Condensation on walls, ceilings, and pipes. These are operating conditions in a refrigerated processing facility.
At least, that often was the case before USDA started emphasizing the contamination risks posed by moisture. “Until five years ago, the [focus and] emphasis for refrigeration engineers was only on temperature,” notes Chuck Taylor, senior vice president of The Stellar Group (https://www.stellar.net/), Jacksonville, Fla. “That has changed. Today, USDA will shut down a plant for condensation problems.”
For several years now, USDA has been enforcing long-standing but seldom observed rules on condensation control in refrigerated facilities.
Why the sudden change? In the past, enforcement had been impractical because moisture in many food plants, particularly refrigerated facilities, was extremely difficult to manage.
“We are literally trying to defy the laws of physics in processing plants by trying to maintain a cold room and, at the same time, control a big latent moisture load,” explains Taylor.
But food safety is a growing concern. Furthermore, moisture problems may be increasing in food plants. To reduce bacterial growth, processors are operating their facilities at lower temperatures, driving up energy costs and humidity challenges simultaneously.
“In all food plants, condensation off any part of the building or pipes is a no-no because of potential contamination from drippage onto product,” says Roland Leavens, vice president of food processing systems for Food Facility Engineering (http://www.foodfacility.com/), Yakima, Wash.
Beads of moisture can become drips of contamination, with the condensation carrying dirt, microbes and other contaminants. At best, condensation poses a threat to product quality and, at worst, it could lead to consumer illness and a major recall. Moisture will also cause rusting and other damage to the facility structure.
That standard industrial refrigeration equipment can control humidity is a mistaken notion, Taylor maintains. The problem stems from the very nature of the processing plant. Mix hot water, moist carcasses, warm-blooded operators and process heat into a 40°F processing environment, and moisture will accumulate. Guaranteed. The moisture the air cannot absorb results in condensation.
“A standard refrigeration unit simply can’t control the water coming off the carcasses, equipment, etc.,” Taylor goes on. “The air won’t have the capacity to absorb more moisture until the air is warmed, and that is not likely to occur until the clean-up shift.”
Condensation means more than slippery surfaces and wet pipes. It can mean big trouble on the food safety front.
The standard solution won’t cut it
Condensation in a processing plant is a complex challenge with multiple components: temperature, moisture, pressure and filtration.
“We don’t even call it condensation control anymore,” says Taylor. “We call it psychrometrics.” The term refers to a relatively obscure branch of science – the science of moist air – that is becoming better known to processors by the day.
A greenfield plant today should include systems that deal directly with the conditions, equipment and materials creating or influencing moisture within the facility. To contend with moisture problems in an existing plant, begin with an air balance study.
A study typically starts with analysis of how air is moving in and out of the plant. This is followed by the introduction of a device to record the temperature, pressure and humidity within the plant over a 48-hour period.
“You need empirical data to have a complete idea of what is going on,” says Taylor.
Sanitation often is the primary, even sole, source of the problem. After two eight-hour processing shifts in a cold environment, the introduction of hot water during the clean-up shift is bound to upset the moisture balance.
“All processing plants are trying to ‘sweat the equity,'” says Taylor. “They want to run the equipment as long and fast as they can for two shifts. They would stretch it to three shifts if they could, but they must clean the plant. When the cleaning shift hoses down with 140° water in a plant that has been operating at 40° temperatures, you have humidity everywhere. The solution may mean pulling in outside air, conditioning the air to 50° and re-heating the air to 80° and pushing it into the room. Then exhaust the air from the room. Hot air can absorb more moisture.”
“Washdown is a challenge,” echoes Leavens. “The walls are cold, but you are using hot water. You need air flow that avoids fog and heavy condensation.”
Still, many different scenarios can play out within the almost endless mix of variables in food plants. Heating rooms is easy. Getting moisture out can be difficult. The constant generation and movement of hot air and cold air creates countless opportunities for condensation and associated airflow challenges.
Bakeries require vapor barriers to prevent condensation caused largely by oven exhaust and the moisture given off by baked product.
An IQF freezer poses a different challenge, yet the same principles apply. “A nitrogen freezer is a tunnel,” says Leavens. “A plant has to exhaust the nitrogen. You must make up for the cubic feet of nitrogen being exhausted.”
One guiding principle suggests leaving no cold pipe exposed in an area where warm air can cause condensation to occur. Pipes may require insulation with a PVC covering and a sealed vapor barrier. This is particularly important during washdown. If warm moist air gets to the pipe, it may leak through the insulation.
“Each project must be looked at from the standpoint of temperature requirements, people requirements and humidity requirements,” says Leavens.
“On the modern cut floor, the air may be changing every 2-1/2 minutes,” says Taylor. “If you have a source of contamination, it will be easy to spread. But if the air is properly filtered, you can scrub the air, filter out bacteria. You are sanitizing the room. So filtration is an important part of psychrometrics, too.”
Controlling condensation can be especially difficult in a plant constructed before the department began its crackdown on condensation.
Plants typically have attempted to resolve condensation problems either with fans to draw warm air in or with exhaust fans to pull cold air out. But this creation of negative air pressure also can lead to condensation and assorted problems. In most cases, solutions require some type of dehumidification technology.
“In a refrigerated process area, you need to cool the air, but you also need to have air changes to meet employee requirements,” says Leavens. “You need outside air, but it must be chilled air before it enters the room or you will create clouds and condensation and drippage.”
Neither fans nor conventional refrigeration units will control humidity. The job generally falls to workers performing proper maintenance and taking the appropriate safety measures.
Regular removal of condensation from ceilings and pipes is a practice that needs to be in employed in all food processing facilities regardless of what other measures might be in place to curb the problem. Inevitably, moisture will collect in certain areas where conditions allow, and even if these areas are kept to safe proximities, the beaded water will begin to flow into unsafe zones increasing the risk of contamination.
Solution: Removal of moisture from ceilings, pipes, or any hard-to-reach surfaces can be accomplished with the proper squeegee system. Some manufacturers offer specialized water-collecting squeegee heads which are designed to capture moisture and drain it safely into a collection bottle. Demo: http://amerisan.com/condensation-squeegee/
Many engineers also prescribe supply fans running on variable frequency drives in the ambient area of the plant. A pressure sensor in the room can be effective in controlling air pressure, reducing the need to draw ambient air.
Count on one constant: every situation is different.
Ironically, the psychrometric principles that are solving condensation problems in refrigerated facilities today have been long employed by HVAC engineers. Why there hasn’t been more rapid carryover into cold processing engineering is puzzling to many, but, as they say, better late than never.
Today’s engineer must understand the tools available to apply the appropriate solution to a moisture or condensation problem.
Whether you are building a new facility or attempting to solve a moisture problem in an existing plant, understanding the dynamics of airflow, heat and humidity of your process and plant will be critical to containing condensation and moisture problems.
For an effective solution, see Amerisan’s hygienic condensation squeegee now in stock: https://www.amerisanusa.com/productdetailI2.aspx?dataid=K48420%2fB