Filter Bags & Leak Testing – How Important is it?
Leak testing being performed in a Baghouse
By Dominick DalSanto
Environmental Technologies Expert & Author
Baghouse.com
Why Periodic Leak Testing of Filter Bags is Vital
Operating a dust collection system with leaking filter bags defeats its sole intended purpose. A few leaking filter bags or even one within a collector/system can result in a substantial emissions increase. Leak testing of your Baghouse filter bags needs to be a regular part of any maintenance program to ensure system efficiency, and maintain compliance with emissions/safety regulations and avoid the fines and/or safety hazards that come with it.
All filter bags will eventually wear all out and need to be replaced. Baghouse maintenance programs should include periodic leak testing to ensure a few or even one faulty bag does not reduce the operating efficiency of the entire system. On occasion, a defective filter will fail early and need to be replaced. In other instances there may be a temporary or unanticipated event that can cause of premature failure of Baghouse filter bags. Once identified these should be investigated to ensure the incident does not occur again, and determine the extent of the damage done to the system. Examples may include: abrasion, thermal durability, and chemical attack.
- Abrasion from several different sources often leads to excessive wear (and therefore premature failure) of the filter bags. The most obvious is caused by excessive particulate loads in the gas stream. This may have been caused by the unexpected failure, or shutdown/maintenance of a pre-filter (such as a cyclone, or air scrubber for NOx and SOx). Poor design may also lead to particulate laden air striking the filters in certain spots more than others such as near the cuff, or dirty-air inlet. Other sources of abrasion damage include: improperly installed filters that rub against each other, and excessive cleaning cycles.
- Degradation of the filter bags’ Thermal Durability may also be a potential cause of early failure. When operating temperatures that rise above the designed limits of the fabric, whether for short or long term, filters will begin to degrade and eventually fail. Changes in the plant process, fuel source, maintenance shutdowns of other systems, etc…may result in temperature spikes that will irreparably damage Baghouse filters.
- Chemical attacks can also result in bag failure. These can occur when gas stream characteristics are not taken into consideration when selecting the filter fabric and/or treatments/finishes. Other times unexpected changes occur in the gas stream that cause changes in the composition of the gas. Operating temperatures may also fluctuate, dropping below the dew point allowing condensation of the chemicals on the fabric.
Filter Bag Leak Testing – How it is Done
To perform a standard leak test several things need to be done before the actual test can take place. First, since testing requires temporary isolation from the facility process, and shutdown, you must determine the best time for each unit and/or compartment to be tested. Second, safety measures for plant personnel must be taken into account when estimating total down time. Units must be given sufficient time for cooling, atmospheric testing to check for harmful gases, and personnel assigned to perform both the test and fulfill any and all safety regulations regarding confined space entry (both OSHA, and In-house). Once the preliminary steps have been taken, the actual testing can begin.
A vital part of any Baghouse system maintenance plan is regular leak testing of the filter bags.
First, florescent leak detection powder is added upstream of the unit such as at a maintenance access in the ductwork. Then after sufficient time has past for the powder to work its way through the system, the unit is shutdown. Once it is possible, a technician will enter into the unit with a UV light source i.e. a black light to examine the filter bags for leaks. The powder fluoresces under the UV light, thereby making it easy for the technician to see even the smallest of holes. The technician makes note of any faulty filters, which can then be replaced.
Regular Maintenance is Key to Getting the Highest Efficiency from Your Baghouse
Baghouse systems are the most efficient, and cost effective solution for particulate matter control in industrial settings – but only if they are maintained properly. A vital part of any Baghouse system maintenance program is regular leak testing of the filter bags. By conducting this and other maintenance tasks, your Baghouse system will operate smoothly, and provide the best of results.
Looking for Leak Testing Services?
Baghouse.com has the expertize to locate and remedy leaks in not only your filters, but also duct work, collector housing, and more. To learn more about Baghouse.com leak testing services and leak testing supplies or receive a free quote on Baghouse leak testing please contact us for a free quote.
I don’t know of any videos out there showing this. However, we are currently planing to produce a series of videos detailing this, and other Baghouse maintenance and operational procedures. When they are ready we will publish them here on Baghouse.com for everyone. Thanks for your comment.
Our bag house cfm continues to drop throughout the day, start up in the morning it’s fine 40000, by 10:00 am it is down to 32000 cfm and slowly drops
Jack,
Thanks for your comment. CFM will drop as vacuum pressure goes down. Vacuum or suction goes down when the differential pressure rises. Differential pressure rises when the filters get dirty. So it sounds like your cleaning system can’t keep up with the load you are putting on your bags, so your bags get dirtier throughout the day and then begin to choke off the airflow.
How long have you been running the current set of bags? What kind of cleaning system do you have (pulse jet, reverse air, shaker)? Many times these kinds of problems arise from using filter bags for too long (i.e. your bags are blinded and need to be replaced but you keep using them) or because the cleaning system is not functioning properly. Since you start out at a higher airflow it seems more likely that your cleaning system is not working at 100%. You might need to change the cleaning cycles, (if pulse jet) the diaphragm valves, pulse pressure, on-time/off-time, etc. Give us a call when you can and we will be happy to discuss a few options for you to look at to fix the problem.
I would like to get some predominant damages in filter sleeves and from their to reach an analysis ,kindly help us with photographs
Hi, I am Saju Simon working in a Filter bag manufacturing company in Quality & Technical service Dept.
I want to know the RABH bag failure : Damage was like abrasion & torn the fabric. Heavy Dust accumulation found in the clean air plenum. Is there any chance of crack in the partition wall?
yes, a leak in the dividing wall is certainly possible. Abrasion is going to come from a few different sources: (1) high velocity inlets, (2) full hoppers disrupting the airflow within the unit, (3) too few bags for the CFM (4) leaks inside the unit. Do a leak test to see if there are any leaks. Next, determine if the filters are all being worn down evenly or in certain spots or only certain sections of the unit.
Do you use leakage powder to detect leaks in filter bags in jet pulse filters? Could you please share a video how to use this product? Could you give brief information about the method