This standard applies to automotive pneumatic brake hoses. GB 7128-1986 Automotive pneumatic brake hose GB7128-1986 Standard download and decompression password: www.bzxz.net

National Standard of the People's Republic of China
Automotive air brake hose
Rubber hose for automotive air brake system This standard applies to automotive air brake hoses (hereinafter referred to as hoses). 1 Structure and specifications
Structure: The hose is composed of an inner rubber layer, a reinforcement layer and an outer rubber layer. 1.1
1.2 Specifications, dimensions and tolerances: The specifications, dimensions and tolerances of the hose should comply with the provisions of Table 1. Table 1
Inside
Child
10
13
inch
diameter
metric
difference
±0.5
Adhesive layer thickness
Inner adhesive layer
1.2
Not less than
Outer adhesive layer
0.8
The wall thickness difference is not greater than
0.5
Note: ① The above table does not include specifications or special requirements, which can be resolved through negotiation between the user and the manufacturer. ②The outer diameter, length and tolerance of the hose are specified by the user and determined with the consent of the manufacturer. 2Technical requirements
UDC 621.843.3
: 629.113-59
GB 7128-86
mm
Outer diameter tolerance
± 0.5
Undetermined
2.1 The bursting pressure of the hose should not be less than 6.2MPa (63.3kgf/cm2). 2.2 The hose should be subjected to an air tightness test for 3 minutes at a pressure of 1.37MPa (14kgf/cm2) and there should be no leakage. 2.3． When the hose is subjected to a tensile test of 1442N (145kgf), the pipe body should not be broken. 2.4. When the hose is maintained at 1.37MP.a (14kgf/cm2) water pressure for 5 minutes, its length change should not exceed +5% ~ -7%. 2.5 The hose is kept at -42±2°C for 72 hours, and then bent 180° around the mandrel specified in Table 2 at this temperature. There should be no cracks or breaks.
Table 2
Inner
Diameter
10
13
Mandrel diameter
90±1||tt ||100 ±1
mm
2.6. After the hose has been subjected to the low-temperature bending test, it should be placed at room temperature for no less than 3 hours for air tightness testing. It should still comply with the requirements specified in 2.2 of this standard.
2.7 hose should be maintained at an ozone temperature of 50±5pphm and a temperature of 40±2℃ for 72h. Use a 7x magnifying glass to check the outer surface. Released by the National Bureau of Standards on December 30, 1986
1987- 10-01 Implementation of
cracking phenomenon.
GB7128—86www.bzxz.net
2.$ The hose shall meet the requirements specified in 2.3 of this standard after being immersed in normal temperature water for 166*2h. 2.9 The adhesive strength between the inner and outer rubber layers of the hose and the braided layer should not be less than 1.47kN/m (1.50kgf/cm). (Hose with an inner diameter of 13mm and below is not subject to adhesive strength testing). 2.10 The physical and mechanical properties of the rubber materials used in manufacturing hoses should comply with the requirements in Table 3. Table 3
refers to
item
item
inner rubber layer
tensile strength, MPa (kgf/cm)
tear off Elongation, %
Hot air aging
(70℃, 72h)
Oil resistance volume change rate, %
not less than
not less than| |tt|| Tensile strength change rate, %
Change rate of elongation at break,
is not greater than
(No. 1 standard dielectric oil for rubber, 100±1℃, 72h ) 2.11. Appearance requirements
2.11.1 The hose is not allowed to have delamination, blistering, cracks and sponging. 6.9(70)
：250
standard
outer rubber layer
.5.9(60)
300
+25~- 25
+10~-30
100
2.11.2 The surface of the hose is allowed to have traces of line layer ripples, water cloth wrinkles and impurities caused by the edges of the cloth. The local unevenness of the layer shall not exceed 0.5mm, but its depth or height shall not exceed 0.5mm, and its cumulative length shall not exceed 10% of the total length of the hose. 3 Test methods
3.1. The inner and outer diameters of the hose are measured with a vernier caliper with an accuracy of 0.05mm, and the length is measured with a meter stick. 3.2 The hose bursting pressure, air tightness, and length change tests are conducted according to GB.5563-85 "Test Methods for Hose and Tape". 3.3 The low-temperature bending test of the hose shall be carried out according to GB5564-85 "Low Temperature Bending Test Method". 3.4 The adhesive strength test of hose shall be carried out according to GB5562-85 "Physical Test Methods for Rubber Layer of Hose". 3.5 The tensile test of the hose shall be in accordance with A.1 of Appendix A. 3.6
The ozone aging test of the hose shall be in accordance with A.2 of Appendix A. 4 Acceptance rules
4.1 The hose shall be batched by the technical inspection department of the manufacturer For acceptance, each batch of hoses should be no more than 20,000m (less than 20,000m will be considered as one batch per quarter), and each batch of products must be accompanied by a product certificate when leaving the factory. 4.2 Each batch of hoses should be inspected for specifications, dimensions and appearance one by one. 4.3 Each batch of hoses shall be randomly inspected according to the quantity specified in Table 4, but not less than once per quarter. If there are any unqualified items, double samples should be taken from the same batch of hoses, and the unqualified items should be retested. If there are still unqualified items after the retest, the batch of products will be deemed to be unqualified. Test items
Burst pressure test
Air tightness test
Tensile test
Length change test
Low temperature bending test
Oxygen aging Test
5 Marking, packaging, transportation, storage
GB7128—86
Table 4.
The hose should have the following obvious markings that are not easy to fall off 5.1
Manufacturer's name or trademark:
a.
b. Product name, specifications and dimensions,
c. Manufacturing year and month.
5.2 The hose should be rolled into rolls and bundled or packed straight. Quantity, root
Number of samples
2
2
2
2
1
1||tt || During transportation and storage, hoses should be kept away from direct sunlight, rain and snow, keep clean, avoid external extrusion and mechanical damage, and prevent 5.3
from acids, alkalis, organic solvents and chemicals that affect rubber quality. material contact and 1m away from the heat source. 5.4 The warehouse where hoses are stored should be well ventilated, with a temperature between -15 and +40°C and a relative humidity of no more than 80%. 5.5 When storing rubber hoses, the stack height should not exceed 1.5m, and they should be turned over once a quarter during storage. 5.6: Under the condition of complying with 5.3, 5.4 and 5.5 of this standard, all performance indicators of the hose shall comply with the requirements of this standard within a storage period of no more than one year from the date of manufacture.
A.1 Tensile test
A.1.1 specimen
GB 7128-86
Appendix A
Hose finished product test
(Supplement)
A.1.1.1 Sample length, cut 400~420mm within 1m from the pipe head. A.1.1.2 Metal joints need to be installed at both ends of the sample. A.1.2 Test steps
Install the prepared sample on the testing machine with a special holder, start the machine, and the speed of the lower end holder is 25~30mm/min until it breaks. || tt |
A.2 Ozone aging test
A.2.1 Hose ozone aging test, conduct the test in a special ozone aging test chamber. A.2.2 Wind the sample around a cylinder with a diameter 8 times the outer diameter of the hose, and wrap both ends of the sample. A.2.3 The cylinder and wrapping should be composed of metal or minimally ozone-depleting materials. A.2.4 Place the sample at room temperature for 24±0.5h, and then place it in a test chamber filled with ozone with a concentration of 50±5pphm for 72h. The temperature in the test chamber is 40±3°C. A.2.5 After taking out the sample, use a 7x magnifying glass to visually inspect the outer surface of the sample for cracks. Additional notes:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China and is under the jurisdiction of the Shenyang Rubber Industrial Products Research Institute of the Ministry of Chemical Industry. This standard is drafted by Shanghai Rubber Factory. The main drafters of this standard are Wang Anfu and Zhou Guoliang. This standard refers to the Japanese Industrial Standard JISD2606-80.
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