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  • Dominick DalSanto

Combustible Dust Safety in the Recycling Industry - Part 1

Updated: Aug 29, 2023

Dominick DalSanto is a guest contributor to the EES blog. Dominick is an environmental technologies expert for www.baghouse.com and has authored numerous articles, whitepapers, and blogs on dust collection systems for industrial sources. This is Part 1 of his series on combustible dust safety.


Introduction


An explosion at the Imperial Sugar plant in Port Wentworth, Ga, on February 7th, 2008 resulted in 14 deaths and many additional injuries. This explosion was caused not by some volatile chemical, or high explosive, but rather by dispersed sugar dust. The tragic result of this accident demonstrates the immense danger presented when the hazards of combustible dusts in an industrial setting are ignored.


Sadly, just prior to this event, the Occupational Safety and Heath Administration (OSHA) in October of 2007 had initiated its Combustible Dust National Emphasis Program (CDNEP) to bring attention to the potential dangers of combustible dust. After the tragic events at Imperial Sugar, OSHA reissued the CDNEP with significant changes to the program, which included increased inspections and enforcement.


The revised plan changed in focus to industries with the most occurrences and most severe incidents, and increased the amount of inspections per year to 300. These inspections cover various industries including the paper products and recycling industries.


Currently, OSHA lacks a comprehensive standard for combustible dust. Enforcement of the CDNEP is being done on the basis of Section 5(a)(1) of the OSHA Act, often referred to as the General Duty Clause. The clause requires employers to “furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees”. Section 5(a)(2) requires employers to “comply with occupational safety and health standards promulgated under this Act”.


The program has very important effects on these industries. Inspections from the program have resulted in over 4,900 violations. The average number of violations per inspection for the CDNEP is 6.5, more than double the average for other inspections. Some violations have resulted in fines exceeding $750,000. Once a violation is found, in addition to fines, OSHA may require the installation of additional dust collection systems to handle the accumulation of dust throughout the facility.


Heavy fines, forced equipment installations, and damaging and deadly fires and explosions can be avoided if you take steps to ensure your facility has an adequate dust collection system now. Here are some guidelines you can follow when you begin the process of designing, installing, and maintaining a dust collector at your facility.


Designing a System Around a Facility


The first step that must be done before installing a dust collection system is to determine what dust emitting sources there are throughout the facility. In the case of a paper recycling facility, a thorough examination of the exact type of shredding equipment, plant layout, and conveying system are crucial to designing a dust collection system to meet your needs.

The amount of dust generated by shredding equipment differs due to factors such as specific type (Hammer Mill, or Rotary Grinder) and speed of the process. In general, hammer mills will create the most dust, and the faster the process the more dust will be generated. Additional reductions in dust with rotary grinding can be gained by rotating cutting teeth regularly, keeping teeth sharp, and using the maximum screen size possible.


Plant layout is also of crucial importance when designing your dust collection system. The size of the collector (measured in CFM or Cubic Feet per Minute) will often determine whether it will be located inside or outside the building. Available floor space is a key factor to be considered, along with ceiling height, and the location of support columns.

Electrical features should also be considered, such as available voltage and amps a system can use without exceeding the facility’s capacity.


Airflow patterns, while often overlooked, can have a large effect on the effectiveness of a collection system, particularly one with unit collection points (i.e. collection hoods). Dust generating equipment should be kept away from doors or loading docks as large wind gusts can have detrimental effects on the efficiency of dust collection systems.


Conveying systems throughout the plant are often the largest sources of fugitive dust. Dust emissions from these sources can be minimized by ensuring that all pick up and transfer points of the conveying system are covered, and have collection hoods – these include conveyor to shredder, conveyor to conveyor, conveyor to baler hopper and baler stroke exhaust.


While incurring higher capital costs than belt conveyors, some plants have chosen to invest in air conveying systems as a means to control dust generation. Air conveyance can dramatically reduce the output of dust within a facility. In addition to moving product throughout the facility, the same ductwork system can be employed with the dust collector for sending dust to the Baghouse for collection.


Once a careful study of all these factors has been accomplished, you will know what requirements you need your dust collector to meet. With this information at hand, you can now proceed to the next phase of designing your facility’s dust collection system. The second phase of design will be discussed in Part 2 of this blog series.


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