that RCFs cause fibrosis and lung and pleural cancer when administered at very high doses (the “maximum tolerated dose” for 6 hours/ day, 5 days/week for 24 months). Worker exposure to RCFs can also increase eye irritation, stuffy nose, and dry cough. NIOSH concludes that RCFs are a potential occupational carcinogen.
The water mist consisted of a standard air atomization nozzle which utilizes compressed air to shear the water stream into a fine mist. A control knob on the spray nozzle allows for the adjustment of the water flow rate. The water flow rate was set to a minimum to prevent degradation of the vacuum formed RCF board. The water mister was placed 20 inches from the belt/disc with the mist directed at the point of operation. The mister was run at the test setting for a period of one hour and the water was collected in a graduated cylinder to estimate water flow rate and determined to be approximately 1.5 ml/min.

Water mister control set up for disc sanding

Water mister control set up for disc sanding
Portions of this entry came from the document: Criteria for a Recommended Standard: Occupational Exposure to Refractory Ceramic Fibers.
ceramic manufacturing
ceramic worker
refactory ceramic
refactory worker
A wet control method consisting of a simple compressed air atomization nozzle which directed a fine water mist at the RCF product during machining resulted in an average reduction of about 80% for disc sanding and about 50% for belt sanding relative to no control.