DOT (Department of Transportation) is the federal regulatory agency that oversees the manufacturing, handling, and transport of oxygen cylinders used in aviation. There are three types of oxygen cylinders approved for aviation use by DOT.
The DOT 3AA (3A) cylinders are made from aluminum and have a service pressure of either 1800 or 2100 pounds per square inch (psi). The 3AA cylinders are commonly used in general aviation and have a white label.
The DOT 3HT cylinders are made from steel and have a service pressure of 1850 psi. These cylinders are heavier and more durable than the 3AA cylinders, and they are often used in commercial and military aircraft. They have a green label.
The DOT-E8162-185 cylinders are also made from steel and have a service pressure of 1850 psi. These cylinders are commonly used in military aircraft and have a yellow label.
According to the Federal Aviation Administration (FAA) regulations, oxygen cylinders used for aviation purposes must be painted green to distinguish them from other gas cylinders, and to indicate their contents. The words “aviator’s breathing oxygen” must be stenciled or printed on the cylinder in white lettering that is at least 1 inch high. This helps to identify the cylinder as containing oxygen that is safe for breathing by pilots and passengers in aircraft.
The green color and labeling also help to prevent confusion with other gases that may be dangerous or incompatible with oxygen, as well as to ensure that the correct type of oxygen is being used in aviation systems. It is important to follow these labeling and marking requirements to ensure the safety and well-being of pilots, passengers, and crew members.
It’s important to note that the different types of cylinders have different requirements for inspection, testing, and maintenance. Oxygen cylinders must be handled and maintained according to DOT regulations to ensure safety and reliability.
Cylinders must be tested every couple years
DOT 3AA, DOT 3HT, and DOT-E8162-185 oxygen cylinders are subject to strict regulations to ensure their safety and effectiveness. The Department of Transportation (DOT) sets these regulations to make sure that the oxygen cylinders meet specific criteria related to strength, quality, and performance.
One important aspect of these regulations is the requirement for testing and requalification of the oxygen cylinders. DOT 3AA cylinders must be tested every 5 years, while DOT 3HT and DOT-E8162 cylinders must be tested every 3 years. The testing process involves a thorough inspection of the cylinder’s integrity, including the threads, neck, and base, as well as the valve and pressure relief devices. The cylinder is also subjected to a hydrostatic test to ensure it can safely withstand its rated pressure. Once a cylinder has passed its inspection and testing, it is stamped with a date indicating when it was last tested.
If an oxygen cylinder fails a test, it cannot be used until it is requalified or replaced. This is done to ensure the safety of the passengers and crew who rely on oxygen during flight. It is also important to note that oxygen cylinders must be properly handled, stored, and transported to prevent damage that could lead to failure during use.
Don’t forget to check the date stamp
It is important to note the date stamp on oxygen cylinders as they have a limited lifespan and need to be regularly tested to ensure they are safe to use. DOT 3AA 1800 or 2100 cylinders must be tested every 5 years, DOT 3HT 1850 cylinders must be tested every 3 years, and DOT-E8162-185 cylinders must be tested every 10 years. Regardless of the type, all oxygen cylinders must have a date stamp indicating the last test date to ensure that they are safe for use. Using an expired or untested oxygen cylinder can be dangerous and potentially life-threatening, so it is crucial to always check the date stamp before use.
Pressure testing oxygen cylinders
To test these oxygen bottles, they are typically subjected to a hydrostatic pressure test, which involves filling the cylinder with water and pressurizing it to a level significantly higher than its maximum operating pressure. This pressure is held for a specific amount of time, typically around 30 seconds, while the cylinder is inspected for any signs of deformation or leakage. If the cylinder passes the test, it is deemed safe for use for another period of time. The test date is then stamped onto the cylinder, so that users can easily determine when the next test is due.
Pressure testing oxygen cylinders in water is safer than using air because water is incompressible. If an oxygen cylinder fails during a pressure test, it can release a large amount of high-pressure gas that can be very dangerous. If the cylinder is filled with air, the released gas can cause an explosion. However, if the cylinder is filled with water and fails during testing, the water acts as a barrier that can absorb and contain the energy released by the cylinder, making it a safer testing method.
Why you should never let your oxygen tank run empty
It’s important to never let an oxygen bottle run empty because if it does, there is a risk that moisture can enter the bottle. This is because as the pressure inside the bottle drops, the outside air can enter through the regulator or valve. If the air that enters the bottle contains moisture, it can condense and form water droplets inside the bottle, which can be dangerous. This can happen with any type of oxygen bottle, including both high and low-pressure bottles.
If moisture gets inside the bottle, it can cause problems when the bottle is refilled. The moisture can react with the oxygen, causing the formation of rust and other types of corrosion inside the bottle. This can weaken the bottle, making it more likely to fail or rupture when it is under pressure. To prevent this from happening, oxygen bottles must be re-certified and tested after they have been empty, to ensure that they are still safe to use.
Fusible Safety Disk
Oxygen bottles typically have a fusible safety disk, which is designed to rupture at a specific temperature, usually between 208-220 degrees Fahrenheit (98-104 degrees Celsius). The safety disk is made of a material that melts at this temperature, allowing the excess pressure to escape from the bottle and prevent it from exploding.
The safety disk is an important safety feature because if the pressure inside the oxygen bottle were to exceed its safe limit, the bottle could rupture, causing serious injury or damage. The safety disk is particularly important in situations where the oxygen bottle is exposed to high temperatures, such as in a fire or if it is stored in direct sunlight.
It is important to note that if the safety disk is ruptured, the oxygen bottle should be taken out of service immediately and sent for inspection and recertification before it is used again. This is to ensure that the bottle is still safe to use and that no damage has been done to its components.
