1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2013 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR825/13 AEROSPACE INFORMATION REPORT AIR825/13 Issued 2003-01 Reaffirmed 2013-1
5、2 Guide for Evaluating Combustion Hazards in Aircraft Oxygen Systems RATIONALE AIR825/13 has been reaffirmed to comply with the SAE five-year review policy. FOREWORDThis document is one of a set of related documents. These documents comprehensively address the “Introduction to Oxygen Equipment for A
6、ircraft,“ and are referred to as slash (/) documents, rather than chapters. The documents may be obtained as a set or individually. As the field of oxygen systems for aircraft has evolved, it became cumbersome for one document to cover the full range of subject matter. The reader who is seeking over
7、all familiarity with oxygen systems for aircraft should read all of these documents that combine to form a general reference to oxygen systems. The reader who is familiar with oxygen systems for aircraft may want to obtain only the slash documents that pertain to topics that are of specific interest
8、.The document set is written as an introductory level, suitable for anyone who would like to understand the basics of oxygen systems in aircraft and specifically for the engineer who has just recently been assigned to aircraft oxygen systems. Many of these documents point the reader toward more deta
9、iled treatments located in other SAE documents.TABLE OF CONTENTS1. SCOPE .41.1 Purpose.42. REFERENCES .42.1 Applicable Documents.42.1.1 SAE Publications.52.1.2 ASTM Publications52.1.3 Other Applicable References 52.2 Definitions .53. BACKGROUND 63.1 What Factors Cause Fires 63.2 Causes of Fires and
10、Explosions93.3 Selection of Metals for Use in Pressurized Oxygen Equipment113.3.1 Metal Choices in Oxygen System Designs .113.3.2 Selection of Non Metals for Use in Pressurized Oxygen Equipment 123.3.3 Critical Locations for Risk of Combustion in Oxygen Equipment 134. THE PROCESS TO REDUCE HAZARDS13
11、4.1 The Issues in Oxygen Equipment Development .134.2 Oxygen Systems Operations and Maintenance154.3 Application of the Hazard Analysis Process165. HOW TO DO AN OXYGEN SYSTEM HAZARD ANALYSIS.175.1 Resources and Program Issues to Consider to Perform in the Process.175.2 Hazard Analysis Overview 175.3
12、 Hazard Analysis Steps 195.4 Contamination Assessment 215.5 Detailed Oxygen Hazard Analysis Procedures .225.5.1 Oxygen Application and Investigation Scope225.5.2 Oxygen Hazard Analysis Team.225.5.3 Component and System Information 235.5.4 Worst-Case Operating Conditions 245.5.5 Material Flammability
13、 245.5.6 Ignition Mechanisms .255.5.7 Secondary Effects Analysis.265.5.8 Reaction Effects Assessment .265.5.9 Recommendations and Conclusions 265.6 Evaluation of Results and Actions Taken27SAE INTERNATIONAL AIR825/13 Page 2 of 31_TABLE OF CONTENTS (Continued)6. AN EXAMPLE.277. NOTES277.1 Key Words.2
14、7APPENDIX A EXAMPLE OF A HAZARD ANALYSIS ACCOMPLISHED ON A NEWDESIGN FOR A PRESSURE-BREATHING REGULATOR ON AHIGH-PRESSURE (2000 PSIG) CYLINDER 29SAE INTERNATIONAL AIR825/13 Page 3 of 31_1. SCOPE:This guide is intended to promote safe designs, operations and maintenance on aircraft and ground support
15、 oxygen systems. This is also a summary of some work by the ASTM G 4 Committee related to oxygen fire investigations and design concerns to reduce the risk of an oxygen fire. There have been many recent technological advances and additional test data is available for evaluating and controlling combu
16、stion hazards in oxygen equipment. Standards that use this new information are rapidly evolving. A guide is needed to assist organizations and persons not completely familiar with this process to provide oxygen systems with minimum risks of combustion. This guide does not necessarily address all the
17、 detailed issues and provide all data that will be needed. For a complete analysis, supplemental publications need to be consulted. This guide does discuss the basics of oxygen systems fire hazards. The hazard analysis process is discussed and a simple example to explain this process. Also, this gui
18、de does not address the overall system safety issues normally evaluated in aircraft programs. This guide does provide some important background and observations about combustion in oxygen systems. Information is given describing how to accomplish a hazard analysis. Furthermore, background is provide
19、d to explain critical locations in oxygen systems that need to be evaluated and other locations that do not require hazard analysis.It is important to note that any effort that requires a comprehensive and effective hazard analysis should use the complete information in the documents referenced here
20、in. In general, the need for a hazard analysis applies primarily to gaseous oxygen equipment at 50 psi and higher pressures. LOX equipment does have hazards concerns as well and is usually treated similarly to GOX equipment at 500 psi. It should be noted that there are other phenomena associated wit
21、h LOX equipment that must be considered. An example is that LOX can combine with hydrocarbons to form a gel, which explodes under impact. On the other hand, since LOX is a very cold liquid it tends to quench most possible ignition sources that could cause promoted ignition. When examining oxygen equ
22、ipment at lower pressures the primary concern is the increased ignition and fire concern with combustible non-metals.1.1 Purpose:This document is intended to provide a guide for minimizing the risk of combustion hazards associated with the design, installation, and maintenance of aircraft oxygen sys
23、tems. This guide also discusses a process of planning and organizing a project assisting someone who wishes to evaluate an oxygen system(s) such that combustion risks are minimized. The use of this guide and supporting documentation in part or whole is entirely elective.2. REFERENCES:2.1 Applicable
24、Documents:The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of
25、this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.SAE INTERNATIONAL AIR825/13 Page 4 of 31_2.1.1 SAE Publications: Available from SAE, 400
26、Commonwealth Drive, Warrendale, PA 15096-0001.AIR1169 Bibliography of References Pertaining to the Effects of Oxygen on Ignition and Combustion of MaterialsARP1176 Oxygen System and Component Cleaning and PackagingAIR4071 Lubricants for Oxygen Use2.1.2 ASTM Publications: Available from ASTM, 100 Bar
27、r Harbor Drive, West Conshohocken, PA 19428-2959.ASTM D 2863 Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index)ASTM G 63 Guide for Evaluating Nonmetallic Materials for Oxygen ServiceASTM G 88 Guide for Designing Systems fo
28、r Oxygen ServiceASTM G 93 Practice for Cleaning Methods for Material and Equipment Used in Oxygen-Enriched EnvironmentsASTM G 94 Guide for Evaluating Metals for Oxygen ServiceASTM G 128 Standard Guide for the Control of Hazards and Risks in Oxygen Systems2.1.3 Other Applicable References:Dees, J., a
29、nd R. F. Poe, Test Plan: Guide for Oxygen Hazards Analyses on Components and Systems, TP-WSTF-713, NASA Johnson Space Center, White Sands Test Facility, Las Cruces, NM July 7, 1993Bamford, L. B., and M. A. Rucker, Guide for Oxygen Component Qualification Tests, TP-WSTF-712, NASA Johnson Space Center
30、, White Sands Test Facility, Las Cruces, NM 19922.2 Definitions:CRES: Corrosion REsistant Stainless (CRES) Steel.Component: On any oxygen equipment item such as a regulator the components are subgroups of function equipment that make up the whole item. For example, the servicing or fill valve, the p
31、ressure relief valve, the pressure gauge, the outlet flow regulating device, and the supply vessel.Flammable: Possible to burn, combustible, capable of being ignited.Stress Risers: Elements that cause increased stress or a tendency to increase the risk of ignition and combustion.Thermal compensator:
32、 Special device in a mechanical design carrying a gas such as oxygen that absorbs heat energy and carry away the heat energy from mechanical parts which are at risk of ignition. The temperature is more rapidly conducted away to the ambient to keep the oxygen temperature inside the tubing minimized.
33、The device can also shut down oxygen flow if a maximum limit is reached.SAE INTERNATIONAL AIR825/13 Page 5 of 31_3. BACKGROUND:3.1 What Factors Cause Fires:Oxygen system fires and explosions are a result of numerous factors that are complex in their interaction and not easily understood. This guide
34、will assist someone not familiar with these phenomena to better understand and analyze any oxygen system hazards. It is always best that an expert be consulted who has years of background with oxygen systems combustion issues when it is important to minimize these risks.Any person thinking about inv
35、estigating these issues to reduce risks must dispense with all biases concerning what is known about normal fires in the earths atmosphere, which is approximately 21% oxygen, 78% nitrogen and 1% inert gases at 101.3 kPa (14.7 psi) at sea level.Fires and fire hazards are most often conceptualized in
36、an environment that is found at ground level. An increase in the partial pressure of oxygen increases the potential for combustion in terms of both initiation and severity. Combustion in 100% oxygen with increased pressure will occur more readily and spread more rapidly. Most persons are not familia
37、r with oxygen fed fires and therefore more information is provided herein to explain how this phenomenon is different. Normal fires at ground level occur in a low concentration of oxygen with a relatively low pressure. The partial pressure of oxygen at sea level is 21.27 kPa (3.087 psi) which is det
38、ermined by 0.21 kPa x 101.3 kPa (14.7 psi). There is 21% oxygen in the earths atmosphere at all altitude levels. The magnitude of the oxygen pressure can be thought of as a stress riser. Figure 1 shows a comparison of stress risers in low and high-pressure oxygen equipment as compared to the partial
39、 pressure of oxygen in air at sea level.A stress riser is also any of a number of key parameters that have been found to make ignition more likely. Stress risers in oxygen systems include:1. pressure2. oxygen concentration 3. other included gases4. temperature5. phase (liquid versus gaseous oxygen)6
40、. mechanical failure7. higher oxygen velocities8. time and ageA thorough discussion of stress risers is available in ASTM G 128-95.SAE INTERNATIONAL AIR825/13 Page 6 of 31_FIGURE 1 - Oxygen Pressure Stress Riser Comparisons for Low and HighPressure Oxygen Equipment3.1 (Continued):Daltons Law states
41、that the total pressure of a mixture of gases is equal to the sum of the partial pressures of each gas in the mixture. In the earths atmosphere the following relationship describes the gas pressures. Total Pressure at Sea Level = Partial Pressure Oxygen + Partial Pressure Nitrogen + Partial Pressure
42、 Inert GasesAny combustion in an oxygen system occurs at an increased oxygen partial pressure and usually 100% oxygen. There will also be the additional pressure used in the supply and dispensing equipment. Normal supply equipment used in aircraft oxygen systems is typically 12,400 to 14,820 kPa (18
43、00 to 2150 psig). Experience and test data show that combustion in pressurized oxygen equipment occur very rapidly and with much violence. Such fires are thought of as explosions by the observer, but high-speed film shows that these so called explosions are actually oxygen fed fires. Technically spe
44、aking, explosions are really detonations. Metal fires are the most violent and should be the greatest cause for concern to an oxygen systems designer.SAE INTERNATIONAL AIR825/13 Page 7 of 31_3.1 (Continued):What are the chains of events that lead to combustion in oxygen equipment and any equipment t
45、hat is nearby? It is helpful to think of a “fire and explosion triangle.“ See Figure 2. One side of the triangle is the oxygen, another side is the fuel and the other side is the ignition mechanism. Take away any side of the triangle and the combustion (fire and explosion) can not occur. The problem
46、 is that one cannot take away any side of the triangle with oxygen equipment.FIGURE 2 - Fire and Explosion TriangleThe oxygen is always present as it is stored and dispensed.The fuel source is always present, as the container for oxygen and the dispensing equipment are metals and nonmetals, which ca
47、n all combust in 100% oxygen. For example, the equipment will consist of pressurized cylinders, regulators, valves, tubing and fittings that are all made of metals and nonmetals. All of these materials can combust with 100% pressurized oxygen.SAE INTERNATIONAL AIR825/13 Page 8 of 31_3.1 (Continued):The ignition side of the triangle is a more difficult issue to unders
