CHEMICAL OXYGEN GENERATORS Chemical Oxygen Generators B/E Aerospace, Inc. is the world’s leader in chemical oxygen equipment for aircraft. B/E Aerospace has been supplying this versatile equipment to the leading airframe manufacturers for over 30 years. In addition to aviation, chemical oxygen generators are being used in a growing list of various other applications, including escape, rescue, first aid, fire fighting and submarine life support. With over 300,000 units placed in service and more than 3 billion flight hours accumulated on this equipment, B/E Aerospace has demonstrated exceptional expertise in chemical oxygen systems. History Oxygen generation from the thermal decomposition of chlorates and perchlorates is not a recent innovation. One of the first applications of chemical oxygen generation was in the production of mine rescue equipment over ninety years ago. However, these early generators were erratic in decomposition rates and required large wet or dry filtration systems in order to achieve a purity level suitable for breathing. During World War II the need arose for an oxygen source that was efficient on a weight/volume basis to protect military personnel from the dangers of anoxia during flight. The National Defense Research Council funded the development of the oxygen candle apparatus (OCA). This chlorate oxygen generator was successfully used to sustain the physiological needs of personnel operating B-17 bombers over Europe. Since then, chemical oxygen equipment has been installed on an ever increasing variety of military and civil aircraft. This technology also has a variety of applications outside aviation, including escape and rescue equipment, first aid, fire fighting, and submarine operations. The uses for chemical oxygen generators continue to expand as more potential users are made aware of these safe, compact and reliable oxygen sources. Function of Chemical Oxygen Generators As shown in Figure 1, the chlorate core is wrapped in insulation and placed in a stainless steel housing. The insulation absorbs shock, partially filters the oxygen produced and retains heat energy within the core for continued chemical reaction after the generator is initiated. Flow from the generator is started by a mechanical flow initiating mechanism as shown in the illustration. The primary chemical reaction in the generator core is: 2 NaCiO3 2 NaCl + 3 O2 (sodium chlorate) (sodium chloride) (oxygen) As the chemical decomposition region or reaction zone travels along the chlorate core from one end to the other, the oxygen is produced. When the oxygen reaches the core locator, a metal plate separating the core from the filter media, the oxygen passes through holes around the perimeter of the lcoator and into the filter. The filter removes particulate matter and traces of contaminating gases which result from the core decomposition. When the oxygen reaches the outlet valve, it is distributed via an oxygen supply line or manifold connected to the generator. The outlet valve seals the unit from moisture which could contaminate the chlorate core in storage, prior to use. Should the outlet valve become clogged, over-pressure protection is provided by the relief valve which vents the oxygen to the atmosphere. The time lapse from initiation of the chemical oxygen generator to full flow of oxygen to the supply lines is typically less than ten seconds. CHEMICAL OXYGEN GENERATORS Aircraft System Design For airline applications, the chemical oxygen generators are typically located in overhead modules. The generators are housed with the oxygen supply lines and passenger masks in an enclosed compartment that is opened automatically by a pressure switch that senses decompression. When decompression occurs, the pressure switch supplies an electrical signal which releases the compartment door, and the masks are presented within reach of the passengers. Oxygen flow from the generators begins upon removal of a release pin from the flow initiation mechanism of each generator. This is accomplished by a lanyard which connects the mask or mask hose to the release pin. When a passenger takes hold of a mask, the lanyard will be at its full length. Bringing the mask to the face will remove the release pin and initiate the flow of oxygen from the generator. Since all masks connected to a single generator have lanyards attached to the common release pin, any of the masks are capable of removing the release pin and starting the flow of oxygen to all masks within that compartment. The chemical oxygen generator is designed to produce oxygen at a rate varying with time, which coincides with the physiological needs of the individual during descent. These needs are stated in FAA regulation FAR 25.1443. Figure 2(a) shows a typical altitude profile (cabin altitude versus time after decompression) plotted with the corresponding flow requirement, Figure 2(b). A trace of the typical output of a chemical oxygen generator is indicated on the flow requirement profile to illustrate the variations in normal output and the margin of extra oxygen normally programmed into B/E Aerospace’s chemical oxygen generators. As can be seen in Figure 2(a), altitude is maintained at 40,000 feet for a short period to allow for normal crew reaction time before descent of the aircraft. Once the aircraft reaches an altitude of 10,000 feet, oxygen is normally no longer required and the generator automatically ceases production after the predetermined descent time has expired. B/E Aerospace has broad capabilities to produce a generator design matched to any aircraft altitude descent requirement. Why Chemical Oxygen Generators? Reduced weight, simplified maintenance, and increased safety are three features which make chemical oxygen generators the preferred choice of airlines. Since the small, lightweight generators are under no pressure, they may be handled easily and safely by ground personnel and conveniently stored for many years. By eliminating pressure gauges and complicated piping which must routinely be cleaned and maintained in a gaseous system, chemical oxygen generators need only be visually inspected to determine the state of the generator. If the expended indicator on the side of the generator and initiating mechanism show no signs of activation or tampering, further maintenance is not required. This further reduces maintenance time, necessary ground facilities and their required personnel. Chemical oxygen generators also allow for a high degree of installation flexibility. Seating configuration may be changed quickly without the time-consuming process of relocating high pressure pipes, gauges and distribution systems which must be checked and tested for leaks. A major concern when working with any oxygen system is fire susceptibility. High pressure oxygen systems are dangerously sensitive to nearby fires, unlike chemical oxygen, which will not explode and is a low fire contributor. Gunfire fragmentation tests have been performed on chemical oxygen generators and even then, there were no signs of combustion within the chlorate core. For economical, practical and safe sources of oxygen for all aviation applications, choose chemical oxygen generators from the leader, B/E Aerospace, Inc. B/E AEROSPACE, INC. Oxygen Systems Products 10800 Pflumm Road • Lenexa, KS • USA • 66215 Telephone (913) 338-9800 • Fax (913) 469-8419 [email protected] www.beaerospace.com REV. 1-01/3000.