The Tank Blanketing Technique

Tank blanketing, also known to as tank padding, is the procedure of smearing a gas to the empty space in a storage tank or container (the term storage container refers to any container that is used to store products, regardless of its size). This techinique is used for a variety of reasons and typically involves using a buffer gas to protect products inside the storage container. Some of the benefits of blanketing include a longer life of the product in the container, reduced hazards, and longer equipment life.

Control board Pressure regulator Flow switch Magnetic level control Pressure / Vacuum Relief Valve

History

Appalachian Controls Environmental (ACE) in In 1970 was the first company to announce a tank blanketing valve. There are now many ready-made systems available for acquisition from a diversity of process equipment companies. It is also possible to piece together your own system using a variety of different equipment. Regardless of which method is used, the basic requirements are the same. There must be a way of allowing the blanketing gas into the system, and a way to vent the gas should the pressure get too high.

Since ACE introduced its valve many companies have engineered their own versions. Though many of the products available vary in features and applicability, the fundamental design is the same. When the pressure inside the tank drops below a set point, a valve opens and allows the blanketing gas to enter. Once the pressure reaches the set point, the valve closes, as simple as that.

As a safety feature, many systems include a pressure vent that opens when the pressure inside exceeds a maximum pressure set point. This helps to prevent the container from rupturing due to high pressure. Since most blanketing gas sources will provide gas at a much higher than desired pressure, a blanketing system will also use a pressure reducing valve to decrease the inlet pressure to the tank.

Practices

The most popular gas used in blanketing is nitrogen; it is widely used due to its inert properties, as well as its availability and low cost. This system is used for a diversity of products including cooking oils, flammable products, and pure water. These techniques also cover a wide variety of storage tanks, ranging from as large as a tank containing millions of liters of vegetable oil down to a quart-size container or smaller.

The use of an inert blanketing gas for food products helps to keeps oxygen levels low in and around the product because the product help to reduce the amount of oxidation that may occur, and increases shelf life. In the case of cooking oils, lipid oxidation can cause the oil to change its color, flavor, or aroma. It also decreases the nutrient levels in the food and can even generate toxic substances. Tank blanketing strategies are also implemented to prepare the product for transit (railcar or truck) and for final packaging before sealing the product.

When considering the application for flammable products, the greatest benefit is process safety. Since fuels require oxygen to combust, reduced oxygen content in the vapor space lowers the risk of unwanted combustion.

Tank blanketing is also used to keep contaminants out of a storage space. This is accomplished by creating positive pressure inside the container. This positive pressure ensures that if a leak should occur, the gas will leak out rather than having the contaminants infiltrate the container.