Just about every processing or manufacturing operation has rooms along the route as product starts out as raw material or sub-assemblies and makes its way onto becoming finished product. Problems arise for sensitive operations such as food processing, pharmaceutical processing, and electronics manufacturing when microorganisms and other contaminants hitch a ride along the way.
According to a significant body of research, sensitive product can be exposed to any number of contaminants at critical control points (CCP)—the areas where contaminations may occur. Rather than just making themselves comfortable in the places they grow, contaminants move along with the process as product moves from room to room.
Cleveland-based Minor’s is one company that makes every effort to control the transmission of pathogen contaminants through their operation. A division of Nestle Professional and one of the country’s leading producers of high quality bases and stock products used by professional chefs, Minor’s food quality program goes beyond the typical standards. Their processing environment is strictly controlled as product makes its way through the facility.
Recently Minor’s increased their production by bringing on-line a two-story, 75,000 sq. ft. addition to the original plan—which dated back to the founding of the company in 1951. During the construction, the contamination control plan included the use of high-speed roll-up doors.
Airborne contaminants represent a serious threat to quality and safety as product moves from one part of the processing plant to another. According to a study commissioned by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) and conducted by Dr. A. J. Heber of Purdue University’s Department of Agriculture and Biological Engineering, bioaerosol emissions may be carried throughout a processing plant via airflow through doorways and other openings. Bioaerosols are airborne contaminants that include bacteria, fungi, viruses, and pollen. These free-floating microorganisms may be present in the air as solids (dust) or as liquids (condensation and water). Controlling airflow at entry points such as doorways can reduce the movement of contaminated air and provide additional benefits for sensitive manufacturing operations.
Simple practices such as keeping doors closed can be essential in controlling air contamination. However, it’s easier said than done. Doors that experience heavy traffic often have maintenance issues that arise from frequent usage and from damage caused by inevitable crashes. Deficiencies in door design can mean that even when the door is closed, contaminants can still find their way through.
At the Minor’s facility, product moves through the plant on specially designed automated guided vehicles (AGVs) that pass through a number of rooms and doorways. All of these areas must meet controlled environment standards. There are seven rooms which handle different product configurations. In each room, MERV-14 filters remove bacteria and other particles to generate hospital-quality air and ensure product quality.
Positive air pressure prevents air infiltration, and the doors are set up in an airlock fashion to maintain this environment. Traffic is expected to use one door going into the room and another door on a different wall to go out.
The roll-up door activation is arranged so that the second door cannot be opened until the first door is closed. On these doors, the functions once performed electrically and mechanically are handled by the electronics in the door controller. The system that controls the AGV operation can ensure that the doors are opened in time and closed promptly.
“The whole packaging area requires positive air pressure,” points out Tom Arthur, Minor’s plant engineer in charge of their plant expansion project, “and what we’ve done is balance the room using this sophisticated door system.”
The first order of business for doors in a clean operation process is to provide a tight seal. When these doors roll up, the curtain travels along stainless steel side guides. These encase the sides of the curtain along the full height of the door and prevent it from blowing out as a result of drafts or pressures. A brush at the top of the doorway seals off the header. At the bottom, the door’s bottom gasket hugs the floor.
Equally important as a tight seal, high-speed doors can limit room exposure to air infiltration and energy loss. Achieving rapid opening speeds of 50 inches/second, the 8-ft. roll-up doors stay open for as little as five seconds. Door speed also maximizes the time the doorway is closed to maintain air balance. A closed door also enables the room to control processing conditions for the different types of products.
The doors at Minor’s sometimes open dozens of times each day. Each doorway is open for a minimal amount of time as the AGVs pass through. In addition, at no point does the AGV have to pause in order to pass into a room.
When a material handling vehicle hits a door, the seal is compromised and the doorway opening could be unprotected for hours until the repair crew arrives, or for days if the panel is damaged. A rapid door speed can help keep this type of accident from occurring.
Cleanability was a major reason Minor’s chose this type of door. The door curtain can be completely extended when the door is closed, preventing microorganisms and debris from collecting around the drum, and the non-porous USDA/FDA-approved curtain fabric easily sheds dirt and debris during wash down. The door’s metal parts are stainless steel, including the frame and the roll-up drum. Frames are removable for easy cleaning.
Wastewater, rinse water, and spilled product that become aerosolized are major sources of contamination in sensitive processing and manufacturing facilities. The door curtain plays an important role, acting like a large catcher’s mitt for aerosolized microorganisms and blocking the entry of these invaders into the next step in the process. However, these pathogens can be rolled up with the door curtain as it opens. As product passes underneath the opening door, the bioaerosol could drip on the product below. To prevent this situation, the door can be designed with a pneumatic drip-catch tray that moves under the roll drum when the door opens, stopping contaminated liquid from raining on the product.
Installation of recirculating air infiltration units, constant monitoring, consistent room temperatures, and even limiting employee traffic are among the many means to reduce contamination throughout the route to the shipping door. Though total confinement of pathogens and contaminants to their place of origin is beyond practicality, proper door selection and application can ensure that sensitive product travels through the plant safely and that an unacceptable level of contaminants does not.
Kurt Angermeier is Vice President of Marketing with Rytec High Performance Doors. Rytec manufactures high-speed, high-performance doors for industrial, commercial, and cold-storage environments. Corporate offices and manufacturing operations are headquartered in Jackson, Wisc. Customer support is provided through national and regional offices and a network of local dealers and installers throughout North America. kangermeier@rytecdoors.com; www.rytecdoors.com
This article appeared in the January 2014 issue of Controlled Environments.
