Asking The Right Questions (continued)

2. Will it fix the problem?

Though compliance is a major issue, it is not the only issue. What else is the dust collector expected to do? Perhaps it must control API emissions to the established OEL, accommodate changes or expansions in the facility, or solve a performance problem experienced with an older dust collection system.

A good way to pinpoint objectives is by using a site survey form available from most equipment suppliers. This form typically calls for information on the process and the material to be collected, operating hours and conditions, electrical requirements, airflow and pressure ratings, and other specifics of the application. The survey will also call for detailed information on the physical properties of the dust (i.e., Kst and MIE, as required by NFPA 68).

New filter designs with open,"breathable" pleats allow better media utilization for more efficient performance.

Even if the dust is a commonly utilized excipient, something in the process may cause it to behave differently. Therefore, dust should always be tested, preferably using a sample collected from used filters. What are the median size and particle distribution of the dust? Is it in the shape of long fibers, needles, uniform spheres or jagged crystals? Is it combustible? Is it sticky or hygroscopic? These are just some of the characteristics that can and should be determined through a series of bench tests available from independent laboratories and many equipment suppliers.

A site survey coupled with lab testing is te best approach for determining the dust collector's required filtration efficiency and pressure drop across the filter media and, from this, what type of collector design and media will be most effective for the application.