1、 Reference number ISO 22538-3:2007(E) ISO 2007INTERNATIONAL STANDARD ISO 22538-3 First edition 2007-09-01 Space systems Oxygen safety Part 3: Selection of non-metallic materials for oxygen systems and components Systmes spatiaux Scurit des systmes doxygne Partie 3: Slection des matriaux non mtalliqu
2、es pour les systmes doxygne et leurs composants ISO 22538-3:2007(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installe
3、d on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobes licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products
4、 used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, plea
5、se inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT ISO 2007 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm,
6、without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2007 All
7、 rights reservedISO 22538-3:2007(E) ISO 2007 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms, definitions, symbols and abbreviated terms. 1 3.1 Terms and definitions. 1 3.2 Symbols and abbreviated terms . 2 4 General. 2 4.1 Background .
8、 2 4.2 Design considerations . 2 4.3 Materials certification. 3 5 Materials control . 3 5.1 General. 3 5.2 Batch/lot testing 3 6 Ignition mechanisms 4 6.1 General. 4 6.2 Ignition conditions 4 6.3 Materials tests . 4 6.4 Ignition factors 4 6.5 Ignition mechanisms and sources 5 7 Material selection 7
9、7.1 General. 7 7.2 Material types 8 Bibliography . 11 ISO 22538-3:2007(E) iv ISO 2007 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is norm
10、ally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in t
11、he work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare
12、 International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some
13、 of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 22538-3 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee SC 14, Space systems and operations. ISO 22538
14、consists of the following parts, under the general title Space systems Oxygen safety: Part 1: Design of oxygen systems and components Part 2: Selection of metallic materials for oxygen systems and components Part 3: Selection of non-metallic materials for oxygen systems and components Part 4: Hazard
15、s analyses for oxygen systems and components The following parts are under preparation: Part 5: Operational and emergency procedures Part 6: Facility planning and implementation ISO 22538-3:2007(E) ISO 2007 All rights reserved v Introduction Polymers, although used extensively, are flammable in oxyg
16、en. The ignitability of polymers varies considerably, but the risk associated with the flammability of polymers can be minimized through proper selection combined with proper design. When selecting polymers for high-pressure oxygen systems, the susceptibility to ignition of the polymer and the possi
17、ble ignition sources in the system are given equal consideration with the structural requirements. The most common cause of ignition of polymeric materials in high-pressure systems is probably adiabatic compression heating of oxygen in the system by rapid pressurization. For this reason, it is impor
18、tant that oxygen systems containing polymers be pressurized slowly. Mechanical impact is rarely a credible ignition source in high-pressure oxygen systems because the level of mechanical impact to which polymeric materials are now exposed is normally well below the energies required for reaction. Ho
19、wever, mechanical valve actuation, which has been largely eliminated from current designs, can cause impact loading of valve seats or other detail parts resulting in failure of the parts or mechanically induced ignition of polymeric materials. Other mechanisms for ignition of non-metallic materials
20、are considered although test data may not exist. Ignition of polymeric materials by impact of metallic and non-metallic particulate is probably feasible, although no conclusive studies have been conducted. Ignition of polymeric materials by burning contaminants has not been studied experimentally, b
21、ut the use of incompatible oils and greases (especially hydrocarbon greases) is one of the most common causes of oxygen-system fires. Improper component design or installation can result in extrusion of polymeric materials with insufficient mechanical strength for the pressure application. The fresh
22、, fine, extruded surfaces are far more ignition-susceptible than the undamaged polymer. Polymer extrusion has been blamed for some fires, but no formal ignition studies have been performed. INTERNATIONAL STANDARD ISO 22538-3:2007(E) ISO 2007 All rights reserved 1 Space systems Oxygen safety Part 3:
23、Selection of non-metallic materials for oxygen systems and components 1 Scope This part of ISO 22538 describes a process for the selection of non-metallic materials for oxygen systems and their components. This part of ISO 22538 applies equally to ground support equipment, launch vehicles and spacec
24、raft. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 4589 (all parts)
25、, Plastics Determination of burning behaviour by oxygen index ISO 11114-3, Transportable gas cylinders Compatibility of cylinder and valve materials with gas contents Part 3: Autogenous ignition test in oxygen atmosphere DIN 53508, Testing of rubber Accelerated ageing ASTM G86, Standard test method
26、for determining ignition sensitivity of materials to mechanical impact in ambient liquid oxygen and pressurized liquid and gaseous oxygen environments 3 Terms, definitions and abbreviated terms 3.1 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.
27、1.1 auto-ignition temperature AIT minimum temperature required to cause a material to ignite spontaneously without the application of a spark or flame in a pressurized oxygen-enriched environment 3.1.2 batch lot collection of material that has all been made under the same conditions and at the same
28、time, using the same starting materials ISO 22538-3:2007(E) 2 ISO 2007 All rights reserved3.1.3 direct oxygen service service in which materials and components are in direct contact with oxygen during normal operations 3.1.4 oxygen-enriched atmosphere mixture (gas or liquid) that contains more than
29、25 volume percent oxygen 3.2 Abbreviated terms FEP fluorinated ethylene propylene polymer GOX gaseous oxygen LOX liquid oxygen PCTFE polychlorotrifluoroethylene PTFE polytetrafluoroethylene 4 General 4.1 Background Experience has shown that a safe oxygen system is not necessarily achieved merely by
30、selecting the best materials available. Experienced designers have gained considerable understanding of the effects of geometry on the design of oxygen systems and their components and have developed design features directed at overcoming the physical limitations of materials. Information required f
31、or selecting materials includes material composition and configuration, environmental and operational conditions, as well as ignition and combustion behaviour of the materials in the operational conditions. Accelerated oxygen deterioration, degradation and durability tests shall be conducted for ove
32、rall evaluation of the materials. Material selection alone cannot preclude ignition but proper choices can markedly reduce the probability of ignition. For example, ignition induced by mechanical impact can be minimized by selecting valve seats that do not shatter under cryogenic conditions. For all
33、 types of ignition mechanisms, selecting materials that have relatively small exothermic heats of combustion will reduce not only the probability of ignition, but also the probability of propagation. Materials with high heats of combustion shall be avoided. Materials used in liquid-oxygen systems sh
34、all meet the requirements for gaseous oxygen and have satisfactory physical properties, such as strength and ductility, at low operating temperatures. 4.2 Design considerations The operational pressure and the structural requirements are given equal attention in the design of the system. While mater
35、ial selection cannot preclude system failures, proper material selection coupled with good design practice can reduce the probability of system failures. Materials evaluation and selection are based on both materials testing for ignition and combustion characteristics and studies of LOX- and GOX-rel
36、ated failures. No single test has been developed that can be applied to all materials to determine either absolute ignition limits or consistent relative ratings. When selecting a material for oxygen systems, its ability to undergo specific cleaning procedures to remove contaminants, particulates an
37、d combustible materials without damage shall be considered. The use of non-metals in oxygen systems is limited and their quantity and exposure to oxygen shall be minimized. Soft goods are necessary in oxygen systems because of their functional properties; however, the limitations involved in their u
38、se shall always be considered. A large experience base and material test database for material selection exist for oxygen systems between 1 MPa and 20 MPa; however, only limited experience exists above 20 MPa. When selecting materials where little experience exists, application-specific materials te
39、sts are always considered. ISO 22538-3:2007(E) ISO 2007 All rights reserved 3 Information required to select materials and evaluate system safety includes material compositions and configurations, environmental and operational considerations (temperature, pressure, flow rate or ignition mechanisms)
40、and ignition and combustion behaviour of the materials in the given environmental conditions. Materials used in LOX systems shall have satisfactory physical properties, such as strength and ductility, at operating temperature. Materials in an oxygen environment below their AIT do not ignite without
41、an ignition source. The rate of energy input shall exceed the rate of heat dissipation before ignition can occur. Ignition temperature is dependent on the property of the material, the configuration, the environment (temperature, pressure, oxygen concentration and fuel characteristics) and the dynam
42、ic conditions for flow systems. Polymers generally ignite at lower temperatures and pressures than metals and may burn at oxygen pressures lower than 7 kPa. The primary concern with polymers in oxygen systems is that, if ignited, they may cause damage to the oxygen system or user. Some damage that m
43、ight result includes propagation of the fire to metallic components, loss of function arising from system leaks and toxic combustion products entering the oxygen system. Although not fully understood, the thermal and physical properties of the non-metals play an important part in ignition and combus
44、tion. Physical properties play an important role in the kindling chain ignition of metals from burning polymers. The exposure of a material to stress may result in aging. The stress may be a result of time, pressure, contact with materials or chemicals, temperature, abrasion, light, gaseous or parti
45、cle impact, tensile or compressive force (either static or cyclic), or other stressors during the service life. Aging may alter the surface, the chemistry and strength of a material and it may affect the ignition properties of a material. 4.3 Materials certification Materials procured for use in oxy
46、gen systems require a material certification from the manufacturer. In addition, it is good practice to confirm the manufacturer-supplied information. 5 Materials control 5.1 General Materials used in LOX, GOX and oxygen-enriched systems shall be carefully controlled. The materials shall be carefull
47、y evaluated and their susceptibility to ignition and the possible ignition sources in the system shall be taken into account. The materials that pass the required tests shall be considered for design. 5.2 Batch/lot testing 5.2.1 Testing Experience has shown that some materials have such variability
48、in manufacturing that different batches of the same material are not always satisfactory for use. A batch or lot may have a sample drawn from it and be inspected to determine conformance with acceptability criteria. The need for testing shall be determined by the responsible design organization. Cri
49、teria for selection of a preferred non-metallic material for oxygen service are as follows: a) few reactions when tested by mechanical impact; b) a high AIT; c) a low heat of combustion; d) a high oxygen index; ISO 22538-3:2007(E) 4 ISO 2007 All rights reservede) a low flame temperature; f) a high threshold temperature; g) a low burn rate. Materials that do not meet the criteria of the required tests and remain candidates for use shall be verified acceptable in the use configuration by analysis or testing an
