Tank blanketing is also referred to as tank padding, and it describes the process of applying an inert gas to the vapor space (or unused space) that exists above the chemical inside a storage tank. Tank blanketing is mainly used to add a layer of gas (usually nitrogen) to keep air or moisture from a chemical inside the tank. Since water and oxygen can degrade some chemicals, a nitrogen blanket may help increase the life of that chemical.
The Benefits of Tank Blanketing
Reducing the amount of oxygen in the vapor space of a chemical storage tank reduces the risk of any sort of explosion when storing combustible chemicals, since air is needed for fire to burn. Oxygen and moisture can corrode the tank when they react with the tank’s contents, as well. Certain materials, like food-grade chemicals and pharmaceuticals, are susceptible to degradation when exposed to O2 and H20, so blanketing protects them and keeps them from spoiling. Edible oils, for example, can be spoiled by reactions with air which compromises the oil’s stability. When edible oils are exposed to water, a chemical reaction occurs that alter the oil’s properties unalterably.
Nitrogen is an inert gas, which means that it does not react with most substances. It is widely available and less expensive than other gases, like argon, which can be ten times as expensive as nitrogen. Carbon dioxide is used in some cases, but it is a more reactive gas than nitrogen.
Over pressurization of a polyethylene storage tank can result in loss of tank contents. Best practices, in the pressure control method, include installing a safety valve or rupture disk as a precaution in the event of a valve or pressure sensor malfunction. Cylindrical polyethylene storage tanks should never exceed a 6 inch water column or .36 psig, or else you risk loss of contents.