Troubleshooting Your Baghouse Dust Collector
Moisture
In a short period of time moisture can cause premature failure of bags in a dust collector. Moisture will cause agglomeration of hydroscopic dust which will plug bags and form a hard brittle cake that cannot be removed during the cleaning cycle. Moisture can also combine with contaminants in the collector to form acidic or basic solutions which could destroy bags if the proper fabrics are not used. The problem can occur in collectors operating at ambient as well as elevated temperatures if they contain moisture. Warm collectors must be watched particularly close so that condensation does not form. This can be avoided by purging the collector with warm dry air prior to startup and after shutdown, keeping the collector above the dew point, with pre-heaters if necessary, and making sure the collector is insulated.
Moisture can also enter the collector through the cleaning cycle on reverse air or pulse type or reverse jet collectors. On reverse air systems check to insure that the heater or dehumidifier on the cleaning air is working properly. On pulse type collectors compressor tanks should not be allowed to build up moisture and air lines should remain dry. Provisions are usually made by the collector manufacturer to protect your bags, however, it is your responsibility to maintain these systems.
The last, but one of the most obvious sources of moisture in a collector, is leaks in the housing. Air can enter through cracks in the housing and seams, or around bad seals bringing moisture into the collector. Periodic examination and maintenance of the collector and all seals is essential.
Temperature
Temperature is closely related to moisture. Fluctuation in temperature can cause condensation and moisture problems if allowed to drop below the dew point and must be closely watched.
The operating temperature was a prime concern in selecting the filter media. If you exceed the rated temperature you can literally burn out a set of bags. Shrinkage can also occur at elevated temperatures. It is best to check with your filter bag supplier for the correct operating temperature, and the maximum surge temperature the bag can withstand. Usually the maximum operating temperature should not exceed 20% of the rated maximum operating temperature for more than 10 minutes per day. The life of the bags decreases sharply as the maximum temperature is reached, so keep your temperature as far below maximum as possible. Likewise, these temperatures were based on dry heat. Moisture and high temperatures can join hand in hand to further degrade your bags. Avoid getting excessive moisture in the collector as previously discussed.
Bag Installation
The proper method of bag installation and tensioning of bags should be specified by the collector manufacturer to insure the longest possible life. In the case of shaker type bags, too loose a bag can cause abrasion between bags, poor cleaning and reduced life. Bags installed too tight can put undue strain on the fabric, supporting clamps, eccentrics, and other mechanical parts.
Poor installation can also mean leaks inside a collector. This usually occurs at the point where the bag seals inside the collector. If your bags use clamps they must be properly tightened to insure a good seal. All metal in contact with the bags must be kept clean to insure a good seal whether using clamps, springs, or snap bands.
Dust can leak inside the collector, fill the bottom of the collector and press against the outside of the bags reducing the diameter. The same total amount of air goes through the bag regardless of the diameter. if reduced in diameter, a sandblasting effect can occur abrading the bags. Two feet of dust in the bottom of a dust collector can cause bag failure within a week’s period of time due to excessive abrasion. The clean air side of the collector must be kept clean.
Maintenance
Do not take your dust collector for granted. If it is working well it is only because you keep it so. A checklist is provided for quick easy reference as well as a guide for problem solving. Use this as a guide, but above all make your own preventative maintenance list. Keep an accurate record of the servicing required of your collector showing bag life, date of installation, date of failure, cause of failure, date of service of the collector and date and type of repairs made to the collector.
The time to take care of trouble is now. If caught soon enough and taken care of, a minimum of downtime may be required. Put it off a few days or weeks, and your downtime may become days or weeks. Treat your dust collector as you would any other piece of equipment in your plant. With normal care in selection, installation, operation, and maintenance, your dust collector will provide you with dependable trouble-free service, and pay you dividends over the years.
Standard Check List:
- Dust hoods to see that they have not been changed, removed or destroyed.
- Duct work for evidence of filling due to drop out.
- Duct work for leaks.
- The air volume being handled by the fan, don’t guess.
- Fan rotation and speed.
- Heaters to insure they are working. Dampers to see that they are working.
- Baffles to insure they are in position and have not eroded.
- Bags for proper installation.
- Bags for blinding, crusting, or evidence of condensation.
- Clean air side for leaks or broken bags. Hoppers to see that they are being emptied.
- Automatic conveyors to insure they are working.
- All moving parts for proper lubrication.
- Cleaning mechanism for proper function.
- Shaker mechanisms to insure they are working.
- Air pressure on reverse jet bag houses.
- Air volume on reverse air cleaning mechanisms.
- Cleaning lines for signs of plugging.
- Compressor tank for moisture.
- Frequency of cleaning cycle.
- Duration of cleaning cycle.