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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 therefr
2、om, 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 2004 SAE International All rights reserved. No part of this publication may
3、 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: 724-776-4970 (outside USA) Fa
4、x: 724-776-0790 Email: custsvcsae.org SAE WEB ADDRESS:http:/www.sae.org AEROSPACE STANDARD AS4251 Issued1988-07 Reaffirmed2004-04 Coupling Assemblies, Non-Locking Probe Style, Self-Aligning, Self-Sealing Disconnects 1.SCOPE: This specification establishes the requirements for a probe type self-seali
5、ng, self-aligning, non-locking coupling intended for aerospace hydraulic and cooling systems. 1.1Classification: Fluid self-sealing disconnect couplings shall be of the following classes: Class 500:500 lbf/in2 rated pressure (psi) Class 4000:4000 lbf/in2 rated pressure (psi) 2.APPLICABLE DOCUMENTS:
6、2.1Issues of Documents: The following documents of the issue in effect on date of invitation for bids, or request for proposal, form a part of this specification to the extent specified herein. 2.1.1Military Specifications: MIL-H-5440Hydraulic Systems: Design, Installation and Test of Aircraft, Gene
7、ral Specification for MIL-H-5606Hydraulic Fluid, Petroleum Base, Aircraft and Ordnance MIL-H-8775Hydraulic System Components, Aircraft and Missile, General Specification for MIL-H-83282Hydraulic Fluid, Fire Resistant Synthetic Hydrocarbon Base, Aircraft MIL-P-83461Packing, Preformed, Petroleum Hydra
8、ulic Fluid Resistant, Improved Performance at 275 deg F MIL-R-8791Retainer, Packing, Hydraulic and Pneumatic, Tetrafluoroethylene Resin MIL-STD-129Marking for Shipment and Storage MIL-STD-130Identification Markings of U.S. Military Property MIL-STD-810Environmental Test Methods SAE AS4251 - 2 - 2.2O
9、ther Publications: 2.2.1Society of Automotive Engineers (SAE): AIR1047BA Guide for the Selection of Quick-Disconnect Couplings for Aerospace Fluid Systems ARP24BDetermination of Hydraulic Pressure Drop ARP1383Impulse Testing of Hydraulic Actuators, Valves, Pressure Containers and Similar Fluid Syste
10、m Components 3.REQUIREMENTS: 3.1Qualification: The couplings furnished under this specification shall be a product which has been tested, and has passed the qualification tests specified herein, and has been approved by the Procuring Agency or Prime Contractor. 3.2General Specification: The requirem
11、ents of MIL-H-8775 apply to this specification except as specified herein. 3.3 Materials: The coupling shall be constructed of materials that will not change the composition of or be adversely affected by specified fluids. Materials, processes and parts shall meet the design requirements and intent
12、of MIL-H-8775 for Classes 500 and 4000, fluids and material compatibility tests shall be conducted by the supplier to demonstrate the satisfactory performance of the couplings. 3.4Design and Construction: The configuration, dimensions, and other details of design of the couplings shall conform to ap
13、plicable Specification Control Drawings. The design objective shall be to obtain the envelope dimensions per Table IV herein and lightest weight commensurate with meeting performance requirements herein. The misalignment provision in the nipple half shall be 0.020 in radial; angular misalignment sha
14、ll be specified by the Procuring Agency. When coupled, the coupling shall be such that it will permit fluid flow in either direction in accordance with the rated flow and pressure drop as specified in Table I. Flow shall not be blocked under surge conditions. (Reference Table IV for Envelope Dimensi
15、ons). A thermal relief valve shall be incorporated as an optional design feature, if specified by the Procuring Agency. SAE AS4251 - 3 - TABLE I - Rated Flow and Pressure Drop 3.4.1Temperature Range: Couplings shall be designed to operate throughout the temperature range specified by 3.6.3. 3.4.2Sea
16、ling and Fluid Loss: The couplings shall, when disconnected, seal the ends of the disconnected lines at the point of disconnection and shall not permit external leakage during any phase of connection or disconnection. Fluid loss (spillage) as specified in Table II is not considered to be external le
17、akage. Both halves of the coupling shall seal fluid under both low and high pressures (see 4.6.4). TABLE II - Air Inclusion and Fluid Loss 3.4.3Seals: The MIL-P-83461 Packing Material and MIL-R-8791 Retainer Material shall be used with MIL-H-5606, or MIL-H-83282 Hydraulic Fluid. Packing and retainer
18、 material for other fluids shall be specified by the Procuring Agency. However, the supplier shall demonstrate that the performance of the coupling is satisfactory with the packing and retainer materials used. SAE AS4251 - 4 - 3.4.4Operation: The couplings shall be so designed that they can be conne
19、cted and disconnected while mounted in their respective manifolds or fixtures. It shall be possible to connect and disconnect with an internal pressure, as shown in Table III, applied to both halves and to each one- half respectively (see 4.6.10). TABLE III - Coupling Forces and Separating Force Wit
20、h the Pressure Indicated in Both Halves SAE AS4251 - 5 - TABLE IV - Envelope Dimensions SAE AS4251 - 6 - 3.5Interchangeability: It shall be impossible to interconnect different tube sizes and couplings of different pressure classes shall not be capable of cross-coupling. Coupling halves of the same
21、part number shall be interchangeable and cross-couple all referenced mating halves. 3.6Performance: The self-sealing couplings furnished under this specification shall perform satisfactorily when conforming to the following performance requirements. 3.6.1Envelope, Weight, Materials: Each coupling ha
22、lf must conform to the applicable purchaser and supplier envelope dimensions, weight control, materials, and finishes. Table IV is provided with some envelope dimension guidelines. 3.6.2Proof Pressure: Each coupling half must meet operational and leakage requirements after being subjected to proof p
23、ressure of 150% of rated pressure for a period of 1 min (see 4.6.2). 3.6.3Extreme Temperature Functioning: Each coupling half shall show no malfunction during or after being subjected to extreme temperature testing from -65 to 275 F unless otherwise specified (see 4.6.3). 3.6.4Leakage: Coupling halv
24、es shall meet specified leakage requirements at 30 in static head of test fluid and at rated pressure (see 4.6.4). 3.6.5Vacuum: The connected and disconnected coupling shall meet inward leakage requirements with no evidence of malfunction or degradation, with equivalent of 10 in of Hg applied and li
25、nes closed for 5 min (see 4.6.5). 3.6.6Surge Flow: Coupling halves shall meet leakage, operational and pressure drop requirements after being subjected to a surge flow of five times the rated flow in each direction (see 4.6.6) as specified in Table I. 3.6.7Vibration: Unless otherwise specified, the
26、connected and disconnected coupling must be capable of withstanding the vibration environment specified without experiencing any malfunction or degradation. Couplings shall be pressurized with 15 lbf/in2 (gage) pressure (see 4.6.7). The level of vibration shall be per Fig. 2 and the test set-up per
27、Fig. 1. -,-,- SAE AS4251 - 7 - FIGURE 1 - Set-up for Vibration Test -,-,- SAE AS4251 - 8 - FIGURE 2 - Composite Vibration Test Curve for Equipment Mounted on Helicopters or Airplanes -,-,- SAE AS4251 - 9 - 3.6.8Impulse: Coupled assemblies shall be capable of withstanding the impulse testing specifie
28、d per ARP1383 without any indication of malfunction. Pressures, rate of rise and impulse form parameters shall be per Table V and Fig. 3 (see 4.6.8). TABLE V - Impulse Test FIGURE 3 - Impulse Test LEGEND: 1.Peak Pressure shall be within this pressure range, 10 - 25% of cycle. 2.Desired wave form. 3.
29、Pressure rise rate. 4.50 - 150 lbf/in2 (gage) back pressure Pr = Rated Pressure SAE AS4251 - 10 - 3.6.9Endurance: Each coupling half shall be capable of withstanding 1000 endurance cycles without any evidence of malfunction or serious degradation, with 15 lbf/in2 (gage) internal pressure applied to
30、each half (see 4.6.9). 3.6.10 Operation and Separating Force: Coupling halves shall be capable of being tested in accordance with specified requirements with no evidence of malfunction, leakage or spillage beyond the specified limits of Tables II and III (see 4.6.10). NOTE: Both coupling halves shal
31、l be installed in systems capable of accommodating some fluid displacement without pressure rise. 3.6.11 Air Inclusion: The air inclusion for all coupling halves shall be within specified limits per Table II and at 30 in of internal fluid pressure applied (see 4.6.11). 3.6.12 Impact: Unless otherwis
32、e specified by the Procuring Agency, connected assemblies shall withstand a 20 g impact test without evidence of damage. Evidence of leakage or malfunction after the test is not permitted (see 4.6.12). 3.6.13 Pressure Drop: Each coupling shall indicate a pressure drop within the limits specified in
33、Table I. The fluid temperature shall be 100 10 F and test set-up shall be as shown in Fig. 4 (see 4.6.13). FIGURE 4 - Set-up for Pressure Drop Test (Reference ARP24) 3.6.14 Burst Test: Coupling halves shall be capable of withstanding 250% of rated pressure at 275 F temperature without fluid loss or
34、rupture (see 4.6.14). SAE AS4251 - 11 - 3.7Identification of Product: The coupling shall be marked for identification in accordance with MIL-STD-130. In addition, each coupling shall be permanently marked with the customer (NSN, MS, Purchaser Assigned) part number, manufacturers part number and the
35、manufacturers name or code identification number. When available surface area precludes complete identification, a tag may be attached. 3.8Workmanship: Workmanship shall be of the quality necessary to produce couplings free from all defects that would affect proper functioning in service. 4.QUALITY
36、ASSURANCE PROVISIONS: 4.1Inspection Responsibility: The supplier is responsible for the performance of all inspection requirements as specified. Except as otherwise specified, the supplier may utilize his own or any other inspection facilities and services acceptable to the Procuring Agency. Inspect
37、ion records of the examination and tests shall be kept complete and available to the Procuring Agency as specified in the contract or order. The government or Procuring Agency, or both, reserve the right to perform any of the inspections set forth in the specification where such inspections are deem
38、ed necessary to assure suppliers and services conform to prescribed requirements. 4.2Classification of Tests: The tests shall consist of qualification tests and acceptance tests (see 4.3 and 4.4 respectively). 4.3Qualification Tests: The qualification tests shall consist of the following tests and s
39、hall be conducted in the following order. All tests are described under 4.6. Unless otherwise specified, one test sample of each size shall be subjected to all indicated tests. Test samples shall be typical production units. (a) Examination of Product(4.6.1) (b) Proof Pressure(4.6.2) (c) Extreme Tem
40、perature Functioning(4.6.3) (d) Leakage(4.6.4) (e) Vacuum(4.6.5) (f) Surge Flow(4.6.6) (g) Vibration(4.6.7) (h) Impulse(4.6.8) (i) Endurance(4.6.9) (j) Operating and Separating Force(4.6.10) (k) Air Inclusion(4.6.11) (l) Impact(4.6.12) (m)Pressure Drop(4.6.13) (n) Burst Pressure(4.6.14) SAE AS4251 -
41、 12 - 4.4Acceptance Tests: The acceptance tests shall consist of the following tests. All tests are described under 4.7. (a) Examination of Product(4.7.1) (b) Proof Pressure(4.7.2) (c) Leakage(4.7.3) (d) Operation(4.7.4) (e) Cleanliness Verification(4.7.5) 4.5Test Conditions: 4.5.1Test Fluid: Unless
42、 otherwise specified, the fluid for qualification testing for Class 4000 couplings shall be either per MIL-H-5606 or MIL-H-83282; other fluids may be specified by the Procuring Agency, if required. The fluid for Class 500 couplings shall be specified by the Procuring Agency. 4.5.2Temperature: Except
43、 where otherwise specified, the tests of this specification shall be conducted at a room temperature of 70 - 90 F and with a fluid temperature of 70 - 110 F, as measured within 12 in of the test sample. The actual temperature of the fluid during the tests shall be recorded in the test reports. 4.5.3
44、Immersion: The couplings shall be immersed continuously in the specified fluid for a period of 72 h at a maximum specified temperature prior to conducting the qualification test (see 4.3). All internal parts of the coupling shall be in contact with the fluid during this immersion. After the 72 h soa
45、k period, the coupling shall be subjected to the next test immediately or remain in the fluid at normal room temperature until such test. Temperature range for the couplings shall be determined by the Procuring Agency. 4.6Test Methods: 4.6.1Examination of Product: Visually inspect the unit to verify
46、 good workmanship and correct markings. Physically measure and record all dimensions noted on applicable assembly drawings to verify correct configuration, envelope mounting requirements, interface dimensions and applicable dimensional tolerances. Record dry weight. Visually check finish and materia
47、l usage. For acceptance tests only, dimensions are not required to be recorded, and weight is only required on a sampling basis. 4.6.2Proof Pressure: The connected coupling and the disconnected halves shall be subjected to a proof pressure of 150% of the rated pressure for a period of 1 min at room
48、temperature. There shall be no leakage greater than specified, nor any permanent distortion or other malfunctioning of the coupling. The coupling shall couple and uncouple normally and seal hydraulic fluid as required after being subjected to this test. This test shall be repeated after all other te
49、sts required have been accomplished but just prior to the burst pressure test (see 4.6.14). This repeat test shall be conducted at 275 5 F for a duration of 5 min for qualification tests. SAE AS4251 - 13 - 4.6.3Extreme Temperature Functioning: The couplings shall withstand the following tests without malfunctioning or leakage in excess of the values specified (see 4.6.4). 4.6.3.1High Temperature: