Fill your own oxygen
Still, getting a portable oxygen system filled can be a difficult—and expensive—proposition at some locations. Setting up an Oxygen Cascade in your garage or your hangar is an easy way to ensure that oxygen is always available when you need it.
Safety First
Before we get started, there are several safety considerations that need to be reviewed. Remember that we are dealing with a highly compressed gas that stores a lot of energy and accelerates combustion.
- Secure your cylinders to prevent the oxygen cylinders from tipping over secure them with chains to the wall, or in a special-purpose cart.
- Keep it clean. Don’t use the same tools you change your plane’s oil with to tighten the fittings on your oxygen tank. Have a separate set of wrenches and tools just for your oxygen system, and make sure that your hands and any rags are oil free.
- Safety glasses are a must when dealing with high-pressure gasses that have a lot of energy!
- Fill Slowly! Remember from your high school physics that in a gas, pressure and temperature are related. As the pressure rises in the cylinder, the temperature will, too. Fill at a rate of no more than 200 psi per minute, so that a full charge should take about 10 minutes.
Maintenance Considerations
Pressure vessels are regulated by the DOT rather than the FAA. Although they have an unlimited life, the aluminum cylinders used in most portable oxygen systems require a hydrostatic test every five years. However, if your cylinder is full of oxygen it can continue to be used until empty. The hydrostatic test date will be stamped on the side of the cylinder along with other markings like the manufacture date and serial number. Other cylinders such as steel or composite have different service life and hydrostatic test requirements.
Cascade
A cascade-type oxygen charging system is required for efficient filling. Filling from a single cylinder will limit how much you can fill your portable system. By using a multiple cylinder cascade, more of the supply cylinder(s) can be used.
In a two-cylinder cascade, one supply cylinder is designated the low-pressure supply and the other is the high-pressure supply. To fill, first open the low-pressure supply cylinder and slowly fill your portable cylinder to about 1,200 psi, or until equilibrium, whichever is lower. Close the low-pressure supply and open the high-pressure supply and continue filling. When the low-pressure supply cylinder is nearly empty, remove it from the cascade and order a new replacement cylinder. The high-pressure supply cylinder then becomes the low-pressure supply, and your new cylinder becomes the high-pressure supply—thus the term “cascade”
Oxygen Made Easy
Aerox makes it easy to set up your own filling cascade so you can feel confident using your oxygen system more often. Aerox has a complete line of oxygen ground support equipment. Aerox Cascade kits come complete with adapters for Scott, CGA540, and PB3 fittings, and options include cascade sizes from two to five cylinders, a pressure regulator, and a bleed valve. Aerox Cascade kits are available at all Aerox distributors and at aerox.com.
