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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 therefr
2、om, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2003 SAE International All rights reserved. No part of this publication may
3、 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: 724-776-4970 (outside USA) Fa
4、x: 724-776-0790 Email: custsvcsae.org SAE WEB ADDRESS:http:/www.sae.org AEROSPACE INFORMATION REPORT AIR825/5 REV. A Issued2002-03 Revised2003-03 Superseding AIR825/5 Liquid Oxygen Systems FOREWORD This document is one of a set of related documents. These documents comprehensively address the “Intro
5、duction to Oxygen Equipment for Aircraft“, 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 matte
6、r. The reader who is seeking overall 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 top
7、ics that are of specific interest. 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 document
8、s point the reader toward more detailed treatments located in other SAE documents. TABLE OF CONTENTS 1.SCOPE.3 2.REFERENCES.3 2.1Applicable Documents .3 2.1.1SAE Publications .3 2.1.2U.S. Government Publications.3 2.1.3NFPA Publications .3 2.2Related Publications 4 2.3Definitions 4 3.LIQUID OXYGEN (
9、LOX).4 3.1LOX Properties 5 Copyright SAE International Provided by IHS under license with SAELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 01:59:51 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR825/5 Revision A - 2 - TABLE OF C
10、ONTENTS (Continued) 3.2LOX Converters and Ground Servicing Equipment .5 3.2.1LOX Converter Assembly.8 3.2.2LOX Ground Servicing Equipment.12 3.3Precautionary Measures 16 3.3.1Possible Injury from Cold .16 3.3.2Clothing and Protective Equipment16 3.3.3Clothing Safety Measures16 3.3.4Treatment for LOX
11、 Contact 16 3.3.5Precautions on Transferring LOX.16 3.3.6Material in Contact with LOX16 3.3.7Ground Surfaces in Transferring LOX17 3.3.8Electrical Grounding Requirements17 3.3.9Lubricants in LOX.17 3.3.10Storage Requirements of LOX .17 3.3.11Location of Storage Containers17 3.3.12Vacuum Failure 17 3
12、.4Comparison of Liquid Versus Gaseous Oxygen 18 3.4.1Advantages of LOX18 3.4.2Disadvantages of LOX .19 3.5Design Issues for Aircraft Installation.20 3.5.1Oxygen System Sizing.20 3.5.2Heat Exchanger Requirements20 3.5.3Tubing Requirements.21 3.5.4Pressure Relief Concerns 21 3.5.5Recharger Outlets21 3
13、.5.6Purging and Cleaning LOX Converters and Supply Equipment.22 3.5.7Other LOX System Features Necessary for Maintenance and Safety.22 4.NOTES22 4.1Keywords .22 Copyright SAE International Provided by IHS under license with SAELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale,
14、03/05/2007 01:59:51 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR825/5 Revision A - 3 - 1.SCOPE: This Aerospace Information Report provides general information to aircraft designers and engineers, regarding LOX, its properties, its storage and its conversion to ga
15、s. Much useful information is included herein for aircraft designers regarding important design considerations for a safe and effective installation to an aircraft. The associated ground support equipment needed to support operations of LOX equipped aircraft is also discussed. It is important to rea
16、lize that LOX equipped aircraft cannot be supported unless this support infrastructure is also available. A significant part of this document will address the specific advantages, disadvantages and precautions relating to LOX systems. These are important issues that must be considered in deciding wh
17、ich oxygen system to install to the aircraft. Also, many commercial and military aircraft use aeromedical LOX equipment that is mostly portable equipment. Aeromedical LOX equipment is not addressed herein as it is beyond the scope of this document. 2.REFERENCES: 2.1Applicable Documents: The followin
18、g 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 this document and refe
19、rences 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. 2.1.1SAE Publications: Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. AS8010Aviators B
20、reathing Oxygen Purity Standard 2.1.2U.S. Government Publications: Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094. MIL-PRF-27210Oxygen, Aviators Breathing, Liquid and Gas 2.1.3NFPA Publications: Available from National Fire Protection
21、Association, 11 Tracy Drive, Avon, MA 02322. NFPA Standard No. 401 B Copyright SAE International Provided by IHS under license with SAELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 01:59:51 MSTNo reproduction or networking permitted without license from IHS -,-,
22、- SAE AIR825/5 Revision A - 4 - 2.2Related Publications: The following publications are provided for information purposes only and are not a required part of this SAE Aerospace Technical Report. MIL-D-19326Design and Installation of Liquid Oxygen Systems in Aircraft,General Specification for TR-56-2
23、60Air Force Handbook of LOX Systems, Volumes I that is, the filler valve assembly and the build-up and vent valve assembly. In portable converter designs, these assemblies may be part of the converter assembly. Most designs that are available now combine the functions of the two assemblies into one
24、unit. 3.2.1.6Converter Vacuum: The principle part of the converter is a vacuum insulated container. It consists of an inner and an outer shell with an evacuated air space between the two walls. Connections for filling and removing the LOX, and for venting the gaseous oxygen are provided between the
25、two concentric containers. Heat transfer from outside the converter to the inner shell can be reduced by the following design features: a.Evacuated space between the shells. b.Most aircraft containers within the converter have a molecular “getter“ in the near vacuum evacuated space to provide adsorp
26、tion of air molecules at cryogenic temperatures. This improves the insulation for the required efficiency to be practical for use with smaller containers on aircraft. Most ground support and transfer storage containers use insulating powder between the walls for additional insulation. Both types of
27、storage containers use silvered and/or highly polished surface treatment of the walls forming the evacuated space. c.Use of low thermally conductive materials in the assembly and a minimum number of support and/or assembly points between the two shells. Copyright SAE International Provided by IHS un
28、der license with SAELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 01:59:51 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR825/5 Revision A - 11 - 3.2.1.7Pressure Relief: Despite the low heat transfer through the walls and assemb
29、ly points of the converter assembly, there will always be some heat transfer and some evaporation of LOX. Pressure relief valves must be provided to allow the escape of gas and to prevent dangerously excessive pressure build-up when the oxygen in the oxygen converter is not being expended to the sup
30、ply line. For reasons of safety to prevent a LOX converter explosion, two pressure relief devices are usually included. The customary design practice on smaller LOX converters is that one is LOX converter mounted and the secondary pressure relief is aircraft mounted. On larger LOX converters, both p
31、ressure relief valves are on the LOX converter. One pressure relief valve called secondary relief is set at a slightly higher pressure setting than the primary relief valve. This enables the system to vent a greater amount of oxygen gas if needed to prevent over pressurization of the LOX converter w
32、hile at the same time minimizing LOX overboard venting for the much longer time periods when slow oxygen gas venting is needed. 3.2.1.8Purge Valve: On larger containers it may be necessary to purge the container for maintenance. It would be impractical to let the liquid oxygen evaporate by the norma
33、l means of loss of supply through the pressure relief from the gradual warming of the LOX supply. This would take many days. Therefore a purge valve is fitted to the lower part of the container to evacuate the remaining liquid before maintenance 3.2.1.9Oxygen Losses: In present day equipment, losses
34、 of LOX from a converter assembly range from 5 to 20% in 24 h depending on size and insulation efficiency of the container. Smaller LOX converters have a greater loss than larger converters as they have less volume of LOX per surface area of the container. Five (5) liter LOX converters lose up to 20
35、% and 75-L LOX converters lose up to 5% in 24 h with existing LOX converters. There will be a maximum 15% filling loss on servicing the LOX converter depending on the skill of the person doing the servicing operation and the method and time period of stabilization of the LOX converter. The evaporati
36、on losses given above are percentages of LOX container size irrespective of the loss encountered during LOX servicing and stabilization. 3.2.1.10 Converter Types: Most existing airborne converters designs that are smaller deliver gaseous oxygen at a pressure of 0.48 MPa (70 psig). These converters h
37、old about 5, 8, 10, or 12 L of LOX. The 8-L converters have the same outline dimensions as the 5-L converters. The 12-L converters have the same outline dimensions as the 10-L converters. A number of larger converters that hold 25 or 75 L of LOX have been produced that deliver 2.07 MPa (300 psig) ga
38、s for use on aircraft with more persons. The higher operating pressure is needed to support many oxygen outlets normally provided on transport aircraft. The higher-pressure assemblies are also installed on transport aircraft to permit the crew to refill their portable oxygen bottles directly from th
39、e aircrafts oxygen system. Proper function of all downstream valves and regulators is provided with the 300 psig, as pressure losses in large systems are unavoidable. The higher-pressure airborne converter assemblies have also been studied for use in the commercial jet transport aircraft. Long suppl
40、y tubing runs are required with associated line pressure drop. Also, high flow rates are required during emergency use of this system. A pressure of 300 psig is essential to allow higher delivery flow rates. Copyright SAE International Provided by IHS under license with SAELicensee=IHS Employees/111
41、1111001, User=listmgr, listmgr Not for Resale, 03/05/2007 01:59:51 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR825/5 Revision A - 12 - 3.2.1.11 Servicing Converters: Converter assemblies may be filled at the aircraft or removed and filled at a remote location dep
42、ending on converter design. Removable converters are designed with a wedge plate mounting that enables rapid removal and replacement. Removable converters are mainly used on smaller military aircraft and can be filled with LOX at the aircraft or at the flight line location. The almost universally ac
43、cepted practice now is to remove the converters the night before and fill them all at once. This is done at the flight line where they are stabilized for several hours. They are reinstalled before the next aircraft flight. This keeps all servicing LOX risks and hazards minimized. Fixed installation
44、converters must be filled at the aircraft where the fill build- up and vent valves are mounted to the aircraft exterior versus on the converter for removable converters. Hazards are minimized through training and procedures. 3.2.1.12 Converter Displays: Liquid quantity indicating equipment used with
45、 converters is available in three types using different design features: Capacitance gauging, electro-mechanical transducer indication, and differential pressure type. Many modern LOX converters use capacitance gauging with a probe mounted vertically in the LOX within the converter. The height or le
46、vel of the LOX sets the value of the capacitance enabling an electronic signal to be transmitted to the cockpit gauge or display. Differential pressure gauging was used in the past and is still used. It measures the difference of pressure between the top and bottom on the LOX container that is a fun
47、ction of the liquid volume. Pressure gauging is often used on the gas side of the aircraft LOX system. 3.2.2LOX Ground Servicing Equipment: Special storage tank and transfer cart assemblies provide ground-servicing equipment for aircraft LOX systems. LOX can be stored indefinitely at sea level as lo
48、ng as it is kept at a temperature below its boiling point. Maintaining a temperature below -182.8 C (-297 F) by mechanical refrigeration is expensive and impractical. Therefore, LOX is usually stored and handled in vacuum-insulated containers. The pressure buildup within a LOX storage container is o
49、btained by vaporization of the LOX. Control valves can regulate this. This energy can be used to provide the optimum pressure 0.21 to 0.27 MPa (30 to 40 psig) for transfer of LOX from the ground equipment to an aircraft converter installation or to another storage tank. For larger converters it may be necessary to service with a higher pressure. When servic