1、AECMA STANDARD prEN 2255 NORME AECMA Edition P 1 AECMA NORM November 1996 PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES IAECMA) Gulledelle 94 - 8-1200 BRUXELLES - Tel. (t321 2 775 81 10 - Fax. (+321 2 775 81 11 Supersedes Corrigendum dated 1997-02.28 CORRIGENDUM No. 2 1998-07-02 ENGL
2、ISH VERSION Aerospace series Flexible hose assemblies in polytetrafluoroethylene (PTFE) - Type 3 - Technical specification Srie arospatiale Tuyauteries flexibles en poiyttrafluorthyine (PTFE) - Type 3 - Spcification technique Luft- und Raumfahrt Schiauchleitungen aus Polytetrafluorethylen (PTFE) Tec
3、hnische Lieferbedingungen - Typ 3 - Replace all pages of Edition P 1, N pages (modifications indicated by a line in the margi I 1 Note: prEN 2255, Edition P I, November 1996, has been distributed by circular AECMABNAE n O 56687 dated 1996- 12-06. Nota - Extra copies can be supplied by 6.N.A.E. - Tec
4、hnopolis 54 . 199. rue Jean Jacques Rousseau - 921 38 iCSY.CES-MOULINEAUX CEDEX Comments should be sent within SIX months after the date of publication ro I Edition approved for publication 1996-1 1-29 AECMA Gulledelle 94 B-1200 BRUXELLES C4 Chairman Mr Staib aecma 1996 - STD-AECIA PREN 2255-ENGL 17
5、9b M LO32331 0032527 7b5 Page 2 prEN 2255 : 1996 Contents list Scope Normative references Definitions, symbols and abbreviations Description of the product Test compliance Qualification Acceptance conditions Quality assurance Annex A (normative) Principle of installation for measuring the elongation
6、 and the intemal volume of flexible hose assemblies STD-AECMA PREN 2255-ENGL L77b LOL23Ll 0032528 bTL Page 3 prEN 2255 : 1996 1 Scope This standard specifies the characteristics of flexible hose assemblies in polytetrafluoroethylene (PTFE) type 3 for pressure classes I, II and III, in accordance wit
7、h EN 2245, used for carrying fluids in aircraft systems. This standard applies each time that it is referred to in a design document. This standard does not apply to flexible hose assemblies intended for oxygen systems. 2 Normative references This European Standard incorporates by dated or undated r
8、eference provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafier. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorp
9、orated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. IS0 2685 Aircraft - Environmental conditions and test procedures for airborne equipment - Resistance to fire in designated fire zones IS0 7258 Polytetrafluoroethylene (PTFE) tubin
10、g for aerospace applications - Methods for the determination of the density and relative density EN 2245 Pipelines for liquids and gases - Definitions - Aerospace series 1) EN 2379 Aerospace series - Fluids for assessment of non-metallic materials 2) EN 3042 Aerospace series - Quality assurance - EN
11、 aerospace products - Qualification procedure 3 Definitions, symbols and abbreviations See EN 2245, 4 Description of the product Each flexible hose assembly consists of a cylindrical hose of constant cross section fitted with a permanent end fitting at each end. Permanent fixing by means of a clamp
12、on the end fitting is not permissible. The hose consists of an inner tube covered with a corrosion resisting steel braiding. The braiding shall be tightly wound and uniform, free from impurities, knots and defects. Broken or missing wires shall lead to rejection. Wires crossing each other do not for
13、m a reason for rejection. The inner tube shall be a seamless extruded tube in polytetrafluoroethylene resin and shall have a uniform wall thickness. The internal surface shall be smooth and free from porosities and pits. Additives may be included in the mixture from which the tube is extruded. The h
14、ose assembly shall be fitted with end fittings suitable for the intended use. Furthermore, the assembly end fittings shall make it possible to conduct the tests. The end fittings shall be free from burrs and all contact surfaces shall be smooth; only annular machining All hose assemblies shall be fr
15、ee from oil, grease, impurities and other foreign matter, inside and outside. I marks of 2,5 pm mm max. are permissible. 1) Published as AECMA Standard at the date of publication of this standard 2) Published as AECMA Prestandard at the date of publication of this standard STD-AECMA PREN 2255-ENGL L
16、77b m 1012333 0032529 538 m Page 4 prEN 2255 : 1996 5 6 5 Test compliance Impulse test Bending test Other tests 1) 350 360 760 460 350 360 760 460 Before use on aircraft, the types of hose and flexible hose assemblies shall have been subjected to the qualification tests specified in this standard. 1
17、0 12 Before installation in the aircraft, each hose and flexible hose assembly shall have been subjected to the acceptance tests specified in this standard. Some of these tests may, however, be carried out at any time of manufacture or assembly. 350 460 760 460 350 530 760 460 6 Qualification 20 25
18、32 6.1 Submission and class of flexible hose for which qualification is required, the manufacturer shall submit samples for tests of which the quantity, test breakdown and test sequence are given in table 9 and the lengths in table 1. I For each DN . 350 700 760 460 350 460 760 460 350 460 760 460 T
19、able 1 : Length of hose assemblies I I 40 350 460 I 760 I 460 1) For the electrical conductivity test, hose lengths are given in 6.4.2.13 64XH-3. For hose assemblies subjected to the fire test, the lengths will be indicated in the specific document for this test (see 6.4.2.14 the rollers shall be ar
20、ranged to prevent inadvertent rotation. The roller angles, specified in table 2, are applicable provided that the inner tube is in a horizontal position and that the pressure of the first set of rollers is applied vertically. The angles given for the last three sets of rollers may be taken as either
21、 clockwise or counterclockwise from the vertical. A tolerance of f 2“ is allowed on each roller angle. A B C D E F Flattening Flattening Rounding Flattening Flattening Rounding O 90 O 45 135 45 The sets of rollers shall be about 300 mm apart. The gap between the inner faces of the rollers, in accord
22、ance with the nominal diameter of the hose assembly, shall not exceed the values given in table 3. 6.3.1.2 The inner tube shall not show any leaks, burst or other evidence of malfunction when subjected to the test pressure specified in table 3 and held for 2 min. The test is done with water or air.
23、STDmAECflA PREN 2255-ENGL 377b 303233l 0032533 37b Page 6 prEN 2255 : 1996 DN 5 6 8 10 12 16 20 25 32 40 Table 3 : Gap between rollers and test pressure Gap between internal faces of rollers for flattening for rounding max. max. 5,s 595 53 693 5,s 799 5,9 9,s 63 12,7 6,s 12,7 63 19,o 799 22,2 93 31,
24、7 5,s 5,s 6.3.2 Electrical conductivity test The inner tube shall be internally cleaned with fluid no. 10 in accordance with table 8, then with fluid no. 11 in accordance with table 8, and thoroughly dried at room temperature. The test shall take place in an atmosphere at (24 f 8) OC of which the hu
25、midity is s 70 %. Fluid no. 6 or no. 9 in accordance with table 8 is used as upper and lower electrode. A voltage of 1 O00 V d.c. is applied between two electrodes attached to the inner tube about 250 mm from each other. The inner tube shall be capable of conducting a current of 10 pA min. for the D
26、N of 5, 6, 8, 10 and 12, and 20 LA min. for larger DN. The current shall be measured with an instrument of a sensitivity of no less than 1 pA. Figure 1 represents an assembly by which this test can be correctly carried cut. Conductor cube I - 1000Vd.c. - Probe Upper electrode (mercury) Non-metallic
27、plug O-ring Dimensions in millimetres Veni (if any) Inner tube in polytetrafluoroathylene I I I I I I I I I I I I I I I ,- Non-metallic containei Lower eiecrrode (mercury) (PTFE) Figure 1 : Diagram for the electrical conductivity test of the inner tube STD-AECMA PREN 2255-ENGL L77b LOL23LL 0032532 O
28、22 = Page 7 prEN 2255 : 1996 DN 5 6 Minimum inside diameter of 2 3,3 the hose assembly (on the end fitting) 6.3.3 Tensile strength The inner tube of the hose assemblies shall be subjected to the tensile strength test. The rate of appli-cation is 50 mmlmin. 8 10 12 16 20 25 32 40 4,9 6,3 8,6 10,9 13,
29、9 19,3 23,s 31,7 The longitudinal tensile strength shall be 21 MPa at (25 f 2) OC for all DN. The transverse tensile strength shall be 18 MPa at (25 f 2) OC. Inner tubes with DN Until a special EN or IS0 Standard for this method has been published, a procedure shall be applied which has been agreed
30、by the purchaser and approved by the relevant authorities. 16 shall not be submitted to a transverse tensile strength test. 6.3.4 Elongation At a temperature of (25 f 2) OC, the elongation shall be 2 200 %. 6.3.5 Specific gravity 6.3.5.1 The apparent specific gravity shall be between 2,125 g/cm3 and
31、 2,155 g/cm3. Apparent specific gravity (to IS0 7258 method B) 6.3.5.2 The relative specific gravity shall not exceed 2,21 O. Relative specific gravity (to IS0 7258 method C) 6.4 6.4.1 Tests on the hose assembly with fittings Check on all hose assemblies 6.4.1.1 Examination of product Each hose asse
32、mbly shall be carefully examined to check whether it has been manufactured correctly and is free from defects. 6.4.1.2 Dimensions, mass Weigh each hose assembly and carry out the measurements to check that they comply with the relevant standards or, in their absence, with the design document. The in
33、side diameter shall exceed the minimum value given in table 4. I 6.4.1.3 63443 Proof pressure The hose assemblies shall show no leak, burst or any other evidence of malfunction when subjected to proof pressure PE which is 2 times PN for a period of 30 s to 5 min. STD-AECMA PREN 2255-ENGL Lb m LOL23L
34、L 0032533 Tb m Page 8 prEN 2255 : 1996 6.4.2 Tests on samples 6.4.2.1 See annex A. The hose assemblies with two gauge marks at a distance of 250 mm are connected to the test machine with one end free. When the nominal pressure has been applied to them for 5 min: Variation in length and volume - the
35、variation in length between the gauge marks shall be between + 2 % and - 3 %; - the increase in volume, under nominal pressure, shall not exceed, for a length of 250 mm: - 0,3 cm3 for the hose assembly of DN 5 and 6; - 0,4 cm3 for the hose assembly of DN 8. NOTE :The volume increase is measured for
36、guidance on hose assemblies of different DN (experiences will later make it possible to determine the values not to be exceeded). 6.4.2.2 Effusion test The hose assemblies are subjected to nominal pressure at room temperature for 1 h. During the second half hour, the leakage from the hose assembly i
37、s collected and measured. This quantity shall not exceed the values of table 5. Air Or nitrogen gas source Invened graduated flask Funnel to cover hose plus one-half of each socket I- / Water bath without wetting agent Hose assernblv under test Figure 2 : Assembly for effusion test Table 5 : Leakage
38、 rate of the effusion test - I DN Is1 61 81 I I I I I I I I I I Maximal auantitv in cm3 I 13 I 13 I 16 I 16 I 16 I 16 I 19 I 26 I 26 I 26 I 6.4.2.3 Oil ageing The hose assemblies are immersed for 168 h at (200 i 5) OC in fluid no. 1 or no. 2 in accordance with table 8 and are then subjected to proof
39、 pressure PE which is 2 times PN. 6.4.2.4 Air ageing The hose assemblies are subjected to ageing in air at a temperature of (200 f 5) OC for 168 h and are then subjected to proof pressure PE which is 2 times PN. STD-AECMA PREN 2255-ENGL 177b m LO1231L 001253q 7T5 m Page 9 prEN 2255 : 1996 6.4.2.5 Pn
40、eumatic surge test The hose assembly is installed in a gas system (air or nitrogen) fitted with rapid action valves as shown in figure 3. The test, conducted at room temperature, consists of 16 times the following cycle : - nominal pressure is held in the hose assembly for 25 min; - it is then rapid
41、ly reduced to atmospheric pressure and held there for 5 min. After this test, the hose assembly shall withstand proof pressure PE which is 2 times PN and shall be visually examined internally and externally. Any obvious degradation shall form a reason for rejection. Exhausr dir or nitrogen gas sourc
42、e Filter A Figure 3 : Pneumatic surge test arrangement 6.4.2.6 Fuel resistance test The hose assemblies are filled with fluid no. 4 or no. 5 in accordance with table 8, and are placed for 48 h under nominal pressure in a chamber held at a temperature of (125 f 5) OC. All the necessary precautions sh
43、all be taken to ensure that the hose assemblies do not come into contact with parts of the chamber which are at a higher temperature and that the chamber temperature cannot reach a high enough value to ignite the fuel. The pressure is then released and the hose assemblies are drained and cookd for 2
44、0 min to room temperature. The hose assemblies are filled with fluid no. 3 in accordance with table 8, nominal pressure is applied and held for no less than 2 h at room temperature. During the test, or after its completion, the hose assemblies shall show no evidence of leakage. 6.4.2.7 a) The hose a
45、ssemblies filled with fluid no. 2 in accordance with table 8, are placed in a chamber held at the temperature of (230 f 5) “C. All the necessary precautions shall be taken to ensure that the hose assemblies do not come into contact with parts of the chamber which are at a higher temperature. Nominal
46、 pressure is held in the hose assemblies for no less than 20 h, and is then gradually released. b) The hose assemblies are removed from the chamber, drained and cooled to room temperature, and then flushed with a quantity of fluid no. 3 in accordance with table 8 at least equivalent to twice the vol
47、ume of the hose assembly. They are drained and again filled with fluid no. 3 in accordance with table 8 and held for no less than 2 h at nominal pressure at room temperature. Combined test (oil resistance, ageing, bending, porosity, thermal shock) STD-AECMA PREN 2255-ENGL 177b M 1012311 0012535 831
48、M Page 10 prEN 2255 : 1996 c) subjected to the operations a) and b) above. d) Closed at their ends and held by the couplings, they are bent over a mandrel of which the diameter is equal to two times the minimum bend radius as given in table 7, and then straightened. e) The tests described in a) and
49、b) are repeated for a third time. 9 Within the next 4 h, the hose assemblies are drained and flushed with fluid no. 10 in accordance with table 8, and placed in a chamber for 1 h at (70 f 5) OC. 9) Within the next 8 h, the hose assemblies are installed in an apparatus similar to that of figure 2 for 15 min at nominal pressure. This pressure is maintained for an additional 5 min and the air escaping from the hose assembly is collected and measured. This quantity shall not exceed the values of table 6. h) The hose assemblies are then filled with fluid no. 2 in acc
