1、AMSC N/A FSC 4820 INCH-POUND MIL-PRF-7908E 18 May 2009 SUPERSEDING MIL-PRF-7908D 26 November 1997 PERFORMANCE SPECIFICATION VALVES, CHECK, AIRCRAFT LOW PRESSURE OXYGEN SYSTEMS Comments, suggestions, or questions on this document should be addressed to: Oklahoma City Air Logistics Center/ENSDAA, 3001
2、 Staff Drive, Tinker AFB, OK. 73145-3036 or emailed to af71tinker.af.mil. Since contact information can change, you may want to verify the currency of this address information using ASSIST Online database at http:/assist.daps.dla.mil. Provided by IHSNot for ResaleNo reproduction or networking permit
3、ted without license from IHS-,-,-MIL-PRF-7908E 2 This specification is approved for use by the Department of the Air Force and is available for use by all Departments and Agencies of the Department of Defense. 1. SCOPE 1.1 Scope. This specification covers aircraft low pressure oxygen check valves. 1
4、.2 Classification. The valves should be one of the following type and style (see 6.2): PIN (see 6.9) TYPE STYLE M7908-1 - Check flared tube to flared tube M7908-2 - Dual check tee, end pipe thread to flared tube M7908-3 - Dual check tee, side pipe thread to flared tube M7908-4 - Dual check tee, flar
5、ed tube M7908-5 - Triple check cross, flared tube M7908-6 - Check pipe thread to flared tube M7908-7 - Check flared tube to pipe thread M7908-8 - Check side pipe thread to flared tube 1.3 Part or identifying number (PIN). The PIN to be used for valves acquired to this specification are created as fo
6、llows: M 7908 -X Dash number (see figures 1-8) Specification number Prefix for military specification 2. APPLICABLE DOCUMENTS 2.1 General. The documents listed in this section are specified in sections 3, 4, or 5 of this specification. This section does not include documents cited in other sections
7、of this specification or recommended for additional information or as examples. While every effort has been made to ensure the completeness of these lists, document users are cautioned that they must meet all specified requirements of documents cited in sections 3, 4, or 5 of this specification, whe
8、ther or not they are listed. 2.2 Non-Government publications. The following documents form a part of this document to the extent specified herein. Unless otherwise specified, the issues of these documents are those cited in the solicitation or contract. AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME
9、) ASME B46.1 - Surface Texture (Surface Roughness, Waviness, and Lay) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-PRF-7908E 3 (Copies of these documents are available from http:/www.asme.org or ASME Information Central Orders/Inquiries, P.O.
10、Box 2300 Fairfield, NJ 07007-2300). AMERICAN SOCIETY FOR QUALITY (ASQ) ANSI/ASQ Z1.4 - Sampling Procedures and Tables for Inspection by Attributes (ASQC documents may be obtained at http:/asq.org or addressed to the American Society for Quality P.O. Box 3005 Milwaukee, WI 53201-3005 or 600 North Pla
11、nkinton Avenue, Milwaukee, Wisconsin, 53203, USA) AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) ASTM B117 - Salt Spray (Fog) Apparatus, Operating (ASTM documents may be obtained at http:/www.astm.org or addressed to the American Society for Testing and Materials, 100 Barr Harbor Drive, West Cons
12、hohocken, PA 19428-2959) SOCIETY OF AUTOMOTIVE ENGINEERS (SAE) SAE AS8010 - Aviators Breathing Oxygen Purity Standard SAE AS4395 - Fitting End, Flared, Tube Connection, Design Standard SAE AS71051 - Pipe Threads, Taper, Aeronautical National Form, Symbol ANPT Design And Inspection Standard (SAE docu
13、ments may be obtained at http:/www.sae.org/ or from Society of Automotive Engineers, Inc., 400 Commonwealth Drive, Warrendale PA 15096.) 2.3 Order of precedence. Unless otherwise noted herein or in the contract, in the event of a conflict between the text of this document and the references cited he
14、rein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 3. REQUIREMENTS 3.1 First article. When specified (see 6.2), a sample shall be subjected to first article inspection in accor
15、dance with 4.2. 3.2 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or environmentally preferable materials should be used to the maximum extent possible, provided that the material meets or exceeds the operational and maintenance requirements, and promotes economi
16、cally advantageous life cycle cost. 3.3 Materials. All materials shall be corrosion resistant or suitably treated to resist Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-PRF-7908E 4 corrosion due to electrolytic decomposition, salt fog, and any
17、 other atmospheric condition that may be encountered during operational use or storage. The use of toxic chemicals, hazardous substances, or ozone depleting chemicals shall be avoided, whenever feasible. 3.3.1 Safety specific materials. All material used shall be capable of operating safely in a pur
18、e oxygen environment without creating a health or fire hazard (see 6.3 and 6.7). 3.4 Interface. 3.4.1 Dimensions. The dimensions of the valve shall be in accordance with the applicable valve type and style shown in figures 1 through 8. 3.4.2 Threads. Tapered pipe threads shall be in accordance with
19、SAE AS71051. 3.4.3 Gripping surfaces. There shall be either a hexagonal surface or flats adjacent to each external threaded section. A valve constructed in parts shall have a hexagonal surface or flats on each individual external part. The hexagonal surface and flats shall fit open end wrenches. 3.4
20、.4 Flow markings. The body of the valve shall be permanently and legibly marked with arrow(s) to signify the direction(s) of flow. 3.5 Performance. 3.5.1 Flow direction. The valve shall allow flow in the direction(s) indicated by the arrow(s) on the valve exterior as shown in figures 1 through 8. Fl
21、ow in the opposite direction(s) shall be checked. 3.5.2 Orientation. The valve shall operate in any position. 3.5.3 Weight. The weight of the valve shall be in accordance with figures 1 through 8. 3.5.4 Leakage. 3.5.4.1 Body leakage. The valve shall not leak while being pressurized from 0 to 450 pou
22、nds per square inch gage (psig). 3.5.4.2 Check leakage. The leakage of the valve shall be no greater than 1 cubic centimeter per minute (cm3/min) when applying 10 to 450 psig in the checked direction. 3.5.5 Pressure drop. The pressure drop through the valve shall not exceed 10 psig. 3.5.6 Proof pres
23、sure. The valve shall withstand a pressure of 750 psig. 3.5.7 Endurance. The valve shall withstand 20,000 cycles of opening and closing. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-PRF-7908E 5 3.5.8 Valve ignition. The valve shall not ignite
24、or show evidence of charring or burning when subjected to 450 psig with a minute leak (see 6.6). 3.5.9 Cleanliness. All surfaces shall be free of visible particulates (50 microns and larger), free of visible fluorinated lubricants, and free of hydrocarbon contamination to a level not greater than 3
25、milligrams per square foot (mg/ft)(see6.4). 3.6 Environmental conditions. The valve shall operate in the following conditions: a. Temperature: -65 to 160 F. b. Vibration: Frequencies from 5 to 50 Hz at a double amplitude of 0.018 and 0.020 inch. 3.7 Item identification. The valve shall be marked wit
26、h the following information (see 6.2): a. Item name. b. Manufacturers identification. c. Manufacturers CAGE code. d. Manufacturers part number (PN). e. Part or Identification Number (PIN). f. Additional identification information (see 6.2). 3.8 Interchangeability. All parts having the same manufactu
27、rers part number shall be functionally and dimensionally interchangeable. 4. VERIFICATION 4.1 Classification of inspections. The inspection requirements specified herein are classified as follows: a. First article (see 4.2). b. Conformance (see 4.3). 4.2 First article inspection. First article inspe
28、ction shall be performed on three valves of each type. First article inspection shall include all tests described in 4.6. 4.3 Conformance inspection. Conformance inspection shall include the tests in 4.3.1 and 4.3.2. 4.3.1 Individual tests. Each valve shall be subjected to the following tests: a. Ex
29、amination (see 4.6.1). b. Check leakage (see 4.6.4.2). c. Pressure drop (see 4.6.5). Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-PRF-7908E 6 4.3.2 Sample tests. In addition to the tests indicated in 4.3.1, the valves and fittings shall be sam
30、pled in accordance with ANSI/ASQ Z1.4 at a normal inspection level unless modified in the procurement document (see 6.2), and shall be subjected to the following tests: a. Dimensions (see 4.6.2). b. Body leakage (see 4.6.4.1). c. Proof pressure (see 4.6.8). 4.4 Test conditions. 4.4.1 Test medium. Ox
31、ygen conforming to SAE AS 8010, Type I, shall be used. 4.4.2 Temperature and pressure. Unless otherwise specified in the individual test description, tests shall be conducted at ambient temperature and pressure. 4.4.3 Multiple checks. For those valve types that have more than one check devices, test
32、s performed shall be applicable to each flow passage through the valve. 4.4.4 Positioning. Valves subjected to leakage and pressure drop tests shall be positioned with the center line of the passage parallel to a vertical plane. Each consecutive valve tested shall be rotated 90 about an axis perpend
33、icular to the vertical plane from the position of the valve previously tested. The rotation shall always be in the same direction. 4.5 Requirements cross-reference matrix. Table I provides a cross-reference matrix of the section 3 requirements tested or verified in the paragraphs below. TABLE I. Req
34、uirements cross-reference matrix Requirement Verification Requirement Verification 3.1 4.2 3.5.4.1 4.6.4.1 3.3 4.6.1, 4.6.11, 4.6.12 3.5.4.2 4.6.4.2 3.3.1 4.6.1, 4.6.10, 4.6.12 3.5.5 4.6.5 3.4.1 4.6.2 3.5.6 4.6.8 3.4.2 4.6.1 3.5.7 4.6.9 3.4.3 4.6.1 3.5.8 4.6.10 3.4.4 4.6.1 3.5.9 4.6.3 3.5.1 4.6.4.2
35、3.6 4.6.6, 4.6.7 3.5.2 4.6.4 3.7 4.6.1 3.5.3 4.6.1 3.8 4.6.1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-PRF-7908E 7 4.6 Tests. 4.6.1 Examination. The valve shall be examined for compliance with the requirements for materials, interface (less
36、 dimensions), weight, interchangeability, markings, and item identification (see 6.3). 4.6.2 Dimensions. The valve shall be examined for compliance with the requirements for dimensions. 4.6.3 Cleanliness. All surfaces shall be free of visible particulates (50 microns and larger), free of visible flu
37、orinated lubricants, and free of hydrocarbon contamination to a level not greater than 3 mg/ft (see 6.4). Cleanliness of the surfaces shall be demonstrated by industrially accepted methods and these cleaning and verification methods shall be identified (see 6.2 and 6.4). 4.6.4 Leakage. 4.6.4.1 Body
38、leakage. With the outlet sealed, the valve shall be immersed in water and the inlet(s) shall be pressurized from 0 to 450 psig. While the valve is immersed, a pressure of 450 psig shall be maintained for 2 minutes. There shall be no breakaway of bubbles after 30 seconds (see 4.4.4 and 6.5). 4.6.4.2
39、Check leakage. The outlet of the valve shall be pressurized from 0 to 450 psig at a rate between 200 and 450 psig/minute. The inlet(s) leakage shall not exceed one cm3/min (see 4.4.4). 4.6.5 Pressure drop. A pressure of 300 psig shall be applied at the inlet(s) of the valve and a flow of 400 standar
40、d liters per minute (SLPM)(see 6.8) shall be maintained through the valve for 1 minute. The pressure drop across the valve shall not exceed 10 psig (see 4.4.4). 4.6.6 High and low temperature. 4.6.6.1 High temperature. With a pressure of 450 psig maintained at the outlet, the valve shall be subjecte
41、d to a temperature of 160 5 F for 3 hours. At the beginning, in the middle, and at the end of this period, the valve shall be subjected to the check leakage test in 4.6.4.2 4.6.6.2 Low temperature. With a pressure of 450 psig maintained at the outlet, the valve shall be subjected to a temperature of
42、 -65 5 F for 3 hours. At the beginning, in the middle, and at the end of period, the valve shall be subjected to the check leakage test in 4.6.4.2 4.6.7 Vibration. A pressure of 450 psig shall be applied to the outlet of the valve. The valve shall be vibrated for 6 hours using a double amplitude of
43、0.018 to 0.020 inch at a varying frequency of 5 to 50 Hz. During the vibration period, the valve shall be subjected to the check leakage and pressure drop tests in 4.6.4.2 and 4.6.5 at six equal intervals Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,
44、-,-MIL-PRF-7908E 8 4.6.8 Proof pressure. A pressure of 750 psig shall be applied to the inlet(s) with the outlet sealed and maintained for 1 minute. The valve shall then be subjected to the body leakage and check leakage tests in 4.6.4.1 and 4.6.4.2. 4.6.9 Endurance. With an inlet pressure of 450 ps
45、ig, a flow of 50 SLPM shall be induced through the valve for 3 seconds (opening the valve) followed by a 0 SLPM flow for 3 seconds (closing the valve). This shall constitute one cycle. The test shall continue for a minimum of 20,000 cycles. The valve shall then be subjected to the individual tests i
46、n 4.3.1 during the test, the pressure 450 psig may drop to 300 psig before recharging to 450 psig. 4.6.10 Valve ignition. With a pressure of 450 psig applied to the valve outlet, the valve shall be opened to create a minute leak (see 6.6). This test shall be conducted three times for a period of 5 m
47、inutes each. The valve shall show no evidence of charring or burning 4.6.11 Salt fog. With the inlet(s) and outlet plugged, the valve shall be subjected to the salt fog test in ASTM B117 for 50 hours. There shall be no damage and the valve shall be subjected to the leakage tests in 4.6.4 4.6.12 Disa
48、ssembly and examination. At the conclusion of these tests, the valve shall be disassembled and show no evidence of deterioration or wear. 5. PACKAGING 5.1 Packaging. For acquisition purposes, the packaging requirements shall be as specified in the contract or order (see 6.2). When packaging of mater
49、iel is to be performed by DoD or in-house contractor personnel, these personnel need to contact the responsible packaging activity to ascertain packaging requirements. Packaging requirements are maintained by the Inventory Control Points packaging activities within the Military Service or Defense Agency, or within the military services
