Understanding Your Dust

Six steps to better dust collection

By Lee Morgan and Mike Walters, Camfil Farr APC

Almost every piece of process equipment in a powder and bulk solids handling plant depends on a dust collector to safely control dust or to reclaim valuable product. So why do most users treat dust collector selection as a mysterious art rather than scientific process, without considering exactly what kind of dust they need to collect and what performance they need? This article helps take the mystery out of the process by explaining how to analyze your application needs and dust characteristics as part of choosing a dust collector. Sections detail the six steps in this process.

Are you happy with your dust collector's performance? If not, you have company: Most users are dissatisfied with how well their collectors operate.

This problem typically stems from neglecting or misunderstanding details about the unit's performance when the collector is selected. After all, in most cases a dust collector doesn't contribute to the plant's bottom line, so the user just doesn't devote the same attention to choosing a collector as to choosing a process machine.

But choosing your dust collector without doing enough research is dangerous. A poorly performing or failing dust collector can shut down your entire plant faster than any other piece of equipment. Without a dust collector, dust from process or handling machines can quickly create unsafe working conditions and the dust can't be reclaimed as product.

The performance you should expect

You can expect the following performance from a properly selected dust collector:

• The dust collector's emissions meet your requirements.
• The dust collector's airflow is consistent to capture dust at its source.
• The filter requires little maintenance at predictable intervals, and the filter media lasts reasonably long.
• The dust collector operates trouble-free with minimal maintenance.
• The captured dust is easy to handle and discard or reclaim.

Selection factors to consider

One problem that often contributes to a poor collector choice is the dust collector manufacturer's concentration on air (or gas) flow to the exclusion of other selection factors. But to ensure the dust collector performs as it should, you need to evaluate several critical factors, including:

• What dust quantity must the unit collect-will it need to capture 2 lb/h or 2 t/h?
• What type of dust do you have? For instance, it's not enough to categorize the dust as silica. Is it sand or fume silica?
• What is the dust's particle size distribution?
• What shape are the dust particles: long skinny fibers, uniform spheres, or jagged crystals?
• Is the dust flammable?
• Is the dust hygroscopic?
• Is the clean air returned to the plant or exhausted to the atmosphere?
• What kind of requirements such as OSHA, EPA, or plant insurance must the dust collector meet?

By taking a close look at your dust, you'll have the information you need to choose the right dust collector. Have your dust analyzed with quantitative, scientific tests. Following these six steps will provide the data you need and help you apply the information to choosing a collector.

1. Do a site survey to gather information about your application.
2. Obtain a dust sample.
3. Send the sample to a lab for analysis.
4. Have full-scale tests run on the sample, if required.
5. Select the appropriate filter media and dust collector.
6. After installation, verify that the dust collector performs as required.

Before exploring these steps in detail, a word about the labs that can provide dust analysis: A handful of independent labs have testing experience specific to dust collection. These labs charge from about $300 to $1,000 for lab tests, depending on the scope of the tests you require, and up to about $10,000 for full-scale tests. Some dust collector manufacturers also offer test services; most offer lab tests and several major manufacturers also provide full-scale tests. A manufacturer's testing services often are free or involve only a nominal charge. An application engineer in the independent lab or at the manufacturer's facility will test your dust and work with you to select the right collector for your needs.