A Brief History of LN Injection
One of the earliest applications of liquid nitrogen dosing systems for pressurizing containers was developed by Reynolds Metal Company in 1982. A machine was developed that could inject predetermined amounts of cold liquefied gas into noncarbonated beverage cans just before they were sealed. This action pressurized the cans and added mechanical strength against collapse from stacking weight.
Shortly thereafter, Toyo Seikan Kaisha Ltd. developed a similar system. That system dropped liquefied gases into cans with the aid of a can-proximity sensor. The droplets of liquid nitrogen were released into the cans from a control valve and reservoir directly above. The reservoir atmosphere was allowed to pressurize, and the nitrogen vapors were directed coaxially with the liquid nitrogen droplets in a shield-gas flow to reduce nozzle freeze-up and clogging with ice from normal room humidity.
In 1989, Thornton Stearns, working for Vacuum Barrier Corp., added the sub-cooling of liquid nitrogen to the injection process. When controlled amounts of liquid nitrogen were added to uncapped containers moving on an assembly line, the immediate flashing to gas was prevented by making sure the liquid nitrogen was cold enough to stay a liquid at atmospheric pressure given its inherent vapor pressure.
Then, in 1998, Vacuum Barrier Corp. released for production an apparatus that located the vacuum-insulated liquid nitrogen reservoir up and away to one side of its dosing injector head. That advance permitted the dosing injector head to be mounted above a beverage canning assembly line. The reservoir was located behind the assembly line and was elevated enough to create a modest hydraulic pressure head at the control nozzle in the dosing injector head.*
Since 1998, other evolutionary changes have taken place principally with liquid nitrogen injection controls and nozzles. These improvements have resulted in better pressurization control and consistency of dosing.