Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/742224
28 AGGREGATES MANAGER / November 2016 EQUIPMENT MANAGEMENT mance. High differential pressures indicate that bags are caked or blinded. Low differential pres- sure can indicate that bags are torn or missing. If visible dust emissions are observed at the baghouse exhaust, this is also a pretty good indicator that bags are torn or missing. Inspect the hopper discharge for any material build-up. If not discovered in time, dust can fill a hopper to its inlet and plug the unit. Whether a rotary valve, screw, or pneumatic conveyor is used to empty the hopper, it should be inspected frequently. Exhaust fans should be inspected semi-annually. Loose or worn belts or an imbalanced impeller will reduce the fan's performance. Any time unusual vibration or squealing is observed, the unit should be thoroughly inspected. The filter media is the most important element of the baghouse, and periodic inspection should be mandatory. Inspect the clean air side of the baghouse for any leaks or tears in the filter media. Ductwork should also be inspected for any leaks or deposition. If the exhaust fan is not able to maintain the air velocity in the duct of at least 3,500 feet per minute, dust will settle out and restrict air flow. Eddies in sharp bends can also result in deposited dust that restricts air flow. If you are going to install or refurbish a baghouse, here are some guidelines to keep maintenance costs down: 1. Make sure they are designed for heavy-duty service. 2. Specify materials of construction that are corrosion resistant. Using cheap metal will result in corrosion that eats holes in ductwork. 3. Avoid sharp bends in ducts that will quickly wear through. This is particularly true if the plant processes hard, abrasive rock such as sandstone or granite. 4. Select filter media that will hold up to your specific stone. Again, abrasive dust will require more resistant media. If the rock contains any sulfides that can pro- duce acidic corrosion when exposed to moisture, you'll need a filter media that is up to the task. 5. Avoid long multiple intake ducts. To save money, many plants install a single big baghouse with tentacles of ductwork that extend to multiple sources. It is difficult to balance air flows with such an arrangement, and you'll be much better off installing multiple baghouses with fewer and shorter intake ducts. Preventive maintenance: Don't wait 'til it breaks! Whether you use wet suppression systems, dry collectors, or a combination of both, insti- tute a routine program of preventive mainte- nance and make sure that the plant pursues it with the same alacrity that it does for production equipment. The program should include a daily inspection recording spray system pressure and/or baghouse differential pressure, as well as a log of any maintenance or repair work. Pollution control equipment may not put more tons into trucks, but it does protect the health and safety of your employ- ees who do. AM Mark Kestner, Ph.D., is also known as Dr. Dust. He is president of Mendham, N.J.- based National Environmental Services Co. (NESCO). Install spray nozzles so that they are easy to see and easy to reach. Filter media should be inspected and replaced regularly to keep a baghouse operating at high efficiency. Spray system pumps and compo- nents should be housed in heated enclosures to protect them from freezing. If air velocity in baghouse intakes falls below the minimum requirement to keep dust in suspension, it will settle out and restrict air flow even more.