BS M 57:1985 pdf free download.High temperature convoluted hose assemblies in polytetrafluoroethylene (PTFE) for aerospace applications.
1 Scope and field of application
BS M 57 specifies characteristics of hose assemblies with corrosion-resistant metallic braid and convoluted polytetrafluoroethylene (PTFE) inner tube for use in aircraft flud systems at temperatures between — 56 and + 200 °C and at nominal pressures, depending on bore size, up to 6,8 MPa. Special approval from the proper national authority may be required if these hoses are to be part of a pressurized gas storage system.
Two types of hose assembly are covered in BS M 57
Standard:
Type 1: Non-conductive inner tube
Type 2: Conductive inner tube
2 References
ISO 756, Propan-2-oI to, industrial use — Methods of test — Pa,t 7: General.
Part 2: Determination of acidity — Titrimetric method.
Part 3: Test for miscibility with water.
ISO 3768, Metallic coatings — Neutral salt spray test (NSS tasti.
3 Requirements
3.1 Qualification
The hose assemblies furrwshed under BS M 57 shall be a product identical to that which has been tested and has passed the qualification tests herein and shall be suitable for use in aircraft fluid systems under conditions specified herein.
3.2 Materials
The hose assembhes shall be uniform in quality and free from detects in material as is consistent with good manufacturing practice. Materials shall conform to applicable specifications and the requirements specified herein.
3.2.1 Metals
Metals shall be of corrosion-resistant type or be suitably treated to resist corrosion due to fluid being conveyed and/or salt
3.8.3 Cleaning
All hose assemblies shall be free from oil, grease, dirt, or any other foreign material, both internally and externally. Unless otherwise specified, hose assemblies shall be cleaned by flushing with suitable degreasing solvent, blow drying with air, and sealing with clean end caps.
3.8.4 Openings and covers
Openings shall be suitably protected against ingress of foreign material; all threads shall be protected against damage. AU protective covers shall be of a configuration that prohibits assembly with the mating part without removal of the cover.
4 Quality assurance provisions
4.1 Classification of tests
The inspection and testing of hose assemblies shall be classified as follows:
a) acceptance (see 4.2);
b) qualification testing (see 4.5).
4.2 Acceptance tests
Acceptance tests shall consist of:
a) individual test;
b) sampling test;
c) periodic control test.
4.2.1 Individual tests
Each hose assembly delivered under BS M 57 shall be subjected to the following tests:
a) examination of product (see 4.4.1);
b) proof pressure test (see 4.4.2).
4.2.2 Sampling test
The following test shall be performed on hose assemblies picked at random from each lot. A lot is defined as 500 assemblies of a given dash size, manufactured by the same process free from any deviations likely to have a significant effect on product quality.
4.2.2.1 One hose assembly shall be consecutively subiected to the following tests:
a) elongation and contraction test (see 4.4.3);
b) leakage test (see 4.4.4).
4.2.3 Periodic control test
A fuel resistance test (see 4.4.8) shall be performed on at least two assemblies for each periodic control test selected from each 5 000 hose assemblies for each dash size, not necessarily manufactured during one continuous production run.
42.4 Rejection and retest
When one item selected from a production run fails to meet the specification, no items still on hand or later produced shall be accepted until the extent and cause of failure are determined and corrective action, as necessary, taken.
For operational reasons, the individual tests may be continued pending the investigation of a sampling or periodic control test failure. Final acceptance of items on hand or produced later shall not be made until it is determined that items meet the requirements on which the rejection was based
4.3 Test conditions
4.3.1 Preparation of specimens
4.3.1.1 General
Length of the sample hose assemblies shall be in accordance with table 2 unless otherwise specified.
4.3.2 Test fluids
Unless otherwise specified, the test fluid shall be a petroleum base hydraulic fluid or water. When a high temperature test is performed, the test fluid shall be a synthetic base lubricating oil unless otherwise specified by the procuring authority.
4.3.3 Temperature measurements
Unless otherwise specified, temperature measurements shall be taken within 150 mm of the hose assemblies under test. All temperatures, unless otherwise specified, shall have a tolerance of °C.
4.3.4 Test pressure
All test pressures, unless otherwise specified, shall have a
tolerance within ±2 %.
4.4 Performance tests
See table 4 for test schedule.
4.4.1 Examination of product
All hose assemblies shall be examined to determine conformance to this specification with respect to material, size. workmanship and identification. Broken or missing reinforcing wires or any other evidence of malfunction shall be cause for rejection. Crossed over reinforcing wires shall not be cause for rejection.
4.4.2 Proof pressure test
All hose assemblies shall be pressure-tested to the values specified in table 2 for a period of not less than 30 s and not more than 5 mm. All complete hose assemblies used for the tests described in BS M 57 shall have this proof pressure test applied to them. Any evidence of leakage from hose or fittings or any other evidence of malfunction shall constitute failure.
The test fluid shall be a synthetic base lubricating oil. All four hose assemblies shall be pressure-cycled from zero to nominal pressure at a rate of not less than 20 cycles per minute or more than 30 cycles per minute. as shown in figure 1.
Any leakage from the hose or hose attachment to the end fittings at less than 50 000 cycles shall be cause for rejection.
4.4.11 Conductivity test
The test specimen shall be a 325 mm length of hose with a fitting attached to one end as shown in figure 2, The inner surface of the tube shall be washed first with a suitable degreasing solvent and then with isopropyl alcohol complying with ISO 756 to remove surface contamination and thoroughly dried at room temperature. The reinforcement shall be flared out to prevent contact with the end of the tube. One steel fitting of appropriate size shall be assembled on the hose end fitting.
The test specimen shall then be arranged vertically. The relative humidity shall be kept below 70 % and room temperature between 15 and 32 °C. One thousand volts. DC. shall be applied between the upper electrode and the lower electrode.
The current shall be measured with an instrument with a sensitivity of at least 1 pA (1 x 10-6 A). The current measured shall be equal to or greater than 6 lIA for sizes DNO6 to DN12 and equal to or greater than 12 pA for sizes DN16 to DN1O5.
4.4.12 Salt corrosion test
Two hose assemblies shall be pressurized to the nominal operating pressure in accordance with table 2, and, at room temperature, the hose assemblies shall be immersed in a 3,5 ± 0,1 % sodium chloride (NaCI) solution for 8 to 10 mEn. then allowed to air dry for the remainder of 1 h. This subsequent immersion and air-drying process shall be repeated no less than 50 times.
NOTE — The NaCl solution should contain a dry basis of not mote than 0.1 $ of sodium iodide and 0.5 $ of total impuñties.
4.5 Qualification testing
The qualification of hose assemblies shall consist of all the tests described in this specification. Unless otherwise specified by the purchaser, qualification samples and test sequence shall consist of:
a) eleven hose assemblies of each size of the length specified in table 2 plus a conductivity specimen in accordance with 4.4.11 when required;
b) the test schedule used shall be as specified in table 4.
5 Ordering data
Procurement documents shall specify the following:
a) size, length and type of hose assemblies to be furnished;
b) type, size, material, or special features of end fittings desired;
c) levels of packaging and packing desired.