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 2016 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/ARP1398A AEROSPACE RECOMMENDED PRACTICE ARP1398 REV. A Issued 1989-02 Revised 200
5、0-11Reaffirmed 2016-03 Superseding ARP1398 Testing of Oxygen Equipment RATIONALE ARP1398A has been reaffirmed to comply with the SAE five-year review policy. FOREWORDChanges in this revision are format/editorial only.1. SCOPE:This ARP delineates requirements for system cleanliness, test gas supply s
6、ystem, test stand design, environmental chamber definition, instrumentation, dynamic test equipment and testing procedures.1.1 Purpose:The purpose of this SAE Aerospace Recommended Practice (ARP) is to establish or outline, or both, methods and procedures for use in testing oxygen equipment.2. REFER
7、ENCE DOCUMENTS:(Use current issue)2.1 SAE Publications:Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096AIR822 Oxygen Systems for General AviationAIR825 Oxygen Equipment for AircraftARP1109 Dynamic Testing System for Oxygen Breathing EquipmentAIR1176 Oxygen System and Component Cleani
8、ng and PackagingAS8010 Aviators Breathing Oxygen Purity Standard2.2 Other Publications:MIL-STD-17B-2 Mechanical Symbols for Aeronautical, Aerospacecraft and Spacecraft UseMIL-STD-167 Mechanical Vibrations of Shipboard EquipmentMIL-STD-810 Environmental Test Methods for Aerospace seamless aluminum is
9、 acceptable for gas pressures below 500 lbf/in2(gage) (3450 kPa); PVC tubing is acceptable for pressures below 200 lbf/in2(gage) (1380 kPa) for air, nitrogen or oxygen.Stainless steel or copper alloy fittings may be brazed-on nipples or regular flared or flareless fittings. Aluminum tubing shall uti
10、lize regular flared fittings with coupling sleeve.3.4.2.1.6 Fittings: Forged, cast and machined fittings such as elbows and tees for stainless steel, copper or aluminum tubing shall be welded or brazed. For low pressures below 200 lbf/in2(gage) (1380 kPa) soldering is acceptable if all traces of flu
11、x are removed. Matching or interfacing dissimilar metals together shall be avoided.3.4.2.1.7 Tubing bends (radii) shall be as large and sweeping as practicable (see 3.4.2.1.2).3.4.2.1.8 Routing: In the interest of minimizing dead air space, the tubing need not be square or parallel to the test stand
12、 sides. Rather, it may go directly from point to point (that is, direct from valve to manometer to test chamber) regardless of the resultant tubing angle(s) to the test stand. However, neatness of appearance and minimum stress in misaligned tubing should be considered. Ease of servicing shall be con
13、sidered in the plumbing layout.3.4.2.2 Valves: Valves of all major types may be used. A partial list includes:a. Poppetb. Rotorc. Balld. Needlee. Plate-Seatf. GateEach valve shall be of a type suitable for its intended use. (For example, a needle valve for fine adjustment.)3.4.2.3 Regulators: Regula
14、tors shall be clearly and permanently marked as to type (demand, vacuum, pressure demand manual, etc.), MIL-Spec number, and functional positions (that is, increase pressure, decrease pressure, etc.), and pressure range.3.4.2.4 Vacuum Systems:3.4.2.4.1 Accumulator or Reservoir: A vacuum accumulator
15、of sufficient volume shall be utilized to prevent excessive fluctuations in vacuum negative pressures. Usually, a preset vacuum regulator shall be positioned between the accumulator and the vacuum source (pump) to maintain a constant negative pressure to the accumulator. Naturally, a vacuum pump of
16、sufficient capacity to maintain constant negative pressure in the accumulator is required. Use of an ejector system is recommended for evacuating oxygen rich atmospheres.SAE INTERNATIONAL ARP1398A 7 OF 363.4.2.5 Filters: The test stand shall include necessary filters insuring that all test supply ga
17、ses or fluids, or both, are filtered upstream of all valving, metering, measuring or control devices. Vacuum bleed valves shall also utilize filters on the upstream side to prevent contamination from entering the test stand system.3.4.2.6 Breathing Machines: For information and recommended practices
18、 on breathing machines, see ARP1109.3.4.2.7 Other Hardware Items:3.4.2.7.1 Standard Hardware Items: Standard hardware items such as nuts, bolts, screws, washers, clamp terminal connectors, switches, etc., shall be MS or AN wherever they are suitable for the intended purpose. Commercial utility hardw
19、are components may be utilized provided they are suitable for the intended purpose. Such commercial utility hardware components may be utilized provided they are suitably protected by plating, etc., and possess all other suitable properties.3.4.2.7.2 Materials: The materials used in the construction
20、 of an oxygen test stand shall be of high quality, compatible with oxygen, entirely suitable for the intended purpose. Whenever plastics are used, they shall be suitable for the intended purpose.3.4.2.7.3 Metals: All metals used in construction with the test stand shall be corrosion-resistant or sha
21、ll be suitably protected to resist corrosion during the normal life of the equipment. Dissimilar metals in intimate contact shall be avoided.3.5 Environmental Test Chambers:Environmental chambers for the testing of oxygen equipment or systems to simulate the effects of high altitude and related ambi
22、ent conditions as contemplated for civil aircraft applications are commercially available. Custom designed chambers for specific applications such as the physiological reaction of humans to environmental extremes are also available. The requirements of the National Fire Protection Association docume
23、nt NFPA 99-1984 must be considered during design, construction and operation of hyperbaric or hypobaric facilities which are man rated.Although not limited to the following, the majority of equipment for civil aircraft use will be subjected to extremes of altitude, temperature and humidity.3.5.1 Com
24、bination Test Chambers:3.5.1.1 Environmental test chambers capable of multiple testing for altitude, temperature and humidity, or any combination thereof, may be utilized.SAE INTERNATIONAL ARP1398A 8 OF 363.5.1.1.1 Chamber Volume: Chamber internal work volume may vary from as small as 1 ft3to as lar
25、ge as 250 ft3(0.028 to 7.08 m3) with some custom built chambers even larger.3.5.1.1.2 Chamber Materials: Internal chamber surfaces shall be constructed preferably of welded stainless steel for purposes of high strength, corrosion resistance, minimization of pressure and temperature loss, and for eas
26、e of cleanliness. Any use of wood construction is to be avoided.3.5.1.1.3 Chamber Insulation: The chamber shall be fully insulated for low heat transfer and impermeability to moisture.3.5.1.1.4 Chamber Strength: Structural integrity of the chamber utilized shall be verified for the altitude range de
27、sired when subjected to vacuum to prevent implosion.3.5.1.1.5 Access Door: A full opening, full width access door provided with a thermal pane fracture-proof viewing window, along with internal illumination, is desirable. The access door shall be provided with a minimum of two peripheral door seals
28、for vacuum and thermal insulation and with rugged, quick release door latches.3.5.1.1.6 Access Ports: Adequate access ports for pressure and instrumentation lines to the test specimen should be located in the chamber side walls. All pressure or electrical line connectors shall be pressure tight.3.5.
29、1.1.7 Circulation Fans: Internal circulation fans with grid protection shall be available for air circulation and reduction of hot or cold spots. The fans shall be provided with externally located motors and on-off controls; a fan on-off door interlock switch is desirable.3.5.1.1.8 Temperature Senso
30、rs: Unless otherwise specified, thermocouples or equivalent temperature sensors utilized to determine or control the specified chamber temperature shall be centrally located within the test chamber where possible or in the return air stream, and shall be baffled or otherwise protected against imping
31、ement of supply air and against radiation effects.3.5.1.1.9 Altitude Indicator: An easy to view, externally mounted mercury manometer shall be utilized for direct indication of altitude within the chamber. Dual calibration in millimeters of mercury and altitude in feet is preferred.3.5.1.1.10 Temper
32、ature Indicator: Various instruments are available for the measurement or recording of chamber internal temperatures. The device utilized shall be selected to provide sufficient accuracy, response, and range for the test being conducted. Devices available include liquid or bi-metal thermometers, the
33、rmowells with electronic readouts, analog or digital readouts with thermocouples or thermistors and strip chart recorders. Electronic readouts designed for use with thermocouples offer certain advantages such as: high accuracy, ability to attach sensors directly to item under test and multichannel c
34、apability. For additional information refer to 3.6.4.SAE INTERNATIONAL ARP1398A 9 OF 363.5.1.1.11 Humidity Indicator: A Wheatstone bridge type hygrometer located externally on the chamber, with a varying resistance humidity sensor located within the chamber, may be used as a direct readout for relat
35、ive humidity. Accuracy of 1% in the range of 1 to 98% relative humidity is required. Correction factors for the variation in chamber temperature are usually necessary with this instrument.Another method for measuring humidity is by the use of a dew point hygrometer. Since dew point is independent of
36、 temperature the control of chamber temperature is less critical, allowing more convenient indication.A third method of measuring relative humidity within the chamber is the use of the conventional wet and dry bulb thermometers. While relatively accurate (1 to 4%), the direct readout types must be p
37、laced directly in the circulated airstream within the chamber, thereby, restricting viewing. By using charts prepared for this purpose, the relative humidity (percent of saturation) can be determined at any given temperature by viewing the difference in reading between the wet and dry bulbs. Remote
38、control recorder indicators using wet and dry bulbs are also available.3.5.1.1.12 Electrical Requirements: All electrical components and wiring shall comply with the national electrical code and OSHA requirements. No exposed wiring shall be allowed within the chamber.3.5.1.2 Low Temperature: Two bas
39、ic methods of cooling environmental test chambers are in current use. One approach is the injection of cold gases (CO2or N2) taken from their liquid state. The more common method is the mechanical refrigeration type with compressor(s) similar in some respects to the household refrigerator.Lower temp
40、erature, lower operating costs, faster cooling and pull-down with improved control accuracy, together with lower frost and ice buildup, are certain advantages normally associated with the mechanical type vs. the gas injection type.Mechanical systems are available in single stage or cascade types whe
41、re extreme low temperatures or rapid pull-down is required.The gas injection type is normally cheaper to procure or construct, and due to less complexity, is usually considered more reliable in operation and startup after long periods of shutdown. These units are usually easier and less expensive to
42、 repair.Liquid CO2or LN2are often used as boosters or as a backup cooling system for the primary mechanical refrigeration system.A third method of cooling, the use of frozen CO2(dry ice), may be more difficult to control.SAE INTERNATIONAL ARP1398A 10 OF 363.5.1.2.1 Low Temperature Range: The test ch
43、amber shall be capable of reducing the temperature of the internal volume to -100 F (-73.3 C) from an ambient temperature of 75 F (23.9 C).3.5.1.2.2 Low Temperature Control Accuracy: After stabilization of the chamber internal temperature at any set point from ambient to -100 F (-73.3 C), the regula
44、tion system shall be capable of maintaining that temperature at the control sensor within 2.5 F (1.4 C). The temperature gradient across the cross sectional area occupied by the test item shall not exceed 0.5 F (0.3 C) per foot in any direction.3.5.1.2.3 Temperature Pull-Down Rate: The chamber with
45、the test specimen installed shall be capable of reducing the internal temperature from ambient to -100 F (-73.3 C) within a time period of 30 to 90 min.Special thermal shock units are available for immediate temperature reduction.3.5.1.3 High Temperature: Heating of the chamber shall be conducted by
46、 open wire staged heating elements for rapid response and close tolerance control. The heating element(s) shall be suitably protected from the working area by a baffle. Blowers shall be employed for proper heat convection and air flow. If the chamber is to be utilized for high oxygen concentrations,
47、 open-wire staged heating elements are potentially hazardous and radiant heating is then recommended.3.5.1.3.1 High Temperature Range: The test chamber shall be capable of raising the internal volume to a temperature of 350 F (177 C) from an ambient temperature of 75 F (23.9 C).3.5.1.3.2 High Temper
48、ature Control Accuracy: After stabilization of the chamber internal temperature at any set point from ambient to +350 F (177 C), the regulation system shall be capable of maintaining that temperature at the control sensor within 2.5 F (1.4 C). The temperature gradient across the cross sectional area
49、 occupied by the test item shall not exceed 0.5 F (0.3 C) per foot in any direction.3.5.1.3.3 Temperature Buildup Rate: The chamber, with the test specimen installed, shall be capable of increasing the temperature from ambient to +350 F (177 C) within a time period of 30 to 60 min. Special thermal shock chambers shall be employed where immediate temperature increase is required.3.5.1.4 Altitude: Pressure eva
