Combustible Dust Control
By John Constance, Professional Engineer, P.E.
The Engineers Collaborative
The same old dust control and pneumatic conveying system problems that you have been living with could now cost you big dollars in production down-time, penalties, and, worst of all, serious accidents. Take a walk around your plant and see how many of these problems you have if the dust is combustible. Don't wait until you are walking through the plant with an OSHA inspector or an inspector from your State's Department of Environmental Protection.
Dust Collector - Filter Receiver Problems
- The filter media pressure gauge is not reading the true pressure drop across the filter media. The gauge is disconnected or plugged with dust. How can this condition cost you money?
- If the gauge reading is outside the range recorded on your State Department of Environmental Protection permit, you could be fined for a permit violation
- The pressure gauge is there to tell you the condition of your filter media. If it doesn't, you may have problems. If the filter media is plugged, exhaust airflow will be reduced. Loss of dust control will occur resulting in possibly causing unacceptable levels of
breathable dust or settlement of dust around the work area. If the dust is combustible, an
OSHA inspector could issue a citation and, depending on the severity, shut down your
- The filter media pressure gauge is continuously reading a high pressure drop above the normal operating range. How can this condition cost you money? If the dust collector filter cleaning system is the on-demand type, the cleaning system will be pulsing continuously in a vain effort to clean the filters. Compressed air costs will increase. It may be time to change the filters.
- The dust collector handling combustible dust is indoors with its explosion vent facing the interior of the building. If the dust collector is outdoors, the explosion vent is directed towards a parking lot, plant equipment and buildings or a normally occupied area. OSHA will most likely issue a citation for all these situations and require that they be corrected.
- The dust collector handling combustible dust is inside the building with its explosion vent ducted to the outdoors. If the explosion vent duct is not designed according to NFPA 68, latest edition, OSHA can issue a citation for this deficiency. If the explosion vent duct was installed by a local HVAC contractor, it could be too light a gauge sheet metal to contain and direct an explosion to the outdoors. If the vent duct "feels" like your air conditioning ductwork, it is not strong enough. Ask the design engineer or the contractor for the design calculations for the vent duct. If the calculations are not available, there were probably none. When the OSHA inspector questions the vent duct construction, you can show him the design documentation and avoid a citation if the vent duct was properly designed and constructed.
Dust Control System Ductwork Problems
- Some dust control hoods are working better than others. Some hoods are not working at all. Measurements show that here is improper airflow in the dust control system branch ducts. Dust is settling inside the ductwork. Excessive noise is occurring in some areas of the ductwork. If some or all of these problems are happening with your system, it could simply be that the system needs to be balanced to the design airflow quantities. It could also be caused by ductwork air leakage. It should be easy to correct these problems. There may be other reasons for these problems as well. If there are no balancing dampers in the ductwork, the system cannot be balanced. If the ductwork has been added to and modified without the proper re-design, there most likely will be no way to correct the problems without a complete re-design of the system. If the dust is combustible, OSHA can issue a citation for these issues.
- The inlet and outlet ductwork attached to a dust collector handling combustible dust need
isolation devices. Without isolation devices, these ducts can vent fire and smoke back into the plant threatening the safety of personnel and causing property damage. Refer to NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids, latest edition.
Combustible dusts are often either organic or metal dusts that are finely ground into very small particles, fibers, fines, chips, chunks, flakes, or a small mixture of these. Types of dusts include, but are not limited to metal dust, such as aluminum and magnesium; wood dust; plastic dust; biosolids; organic dust, such as sugar, paper, soap and dusts from certain textiles. OSHA inspectors are trained to recognize combustible dust issues during their plant inspections. It is now just a matter of time before your plant will need to address these issues.
The Engineers Collaborative is the dust collection and industrial ventilation expert that you need on your project!
Contact us today at (215) 300-9563, to find out more about how we can help you with your industrial ventilation or dust collection review, analysis, or design or go to www.engcollab.com.