Understanding Your Dust (continued)

1 - Do a site survey to gather information about your application

To gather data about your application, do a site survey. This information should accompany the dust sample (as discussed in step 2) you send for testing because the data provides a context for the tests and ensures the results will be meaningful.

Typically, you'll supply the site survey information on a data sheet, as shown in Figure 1. In addition to the information listed on the form, supply other facts to make the analysis more complete. This additional data should answer questions like these:

• Does your plant currently have dust collectors that filter this dust? If so, how well do they perform?
• Where do you intend to locate the new collector? Is headroom limited in this spot?
• How does the dust behave: Is it sticky some of the time? Does it cling to vertical surfaces or solidify after it sits in the open air?
• What service life do you want from the filter media?
• How do you want to handle the dust after it's collected? For instance, will you collect it in drums or convey it to a large silo?

Figure 1 - Typical site survey data sheet

2 - Obtain a dust sample

Even if your dust seems to be a common type, such as grain or wood dust, something in your process can cause the dust to behave differently than the norm. This is why all dusts must be sampled for testing.

Before collecting your sample, review the dust's Material Safety Data Sheet (MSDS) so you can protect yourself from any hazards associated with the dust.

Collect your sample properly

For the lab analysis, you'll need about a 1-pint sample; if you require full-scale tests as well, you'll need a much larger sample (as discussed in step 3). Be sure the sample represents the dust, with the same particle size and moisture content as the dust to be captured by the collector. For instance, a sample taken from dust swept from your plant floor isn't representative of dust that will be captured from the air by the dust collector; the floor sweepings will contain impurities and larger particles with enough mass to have fallen to the floor. If the dust comes from an existing collector's hopper, the sample won't represent the dust's true particle size distribution because it doesn't contain the particles collected on the filters.

If you have an existing dust collector, the best sample to send to the lab is a dirty filter bag or cartridge. If you don't have an existing collector, consult the lab for information about collecting a representative sample. Regardless of how you collect the sample, transport it to the lab in an airtight container to preserve the sample's moisture content.

Send a copy of the MSDS with the sample

The MSDS is important to the application engineer because it provides information about your dust's chemical reactants and OSHA-mandated personal exposure limits.