Explore this issueAugust/September 2014
Contamination control is critical in a wide spectrum of industries, none more so than food manufacturing and processing. From the mixing and packaging of powdered ingredients and spices to grain storage and loading dock operations, control is vitally important to a myriad of food industry processes.
At the very least, particulate matter in the air is a nuisance. However, it can cause serious quality and safety issues as well. At the nuisance level, particulate generated from cutting, grinding, mixing, etc., can settle on surfaces significant distances from the operation if containment equipment is not in place. Dust on neighboring equipment, furniture, office equipment, windows, and floors becomes a constant drain on cleaning and maintenance resources. On the more serious end of product quality, uncontrolled particulate matter can spoil or degrade batches of differing critical materials, particularly in food processing.
From a safety standpoint, there are many circumstances where high enough concentrations of airborne dust-sized particulate in a closed space can become explosive or flammable. This includes seemingly innocuous products we wouldn’t normally think of as explosion hazards—including grain, flour, sugar, and powdered milk. Additionally, airborne particulate can be a health threat to employees. These risks can range from a skin, eye, or bronchial irritation to more serious issues for people with asthma. Most serious can be the potential for particulates to cause lung diseases like cancer.
Controlling Particulate Contamination
Several methods can be used to keep particulate in one space from contaminating another, including:
- Local exhaust – a high-velocity airflow stream captures particles at the point they are generated and carries them away;
- Exhaust with filtration – a high-velocity airflow stream captures particles and recirculates them through a filter medium, where they are removed;
- Area exhaust – a high-volume exhaust fan draws air from the full room volume to an outside vent or recirculates through a filtration/separation device; and
- Barrier separation – simply a wall or partition between affected areas. These are especially effective when used to separate clean from ambient spaces in a positive or negative air pressure environment, such as between a loading dock and a food processing area, or between food processing or packaging lines and surrounding areas.
Exhaust separation methods rely on moving a volume of air containing the contaminate particles. Barrier separation can be enhanced by creating a positive or negative pressure differential across the barrier. Each of these could be accomplished through the use of exhaust fans through ducts to create a negative air pressure environment. A local exhaust setup would incorporate some type of hood designed to collect the air and particulate being moved and funnel it into the exhaust ductwork. Area exhaust would include multiple draw points through louvered openings in the ceiling or wall. Either of these methods could, and most likely would, include some type of filtration or particle separator in line to remove particulate from the air stream. This is necessary prior to either recirculation of the air back into the space, or discharge of the air into the atmosphere.
Conversely, in a clean space where offending particulate is not generated, but adjacent space contains foreign matter that could contaminate product in the clean space (e.g. food processing or packaging), a positive air pressure environment would be desired. In this case, filtered air would be pumped into the clean space, creating a positive air pressure within the space and preventing inwardly flowing air currents that could carry foreign particulate matter.
In some cases, a simple partition (wall) between a clean space and an uncontrolled ambient space (such as between a processing area and a loading dock) is an effective means of separation. If negative air pressure differential exists across the wall between the clean and ambient space, the wall acts as a physical barrier, blocking most of any potentially contaminating foreign matter from crossing the barrier. Depending on the degree of particle separation required, and the need and frequency for traffic to move through the partition, a more effective solution would be to introduce a positive air pressure differential to the clean space, as described in the paragraph above.
Fabric Curtain Walls Can Help
Curtain walls can significantly improve the effectiveness of these systems, as well as offer the opportunity for cost savings, both in the initial cost of the equipment and in the direct operating cost.