Aircraft Fluid Handling: Closed-containment Systems

By Bob Benson, CEO, US MFG & Design Inc

Waste still exists in the airline industry. One area that has not advanced as it could have for the past decade is the life-blood transfusion of the aircraft body — aircraft fluid handling. With environmental issues coming to the forefront, and the costs associated with fluid handling on the rise — not to mention concerns about aircraft fluid protection — it is time to recognize the importance of new technology in the fluid handling aspects of the airline industry. Airlines are recognizing this and are very closely looking at closed-containment systems to reduce the use of the quart can.

Oil Transfusions- Opening the can
In most of the airline industry, the quart can is still being used to dispense and store oil. There is no chance of contamination from particulate or condensation because it is sealed. It is practical, because it can be stored for long periods of time and there is a given amount of oil in each can. This makes it easier for the mechanic to enter the amount of oil added into the log books, and to inventory the current supply.

Drawbacks
First, there is the expense of buying the oil can. Then you have to store it until it is used. A maintenance person has to collect the new cans and take them to the aircraft. The oil cans have to be opened and the contents poured into the aircraft component, as much as they can get out of the can.

The opening of the can is where problems can begin. From simply the improper opening of cans, your entire system can be contaminated and this can lead to component failure. Then there is the potential for spills and the cost associated with waste handling. In the late 1980s and early 1990s, the EPA clamped down on spills and waste handling. This process was the basis of the creation of the current regulations. This awareness created the need for the self-sustaining environmental impact assessments that brought about due diligence in concern for our future and the health of the airline industry. Despite seeming like a huge nuisance, it is actually an important problem because of the environmental impact and the potential fines which can bring tremendous expense to the airline industry and the military.

Potential Costs of the Open Can
Once the can is opened, there could be the following expenses:

  • the possible contamination of the aircraft components due to metal fragmentation from opening the can with either a proper can opener or a screw driver
  • the potential of the maintenance person becoming injured opening the can
  • the contamination of aircraft components due to exposing the oil to the atmosphere
  • the contamination of the interior of the component exposed to atmospheric conditions due to the open fill cap on the aircraft
  • the hazard of spilled oil on the cowling interior, which could cause smoke or fire on the aircraft or the flight line
  • the expense of the maintenance person collecting the used cans and transporting them to the recycling center
  • the recycling personnel having to prepare the cans for draining
  • the expense of the cart to drain the used oil
  • the hazmat expense

Keep in mind that the quart cannot go away. The can is a measured amount and will keep the oil contaminant free for long periods of time, along with being easy to transport and easy to store. What I would like to address is the mass dispensing of oil that requires multiple aircraft servicing in one session with a large volume of oil — an application that would require a large number of oil cans. There are other cost-effective and environmentally sound options available today, such as using a closed-containment system to transfer fluids from a bulk fluid container to an aircraft.

Closed-containment Technology
One type of technology introduced to the market uses a polyethylene-insulated container. It was designed as an answer to one airline’s problem with metal containers. Water was forming on the inside of these containers, due to condensing characteristics of the metal wall when they were exposed to changing temperatures. It was to the point where it was saturating the hygroscopic synthetic oil.

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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