The Importance of Dust Testing to Effectively Control Airborne Particles

Controlling dust produced during dry processing and bulk materials handling is imperative for several reasons: It helps maintain indoor air quality, safeguards the health of employees, preserves product integrity, protects equipment, and ensures compliance with regulations. However, there’s no one-size-fits-all solution for dust safety. To effectively manage process dust, you need to understand the specific dusts you are generating. Knowing the unique characteristics of these dusts is essential for implementing appropriate dust collection and safety measures.

Dust testing is important whether you are installing a new dust collection system, initiating a new manufacturing activity, or have been handling the same type of dust for years. Adjustments to machinery, processes, environment, or products can have a considerable influence on dust properties.

If your dust collector is exerting excessive effort to clean the air, consuming an inordinate amount of energy or failing to perform effectively, it might not be appropriately designed for the specific types of dust it is handling.

Having your process dusts analyzed by experts enables you to get a dust collection system that is designed specifically for your operation. Knowing your dust ensures effective capture, conveyance, and filtration of airborne particles. With the data from dust characteristics testing and a dust hazard analysis, your dust collector provider can ascertain the appropriate filter housing size, ductwork system configuration, and hopper discharge design specifically for the type of dust being handled. A well-designed setup helps the dust collection system to operate more efficiently, resulting in reduced energy use, less consumption of compressed air and improved dust collection.

Specialized Labs for Comprehensive Dust Analysis

There are two categories of specialized dust testing facilities:

1. Bench Testing Laboratories: These labs are outfitted to conduct a comprehensive series of bench tests on your dust samples. The objective is to decode the unique properties of the dust generated at your site. Specialists assess the dust’s composition, granularity, and potential health hazards. This crucial information guides the development of the optimal dust collection system and filters customized for your needs.

2. Combustible Dust Testing Facilities: Distinct from characteristic analysis, combustible dust testing adheres to the stringent standards set by the National Fire Protection Association (NFPA). As a manufacturer, it is your responsibility to prove that the dust is not combustible. Therefore, it is imperative to engage a certified third-party lab for process dust testing and maintain documentation as evidence of non-combustibility. If your dust is identified as combustible, consult with a specialist to integrate explosion protection into your dust collection system.

Dust Characteristics Testing

To obtain a thorough understanding of the airborne particles generated at your facility, you will need to furnish the test lab with comprehensive details about your dust-producing operations. The lab will evaluate crucial characteristics of the dust, such as particle size and shape, influence of gravity, moisture content, and abrasiveness.

Prior to gathering a dust specimen, consult the material’s safety data sheet to mitigate any risks linked to the dust. If you have a dust collection system in place, a used filter provides an excellent sample. In the absence of a dust collection system, gather a representative sample of the type of dust that the system would capture. Avoid using dust from the floor, as it may be tainted with other substances. Similarly, dust from a hopper is unsuitable, as it won’t accurately reflect the dust’s true particle size distribution the filters would collect. For advice on correct sampling methods, reach out to the testing laboratory.

Here are important dust characteristics to analyze:

Particle Size

Particle size plays a crucial role in determining the filtration efficiency necessary to meet emissions standards, air quality goals, dust hazard control, and OSHA compliance. Dust particle testing provides information on size, down to the submicron range. Using a dual-laser particle analyzer, lab personnel can precisely identify the number of specifically sized particles and the volume or mass distribution of the dust.

Understanding both the particle count and volume is essential because many dust types consist of a mixture of particles, ranging from submicron sizes to significantly larger ones. Testing remains the sole method for accurately determining dust particle size, which, in turn, enables the selection of appropriate filter media to maintain optimal indoor air quality.

Particulate matter (PM) size comparison (Camfil Air Pollution Control)

Moisture

Detection of moisture in dust is crucial for selecting the appropriate filter media. A hygrometer is an instrument that reveals moisture presence within the dust. This information aids in determining equipment design elements, such as hopper angle and conveying velocities. Additionally, identifying moisture issues is essential because sticky dusts can lead to filter cartridges clogging when using the wrong type of media.

Abrasion

Abrasion testing is crucial for engineering the most effective dust-handling components based on the coarseness of the dust. Test results inform the configuration of inlets, baffles, discharges, and ductwork. For example, highly abrasive materials such as cast-iron grindings necessitate a collector designed to operate with a low inlet velocity. A velocity that’s too elevated will result in the dust eroding the filters, leading to early deterioration.

Shape, Structure, & Oil

Identifying the shape and structure of particles is necessary if you need to use specialized filters in your dust collection system. For instance, analysis can reveal whether the dust has a crystalline structure with jagged edges, as seen in materials like fumed silica—a toxic dust that necessitates a high-efficiency filter chemically treated with an additional layer of nanofibers or PTFE. Furthermore, the presence of oil in dust can cause serious damage to a dry dust collector if filter media with an oil-resistant coating is not used.

Analysts use an optical microscope to observe the shape of dust particles, while a scanning electron microscope (SEM) provides structural analysis and detailed media images. By combining this data with particle size information, engineers can determine the most suitable dust collector and filters for various types of dust.

Combustible Dust Testing

To determine whether your dust is combustible or explosive, presume it is unless testing confirms an explosive index (Kst) value of zero. For commonplace substances like flour or sugar, where particle size and moisture levels match previous samples, documented data from previous tests will suffice. However, you should have a certified testing agency evaluate new or unique dust types and provide you with a record of the results.

If tests prove the dust is combustible, the next step is to measure the Kst and maximum pressure increase (Pmax). Any dust with a Kst value greater than zero is deemed explosive, which applies to most dust types. Notably, finer particles pose a heightened risk.

Conducting a dust hazard analysis helps to identify potential combustion and explosion risks and to determine the necessary fire and explosion protection measures. This analysis can be performed in house or by external experts, but in either case, the authority having jurisdiction will need to validate the outcomes. To design appropriate explosion venting or suppression systems, your dust collection equipment provider will require the Kst and Pmax figures.

Conclusion

Controlling airborne dust is essential for preserving indoor air quality and protecting against health issues caused by dust exposure. By testing your process dust, you obtain a clear understanding of its unique properties. These accurate insights allow you to avoid uncertainty and make savvy choices when purchasing dust collection equipment, ensuring the air in your facility remains safe to breathe.

Jason Clugston is an OEM account specialist for Camfil Air Pollution Control, manufacturer of dust and fume collection equipment for challenging industrial applications. For more information call 800-479-6801, email [email protected], or visit camfilapc.com.