Plant managers and production managers in large facilities that produce a high volume of noncarbonated beverages — such as water, juices, teas, coffee products, energy drinks, and more — face an increasingly challenging production environment.
At the same time that production volumes and line speeds are increasing — as fillers are getting faster and faster — the number of SKUs is growing. This is because beverage companies are offering more flavors and sizes with different container form factors — meaning more changeovers. Yet, despite the increase in volume and changeovers, managers are under more pressure than ever for high levels of uptime and high reliability.
Liquid nitrogen remains the industry standard
Originally developed in the 1980s, liquid nitrogen dosing is not a new technology. But its widespread use in noncarbonated beverages, as well as for some food products, has never been more important.
Used primarily for pressurizing a container to add stability and for inerting food, the benefits of liquid nitrogen are that it is abundant, easy to handle, efficient to use, relatively inexpensive, and safe.
To get the most out of liquid nitrogen, it is important to keep the following best practices in mind.
Use the right equipment, especially nitrogen dosing equipment
Handling liquid nitrogen on a production line poses challenges, whether pressurizing or inerting food or beverage containers. Liquid nitrogen has a boiling temperature of −320°F (−196°C), and will rapidly boil away when exposed to room temperatures.
Therefore, insulated equipment must be used to ensure efficiency and safety. This equipment includes an injection device capable of metering small doses of liquid nitrogen into food or beverage containers, storage vessels, or tanks, and piping to transport the liquid nitrogen to the injection location.
The equipment’s common feature is vacuum jacketing. This is a double‐wall construction with inner and outer walls separated by a vacuum space which provides insulation between the cryogenic temperatures inside and the ambient temperature outside, allowing the outer surface to remain at ambient temperatures. This vacuum space greatly reduces heat losses, making the pipe efficient.
Typically called a “doser,” nitrogen dosing equipment is the main component of a liquid nitrogen system. It’s often what production facilities are most interested in as the doser directly affects facilities’ ability to meet pressurization or inerting goals and must operate frost‐free and efficiently during dosing or idle times.
The reliability of a doser on a production line is very important as losses are calculated in minutes of downtime. As with any cryogenic device, internal exposure to moisture must always be limited, as it’s a doser’s biggest enemy. Care must be taken during nozzle changes and maintenance to prevent contamination by moist air. In certain industries, there may be a requirement that the liquid nitrogen be delivered aseptically, and therefore, the unit must be capable of being sterilized.
The exterior design of the doser is important. It should be sleek without crevices that can lead to contamination. The doser and cables should withstand chemical washdown, and heater blocks should eliminate moisture ingress.
Use dosers that can help you meet ambitious production goals
Aside from operating frost‐free, a doser must also meet the goals of the production facility. Any bottling or canning operation will look for consistent pressurization or inerting of their containers. This requires the doser to consistently output an accurate dose of liquid nitrogen, whether dosing discretely or steady‐streaming. Too small of a dose can lead to unstable containers and the possibility of collapse. For inerting processes, this could lead to food spoilage. If dosed with too much nitrogen, there is a risk of containers bulging or bursting, which could cause jamming and downtime.
The challenge for the dosing equipment is to reliably and accurately control the liquid nitrogen dose for each container up to speeds of 2000 bottles per minute. For the production goals of pressurization to be met, a doser relies on consistent fill heights from the filler. Even a small change in fill height can lead to under‐ or over‐pressurization.
The doser does have the ability to adjust to changes in line speed of the filler. As the line ramps up or down, timing is adjusted automatically to ensure each dose enters the container. Likewise, dose compensation adjusts the amount of LN₂ dispensed as the line speed changes.
Modern servo technology incorporated into dosers allows for much finer control of LN₂ dosing. Precise metering can be achieved in both steady stream and single dose operation, through simple parameter adjustments on the control panel. Quick “on the fly” adjustments reduce or eliminate the need for mechanical nozzle changes, which limits downtime during production changeover.
Servo actuators are robust and reliable, allowing for billions of cycles of operation without required maintenance, which saves on downtime and replacing wear items.
Other factors on the production line must also be considered to ensure proper pressurization:
- Travel time from the doser to the seamer or capper should be minimized to prevent excess boiling or loss of nitrogen.
- Shaking or bouncing containers on the conveyors can force nitrogen and product out of the package before closure.
- Reliable sealing closures are needed to maintain the pressure within the container after dosing.
Developments in heater block design allow for servo technology to be fully realized among a wide array of beverage products and container form factors. These heater blocks can provide additional nitrogen gas purging capabilities to help limit freeze‐ups during/after washdown cycles, or in hot‐filled products with lots of humidity. Other heater blocks enable discrete or steady streaming into very low headspace containers, commonly cans at high speeds, which is critical for maintaining tight can pressure tolerances.
Make safety a top priority
Addressing workers’ and machine safety when dealing with liquid nitrogen is essential.
When boiling from liquid to gas, nitrogen expands roughly 700 times. Safety relief valves (SRVs) are installed on tanks, piping, and dosers to prevent over-pressurization and potential equipment ruptures. Where there are shut-off valves in a system, there is potential for nitrogen to be trapped. A safety relief valve must be placed between any two such valves.
On bulk tank‐fed systems, the lowest‐rated relief device typically is placed outdoors. If a safety relief valve does relieve, it is safer if it happens outdoors rather than inside where workers are present.
Modern codes dictate that safety relief valves must provide a means of routing gas to a safe location outside of the building in order to reduce asphyxiation risks. When located inside of a production facility, cryogenic equipment should be equipped with inline or “pipe‐away” SRVs.
Conclusion
In today’s demanding high‐speed production environment, managers have their hands full. But with a sound approach and use of best practices, managing liquid nitrogen doesn’t have to be a challenge. The keys include having the right nitrogen dosing equipment, using modern servo technology, considering other key factors on the production line to ensure proper pressurization, and ensuring safety with properly placed safety relief valves. When used properly, liquid nitrogen provides a host of benefits, including ease of handling, efficiency, cost efficiency, and safety — and the challenges can be overcome.
