Air Separation Modules – Keeping Aviation Safe

How Air Separation Modules Keep Aviation Safe

From the very beginning of aviation operations more than 100 years ago, through the beginning of the jet age six decades ago, to the present day, there has been a continuous focus in the aviation industry on finding reliable and effective ways to improve safety.

Aircraft safety is an essential factor for many parts of our society, from passengers traveling on commercial airlines to companies shipping their goods on freight aircraft, pilots and flight crews to airline operators, ground handlers and airports. We can even say that the entire world relies on the safety of aviation operations.

While the outside of aircraft has not undergone significant changes, in the past 30 or so years there have been substantial technological advancements to how things work on the inside – taking aircraft efficiency, reliability and safety to new heights. Still, that doesn't make aviation safety a challenge-free space.

An example of a challenge in aircraft safety

Take fuel tanks. Now kept under control with the help of reliable and effective technologies like the air separation module (ASM), fire hazards in the aircraft fuel tank were a  threat some decades ago. Such a fire could happen when the elements that can start and sustain combustion are present in the tank simultaneously in quantities that exceed specific amounts.

Also called the fire triangle, these elements are fuel, oxygen and an ignition source. Keeping the concentration that any one of the first two elements has in a fuel tank within a certain threshold prevents the ignition. If that does not happen, a fire can ignite in the ullage – the space that exists above the liquid fuel in the fuel tank of an aircraft – possibly generating an overpressure in the tank that could damage the airframe. However, thanks to the inerting system, these today are very rare events.

What is an inerting system?

An inerting system dramatically reduces the chances of combustion happening in a fuel tank by introducing an inert gas – such as nitrogen – to displace the oxygen in that environment. This type of inerting system is called a Nitrogen Generation System (NGS). Nitrogen dilutes the amount of oxygen present in the tank, thus lowering the risk of flammability. As already mentioned a couple of paragraphs earlier, this entire process takes place with the help of an air separation module – one of the most significant elements of an aircraft's inerting system.

What is an air separation module, and how does it work?

The air separation module is an integral part of the nitrogen generation system that introduces nitrogen inside aircraft fuel tanks to keep the oxygen level under a specific threshold, thus reducing the risk of flammability. The air separation module uses semi-permeable, hollow fiber membranes packaged in a cylindrical canister that removes oxygen from a compressed air stream to generate a stream of nitrogen-enriched air (NEA).

What is the level of oxygen produced by the air separation module?

The air separation module isolates the oxygen from engine bleed air which is the air supplied by the engines to an aircraft cabin to pressurize the cabin and run ancillary aircraft systems. This process of separation enables the creation of nitrogen-enriched air, which gets delivered to the fuel tank, generating an in-tank atmosphere typically comprised of less than 12% oxygen. This percentage is far smaller than the 21% that normally exists in the outside air and is too low to enable fuel vapors to sustain combustion.

Advanced technologies elevate aviation safety

Aerospace is a very demanding industry which requires durable technologies that are both reliable and effective in enhancing overall safety. 737NG operators can now install our new ASM Kit (Air Separation Module Kit) to get the benefit of a 7 year warranty along with rapid ASM replacement times as ASM’s come insulated out of the box.

Longer life and higher durability eliminate the need for unscheduled ASM removal and replacement efforts, planning and costly aircraft downtime. The Honeywell ASM kit comes fully equipped as a modular assembly which eliminates the need for operators to spend over six hours disassembling, removing and storing blankets and brackets for reuse, as well as costly efforts to repair or replace hardware damaged during maintenance activities.