1、BRITISH STANDARDBS ISO 22538-2:2007Space systems Oxygen safety Part 2: Selection of metallic materials for oxygen systems and components ICS 49.140g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g
2、3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS ISO 22538-2:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 December 2007 BSI 2007ISBN 978 0 580 53675 5National forewordThis British Standard is the UK implementation of ISO 22538-2:20
3、07.The UK participation in its preparation was entrusted to Technical Committee ACE/68, Space systems and operations.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contra
4、ct. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsReference numberISO 22538-2:2007(E)INTERNATIONAL STANDARD ISO22538-2First edition2007-09-01Space systems Oxy
5、gen safety Part 2: Selection of metallic materials for oxygen systems and components Systmes spatiaux Scurit des systmes doxygne Partie 2: Slection des matriaux mtalliques pour les systmes doxygne et leurs composants BS ISO 22538-2:2007ii iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Nor
6、mative references . 1 3 Terms, definitions and abbreviated terms . 1 3.1 Terms and definitions. 1 3.2 Abbreviated terms 1 4 General. 2 4.1 Overview 2 4.2 Background . 2 4.3 Design considerations . 2 4.4 Materials certification. 3 4.5 Materials control . 3 5 Ignition mechanisms 3 5.1 General. 3 5.2 I
7、gnition conditions 3 5.3 Materials tests . 3 5.4 Ignition factors 3 5.5 Ignition mechanisms and sources 4 6 Metallic materials 6 6.1 Nickel and nickel alloys . 6 6.2 Copper and copper alloys 7 6.3 Stainless steels . 8 6.4 Aluminium and aluminium alloys 8 6.5 Iron alloys 9 6.6 Other metals and alloys
8、 . 9 7 Component housings. 10 8 Configuration testing 10 Annex A (informative) List of materials 11 Bibliography . 15 BS ISO 22538-2:2007iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of prepar
9、ing International Standards is normally 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 li
10、aison with ISO, also take part in the 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
11、 technical committees is to prepare 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
12、 drawn to the possibility that some 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 22538-2 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee SC 14, Space
13、 systems and operations. ISO 22538 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 sy
14、stems and components Part 4: Hazards analyses for oxygen systems and components The following parts are under preparation: Part 5: Operational and emergency procedures Part 6: Facility planning and implementation BS ISO 22538-2:2007vIntroduction Metallic materials, although used extensively, are fla
15、mmable in oxygen. The ignitability of metallic materials varies considerably, but the risk associated with the flammability of metallic materials can be minimized through proper selection combined with proper design. When selecting metallic materials for high-pressure oxygen systems, the susceptibil
16、ity to ignition of the metal and the possible ignition sources in the system are given equal consideration with the structural requirements. Mechanical or particle impact is a credible ignition source in high-pressure oxygen systems. Other mechanisms for ignition of metallic materials are considered
17、, although test data may not exist. Ignition of metallic materials by burning contaminants has not been studied experimentally, but the use of incompatible oils and greases (especially hydrocarbon greases) is one of the more common causes of oxygen-system fires. Improper component design or installa
18、tion can result in a fire when metallic materials with insufficient mechanical strength are chosen for the given application. BS ISO 22538-2:2007blank1Space systems Oxygen safety Part 2: Selection of metallic materials for oxygen systems and components 1 Scope This part of ISO 22538 describes a proc
19、ess for the selection of metallic materials for oxygen systems and their components. This part of ISO 22538 applies equally to ground support equipment, launch vehicles and spacecraft. 2 Normative references The following referenced documents are indispensable for the application of this document. F
20、or 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), Plastics Determination of burning behaviour by oxygen index 3 Terms, definitions and abbreviated terms 3.1 Terms and de
21、finitions For the purposes of this document, the following terms and definitions apply. 3.1.1 direct oxygen service service in which materials and components are in direct contact with oxygen during normal operations 3.1.2 indirect oxygen service service in which materials and components are not nor
22、mally in direct contact with oxygen but might be as a result of a malfunction, operator error or process disturbance 3.1.3 oxygen-enriched atmosphere mixture (gas or liquid) that contains more than 25 volume percent oxygen 3.2 Abbreviated terms AIT auto-ignition temperature GOX gaseous oxygen LOX li
23、quid oxygen BS ISO 22538-2:20072 4 General 4.1 Overview Metals are the most frequently used construction materials in oxygen systems. Metals are generally less susceptible to ignition than polymers. They are often ignited by a kindling chain reaction from a polymer or hydrocarbon contaminant. Select
24、ion of the proper metals in an oxygen system, coupled with good design practice, can minimize the hazards of ignition and combustion of the metal. While selecting metals for oxygen service, situational or configurational flammability shall be evaluated. 4.2 Background Experience has shown that a saf
25、e oxygen system is not necessarily achieved merely by selecting the best materials available. Experienced designers have gained considerable understanding of the effects of geometry on the design of oxygen systems and components and have developed design features directed at overcoming the physical
26、limitations of materials. Information required to select materials shall include 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, degradatio
27、n and durability tests shall be conducted for overall evaluation of the materials. Material selection alone does not preclude ignition, but proper choices can markedly reduce the probability of ignition. For example, ignition induced by particle impact can be minimized by selecting metal alloys that
28、 do not ignite in a particle impact test performed at the use conditions. Galling can be largely eliminated if potential rubbing surfaces are made from materials with widely differing hardness. For all types of ignition mechanisms, selecting materials that have relatively small exothermic heats of c
29、ombustion 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 shall meet the requirements for gaseous oxygen and have satisfactory physical properties, such as str
30、ength and ductility, at low operating temperatures. See Annex A for test data. 4.3 Design considerations The operational pressure and the structural requirements are given equal attention in the design of the system. While materials selection does not preclude system failures, proper materials selec
31、tion 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 liquid-oxygen (LOX) and gaseous-oxygen (GOX) failures. No single test has been devel
32、oped that can apply 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 and combustible materials without damage shall be c
33、onsidered. Information required to select materials and evaluate system safety shall include material compositions and configurations, environmental and operational considerations (temperature, pressure, flow rate or ignition mechanisms) and ignition and combustion behaviour of the materials in the
34、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 auto-ignition temperature (AIT) do not ignite without an ignition source. The rate of en
35、ergy input shall exceed the rate of heat dissipation before ignition can occur. Ignition temperature is dependent upon the property of the material, the configuration, the environment (temperature, pressure, oxygen concentration and fuel characteristics) and the dynamic conditions for flow systems.
36、BS ISO 22538-2:20073The 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 particle impact, tensile or compressive force (either static or cyclic) or other stressors during
37、the service life. Aging may alter the surface, the chemistry and the strength of a material and it may affect the ignition properties of a material. 4.4 Materials certification Materials procured for use in oxygen systems require a material certification from the manufacturer. In addition, it is goo
38、d practice to confirm the manufacturer-supplied information. 4.5 Materials control Materials used in LOX, GOX and oxygen-enriched systems shall be carefully controlled. The materials shall be carefully evaluated, and their susceptibility to ignition and the possible ignition sources in the system sh
39、all be taken into account. The materials that pass the required tests shall be considered for design. 5 Ignition mechanisms 5.1 General In oxygen and oxygen-enriched atmospheres, the ignition of fuel-oxygen mixtures occurs with lower energy inputs and at lower temperatures than in air. For example,
40、the minimum spark energy required for the ignition of hydrogen in air is 0,019 mJ at 1 atmosphere, but the minimum spark energy for the ignition of hydrogen in 1 atmosphere of oxygen is only 0,001 2 mJ. 5.2 Ignition conditions The usual conditions for ignition are a function of temperature, time and
41、 turbulence. The temperature shall be high enough to cause melting, vaporization and significant reactions. The time shall be long enough to allow the heat input to be absorbed by the reactants so that a runaway thermochemical process can occur. The turbulence shall be high enough to allow good mixi
42、ng between the fuel and the oxidizer, so that heat can be transferred from the reacted media to the unreacted media. 5.3 Materials tests To date, no single test has been developed that can produce either absolute ignition limits or consistent relative ratings for all materials. Materials are evaluat
43、ed by testing for their ignition and burning characteristics and by studying oxygen-related failures. An assessment of the causes of accidents and fires suggests that materials and components used in oxygen systems could be vulnerable to ignition that may lead to catastrophic fires. 5.4 Ignition fac
44、tors Factors affecting the ignition of solid materials include material composition and purity, size, shape and condition of the sample, characteristics of oxide layers, testing apparatus, ignition source, gas pressure, and gas concentration and composition. BS ISO 22538-2:20074 The ignition process
45、 depends upon the geometry and operating conditions; therefore, caution shall be taken in interpreting the results of any ignition experiment and in generalizing ignition data. Care shall be taken in applying ignition temperature data, especially for metals, to actual components. Ignition temperatur
46、es are not inherent materials properties but are dependent upon the items listed previously. When applying ignition temperature data, it shall be ensured that the ignition temperature data were obtained in a manner similar to the end-use application. Failure to do this can result in erroneous materi
47、als selection decisions. For example, the ignition temperatures of aluminium in oxygen vary from 660 C (which is the melting point of aluminium) to 1 747 C (which is the melting point of aluminium oxide). The ignition temperature depends on whether or not the oxide is protected during the ignition p
48、rocess. Should ignition occur, several properties affect the ability of the material to damage adjacent construction materials. The heat of combustion, mass, flame propagation characteristics, filler content, char formation and shape stability affect the propensity to ignite surrounding materials. 5
49、.5 Ignition mechanisms and sources 5.5.1 General Potential ignition mechanisms and ignition sources to consider include particle impact, mechanical impact, pneumatic impact, promoted ignition, galling and friction, resonance, electrical arcing, oxygen index, and threshold pressure. 5.5.2 Particle impact Heat may be generated from the transfer of kinetic, thermal or chemical energy when small particles moving at high velocity strike a component. This heat, which is adequate to ignite the particle, may be caused by th
