BS 4749:1984 download.Textile reinforced rubber hydraulic hoses and hose assemblies.
1 SCOPE AND FIELD OF APPLICATION
BS 4749 specifies requirements for four types of textile reinforced rubber hoses and hose assemblies for use with common hydraulic fluids, such as mineral oils, soluble oils, oil and water emulsions, aqueous glycol solution, and water, at temperatures ranging from — 40 to + 100 °C. These four types of hoses are distinguished by their design working pressure (see table 2) and minimum bend radius (table 3).
The hoses are not suitable for use with castor oi[based and ester-based fluids.
BS 4749 does not include specifications for end fittings. It is limited to the performance of the hoses and hose assemblies.
2 REFERENCES
ISO 1307, Rubber hose — Bore sizes, tolerances on length, and test pressures.
ISO 1402, Rubber hose — Hydrostatic testing.
ISO 1436, Rubber products — Hoses and hose assemblies — Wire reinforced hydraulic type.
ISO 1817, Vulcanized rubbers — Resistance to liquids — Methods of test.
3 MATERIALS AND CONSTRUCTION
3.1 The hose shall consist of a seamless oil- and water- resistant synthetic rubber tube, one or more layers of suitable textile yarn and an oiI and weather-resistant synthetic rubber cover.
3.2 The hose shall be concentric in accordance with the following specifications:
The measurements of the wall thickness at different points
shall not differ by more than the following values:
— up to and Including 6,3 mm nominal bore: 0,8 mm;
— over 6,3 up to and including 19 mm nominal bore:
1,0 mm;
— over 19mm nominal bore: 1,3 mm.
33 Hose assemblies shell consist of a length of hose complying with the requirements of this International Standard together with suitable couplings at each end.
4 DIMENSIONS
NOTE — Hose outilde diameter is not specified In BS 4749 but the range of values for widely used hoses complying with BS 4749 Is given In annex A.
The bore of the hose shall meet the requirements of table 1.
5.2 The hoses shall withstand without damage a proof test pressure of twice the design working pressure, maintained by the method described in Iso 1402.
5.3 The change in length of the hoses at design working pressure shall not exceed %.
6 MINIMUM BEND RADIUS
The hoses shall be capable of performing at design working pressure when curved to the radius given in table 3 as measured to the inside of the bend. Should any portion of the hose be curved to a radius smaller than the specified bend radius, performance capability of the hose is reduced.
7 TOLERANCE ON LENGTH
7.1 The hoses shall be supplied in lengths as specified by the purchaser, subject to a tolerance on the specified lengths of ± 1 % or ± 3 mm, whichever Is the greater.
7.2 When no specific lengths have been ordered, the percentages of different lengths In any given delivery shall be as follows
— over 13 m: not less than 65 %;
— 7,5 to 13 m: not more than 35%;
— 1 to 7.5 m: not more than 10 %.
8 IMPULSE TEST REQUIREMENTS
(not applicable to type I)
Four unaged samples of hose with end fittings or sample hose assemblies shall be tested as follows:
8.1 Means shall be provided for applying a pulsating pressure internally to the hose or hose assembly at a rate of between 0,5 and 1,7 Hz (30 and 100 cycles/mm). Each cycle shall comply with the requirements of the pressure impulse cycle as specified In ISO 1436 as appropriate to the pressure rating of the hose.
The hoses or hose assemblies, when tested at 133 % of the working pressure for hoses of nominal bore 25 mm and smaller, and 100 % of the working pressure for nominal bore 31,5 mm, at a temperature of 93 ± 5 °C using circulating petroleum-based test fluid, shall withstand a minimum of 200 000 Impulse cycles.
There shall be no leakage or other malfunction.
Any failures adjacent to the end fittings shall be disregarded and repeat tests carried out. Failure due to coupling blowoff or rupture adjacent to the fittings (within 25 mm) shall not be interpreted as a true hose burst but as failure due to the fitting attachment and shall be recorded as such.
8.2 The free length of hose under test shall be as follows:
Bend Fre length
900 0,5itr+2d
180° ir+2d
where r is the minimum bend radius, and d is the outside diameter of the hose.
8.3 The test pieces shall be connected to the apparatus
and, In the case of hoses up to and including 25 mm
nominal bore, they shall be bent through either 90° or
1800. at the specified minimum bend radius. Hoses over
25 mm nominal bore shall be bent through 900.
9 COLD FLEXIBILITY REQUIREMENTS
Hoses and/or hose assemblies shall be subjected to a temperature of —40 °C for 24 h. After this period and while still at —40 °C, the specimens shall be flexed in a period of 10 ± 2 s over a mandrel having a diameter equal to twice the minimum bend radius specified in table 3. Hoses up to and including 19 mm nominal bore shall be bent through 180° over the mandrel and hoses over 19mm nominal bore shall be bent through 90° over the mandrel.
After flexing, the sample shall be allowed to warm to room
temperature and shall be visually examined for cover cracks and subjected to the proof test. There shall be no cover cracks or leakage.
10 OZONE RESISTANCE
When tested In accordance with ISO 1431 • no cracking or
other deterioration of the cover shall be visible at a
magnification of 2 X after exposure for 72 h at 40±2 °C
to an ozone concentration of (0,5 ± 0.05) x 106 (V/V)
(0,5 ± 005 ppm) using test pieces as detailed In annex B.
11 OIL RESISTANCE
The lining and the cover, when tested by the method described in ISO 1817. immersing in oil No. 3 for 72 h at a temperature of 100 °C, shall show no shrinkage and shall not show volume swelling greater than 100 %.
12 MARKING
The hoses and hose assemblies shall be marked with Information as agreed between the purchaser and the manufacturer.
Such marking, If agreed, shall include a reference to BS 4749.