Food Processing: Bulk Food Ingredient Handling

Introduction to Bulk Material Handling for the Food Processing Industry

Bulk food ingredient handing encompasses the front end of the food processing industry, where raw grains and other bulk ingredients are transported by truck or rail car, pneumatically conveyed into silos for storage, moved via conveyors or high-velocity pipes, and dry mixed. These are among the dustiest processes in the food processing industry.

Dry bulk materials in the food industry include all kinds of grains, flours, starches, spices, sugar, cocoa, dry beans and legumes, nuts and other dry ingredients. Processes included in bulk material handling of food ingredients are:

  • Food Ingredient Transport/Conveyance
  • Dry Mixing
  • Silo Filling

Dust Collection Challenges for Bulk Food Material Handling

Moving, mixing and storing bulk dry ingredients creates a large amount of dust, which can build up in silos, storage bins and conveyor systems if not controlled. Some of the biggest challenges at this stage of the food processing industry are:

  • Combustion risk: Many bulk food/dry raw ingredient dusts—including grain dust, flour dust, sugar dust, starch dust and cocoa—are highly combustible. That means they can generate an explosion when allowed to concentrate in the air or inside a dust collection machine. Combustion risk is heightened at this stage of the food processing industry when dust is allowed to accumulate inside closed silos or conveyor systems. Containment is one of the risk factors for a combustible dust explosion; when combustible dusts build up to the right concentration within an enclosed area, an explosion can occur. The enclosed environment of a silo can create ideal conditions for a combustible dust explosion.
  • Cross-contamination: Cross-contamination is a big concern for the food processing industry due to the prevalence of life-threatening allergies in the population. Many people are allergic to nuts, wheat, soy and other food products commonly transported in bulk. Cross-contamination concerns come into play if the areas where bulk foods are stored and distributed are shared by different food items. Dust will need to be controlled in this case to prevent contamination of food products in one silo or conveyor system from being contaminated by dust escaping from a neighboring silo or conveyor.
  • Nuisance dust: Uncontrolled dust from bulk food products can become a nuisance and a housekeeping concern if it is allowed to escape from silos, storage bins and conveyor systems in an indoor facility. Because many food ingredient dusts are allergens, uncontrolled dust in the facility can pose a health risk for susceptible workers. Dry food ingredient dust can also be a lung irritant even if the dust itself is not considered hazardous.
  • Microbial growth: Grains and other bulk foods create an ideal breeding ground for microbial growth. Grain dust or other food dust that is allowed to accumulate on surfaces outside the silos, bins and conveyors can easily become contaminated with bacterial pathogens, molds and fungi. These pathogens can create health risks for workers as well as contamination concerns for food products as they are moved to the processing stage.

Sugary Factory Conveyor

Regulations for Bulk Food Ingredient Handling

The food processing industry is highly regulated. Companies involved in transport, silo filling or dry mixing of bulk dry ingredients are subject to both food safety regulations from the Food and Drug Administration (FDA) and U.S. Department of Agriculture (USDA) and occupational safety regulations from the Occupational Safety and Health Administration (OSHA) and National Fire Prevention Association (NFPA). Some of the most critical regulations for this stage of the food processing industry include the following.

  • Combustible dusts: Combustible dusts are regulated under OSHA’s General Duty Clause (Section 5(a)(1)) with additional requirements under the Hazardous Locations (§1910.307), Hazard Communication (§1910.1200) and Housekeeping (§1910.22) standards. In addition, manufacturers dealing with combustible dusts must follow National Fire Protection Association (NFPA) standards for prevention of fires and explosions. Food dusts fall under NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agriculture and Food Processing, as well as NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids. Dust collection systems for food processing dusts must also meet NFPA 68, Standard of Explosion Protection by Deflagration Venting, and NFPA 69, Standard on Explosion Preventing Systems. OSHA’s Combustible Dust National Emphasis Program (NEP) outlines policies and procedures for inspecting workplaces that create or handle combustible dusts. Companies moving, transporting and storing bulk grains and other dry bulk ingredients also must conduct a dust hazard analysis (DHA) to determine their combustion risks and put appropriate mitigation strategies in place.
  • Nuisance dusts: Many food processing dusts fall under the OSHA definition of “nuisance dusts,” which are regulated under the general particulate matter concentration limits set by OSHA. The general limit for “Particulates Not Otherwise Regulated” (PNOLs) is 15 mg/m3 (8-hour TWA limit) for total particulate and 5 mg/m3 for respirable particulates. Employers must also follow general Housekeeping standards (OSHA 1910.22, Walking-Working Surfaces) to prevent accumulation of dust on surfaces.
  • Grain processing facilities: OSHA has issued additional regulations for Grain Processing Facilities (1910.272) due to their exceptionally high combustion risk. Grain handling facilities must have a written plan for control of fugitive grain dust, including engineering controls and housekeeping measures to prevent the accumulation of dust both in the air on surfaces.

Read more about regulations for food processing dusts.

Dust Control Solutions for Silo Filling and Dry Mixing

Silo filling and dry mixing are extremely dusty processes. The volume of dust produced while grains and other dry bulk food ingredients are moved, along with the unique physical characteristics of grain silos and conveyors, requires specialized dust control solutions.

During silo filling and dry mixing, product is conveyed into the silo using high-speed pipes or a pneumatic conveyor. This process generates both a lot of dust and excess air inside the silo. In addition to controlling the dust, the solution must vent the excess air to prevent too much pressure from building up inside the silo.

Bin Venting is used to create a relief point and vent excess air from the silo. To prevent dust from escaping the silo, this is typically done by mounting a dust collector directly to the top of the silo. Filtered air is vented to the outside. Dust from the filters can be pulsed right back into the silo, where it settles back with the grain. Bin venting using the dust collector prevents air pressure from building up inside the silo while it is filled, while simultaneously keeping dust contained inside the silo. Bin venting can also be accomplished through natural aspiration or with forced airflow using a fan to pull air from the silo.

Additional considerations for design of a dust control system for silo filling and dry mixing include:

  • Combustion mitigation: Special care must be taken when collecting combustible food processing dusts to minimize the risks of an explosion inside the dust collector. The dust collector should be equipped with a deflagration system to prevent pressure waves from propagating back into the silo or facility if an explosion should occur. A separate deflagration system must be in place for the silo itself; venting of the silo should not be done through the bin vent.
  • Filtration: An appropriate filter media must be selected for the high volumes of dust produced by these processes. A pulsing system is also needed to pulse off excess dust on a regular basis. The right filter will allow excess dust to easily pulse off, so the filter does not become loaded too soon.
  • Airflow: The dust collector must have high airflow to keep up with the volume of dust generated and vent excess air as it enters the silo. Airflow is measured in Cubic Feet per Minute (CFM). It is important to ensure that the dust collector has a high enough CFM rating for effective bin venting and dust control.
  • Maintenance: Since these dust collection systems are generally remote, it is important to have a dust collector and filter combination that will reduce maintenance requirements. A remote pressure drop sensor is useful to detect excess pressure drop that indicates that filters need to be changed.

Dust collection for silo filling, dry mixing and conveyance of bulk food goods requires unique and customized solutions. Our engineers will evaluate your processes and help you select the right dust collector and filter media. We can also design an industrial ventilation and makeup air solution for you to ensure optimal dust collection, reduce cross-contamination concerns and mitigate health and safety hazards.

RoboVent can also help you meet OSHA and NFPA regulatory requirements and safety guidelines for management of combustible dusts. We can conduct a dust hazard analysis (DHA) for your operations under the NFPA Combustible Dust Standard (NFPA 652) and put dust control systems in place to mitigate the risks of a combustible dust explosion from grain and food dust.

Our experienced air quality engineers will work with you through the whole process, including needs analysis, system design and engineering, collector and ductwork installation, filter selection, HVAC system integration, startup and commissioning, and aftercare and service.

Solutions

Senturion®

Senturion is the most flexible and versatile industrial dust collector on the market today.

PleatLock Cartridge Filters

PleatLock Dust Collector Cartridge Filters

RoboVent's premium filter engineered to provide the best filtration protection for your plant and employees. A widened pleat and proprietary filter media help deliver top performance.

Deflagration System on Fusion 4.5

Deflagration System

Protecting your workers and facility from the risks of combustible dust, RoboVent's Deflagration System employs multiple devices and technologies to mitigate dust explosions.