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When some items are stored, they must be protected from the air to prevent damage or a chemical reaction with the oxygen. In order to protect these items, they are often covered, or blanketed, with a layer of gas that keeps oxygen away from them. This process is called tank blanketing, and is often used in the food industry and to protect flammable products.
The gas most often used in tank blanketing is nitrogen. A layer of nitrogen is added to the empty space in a storage container, effectively blanketing the contents from the air and protecting them from moisture. Nitrogen is used because it is an inexpensive, inert gas that can be used in nearly all situations without causing a reaction with the contents of the storage container.
Tank blanketing is common in the food industry, and is used to help to preserve products and give them a longer shelf life. In some cases, such as with cooking oils, exposure to oxygen destroys the flavor and overall quality of the oil. The application of nitrogen prevents the oxygen from coming into contact with the oil, preserving its value as a food product.
In some cases, the nitrogen not only protects the product by preventing oxygen from reaching it, it also is used to protect the contents of storage containers against leaks that might allow other contaminants into the system. This is done by creating a tank blanket that has a positive pressure. If the container should happen to spring a leak, the pressurized nitrogen pushes out of the leak, preventing anything from coming in. This technique is used on anything that must be kept clean, such as purified water.
Flammable products are also stored in containers that make use of tank blanketing. For items that are at risk of exploding or bursting into flames, tank blanketing is used as a safety device that effectively protects the product, the facilities and the workers. The layer of nitrogen ensures that no oxygen can reach the product and possibly result in a fire or an explosion.
The process of tank blanketing was formerly carried out by hand. A control valve was developed in 1970 that allowed for filling and monitoring of the gas that was introduced into the system. Such valves are now an industry standard. Valves allow the blanketing gas to be introduced into the tank and provide a means for it to escape should the internal pressure get too high. This adds safety to the storage system, typically without the need for human intervention.