Food Safety Whitepaper

FOOD SAFETY MANUFACTURING

ENGINEERING DESIGN SYSTEMS

FOOD SAFETY MANUFACTURING- ENGINEERING DESIGN SYSTEMS

There are three important categories for the safe manufacturing of food. The three categories that we will be addressing are:

• 1. PRODUCT FLOW

  2. TRAFFIC FLOW

  3. HVAC

  4. PRODUCT FLOW

Product Flow in a food manufacturing facility is the best starting point to design a food safe environment for the manufacture of food on a large scale or small scale.

In any food manufacturing facility there are different hygienic zones that determine product flow through a facility. Quite a few food manufacturing firms use a color coding system to identify these various hygienic zones in their facilities.

A typical color coding system is shown here and the various zones are described as follows:

• • Red Zone: receiving/raw materials.

  • Yellow Zone: Processing (Kill Zone)

  • Green Zone: Processing (Post Kill)

  • Blue Zones: Finished/Warehouse

The critical path for a food safe environment through these zones should be linear. Raw product that enters the facility through receiving docks would be in the Red Zone (this is also call the High Risk Area or pre-kill zone.) The Processing area, Yellow Zone, is a moderate to high risk area (or commonly referred to as the Kill Zone.) The Processing #2 area, Green Zone, is a moderate risk area (referred to as Post-Kill Zone.) The Finished and Warehouse area, Blue Zone, is a low risk area where the final product is packaged and ready for shipment.

Trash is certainly a by-product of any food manufacturing facility. Handling of trash should be in the opposite direction of Product flow. Trash produced in the warehouse and packaging area should be transported back through the processing areas and eventually through the raw product area. Other options for trash flow would allow for staging areas in each section and removed from the facility other safe access openings.

II. TRAFFIC FLOW

Traffic Flow patterns through a food manufacturing facility are very important in maintaining a Food Safe environment. There are certainly two categories for traffic patterns:

• • Employee Traffic.

  • Equipment Traffic.

Employee traffic patterns that do not spread contamination involve wash stations at critical points. Certainly if an employee is moving from a high-risk area (raw product) to a low risk area, wash stations with buffer zones need to be used. Where possible, separate employee groups should be used for the high risk and low risk zones. If this is not feasible, then employees should be required to change foot wear and gowns when moving from high risk to low risk areas of the plant.

Equipment traffic patterns have the potential for a high degree of contamination risk. It is pretty obvious that forklifts or pallet jacks, handling material from a high risk zone, can carry contaminants to a low risk zone. Personnel can then transfer these pathogens by handling the transported material. However, the greatest risk factor are the wheels on this equipment, especially the fork lifts. If a forklift is traveling through a high risk area that contains moisture on the pavement, the wheels can propel droplets (aerosols) into the air. Airborne pathogens are, without a doubt, the worst case scenario a food safe environment can experience. Of course the answer to this scenario is limit forklift traffic patterns; stop high-risk zone forklifts from travelling to low risk zones. Good answer but not always practical.

Here is where Airlocks play an important role in Food Safety Management. Airlocks consist of room enclosures that connect two rooms. A typical enclosure for equipment movement and employee movement would measure 8’ wide, 16’ long and 10’ tall. On each end of the enclosure are quick acting roll up doors. On the roof of the enclosure is a supply fan with a MERV13 or as high as a MERV17 filter. The supply fan pressurizes the enclosure with clean air. A fork lift bringing product into a low risk room would enter the airlock, drop off the product in the airlock. A forklift from the low risk room would pick up the product from the airlock and place it in the room.

The diagram below shows a typical example of an airlock for forklifts and personnel traffic:

• 1. HVAC

The HVAC aspect of Food Safe Manufacturing is another very important category. We refer to it as “the invisible contaminant.” Contaminants that float in the air are most times micron and sub-micron sized particles which make them pretty much invisible to the naked eye. As a result, special design considerations must come into play to keep food manufacturing facilities safe from airborne contaminants.

The following schematic will show proper airflow patterns that are necessary to maintain a food Safe Manufacturing environment:

The schematic above shows various risk zones for food manufacturing facilities. The highest risk zone (red) is where the raw food product enters and the lowest risk zone (blue) is where the product is finished, packaged and ready for shipment to the consumer. As the diagram above shows, we recommend introducing fresh makeup air, filtered of course, into the lowest risk zone and cascading the fresh air through the building using transfer fans instead of ductwork. The makeup air is then transferred to the moderate risk, then to moderate to high risk zone and then finally to the highest risk zone and exhausted to atmosphere (assuming there are no seeable particulates or VOC’s. in the air streams.) The overall scene of system design is to maintain airflow through the facility in the opposite direction of product flow.

The transfer fans in the diagram show a + and – on each side of the fan. The room that has the + designation will have a positive air pressure condition relative to the room with the – designation. This is controlled by using a pressure sensor in each room that controls the speed of the fan by the use of a variable frequency drive (VFD) on the fan motor. The positive air pressure condition needs to be maintained to ensure that aerosol contaminants do not migrate through wall openings or doors from the higher risk rooms to the lower risk rooms.

Another item that is on the high priority list is the use of transfer fans versus ductwork for supplying makeup air and exhaust of contaminated air. Our field experience shows that any enclosed, dark, hard to clean area in a food manufacturing facility leads to growth and spread off contaminants. Ductwork (even stainless steel) fits this description quite well. This is why we recommend transfer fans for air movement. In some cases, ductwork has to be used; process exhaust is one of those cases. In one recent application, there was an incident at a brand new manufacturing facility and our recommendation was to remove a couple thousand feet of ductwork and install transfer fans; it had to be done. Most large food manufacturing facilities have multiple floors and transferring air from room to room is easy with wall fans. How do we recommend transferring air floor to floor? See the picture at the right; that works and itis still quite easy to clean if it is installed correctly.

Air filtration is probably at the top of the priority list for HVAC system design in any Food Safe Manufacturing facility today. The other significant design flaw we see with air handling units is that the filtration is on the inlet of the unit only. This approach has pretty much been accepted for years and even today; the new units being installed only have filtration on the inlet. New research going on today highly recommends having filtration on the inlet and the outlet as follows: MERV 12 on the inlet and a MERV 17 on the outlet of filtration systems. This definitely applies to air handling units that recycle air for heating and cooling, however, it is highly recommended for air handling units that bring in 100% of its air from outside. The reason this has become important is that the air handling unit is an enclosure that can contain moisture; and both cooling units and heating units can contain moisture. The moisture is an important part of growing, for example, salmonella. In a food production area in a facility, cleaning and sterilizing is done consistently and daily. How often, however, have we seen the cleaning crew go inside of an air handling unit? Not often! Contaminants can start to grow inside the air handling units, and be picked up and blown back into the production facility. And just a note, salmonella can be airborne, along with many other types of contaminants. As a summary; a filtration system should be on the inlet and outlet of any air handling system within a food production facility.

A design technique that we use to improve plant ventilation and save operating costs in a Food Safe Manufacturing facility is called “cascading makeup air supply.” The following two diagrams demonstrate the technique:

The above diagram shows a typical makeup air installation. The placement of the makeup air units (in this case 50,000 cfm each) are located in each section of the building structure. If this facility was located in the northern part of the US, the operating costs for natural gas alone at $0.50 per therm would be $212,284 per year (based on a room temperature of 680F.)

The above diagram demonstrates a cascading airflow design. Two of the 50,000cfm units are located in the cleanest part of the facility and transferred to the second and third sections using transfer fans. The key to this design is that the makeup air is used two or three times before it is exhausted to atmosphere. This design is food safe since we are transferring the makeup air from the cleaner rooms to the less clean rooms. The operating cost for natural gas only would be $127,370 per year. There are additional savings based on initial capital cost. If the price for 1- 50,000cfm makeup air, with HEPA filtration, installed would be $100,000, the initial capital cost savings would be $200,000 for the cascading airflow design.

The dollar savings summary for the cascading design technique would be as follows:

Whitepaper by:

David Swinehart

Controlled Environment