1、 ISO 2012 Space systems Safety and compatibility of materials Method to determine the flammability thresholds of materials Systmes spatiaux Scurit et compatibilit des matriaux Mthode de dtermination des seuils dinflammabilit des matriaux TECHNICAL SPECIFICATION ISO/TS 16697 First edition 2012-08-01
2、Reference number ISO/TS 16697:2012(E) ISO/TS 16697:2012(E) ii ISO 2012 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2012 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
3、 photocopying and microfilm, 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 i
4、n Switzerland ISO/TS 16697:2012(E) ISO 2012 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope 1 2 Normative references . 1 3 Terms and definitions . 1 4 Test criteria 1 5 Sample preparation . 2 6 Test system . 2 7 Pre-test procedures 2 8 Test procedures . 2 8.1 Determining the
5、 upward limiting oxygen index (ULOI) . 2 8.2 Determining the maximum oxygen concentration (MOC) 3 9 Recording and reporting . 3 10 Precision 3 Annex A (informative) Alternate determination with increased precision of upward limiting oxygen index (ULOI) 4 Annex B (informative) Data sheet for upward f
6、lame-propagation oxygen-concentration flammability threshold test . 6 Bibliography . 8 ISO/TS 16697:2012(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is n
7、ormally 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 i
8、n 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 technical committees is to prep
9、are 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. In other circumstances, particularly when th
10、ere is an urgent market requirement for such documents, a technical committee may decide to publish other types of document: an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in an ISO working group and is accepted for publication if it is approved b
11、y more than 50 % of the members of the parent committee casting a vote; an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting a vote. An ISO/PAS or
12、ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed, it is reviewed again after a further three years, at which time it must either be transfor
13、med into an International Standard or be withdrawn. Attention is 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/TS 16697 was prepared by Technical Committee
14、ISO/TC 20, Aircraft and space vehicles, Subcommittee SC 14, Space systems and operations. iv ISO 2012 All rights reserved ISO/TS 16697:2012(E) Introduction Spacecraft fire safety emphasizes fire prevention, which is achieved primarily through the use of fire-resistant materials. Materials selection
15、for spacecraft is based on conventional flammability acceptance tests, along with prescribed quantity limitations and configuration control for items that do not pass these acceptance tests or are questionable. ISO 14624-1 and ISO 14624-2 are the main methods used to evaluate flammability of polymer
16、ic materials intended for use in the habitable environments of spacecraft. These methods are upward flame- propagation tests initiated in static environments and using a well-defined igniter flame at the bottom of the sample. The pass/fail test logic of ISO 14624-1 and ISO 14624-2 does not allow for
17、 a quantitative comparison with reduced-gravity or microgravity test results; therefore use of these methods is limited for in-depth theoretical analyses and realistic estimates of spacecraft fire extinguishment requirements. To better understand the applicability of laboratory test data to actual s
18、pacecraft environments, this Technical Specification has been proposed which, as an alternative to qualifying materials as pass/fail, measures the actual upward flammability limit for the material. 1A working group established by NASA to provide recommendations for exploration spacecraft realized th
19、e importance of correlating laboratory data with real-life environments, and recommended the development of a flammability threshold test method 2 . The working group indicated that “the flammability threshold information will allow identification of materials with increased flammability risk from o
20、xygen concentration and total pressure changes, minimize potential impacts, and allow for development of sound requirements for new spacecraft and extravehicular landers and habitats”. Furthermore, recent research using this method has shown that conventional normal-gravity materials flammability te
21、sts do not correlate with the flammability in ventilated, micro- or reduced-gravity conditions. 34Currently, the materials selection for spacecraft is based on the assumed extension of ground flammability test results to spacecraft environments, an assumption which needs to be validated by further t
22、esting. In contrast to pass/fail data, materials flammability threshold data acquired in normal gravity can be compared with data obtained in microgravity or reduced- gravity experiments 5and, consequently, a more accurate assessment of the margin of safety of the material in the real spacecraft env
23、ironment can be made. In addition, this Technical Specification gives the option of selecting better or best space system materials, as opposed to what would be considered just “acceptable” from a flammability point of view, and realistic assessment of spacecraft fire extinguishment needs, which cou
24、ld result in significant weight savings. The knowledge afforded by this technique allows extrapolations of flammability behaviour to conditions not specifically tested and this could potentially result in significant cost and time savings. 6This Technical Specification presents a method for evaluati
25、ng oxygen-concentration flammability extinguishment limits when a material is exposed to a standard ignition source under total pressure, temperature, convective flow, and gravity-level conditions. However, the method can also be used to determine other flammability extinguishment limits, such as th
26、e total pressure 7or forced convective velocity thresholds, while maintaining other test conditions constant. The intent of this Technical Specification is to highlight the importance of correlating laboratory test data with real-life space system applications. The method presented is just one of th
27、e possibilities believed to lead to a better understanding of the applicability of materials flammability test data. International feedback on improving the proposed method, as well as suggestions for correlating test data with space system applications, are being sought. ISO 2012 All rights reserve
28、d v Space systems Safety and compatibility of materials Method to determine the flammability thresholds of materials 1 Scope This Technical Specification provides a method to determine the oxygen concentration threshold when a material exposed to a standard ignition source self-extinguishes at a giv
29、en constant total pressure, temperature, convective flow, and gravity-level conditions. The method can also be used to determine other flammability limits, such as the total pressure or forced convective velocity thresholds, while maintaining other test conditions constant. The flammability threshol
30、ds can also be determined with alternate pass/fail criteria, sample configurations and/or size, ignition mode, etc. to allow correlations with test data obtained, for example, under microgravity or reduced-gravity conditions which may have limited testing time in ground experiments. NOTE The method
31、described provides an assessment of the flammability of aerospace materials under laboratory conditions only. Nevertheless, the results may be used as elements of a fire risk assessment which take into account all the pertinent factors for an assessment of the fire hazard in space systems. Studies o
32、n parametric effects have been initiated to better understand the applicability of the data. 8 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 ed
33、ition of the referenced document (including any amendments) applies. ISO 14624-1, Space systems Safety and compatibility of materials Part 1: Determination of upward flammability of materials ISO 14624-2, Space systems Safety and compatibility of materials Part 2: Determination of flammability of el
34、ectrical-wire insulation and accessory materials 3 Terms and definitions For the purposes of this Technical Specification, the terms and definitions given in ISO 14624-1 and ISO 14624-2 and the following apply. 3.1 upward limiting oxygen index ULOI oxygen concentration where approximately 50 % of sa
35、mples fail the test criteria described in Clause 4 3.2 maximum oxygen concentration MOC highest oxygen concentration where all samples tested (at least five) pass the test criteria described in Clause 4 4 Test criteria This test method attempts to determine the self-extinguishment limits of material
36、s. Individual samples are considered to self-extinguish when the burn length is less than 15,2 cm when tested in accordance with ISO 14624-1 or ISO 14624-2. The material is considered to self extinguish when all samples tested (at least five) pass the burn length criteria for individual samples. TEC
37、HNICAL SPECIFICATION ISO/TS 16697:2012(E) ISO 2012 All rights reserved 1 ISO/TS 16697:2012(E) 5 Sample preparation A minimum of 20 samples shall be prepared. Preparation of samples for testing involves the following tasks: a) receiving and visually inspecting the material; b) preparing samples to th
38、e proper dimensions; c) cleaning the samples; d) inspecting the samples (samples should be prepared exclusively for use in this test). The sample length should be at least 15,2 cm. A standard sample length as indicated by ISO 14624-1 and ISO 14624-2 is recommended if a direct correlation with these
39、standards is required. Otherwise, the samples shall be prepared as required in ISO 14624-1 or ISO 14624-2. 6 Test system The test system shall comprise the components identified in ISO 14624-1 or ISO 14624-2. 7 Pre-test procedures Before testing, all pertinent information (including sample identific
40、ation, pressure, and oxygen concentration) shall be recorded on the data sheet (see Annex B). The system shall be visibly clean, and all measuring devices shall be in current calibration. The exposed centre section of standard-sized samples shall be 5,1 cm wide. Samples shall not be overly stretched
41、 or tightened, which would cause lines of horizontal stress; thin films shall be mounted with 1,3 cm of slack in the width to allow for shrinkage. The igniter specified in ISO 14624-1 or ISO 14624-2 shall be placed parallel to the lower edge of the sample and centred along the plane of the front sur
42、face of the sample. The igniter shall be placed (0,6 0,3) cm below the lower edge of the sample. Finally, the K-10 paper shall be mounted horizontally 20,3 cm and centred directly below the sample. 8 Test procedures 8.1 Determining the upward limiting oxygen index (ULOI) Start testing at an oxygen c
43、oncentration corresponding to the ULOI for similar materials. Conduct the testing in accordance with ISO 14624-1 or ISO 14624-2; if the sample burns less than 15,2 cm, record this as an “O” response, while if the sample burns at least 15,2 cm, record it as an “X” response on the data sheet. Observe
44、and record the materials burning behaviour such as sparks, flame jets, burning/melting/dripping of material, and if ignition of K-10 paper occurs. Video record the tests if possible. Select the oxygen concentration to be used for the next test as follows: a) decrease the oxygen concentration if the
45、burning behaviour of the preceding specimen gave an “X” response; b) increase the oxygen concentration if the burning behaviour of the preceding specimen gave an “O” response. Repeat the test procedures using oxygen concentration changes of any convenient step size until two oxygen concentrations, i
46、n percent volume, have been found that differ by 1 % oxygen and of which one gave an “O” response and the other an “X” response. The two results at oxygen concentrations 1 % apart which gave opposite responses do not have to be from successive specimens. The ULOI is the lower oxygen concentration wh
47、en the specimen fails the 15,2 cm burn length criteria (“X” response). NOTE 1 The oxygen concentration change of 1 % has been determined to be adequate for most conditions. Using a lower oxygen concentration change may yield higher precision but could require more tests. Using a step size of 2 % wil
48、l yield quicker results and could be employed when lower precision is acceptable. This step size is especially suitable when higher oxygen concentration thresholds than approximately 30 % by volume are expected. 2 ISO 2012 All rights reserved ISO/TS 16697:2012(E) NOTE 2 The procedure outlined in Ann
49、ex A can be used to determine the ULOI when a higher precision is needed. See also ISO 4589 9for additional details. 8.2 Determining the maximum oxygen concentration (MOC) From the set of data obtained, determine the highest oxygen concentration where the specimen passed the burn length criteria (“O” response) and which is 1 % below the lowest oxygen concentration where the specimen failed (“X” response). Conduct additional tests at this oxygen concentration until a total of five tests have been completed wit
