How to Select Pharmaceutical Dust Collectors in Accordance with the New ASHRAE Standard 199

Pharmaceutical processes that require dust collectors include tablet coating and tablet presses, fluid-bed drying, spray drying, blending, granulation, and general room ventilation. The pharmaceutical industry now has a way to accurately evaluate and compare dust collection systems that are self-cleaning (i.e., use compressed air to discharge the dust cake from the filter without taking the air filter off line). The new American National Standards Institute (ANSI)/American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 199-2016, “Method of Testing the Performance of Industrial Pulse Cleaned Dust Collectors,” (1) provides manufacturers with a methodology for comparing performance results based on true operating conditions.

The test process analyzes how dust collectors perform as a whole and how well the filters clean, providing real-world data to help processors make purchasing decisions. The methodology also provides comparative data on operational and energy costs and emissions, which will help guide pharmaceutical companies in making long-term decisions such as the necessity of secondary high-efficiency particulate air (HEPA) filtration, how to extend filter life, and achieving cost savings using different primary filters.

What Standard 199 measures

• Emissions: The tests used in Standard 199 measure initial emissions and emissions over the duration of testing, measured in milligrams per cubic meter of air.

• Pressure drop: The better a dust filter can release dust and the more it can hold will reduce cleaning frequency, which helps the system maintain a low pressure drop throughout service life of the filter.

• Compressed air usage: How much air the system consumes varies according to how self-cleaning the filter is. The better the cleaning characteristics, the less compressed air the system needs.

• Energy consumption: A filter with a low pressure drop, used in conjunction with a variable-frequency drive as prescribed in Standard 199, extends the service life of the filter and reduces electricity usage.

• Emission reading: The standard tests for how much dust penetrates the system at specific particle masses and reaches the outlet.

How Standard 199 testing works

The intent of the testing is to challenge the dust collector in a way that mimics real-life use. The standard requires tests to use calcium carbonate dust and specifies particle size, bulk density, and moisture content.

Stage 1: Dust is fed to the collector at a specified rate, without pulse cleaning, until a specified differential pressure is reached.

Stage 2: On-demand pulse cleaning, the most common cleaning method used in the pharmaceutical industry, begins while the airflow and dust feed continue. The cleaning interval is determined by high and low differential pressure set points provided by the manufacturer of the dust collector.

Stage 3: Continuous pulse cleaning of filters is performed at specified intervals, while maintaining the airflow and dust feed, for 24 hours or until the specified maximum differential pressure is reached.

Stage 4: Final dust loading with on-demand cleaning is tested by maintaining the airflow and dust feed. . Similarly to Stage 2, the frequency of cleaning is is triggered by high and low differential pressure setpoints and  will vary depending on the performance (i.e., pressure buildup) of the system.

Stage 5: The dust feed is maintained while suspending pulse cleaning to mimic how the dust collector would perform in an upset condition.

Stage 6: A process commonly known as “downtime cleaning” is replicated to simulate a post-upset scenario.

Benefits to pharmaceutical manufacturers

The information gleaned from Standard 199 testing will help pharmaceutical companies make more informed decisions when purchasing dust collection systems. They will be able to do accurate system comparisons. As more dust collector manufacturers and suppliers adopt the standard, the pharmaceutical industry will benefit from real-world data that demonstrates the need for things such as secondary HEPA filtration and specific filters that reduce cost and perform better in their specific application.

Because complying with Standard 199 is voluntary, however, it may take some time for individual dust collector and filter manufacturers to develop their own compliance plan. Potential involvement of the International Organization for Standardization (ISO), which is currently looking at adopting the standard, will impact equipment suppliers and customers worldwide.

Reference

1. ANSI/ASHRAE Standard 199-2016, “Method of Testing the Performance of Industrial Pulse Cleaned Dust Collectors” (2016).

About the author
David Steil is pharmaceutical market manager at Camfil Air Pollution Control.