May/June 2019
Moisture in Your Baghouse?
What Can You Do?

Little things can cause big problems in baghouse dust collectors. Inefficient collectors increase utility costs. Faulty collectors can lead to costly downtime or even jeopardize employee health.

Moisture impacts dust collectors in a disproportionate way. It only takes a little moisture and a short amount of time for moisture to wreak havoc in your collector. You may encounter:
  • Dust buildup on housing walls
  • Bridging of dust at the hopper discharge
  • Dust accumulation on the vanes of the hopper's rotary airlock valve potentially causing the airlock to seize
  • Dust accumulation on pressure sensors resulting in false readings
  • Dust settling on duct surfaces causing excessive weight
  • Corrosion of internal metals.  
  • Plugged filter media.
  • Premature failure of filter bags.

Common Causes of Moisture in Baghouses
  1. Condensation
  2. Humidity changes
  3. Temperature differentials
  4. Hygroscopic dust (sugars, salts, fertilizers, wood products, metal oxides, polymers, etc.)
  5. Mists or sprays added to the process airstream
  6. Moisture entering the collector through the cleaning cycle on pulse jet collectors
  7. Moisture entering through leaks in the housing and seams, or around bad seals  
Recognizing Moisture in a Baghouse

Too often, high pressure differential readings and low airflow rates are the first indication that something is wrong and by then, much damage is done. 

Because moisture may appear in your baghouse intermittently, check for moisture when the possibility of moisture is high and the dust collector is not operating. Wear protective clothing. Inspect the inside walls of the dust chamber for signs of moisture or rust formation.

Conduct a simple moisture test by taking a dust sample from the chamber wall and placing it on a paper towel. Squeeze the paper towel with the dust sample inside. If any moisture or oils are transferred to the paper towel, you have a moisture problem.

Ways to Prevent Moisture Related Problems

Avoid condensation and you eliminate most moisture related problems. A properly engineered baghouse design is the easiest way to do this. For existing systems, consider the following to catch, reduce or prevent moisture problems. 
  • Examine collectors and repair leaks in the housing, seams and seals where air can enter. 
  • Avoid condensation.
    • Insulate the baghouse and inlet and exhaust ductwork surfaces to help maintain collector wall temperatures above the moisture dew point.
    • Don't overlook the interior walls of the hopper, typically the coldest temperature inside a collector. Dust from filters falling onto wet hopper walls can be just as disruptive as muddy filter bags, often leading to bridging in the discharge opening. Are heating elements on the outside of the hopper appropriate for your application?
    • Use process controls to monitor and maintain the target airstream properties. 
    • Bleed dry air into the airstream reducing the potential for condensation.
    • Locate the dust collector close to the process to minimize airstream cooling in the ductwork between the process and collector.
    • Properly size compressed air dryers.
  • Use a differential pressure gauge for earlier detection.
  • Choose the correct filter bags for your application. Not all filter media handle moist heat. With many common synthetic materials, moisture combines with contaminants in the collector to form acidic or basic solutions which break down the media. Chemical characteristics and operating temperature are key factors when selecting filter media.
  • Utilize proper start-up and shut down procedures.
  • Practice preventive examination and maintenance.

For more information, contact your TEC representative.
In This Issue

How many triangles are located in the image below?
Start-up Procedure for a Dust Collector or Baghouse
Start-up Procedure for a Dust Collector or Baghouse

"One man's "magic" is another man's engineering. "Supernatural" is a null word. "

-- Robert A. Heinlein
Technical Resources

Contact US

Steven Duke
Birmingham, AL
Bob Hodges
Covington, LA
Harvey Kinsey
Atlanta, GA
Lance Steed
Mobile, AL

TEC Engineering, 700 Century Park South, Suite 223, Birmingham, AL 35226
Sent by in collaboration with
Constant Contact
Try email marketing for free today!