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Oxidation is a chemical reaction where a substance, surface or product reacts with atmospheric oxygen in the surrounding air. This can have many undesirable outcomes, including unwanted chemical reactions, the risk of explosion, metal embrittlement and degradation of quality, especially in the case of foodstuffs.
The main aim of inerting is to prevent oxidation by controlling or minimizing the level of oxygen in a given space. The basic principle entails fully or partially replacing the air around or on top of a product with a dry, inert gas. This forms a protective, safe layer of gas on the substance, preventing oxygen and/or moisture from coming into contact with reactive or absorptive products. In addition, inerting can be used to dispel flammable or poisonous gases. An inert atmosphere is particularly important when storing highly volatile substances or products prone to oxidation.
Oxidation attacks on food, for instance, can take place at or below ambient temperatures (i.e. during normal storage of beverages, oils, fruit or finished products). But it can also occur at elevated temperatures, such as during processing or deep-fat frying. Other common industrial processes such as welding, brazing and sintering are also prone to the adverse effects of oxidation at elevated temperatures.
What industries rely on inerting?
Many industrial processes rely on inert or modified atmospheres to protect against unwelcome reactions, keep moisture away from sensitive substances, control critical reactions and ensure safety during maintenance work. These include refining, basic chemistry, petrochemistry, the manufacture of specialty and fine chemicals, metal fabrication and welding, heat treatment, food and beverages, (additive) manufacturing and water treatment.
In the food industry, for example, inerting is typically used to keep oxygen levels in and around food products low. An inert or modified atmosphere also stabilizes the product and increases shelf-life. Looking at the chemical industry, reactors, stirring tanks, centrifuges, vacuum filters, grinding and mixing plants, dryers and filling facilities are all often inerted. Mines and silos also rely on inert gases for enhanced safety and fire protection. Many heat treatment furnaces purge flammables, oxygen and water from the furnace for safety reasons and to avoid oxidation of the part being treated. In a more general sense, inerting is also essential for purging pipes and vessels during maintenance and repair work on industrial plants.
What gases are best for inerting?
Nitrogen is the gas most commonly used for inerting. Less frequently, carbon dioxide or – in exceptional cases – argon may also be used. Special industries or applications rely on bespoke inerting mixtures. In welding, for instance, shielding gas mixtures combine argon with hydrogen, carbon dioxide, nitrogen and helium. By comparison, modified atmospheres for food generally rely on gas mixtures combining carbon dioxide, nitrogen and oxygen with other gases such as nitrous oxide, argon and hydrogen. Heat treatment furnaces typically deploy nitrogen, argon, hydrogen and other gases.
To find out more about the different inerting methods and their range of applications, read our ebook.
Help from Linde
We deliver individual gases and bespoke mixtures to fit all inerting challenges – from welding through refining to food packaging. These range in purity from industrial up to food grade. In addition, we have developed a number of innovative gas delivery solutions to give manufacturers precise control over inert atmospheres in production environments. Our inerting equipment extends from measuring and metering stations for secure gas supplies to special inert gas valves and injection nozzles. For vessels used in batch processes, which are filled and emptied on a regular basis, we have also developed special inert gas sluices, which effectively prevent the entry of oxygen into filling systems.
Linde engineers have pioneered many process innovations to increase the efficiency of inerting, blanketing, purging and sparging applications. Simply click on the processes below to discover how we can tailor the composition of your gas atmosphere to your precise safety and productivity goals.
Alternatively, speak to one of our experts.