In 2016 ASHRAE issued Standard 199 that provides a method to test the performance of cartridge, bag and envelope industrial dust collectors that use pulse cleaning with compressed air to discharge dust from the filters. For the first time dust collector manufacturers and end users could compare performance based on true operating conditions and real-world performance data on emissions, pressure drop, compressed air usage, energy consumption and emission readings.
Why ASHRAE Developed Standard 199?
Prior to Standard 199 the only filtration test available for dust collection was ASHRAE 52.2. The testing methodology provides useful information about pressure drop and filter efficiency. However, it doesn’t account for filter life. In addition, Standard 52.2 is designed for static-loading filters, basically ones you throw away when they become loaded with dust. This isn’t how dust collectors operate. Their filters load with dust, get cleaned off and the cycle repeats. Filters that perform well on the 52.2 test, demonstrating efficiency and good pressure drop, won’t clean well because they aren’t designed to release the dust.
Standard 199 addresses these significant differences between static-loading filters and the dynamic-loading filters used in industrial dust collectors. It takes into account the unit from inlet to outlet and how well the filters clean. Standard 199 testing lets you know that the dust is releasing properly from the filters and indicates longevity of filter life.
The test requires several constants, so that it is performed consistently from lab to lab. Calcium carbonate is the specified test dust. It’s readily available, and because it is a manufactured dust, it has a known standard particle size that doesn’t change.
Another constant is that you have to feed the dust at one grain per cubic foot. So, you have to calculate this requirement at the air flow cubic feet per minute (cfm) that you are using. This is your inlet loading concentration.
When it comes time to pulse clean, the requirement is that you can only pulse 25% of your media at once. For example, if you are using four cartridges, you will pulse one at a time.
There are also parameters for temperature and humidity. The temperature must be within a certain range because it can affect how dust reacts. Humidity is more important because when it’s too low, the dust becomes electrostatically charged. If humidity is too high, the dust will clump.
Performing the Test
This test has several different phases to simulate how a dust collector works in real-world operation. The first thing experts do when they install a dust collector in the field is to load it up with dust. Therefore, the first stage in 199 testing is dust loading. Brand-new cartridges are installed and fed dust up to a specified high differential pressure (dp) set point in inches. The system is put into operation without pulse cleaning, and this first stage ends when the dp parameter is met. At this point we learn about the performance of the filters because some of them will take a longer time to reach the parameter.
The second stage is to perform on-demand pulse cleaning a certain time, usually four hours, while maintaining air flow and dust feeding.
Stage three moves from on-demand cleaning to 24 hours of continuous pulsing, while maintaining airflow and dust feeding. If the predetermined maximum dp is reached before 24 has transpired, the test ends. Filters are cleaned at specified time intervals, generally every 10-15 seconds.
This step involves final dust loading with on-demand cleaning, while still maintaining airflow and dust feed for an additional 24 hours. Cleaning is determined by set high and low dp points.
These four pulsing stages are designed to simulate various real-world pulsing applications, and we look for how well the filters operate under these dust load and pressure situations. For example, on-demand cleaning conserves compressed air while keeping the filter pressure drop in an effective zone, allowing adequate airflow from the dust-generating process. However, some applications are so difficult you have to pulse continuously to achieve adequate filter life.
These test take approximately 40 to 50 hours to complete, depending how the filters perform. If the dp starts trending upward in the first stages, the test is stopped because the filter isn’t going to make it through the rest of the phases.
After testing for dust loading, the system is tested for performance during an upset condition, such as power outage, equipment malfunction or loss of compressed air. In stage 5 dust feed is maintained, but pulse cleaning is stopped. This stage continues until dp reaches the predefined maximum, usually 10 inches of water gauge. At this point, dust feed is stopped.
This is the recovery stage and is used to simulate a post-upset condition, also known as downtime cleaning. Airflow is reduced to 25 percent of specified value, and continuous pulse cleaning performed for ten cycles. The system is then returned to the specified airflow and dp is calculated. Dust feed is restarted, and final dp measurements are taken.
A filter with a high dust-holding capacity and good dust release characteristics will require less frequent cleaning and maintain low pressure drop throughout the life of the filters. However, sometimes filters won’t recover completely. If the final dp climbs, the filter hasn’t performed well.
The Standard 199 test also examines compressed air usage. Compressors are inefficient and use a lot of energy. The goal is to clean the filters effectively using the minimal amount of compressed air for cost savings. This varies depending on the self-cleaning abilities of the filters. The better the cleaning characteristics, the less compressed air will be needed.
Downstream Emissions Testing
With the Standard 199 test you can also measure downstream emissions using a spectrometer. The results are an important consideration with regard to OSHA, EPA and state regulations. This reading includes particulate mass less than 1 μm (PM1), less than 2.5 μm (PM2.5) and less than 10 μm (PM10).
We don’t get approached by a customer to do 199. We use it for our internal R&D to develop a better product. Gives a good baseline for performance metrics for our filters and hardware.
Standard 199 for Research & Development
Here at Camfil APC, we use Standard 199 testing as part of our internal R&D because it covers all of the important performance metrics. We have our own Standard 199 test rig and use it to conduct research issues like how to optimize the pulse cleaning system and filter design, as well as which vendor’s hardware performs the best. With this detailed information we can acquire specific information to achieve the best possible performance.
Importance of Standard 199 Testing for End Users
Manufactures looking to purchase a dust collection system can use data derived from Standard 199 testing to evaluate how well the filters clean and how the collector performs as a whole. With specific information on operation performance, energy costs and particle emissions based on true dust collector operating conditions, they can make informed decisions in selecting a system that will perform efficiently for a long time.