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Respirable Dust Cyclones |
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ApplicationsFor more than 25 years the respirable dust cyclone has been an important adjunct to personal sampling in all of the dusty trades. In many instances this type of sampling is mandated by federal regulations on a routine basis, for each employee exposed. In all dusty applications, respirable dust samplers should be utilized to guard against excessive exposure, minimizing both worker risk and potential litigation/fines. HistoricalIn America we have typically utilized a non-conducting plastic cyclone and 37mm disposable cassettes while conforming (approximately) to the ACGIH Respirable Dust Curve1. (D50=3.5µm). The flow rate was 1.7 lpm. In the U.K. and Europe a metal cyclone was used (Simpends 70)2, which conformed to the Johannesberg Conference Curve3 (D50=5µm). The flow rate was 1.9 lpm. This U.K.-developed instrument conformed to the respirable curve very well and was not affected by non-conducting dust and static charge effects as was the American unit. Recently, the U.S., U.K., and Europe, have agreed on the Soderholm respirable dust curve, with a 50% cut at 4 micrometers. (D50=4µm).4,5 DesignBGI has combined the best features of the preceding instruments to develop the BGI4L Respirable Dust Cyclone. The unit is of all metal construction. The cyclone body is fabricated from nickel plated aluminum. The dust cup (grit pot) is fabricated from aluminum and is threaded to the cyclone body with an "O" ring seal. Filtration is accomplished with a 37mm disposable cassette, which is pressed on over the "O" ring seal. Cassette security is maintained by the spring steel lapel clip which prevents accidental dislodgment of the cassette and provides a secure, tangle free mounting for the suction hose. This instrument has a recommended flow rate of 2.2 Lpm to match the new 4 micrometer, 50% cut, respirable curve5 and is not sensitive to charge effects6,7. The new high flow rate confers an immediate advantage in sensitivity since existing American units sample 23% less air per minute. In addition to the BGI4L metal cyclone, we also offer a similar unit, wherein the cyclone body is molded from electrically conductive acetal plastic. The grit pot, which snaps onto the body, is a soft elastomer. This plastic body is fabricated to the same dimensions and tolerances as our stainless steel unit and has been the subject of a careful study by the (U.K.) Health and Safety Executive7 . We are also pleased to offer the U.K./European version of the respirable dust cyclone, which is identical to the U.S. version in performance, internal dimensions and test results8. However, this U.K. manufactured instrument offers the option of a reusable cassette. This feature is requested by investigators requiring a minimal cassette opening in the work area or an ultralight compact instrument. Additional ApplicationIt has been pointed out by A. D. Maynard in a seminal investigation of Thoracic Samplers that the cyclones described herein will collect a Thoracic sample (PM10) at a flow rate of 0.8 lpm.
Copyright © 2006 by BGI / Modified:
Wednesday, July 29, 2009
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