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Thursday, June 4, 2009

Dust Characteristics and Venting

Collecting and Testing Dust
Knowing dust characteristics facilitates ventilation equipment selection
By Lee Morgan, Farr APC

In 1998, both the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) issued more stringent requirements relating to the use of respirators in plants. Though respirators are critical to shielding workers from ambient dust and fumes, they are not the total answer.
The new OSHA standard (29 CFR 1910.134) states that employers are expected to use engineering controls to protect workers from air contaminants and not rely on respirators alone. While respirators do a good job of protecting workers' lungs, they do nothing to safeguard machinery and process areas from contamination that may result in costly equipment failure, constant rework, or general cleaning nuisances.
The equipment currently used in fabricating plants has reached a new level of sophistication. High-definition plasma cutters, laser cutters, and other computerized systems are more sensitive than machinery was 10 or 20 years ago. If dust is not collected properly from laser tables, welding stations, and similar areas, a million-dollar investment can be ruined in no time.
A well-designed and maintained dust and fume collection system is needed to prevent such problems and keep facilities in compliance with current air-quality requirements. In some cases, a good dust collection and ventilation system can eliminate the need for personal respirators and the challenge of getting employees to wear them.
Despite the importance of dust collection, most equipment decisions are based solely on guesswork, on previous experience, or on general recommendations from suppliers. Finding the right dust collection system is a complex task affected by dozens of variables. The situation does not lend itself to guessing games.
Figure 1 - A dual-laser particle analyzer is used in bench testing to perform particle size analysis.
Fabricators often are unaware that dust and fume collection can be approached scientifically using dust sample testing as the basis for sound and accurate equipment selection.
Testing dust is beneficial in many ways. By identifying the dust characteristics properly, you can determine the right type of collector (such as baghouse or cartridge system) and filtration media for your needs and determine the size equipment you need for optimal energy savings and operational efficiency. By using the right equipment, you can minimize maintenance problems and reduce emissions while extending filter life.

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