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/AIR4092A AEROSPACE INFORMATION REPORT AIR4092 REV. A Issued 1988-04 Revised 1996-
5、10 Reaffirmed 2013-01 Superseding AIR4092 Investigation of PTFE “Melt“ Phenomenon for High Pressure Hoses RATIONALE AIR4092A has been reaffirmed to comply with the SAE five-year review policy. TABLE OF CONTENTS1. SCOPE .22. APPLICABLE DOCUMENTS23 ABSTRACT.24. HISTORY35. TEST PROCEDURE.46. PURPOSE 47
6、. TEST EQUIPMENT 48. TEST RESULTS .49. CONCLUSIONS .510. RECOMMENDATION.5FIGURE 1 THROUGH 3 - HOSE ASSEMBLY SPECIMENSFIGURE 4 - TEST SETUPFIGURE 5 AND 6 - BARE 230 L.W. HOSE FAILUREFIGURE 7 AND 8 - 230 WITH INTEGRAL FIRESLEEVE, L.W. HOSE FAILUREFIGURE 9 AND 10 - 660 H.P. TESTED - NO FAILURESAE AIR40
7、92A Page 2 of 14 1. SCOPE:To provide information regarding a unique failure mode and alternate solutions for consideration by application designers.2. APPLICABLE DOCUMENTS:The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications sha
8、ll 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 references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes appli
9、cable laws and regulations unless a specific exemption has been obtained.2.1 SAE Publications:Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.AS115AS604AS621AS13392.2 U.S. Government Publications:Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue
10、, Philadelphia, PA 19111-5094.MIL-H-383603. ABSTRACT:The lightweight, high pressure hose with high density braid is susceptible to PTFE innercore melt from induced and applied axial vibration starting at double amplitudes of about 0.180 and frequency of 20 Hz. The use of an integral silicone firesle
11、eve helps to “dampen“ out these vibrations, and it increases the threshold for damage to about 0.300 double amplitude. The use of heavy duty, spiral wrapped, high pressure hose, as a practical thing, eliminates the PTFE “melt“ phenomenon. This heavy duty hose does have an axial displacement damage t
12、hreshold of about 0.750 double amplitude, but the mode of failure is mechanical wire breakage not PTFE “melt“. There were no failures of the spiral wrapped hose below 0.750 double displacement.The problem is international, and there have been failures on commercial and military aircraft using AS1339
13、 (AS115.etc.) assemblies with bare hose and hose with integral firesleeve. There are no failure reports for AS604 hose (AS621.etc.) assemblies.There have been no additional failure reports since 1984, primarily due to SAE G-3 activity to alert the aerospace community.SAE AIR4092A Page 3 of 14 4. HIS
14、TORY:Starting in 1978, Titeflex began receiving reports from the field that in certain main pump and auxiliary pump applications, the PTFE, high pressure product lines with high density, lightweight braid construction were failing after as little as 7 h of service due to melting of the PTFE liner wh
15、ich, among other symptoms, showed PTFE extrusion (“porcupining“) through the braid.From 1978 - 1983, multiple failures were reported and confirmed for hoses on pumps in hose sizes -6, -8, and -10.These included confirmed reports from:DeHavillandCanadairBoeing VertolSNIAS (Air Bus)Other unconfirmed r
16、eports of similar failures were received from:U.S. Air ForceS.A.S.McDonnell/DouglasFailures reported involved hoses made by all of the suppliers of the high density braid, lightweight, high pressure hose. In some cases, where Titeflex high density, braided hoses failed, Titeflex had been using heavy
17、 duty spiral-wrapped hose for many years without difficulty. The substitution to high density/lightweight hose was made to save weight. Immediately after the substitution was made, the failures began. When the heavy duty, spiral-wrapped hose was reinstalled, the problem disappeared. In all cases whe
18、re the problem has occurred, Titeflex has recommended the installation of the heavy duty spiral-wrapped hose. There has never been a “melt Teflon“ failure using the heavy duty hose.The second manufacturer of this lightweight construction experienced the “melt PTFE“ failures in frequencies and severi
19、ty equivalent to the Titeflex experience. Reports from that source indicated that the application of a heavy integral, elastomeric sleeve provided sufficient “dampening“ to prevent the problem from occurring.In the period since January 1983 - January 1984, there have been no further confirmed failur
20、es due to PTFE “melt“.NOTE: After this report was made (early 1984), there was a field failure using hose with integral firesleeve. No failure reports were received after 1984.Early in 1982, the SAE G-3D Hose Subcommittee established project G-3D82-1 to monitor this melt failure phenomenon and to es
21、tablish corrective action. After due consideration in March 1987, G-3D established project G-3D87-2 to prepare an AIR4092, Lightweight Hose in Pump Applications, to be referenced in AS115etc. to assure that future users are advised of the potential problem.SAE AIR4092A Page 4 of 14 5. TEST PROCEDURE
22、:5.1 Prelude:Before establishing the given test procedure, Titeflex did extensive testing to develop a test specimen and installation geometry, together with operating criteria, that would:a. Generate the “melt“ mode of failure in lightweight, high pressure hose.b. Use a test specimen that could rea
23、sonably be representative of service conditions.5.2 Test Specimens:1. 18 in long, “230“ Series, -8 size assemblies using straight to straight flared fittings. This is the lightweight, high pressure hose (see Figure 1). Conforms to AS1339 and AS115 (bare hose) and MIL-H-38360.2. 18 in long assembly i
24、s identical to sample 1, except it has an integral silicone firesleeve (see Figure 2). Conforms to AS1339 and AS115 (integral firesleeve) 15 min and MIL-H-38360.3. 18 in long assembly, “660“ Series, -8 size assemblies using straight to straight flared fitting. This is the heavy duty spiral-wrapped,
25、high pressure hose (see Figure 3). Conforms to AS 604 and AS 621 (bare hose) and MIL-H-38360.NOTE: The -8 size was selected because failures occurred in -6, -8, and -10 sizes only. The -8, therefore, was most representative of the failed assemblies.6. PURPOSE OF TEST PROGRAM:To reproduce the “melt T
26、eflon“ failure mode for high pressure, PTFE assemblies using high density braid reinforcement and to examine the effectiveness of spiral wraps or integral sleeve elastomeric dampeners, or both, to reduce or eliminate the “melt Teflon“ phenomenon.7. TEST EQUIPMENT AND SET UP (SEE FIGURE 4):The specim
27、ens were installed in a vertical attitude and essentially in a straight position. The bottom fitting was attached to the top of an MB shaker table. The top fitting was attached to a fixed terminal with a pressure supply. The hose was filled with water at 3000 lbf/in2throughout the test.The shaker ta
28、ble was oscillated up and down at various frequencies and amplitudes to establish thresholds of sensitivity for the PTFE “melt“ characteristic in each type of hose.8. TEST RESULTS:Table 1 documents the test results. Frequency, so long as it exceeded 20 Hz, did not appear to be a principal contributi
29、ng factor in the “melt“ phenomenon, nor did the “G“ load acceleration highlight the susceptibility to the PTFE “melt“ phenomenon. Amplitude was very significant and, together with the minimum frequency requirement, served as the principal variable to induce the PTFE “melt“ phenomenon.SAE AIR4092A Pa
30、ge 5 of 14 8. (Continued):Examination of the hoses after failure indicated the following:1. Bare “230“ series, lightweight hose assembly showed heavy Teflon extrusion of PTFE through the braid and some broken braid externally and major deterioration of the innercore internally (see Figures 5 and 6).
31、2. The “230“ series, lightweight hose with integral firesleeve showed light extrusion of PTFE through the braid and some broken braid externally and major deterioration of the innercore internally (see Figures 7 and 8).3. The “660“ series showed no extrusion of PTFE through the braid but did have br
32、oken wires externally, and it showed deformation of the innercore but no heat deterioration of the PTFE internally (see Figures 9 and 10).9. CONCLUSIONS:The PTFE “melt“ phenomenon is a characteristic associated with the high density braid of the lightweight, high pressure hose. We were not able to c
33、reate this “melt“ phenomenon when the hose was vibrated at right angles to the axis even at prolonged 50 g vibration levels of high amplitude. We were able to generate the “melt“ phenomenon when the vibration had an axial component and the hose gave significant resistance to the axial force. This co
34、ndition will occur when there is only a small bend or no bend in the hose. Based on these tests, the threshold for damage at 20 Hz or greater is as follows:a. Bare lightweight hose - 0.180 Double Amplitudeb. Lightweight hose w/integral firesleeve - 0.320 Double Amplitudec. Bare heavy duty hose - 0.7
35、50 Double AmplitudeNOTE: In the case of the heavy duty hose, the failure mode was broken wires. There was no evidence of innercore melt.10. RECOMMENDATION:For hose assembly applications where the hose can be subjected to applied or induced vibration with high displacements along the axis of the hose
36、, use the heavy duty spiral-wrapped type of hose. One typically critical application is the pump discharge hose for main and auxiliary pumps on aircraft. When the application requires an integral firesleeve to meet fire resistance of TSO or AS specifications, consideration can be given to the use of
37、 the lightweight hose and firesleeve combination as the most cost effective solution, provided the axial component of the vibration to be experienced does not exceed 0.200 double amplitude for an 18-in length of hose.PREPARED BY SAE SUBCOMMITTEE G-3D, AEROSPACE HOSE OFCOMMITTEE G-3, AEROSPACE COUPLI
38、NGS, FITTINGS, HOSE & TUBING ASSEMBLIESSAE AIR4092A Page 6 of 14 TABLE 1SAE AIR4092A Page 7 of 14 FIGURE 1SAE AIR4092A Page 8 of 14 FIGURE 2SAE AIR4092A Page 9 of 14 FIGURE 3SAE AIR4092A Page 10 of 14 FIGURE 4SAE AIR4092A Page 11 of 14 FIGURE 5SAE AIR4092A Page 12 of 14 FIGURE 6SAE AIR4092A Page 13 of 14 FIGURE 7FIGURE 8SAE AIR4092A Page 14 of 14 FIGURE 9FIGURE 10
