A “Leak Detection Test” – or fluorescent dye powder test – is a common practice used to help facilities when encountering emissions problems. You may have already learned the hard way that a few leaking bags within your dust collector can result in an emissions increase that can impact your ability to stay in environmental compliance. Leak tests can precisely identify filter bags that have failed or uncover a breach between the dirty air and clean air plenum in your baghouse system. These are often difficult – or nearly impossible – to identify and properly locate using the naked eye. Fabric filter bag failures can come from many sources including improper bag fit, spark holes, abrasion, thermal excursions, or chemical conditions in the gas stream, to name a few sources.
To help keep your plant in compliance – and as part of a baghouse preventative maintenance program – we recommend contracting with a professional APC service team to perform a thorough baghouse system inspection. This inspection program should include a leak detection test using fluorescent dye powder. Performing a dye test will confirm that all filter bags are properly installed and that there are no paths through the dust collector structure or failure of the filter media that will allow dirty air from the inlet gas stream to contaminate the clean air side of the collector.
Performing a dye test isn’t only limited to bags that have been in operation for an extended period of time. Even newly-installed filter bags can be leak tested. Make sure to protect your filter bag investment and dye test your collector after a filter bag change out has been performed. This will help you identify filter bags that may have been improperly installed or identify a manufacturing or fabric defect that may have not been identified during the QA/QC process.
Here are 10 best practices to ensure a successful leak detection test on your baghouse system, whether you are contracting out this procedure to qualified, trained and certified baghouse service professionals or having your own personnel perform it. Safety should always be a top priority.
1. Locate an injection port on the negative side of the gas stream to inject the fluorescent dye powder. Ensure that the location is as close to the inlet of the baghouse as possible. (Notes: (1) Avoid injecting dye powder through a hopper door as the air flow pattern will be affected and some areas in the filter bag array will not be coated with dye powder. (2) Install/weld a 3” or 4” pipe with a Cam Lock coupling to aid in the safe and metered injection of the dye powder.)
2. Ensure that the baghouse/compartment hopper is clear of accumulated material.
3. Deactivate the baghouse cleaning mechanism while still operating the exhaust/ID fan.
- If your system is a Pulse Jet Dust Collector, shut off and lock out the main airline feeding the cleaning system and bleed all the air pressure from the header.
- If your collector is a Mechanical Shaker or Reverse-Air System, de-energize and do a LOTO on the appropriate electrical and pneumatic devices.
4. Inject the fluorescent dye powder into the system using the appropriate amount of powder for your specific baghouse design & application. Keep in mind different applications require specific fluorescent powder colors so the leaks can be identified during inspection. Contact us to ensure you choose the correct product for your particular application.
5. After completion of material injection, allow up to five minutes for the leak detection powder to work its way through the system.
6. Shut down the exhaust/ID fan.
7. Prior to entering the baghouse, ensure that all OSHA/MSHA and site-specific company practices are followed including but not limited to LOTO & Confined Space Entry, before performing the test.
8. Enter the clean air side of the baghouse or compartment being tested. Using a black light and wearing UV filtering glasses, shine the light on the tubesheet, filter bag, snap band/seating surface, and all other areas on the clean air side of the collector which the inlet gas stream will contact. If there is a leak present, the fluorescent dye powder will “glow” under the black UV light, thus pinpointing the affected area. For best results, the dye test should be performed in darkness with minimal light.
9. Track all filter bag failures on a grid sheet and keep these for future reference. Recurring bag failures may be an indication of dust collector system design or operation problems. If self-performing the leak test, share these findings with your baghouse service provider or filter bag manufacturer to help troubleshoot the root cause of your failure.
10. After your inspection – and appropriate repair work is performed – you will want to perform a leak detection retest to ensure that all failures were identified and repaired. When retesting, use a contrasting fluorescent dye powder color so as to easily find failures that were missed or previously unidentified.
Contact us or call us at 800.915.1273 and talk to our industry-leading sales and service experts to request a quote on our baghouse maintenance services, preventative maintenance programs, and filter media options and let our experts help you in meeting and maintaining environmental compliance with your baghouse system.