Successful food production is largely dependent upon cold temperature control of the product through storage, processing and shipment. Though a food product may only be harvested once a year, the food manufacturer must be able to sell the product continuously, Manufacturers depend upon reliable cooling systems throughout the entire process to ensure success.
Cooling system designs used in the food-and-beverage market are undergoing rapid change, mainly due to environmental regulations. Regulatory goals are aimed at reducing refrigerant charge or eliminating certain types of refrigerants completely.
Consequently, more end-users and general contractors are thinking long term when designing refrigeration and cooling systems for new builds. They want any new systems to comply with current regulations and accommodate anticipated regulations in the future. The common goal is an environmentally friendly plant with zero ozone-depleting potential (ODP) and global warming potential (GWP).
Options for Refrigeration in Cold Storage Facility
As a result of this goal, companies have migrated toward use of natural refrigerant gases such as ammonia (NH3), or R717, or propane gas for cooling instead of man-made Freon gas. This has been a step in the right direction.
Further progress beyond that is now being made with safer choices in both coolant type as well as piping material. One of these alternatives is the use of secondary refrigeration systems. These systems reduce the amount of the primary charge (Freon gas, ammonia, etc.) in a plant by about 80 percent by using a safer secondary coolant as the predominant means for cooling throughout a plant.
Leaks in standard refrigeration systems in metal piping systems can be as high 35 percent of the original charge per year. This is damaging to the environment and presents a safety hazard. It also is costly to refill the system. Secondary cooling systems can offer higher safety, lower refill costs, higher temperature stability and control, lower maintenance costs and environmentally friendly characteristics.
Tasteful Selections LLC, a specialty potato grower and potato processing company in Bakersfield, Calif., faced a myriad of choices when company executives decided to move its fast-growing business from a leased building to a much larger, new 200,000 ft2 plant.
According to Nathan Bender, co-owner and operations manager of Tasteful Selections, “The new build gave us the opportunity to start with a blank page and design a cooling system that was completely safe for our employees as well as our products. At our previous leased location, about 75 percent of our cooling system was ammonia. This posed a huge safety threat to our employees as well as our products. If you hit one of those pipes, you’re dead… there’s no going back from that.”
Says the potato producer, with so much of the building having ammonia piping, the chance of a leak or the risk of hitting a pipe or other system malfunctions weighed heavily. “We were constantly on the alert for pinhole leaks caused by corroding metal pipes,” says Bender. “We really wanted to get away from this type of hazard at our new plant. That was the biggest decision we made — we just didn’t want the risk of having ammonia through our whole facility.”
Operating in this type of environment, the company would hold regular meetings to be prepared for any ammonia accident. On top of that, it was necessary to repaint corroding pipe areas every so often and have the pipe X-rayed to make sure there was not any corrosion inside.
Tasteful Selections’ vision for its new plant was one that would provide safety using technology for improved temperature control throughout the facility. The company executives also wanted any design to allow for future expansion while keeping regulatory compliance in mind.
The executives tapped Techmark Inc., a technology solutions provider of computerized ventilation systems used in food and agricultural applications for their primary contractor on the HVAC system. The system Techmark proposed turned out to be spot on for Tasteful Selections.
According to Todd Forbush, vice president at Techmark, “We saw this as an opportunity to design a system that helped with power savings over other direct-expansion type systems as well as an opportunity to isolate the refrigerant from the workspace and the product. The goal was to keep the refrigerant levels low, so there wouldn’t be as much as there is when you’re plumbing a whole facility with refrigerant. The second goal was to confine and maintain the refrigerant in the machine room and condensers to keep it out of the real workspace.”
In this system design, ammonia would be used in a limited area of controlled space — the machine room, receiver and condensers — to chill nontoxic, food-grade liquid glycol. Then, the chilled glycol would be pumped and conveyed via pipe throughout the plant to provide the proper cold temperature level for each area. The secondary refrigeration system served the storage area where the potatoes were kept, for up to several months, in preparation for processing, the processing area and the finished product area. The entire facility would be temperature controlled using glycol. In addition to proper cooling, Techmark’s design also included special rooms and systems to control airflow and humidity to allow for the potatoes’ sensitivity to these elements.
“By using indirect or secondary cooling, we were able to isolate the refrigerant from the workspace, accomplishing two very important things,” says Forbush. “It keeps the refrigerant level low, and it confines the refrigerant to a controllable area.”
With new regulatory requirements, keeping refrigerant levels as low as possible limits the environmental exposure. Local ordinances vary, but the amount (in pounds) of refrigerant that is on the site determines the level of government regulations that apply and also changes the exposure to the environment.
“Handling refrigerant is a regulated process,” Forbush says. “If you can reduce the total amount of refrigerant used in any cooling system, it’s going to help meet local ordinances and regulations. With Tasteful Selections’ new HVAC system, changing to glycol secondary cooling made a huge difference. The whole 200,000-square-foot plant has piping filled with liquid food-grade glycol.”
In addition to the environmental compliance issues resolved by using glycol, any system leak would pose little environmental risk and little risk to personnel or product. At Tasteful Selections, where personnel labor, product is stored and where potatoes are processed, primary refrigerant is not used. Liquid cooling delivers the cooling in all of those areas.
Techmark used a subcontractor for the next step of the project: specifying and designing the piping system to be used. California Controlled Atmosphere (CalCA), a design-build industrial refrigeration contracting firm was called in because Techmark was familiar with their expertise. CalCA specializes in large-scale plant design.
Historically, piping refrigerant systems used for cold storage and cold processing in food manufacturing plants have been welded steel or other types of metal, which would be post-insulated on-site. The quality of the insulation used in terms of energy efficiency was difficult to evaluate. Damaged or incorrectly installed insulation allowed condensation and moisture penetration. This caused energy losses, dripping and corrosion of the metal, which compromised the operation. Condensation could drip onto the food being stored or processed and cause contamination and product loss.
Additionally, metal piping is susceptible to corrosion from caustic chemicals like ammonia, causing leaks requiring sometimes costly maintenance. Metal pipe also is heavy and can be cumbersome to install or maintain in overhead installations.
“When we became involved in the job, it had already been decided to use nontoxic, food-grade propylene glycol instead of ammonia for the coolant in the secondary cooling system of their new building,” says Jay Kliewer, president of CalCA. “With glycol already selected for the coolant, this gave us more choices for piping selection.”
Kliewer was familiar with a preinsulated piping system used food cooling and thought it would be suitable for Tasteful Selections’ new plant. Ryan Herco Flow Solutions, a distributor for GF Piping Systems, had introduced Kliewer to the GF's Cool-Fit preinsulated ABS pipe and fittings.
“By using the plastic piping system, we could eliminate the difficulty of installing heavy metal pipe. And because frictional pressure losses in the plastic are lower than in steel, we were able to use smaller pipe sizes, which saved not only on pipe cost, but also saved space and installation time.”
The final design and installation included more than 3,000’ of preinsulated ABS pipe and fittings throughout the whole Tasteful Solutions’ plant. The preinsulated system prevents condensation, reduces on-site installation time compared to metal and increases the efficiency of the refrigeration system.
Having the ammonia contained in a small, controlled area of the plant also brought other advantages. With the much lower level of ammonia refrigerant now used by Tasteful Selections, they are below the regulatory level requiring additional safeguards such as 24-hour security monitoring and the need for several ammonia-certified staff members.
When the glycol and all-plastic system was proposed to Tasteful Selections, company executives were immediately sold. “With a food-grade glycol in a plastic piping system, with most of it overhead, if there were a leak, or if someone were to hit a line, it’s going to be water, air or glycol,” says Bender. “It’s still an accident, but not a life-or-death accident. The glycol system has really given everyone here more peace of mind. In addition to the safety benefit of using glycol, we were also able to take advantage of the plastic piping. Its lighter weight made for easier installation and there was no need to beef up the roof structure to carry the load. So we saved on installation and construction costs. And with the plastic pipe, it’s out of sight and out of mind. We don’t have to worry about corroding pipes, repainting or having the pipe X-rayed.”