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 theref
2、rom, 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 2010 SAE International All rights reserved. No part of this publication ma
3、y 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: +1 724-776-4970 (outside US
4、A) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AMS7270LAEROSPACEMATERIALSPECIFICATIONAMS7270 REV. L Issued 1949-03 Revised 2010-05 Superseding
5、 AMS7270K Rings, Sealings, Butadiene-Acrylonitrile (NBR) Rubber Fuel Resistant 65 - 75 RATIONALEAMS7270L is a Five Year Review and update of this specification adding QPL requirements. 1. SCOPE 1.1 Form This specification covers a butadiene-acrylonitrile (NBR) rubber in the form of molded rings. 1.2
6、 Application These rings have been used typically as sealing rings at temperatures as low as -67 F (-55 C) where resistance to fuel is required, but usage is not limited to such applications. The cross-section of such rings is usually not over 0.275 inch (6.98 mm) in diameter or thickness. Each appl
7、ication, however, should be considered individually. 1.3 Safety - Hazardous Materials While the materials, methods, applications, and processes described or referenced in this specification may involve the use of hazardous materials, this specification does not address the hazards which may be invol
8、ved in such use. It is the sole responsibility of the user to ensure familiarity with the safe and proper use of any hazardous materials and to take necessary precautionary measures to ensure the health and safety of all personnel involved. 2. APPLICABLE DOCUMENTS The issue of the following document
9、s in effect on the date of the purchase order forms a part of this specification to the extent specified herein. The supplier may work to a subsequent revision of a document unless a specific document issue is specified. When the referenced document has been cancelled and no superseding document has
10、 been specified, the last published issue of that document shall apply. SAE AMS7270L Page 2 of 82.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.AMS2817 Packa
11、ging and Identification, Preformed Packings AS568 Aerospace Size Standard for O-Rings AIR851 O-Ring Tension Testing Calculations AS871 Manufacturing and Inspection Standard for Preformed Packings (O-Rings) 2.2 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700,
12、 West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.org.ASTM D 297 Rubber Products Chemical Analysis ASTM D 395 Rubber Property - Compression Set ASTM D 412 Vulcanized Rubber and Thermoplastic Elastomers - Tension ASTM D 471 Rubber Property - Effects of Liquids ASTM D 573 Rubber Property
13、- Deterioration in an Air Oven ASTM D 1414 Rubber - Testing O-Rings ASTM D 2240 Rubber Property - Durometer Hardness 3. TECHNICAL REQUIREMENTS 3.1 Material Shall be a compound, based on a butadiene-acrylonitrile (NBR) elastomer, suitably cured to produce sealing rings meeting the requirements of 3.2
14、. 3.2 Properties Rings shall conform to the requirements shown in Table 1; tests shall be performed on the rings, in accordance with ASTM D 1414, insofar as practicable. Tensile strength testing is not required on rings which are too small to permit assembly on rollers and are, after cutting, too sh
15、ort to permit testing at a single strand. Eliminating testing for tensile strength does not eliminate testing for elongation; elongation test can be done by stretching a ring over a mandrel of a size which will stretch the ring sufficiently to produce the required elongation when figured on the ID o
16、f the ring. Calculations of tensile strength and elongation may be made in accordance with AIR851. SAE AMS7270L Page 3 of 8TABLE 1 - PROPERTIES Paragraph Property Requirement Test Method 3.2.1 Hardness, Durometer “A” or equivalent 70 5 ASTM D 2240 3.2.2 Tensile Strength, min 1500 psi (10.3 MPa) ASTM
17、 D 412 3.2.3 Elongation, min 150% ASTM D 412 3.2.4 Corrosion Nil 3.2.5 Specific Gravity Preproduction Value 0.02 ASTM D 297 (Hydrostatic Method) 3.2.6 Aromatic Fuel Resistance ASTM D 471 (ASTM Ref. Fuel B) Temperature: 68 to 86 F (20 to 30 C) Time: 168 hours 0.53.2.6.1 Hardness Change, Durometer “A”
18、 or equivalent -25 to 0 3.2.6.2 Tensile Strength Change, max -65% 3.2.6.3 Elongation Change, max -55% 3.2.6.4 Volume Change 0 to +40% 3.2.7 Aromatic and Non-Aromatic Fuel Resistance 4.5.1 3.2.7.1 Volume Change, max (based on unimmersed volume)Ring Cross Section Diameter, 0.066 to 0.110 inch, incl (1
19、.68 to 2.79 mm, incl) Over 0.110 inch (2.79 mm) -8% -5% 3.2.8 Oil Resistance ASTM D 471 IRM 903 Temperature: 302 F 5 (150 C 3) Time: 70 hours 0.5 3.2.8.1 Hardness Change, Durometer “A” or equivalent -25 to 0 3.2.8.2 Volume Change +15 to +35% 3.2.9 Dry Heat Resistance ASTM D 573 Temperature: 212 F 2
20、(100 C 1) Time: 70 hours 0.5 3.2.9.1 Hardness Change, Durometer “A” or equivalent 0 to +10 3.2.9.2 Tensile Strength Change, max -25% 3.2.9.3 Elongation Change, max -40% 3.2.9.4 Bend (flat) No cracking or checking 3.2.10 Compression Set Percent of Original Deflection, max Ring Cross Section Diameter
21、0.066 to 0.110 inch, incl (1.68 to 2.79 mm, incl) Over 0.110 inch (2.79 mm) 8575ASTM D 395 Method B Temperature: 257 F 4 (125 C 2) Time: 70 hours 0.5 3.2.11 Low-Temperature Brittleness Pass 4.5.2 SAE AMS7270L Page 4 of 83.3 Quality Product, as received by purchaser, shall be uniform in quality and c
22、ondition, smooth, as free from foreign material, as commercially practicable and free from internal imperfections detrimental to usage of the rings. Surface imperfections shall be no greater than permitted by AS871 for minor defects. 3.4 Sizes and Tolerances Shall be as specified on the drawing. Sta
23、ndard sizes are as shown in AS568. Inspection for conformance to dimensional requirements shall be made in accordance with AS871. 4. QUALITY ASSURANCE PROVISIONS 4.1 Qualification 4.1.1 Seals that qualify are placed on a Qualified Product List (QPL) maintained by the QPL agency. To qualify, seals sh
24、all meet the tests specified in Table 1, performed in accordance with the provisions of 8.2. 4.1.2 Qualification shall be in accordance with the provisions of 4.1.4 and 4.1.5. 4.1.3 Recertification of qualification is required every three years. Recertification consists of complete qualification tes
25、ts in accordance with the requirements listed in Table 1.4.1.4 Qualification testing, review of test results, approval, re-approval, and recertification of qualification for QPL listingshall be in accordance with PD 2000 or equivalent and the instructions from the responsible QPL agency. 4.1.5 Seals
26、 furnished to this specification will be listed or approved for listing on the qualified products list (QPL) in accordance with the provisions of 8.2 and 8.3. Changes in the product formulation, basic methods of manufacturer, or plant site, for qualified NBR rubber seals listed or approved for listi
27、ng on the “QPL”, are not permitted without first notifying the responsible QPL agency to assess the need for requalification and/or revision to the QPL. 4.2 Responsibility for Inspection The manufacturer of product shall supply all samples and shall be responsible for the performance of all required
28、 tests. Purchaser reserves the right to sample and to perform any confirmatory testing deemed necessary to ensure that the rings conform to specified requirements of this specification. 4.3 Classification of Tests 4.3.1 Acceptance Tests 4.3.1.1 Acceptance Tests for O-rings Requirements shown in Tabl
29、e 2 are acceptance tests and shall be performed on each lot. Acceptance tests shall be performed on the rings supplied that are suitable for test and in accordance with ASTM D 1414.For all other sizes compression set and specific gravity tests shall be conducted on the end item or a section removed
30、from the end item. Testing performed on a size -214 O-ring of the same batch and state of cure shall satisfy the remaining acceptance tests as long as the testing was performed within 90 days of the manufacture of the subject lot. NOTE: O-rings from the same lot which have not passed visual inspecti
31、on but are otherwise expected to meet the physical properties of this specification may be used for specific gravity and compression set testing. SAE AMS7270L Page 5 of 84.3.2 Acceptance Tests for All Other Seal Geometries Specific gravity and volume swell (3.2.6.4) tests shall be conducted on the e
32、nd item or a section removed from the end item. Testing performed on a size -214 O-ring of the same batch and state of cure shall satisfy the remaining acceptance tests as long as the testing was performed within 90 days of the manufacture of the subject lot.NOTE: Parts from the same lot which have
33、not passed visual inspection but are otherwise expected to meet the physical properties of this specification may be used for specific gravity and volume swell testing. TABLE 2 ACCEPTANCE TESTS Requirement Paragraph Hardness 3.2.1 Tensile Strength 3.2.2 Elongation 3.2.3 Specific Gravity 3.2.5 Volume
34、 Change in fuel 3.2.6.4 Compression Set 3.2.10 Quality 3.3 Tolerances 3.4 4.3.3 Qualification Tests All technical requirements are Qualification tests and shall be performed prior to or on the initial shipment of product by the manufacturer and when a change in ingredients and/or processing requires
35、 re-approval as in 4.5.1. 4.4 Sampling and Testing Shall be as follows: 4.4.1 For Acceptance Tests Sufficient product shall be selected at random from each lot to perform all required tests; the number of determinations for each requirement shall be as specified in the applicable test procedure or,
36、if not specified therein, not less than three. 4.4.1.1 A lot shall be all rings of same size from the same batch of compound, processed in one continuous run, and presented for manufacturers inspection at one time. 4.4.1.2 A batch shall be the quantity of compound run through a mill or mixer at one
37、time. 4.4.1.3 A statistical sampling plan acceptable to the purchaser may be used in lieu of sampling as in 4.4.1. 4.4.1.4 Sampling Plan The sample unit shall be one molded part. Acceptance is based on zero defects. Sample size for visual and dimensional requirements shall be as shown in Table 4. SA
38、E AMS7270L Page 6 of 8TABLE 4 - VISUAL AND DIMENSIONAL INSPECTION Lot Size Sample Size 2 to 8 Entire Lot 9 to 90 8 91 to 150 12 151 to 280 19 281 to 500 21 501 to 1 200 27 1 201 to 3 200 35 3 201 to 10,000 38 10,001 to 35,000 46 35,001 to 150,000 56 150,001 and Over 65 4.4.2 For Qualification Tests
39、Sufficient number of samples shall be produced from the same batch of material to meet this specification requirement. 4.5 Approval 4.5.1 Manufacturer shall establish, for each size of ring, parameters for the process control factors which will produce rings meeting the technical requirements of thi
40、s specification. These shall constitute the approved procedures and shall be used for manufacturing product. Production product made by any revised procedure shall not be shipped prior to receipt of re-approval. If necessary to make any change in parameters for the process control factors, manufactu
41、rer shall submit for re-approval a statement of the proposed changes in ingredients and/or processing and when requested, sample rings. Production product incorporating the revised procedure shall not be shipped prior to receipt of re-approval. 4.5.2 Manufacturer shall make no significant change to
42、materials, processes or controls from those on which the approval was based, unless the change is approved by the cognizant engineering organization. A significant change is one which, in the judgment of the cognizant engineering organization, could affect the properties or performance of the parts.
43、 4.5.2.1 Control factors for producing product include, but not limited to, the following: Compound ingredients and proportions thereof within established limits Sequence of mixing compound ingredients Type of mixing equipment Method and equipment for preparing preforms Basic molding procedure (comp
44、ression, transfer, injection) Curing time and pressure; variations of 10% are permissible Finishing methods Methods of inspection 4.5.2.2 Any of the above process control factors for which parameters are considered proprietary by the manufacturer may be assigned a code designation. Each variation in
45、 such parameters shall be assigned a modified code designation.SAE AMS7270L Page 7 of 84.6 Test Methods 4.6.1 Aromatic and Non-Aromatic Fuel Resistance The specimen shall be immersed, in accordance with ASTM D 471, in AMS2629 JRF at 68 to 86 F (20 to 30 C) for 48 to 72 hours and then in ASTM Referen
46、ce Fuel A at 68 to 86 F (20 to 30 C) for 48 to 72 hours. After the last immersion, the specimen may be allowed to dry in air for such time as may suit the testing schedule and shall then be dried in an oven at 158 F 2 (70 C 1) for 24 hours 0.5. 4.6.2 Low-Temperature Brittleness 4.6.2.1 The specimen
47、for rings 2 inches (51 mm) and under in nominal ID shall be a complete ring; the specimen for rings over 2 inches (51 mm) in nominal ID shall be a piece 3 inches (76 mm) long cut from a ring. The specimen shall be alternately immersed in ASTM Reference Fuels B and A in accordance with 4.5.1 and shal
48、l be transferred from the Fuel A at 68 to 86 F (20 to 30 C) to a suitable container of Fuel A in a refrigerator at -40 F 2 (-40 C 1) and held at that temperature for 5 hours 0.1. At the end of the refrigeration time, the specimen, while in the refrigerated fuel, or within 10 seconds after removal fr
49、om the fuel, shall withstand, without cracking, bending as follows: The complete ring shall be ovalized until the minor axis is equal to 50% of the original ID; the 3-inch (76-mm) specimen shall be bent around to form a circle. 4.6.2.2 Should the testing schedule be such as to make it inconvenient to transfer the specimen directly to the fuel at -40 F (-
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