Aircraft Fluid Handling: Closed-containment Systems

A look at one type of technology introduced on the market to help protect fluid.


Polyethylene, in contrast, can withstand temperature changes and is impervious to most chemicals. It is also impact resistant, which is an important characteristic. Making the walls thick would allow a container to be able to take more punishment and enhance the insulating ability. When it is used in the natural color with the proper wall thickness, it proves to be the answer to the condensation problems. Beyond all that, it is recyclable. The soft pliable walls of the container will resist impact as low as 60 degrees below zero fahrenheit. The natural color makes the oil levels visible to the operator. Some of the things you do not want to do with this material for this application is to fluorinate the inside, because it will contaminate the oil. Also you should not use anything harder than low-density polyethylene. Overall, the polyethylene container has found a place in the aviation industry.

Closed-loop system
Now let’s talk about the closed-loop system in combination with this new container. By removing the fill cap and adding a quick disconnect coupler, the possibility of external contaminants from entering has been eliminated. A quick disconnect coupler is installed on the fill port on the container to avoid particulate and chemical intrusion. The quick coupler has a built-in valve that will keep the fill port closed and sealed. Each coupler is unique to the fluid being used and helps to prevent fluids from being mixed. The coupler has an internal valve that is opened only when the mating coupler is properly attached. It allows liquid to flow into the container and closes when not in use.

To allow venting, a desiccant drying filter has been added to the vent opening. Now there is an insulated container with clean dry air entering into it. As the container breathes during fill and dispensing, the filter will only allow dry air to enter the container. Drying filters come in two styles: desiccant crystal and coalescing. The desiccant filter is more effective. The air drying characteristics of filter media vs. air volume will keep the dew point inside of the container low enough to prevent condensation. This is designed to prevent condensation of any kind from entering and affecting the effectiveness of the oil. The only way to contaminate the oil is to pump it in from a contaminated source.

Now there is a container that will protect the integrity of the fluid from the bulk container to the aircraft. This is called closed-containment technology. The fluids that are contained within this system are protected from the environment. Spilling of fluids is virtually eliminated since the valves in the quick disconnect coupler and the drying filter will not allow fluid to leak out, even if the container is held upside down. This system can both protect the fluid integrity and remain environmentally sound.

About the author: Bob Benson’s experience includes four years in the U.S. Air Force. He was also a senior engineer in advance engineering at Northwest Airlines. He is currently CEO of US MFG & Design Inc.

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