QC/T 746-2006High-pressure pipelines for compressed natural gas vehicles (English PDF)

3.1 High-pressure pipelines

A generic term of all pipe fittings and joints that are installed to natural gas vehicles and connect air cylinder with decompression regulator.

3.2 Connectors

Parts in natural gas fuel system that connect devices or pipelines.

3.3 Rigid high-pressure fuel pipes

High-pressure steel pipes that connect parts of natural gas fuel system for circulation of natural gas.

3.4 High-pressure flexible fuel pipes

Flexible pipes that connect parts of natural gas fuel system for circulation of high-pressure natural gas.

4.2.1.3 Ultra-torque characteristics

High-pressure pipeline shall be subjected to ultra-torque characteristics test according to the test prescribed in 5.5; test piece shall be free of thread damage, deformation and break; air tightness test shall conform to the provisions of 4.2.1.2.

4.2.1.4 Durability

High-pressure pipeline shall be subjected to durability test according to the test method prescribed in 5.6; air tightness test shall conform to the provisions of 4.2.1.2.

4. 2.1.5 Corrosion resistance

After high-pressure pipeline receives salt spray corrosion test according to the method prescribed in 5.7, air tight test shall conform to the provisions of 4.2.1.2.

4.2.1.6 Compatibility

After high-pressure pipeline receives compatibility test according to the test method prescribed in 5.8.1, test piece is inspected by 25-times magnifying glass, and shall be free of conspicuous fracture traces.

4.2.1.7 Bending resistance

After high-pressure pipeline receives bending test according to the test method prescribed in 5.9; test piece shall be free of cracks or fracture.

4.2.1.8 Pull strength

High-pressure pipe shall be subjected to pull strength test according to the test method prescribed in 5.10; if F>=f, then test piece passes the test, .

4.2.1.9 Vibration resistance

After high-pressure pipeline receives vibration test according to the method prescribed in

5.11; air tight test shall conform to the provisions of 4.2.1.2.

4.2.2 High-pressure flexible fuel pipe

4.2.2.1 Hydrostatic pressure strength

a) High-pressure strength shall be subjected to pressure test according to the test method prescribed in 5.3.2.1; pressure-containing parts of high-pressure pipeline shall be free of leakage.

b) High-pressure pipeline shall be subjected to bursting pressure test according to the test method prescribed in 5.3.2.2; pressure-containing parts of high-pressure pipeline shall be free of fracture.

5.1 Test conditions

5.1.1 General provisions

Unless otherwise specified, tests prescribed in this Standard shall be carried out under following conditions:

a) Test environment temperature is 20°C±5°C;

b) Test medium shall be clean dry air or nitrogen.

5.1.2 Requirements for precision of test instruments

a) Pressure instrument: Accuracy is not lower than grade 2.5; measurement error is less than ±10% of reading.

b) Flow instrument: Accuracy is not lower than grade 2.5; measurement error is less than ±10% of reading.

c) Temperature instrument: Accuracy is ±0.5°C; the minimum resolution is not greater than 2 times the accuracy.

5.2 Visual inspection

Inspect high-pressure pipeline assembly visually; the results shall conform to relevant provisions in chapter 4.

5.3 Hydrostatic pressure strength test

5.3.1 High-pressure rigid fuel pipe

Securely install test piece to an enclosed special test bench; block off the outlet of test piece; test hydraulic pressure is slowly added to test piece; pressurizing duration shall not be less than 3min; make it reach 45Mpa; stabilize the pressure for 3min and release the pressure.

Samples that have received this test must not be used for other tests.

5.3.2 High-pressure flexible fuel pipe

5.12 Tensile strength test of high-pressure flexible fuel pipe follows the provisions GB/T

528.

5.13 Ozone resistance test

Ozone resistance test of high-pressure pipe follows the provisions of GB/T 9571.

5.14 Low-temperature bending test

High-pressure flexible fuel pipe follows the provisions on method B in GB/T 5564; place at a temperature of -40°C±2°C for 24h; check the surface of test piece with 2-times magnifying glass.

5.15 Oxygen aging resistance test

Hang the samples vertically in oxygen pressure vessel, in a free state. Samples shall not be crowded, or contact each other, or touch container wall. Samples with different formulas may not be tested in the same container. Heat the constant temperature control system; after the medium is preheated to working temperature, place container with samples into heading medium; pressurize with pressurized oxygen when test temperature is constant; calculate aging time when the pressure reaches the predetermined value. It is required to drop container pressure to normal pressure slowly and evenly, in at least 5min, after reaching predetermined time and before taking samples out of the container.

5.16 Leakage test

Leakage test of high-pressure flexible fuel pipe follows the provisions in annex A.

5.17 Impact test of high-pressure flexible fuel pipe

This test shall adopt brand new test piece.

Install test piece to impact special test bench; start the test after inspecting installation reliability, and make a record. Impact test of high-pressure flexible fuel pipe and connector assembly is completed for 15, 000 times, by using the circulation oil of which the temperature is 93°C±3°C, the pressure is 3MPa. One working cycle procedure is as follows:

a) Close outlet of sample piece;

b) Apply an oil pressure of which the temperature is 93°C±3°C to inlet; slowly […]

6.3 Type inspection

Products shall receive type inspection according to Table 4, in one of following cases.

Newly designed products shall receive product design review according to 4.1 general requirements.

a) Type identification of new product or there are significant changes in product structure, material and process, which may affect product performance;

b) Production of products is resumed after production is shutdown for over 1 year;

c) Exit-factory inspection results are significantly different from previous type inspection;

d) Product quality supervision agency proposes type inspection requirements.

7 Marking, packaging, operation instructions, transport and storage

7.1 Marking

Products shall have the following permanent marks at obvious positions:

a) Product specification and model;

b) Nominal working pressure;

c) Date of production and batch No.;

d) Trademark of the manufacturer;

e) Identification mark “CNG”.

7.2 Packaging

7.2.1

Packaging shall prevent corrosive medium from immersing into products, and protect products from damage during transportation process.

7.2.2

Outer packing shall bear product model, name, manufacturer, address, contact number, and date of manufacturing.

7.2.3

Packaging inside shall be accompanied with product conformity certificate and operation instructions. Product conformity certificate shall have following contents:

a) Product model, name, manufacturer's logo;

b) Nominal diameter;

c) Nominal working pressure;

d) Product serial number;

e) Signature of inspector and date of inspection.

7.3 Operation instructions

Preparation of operation instructions shall conform to the provisions of GB 9969.1.

7.4 Transport

Packing cases shall be handled gently; avoid heavy load and impact during transportation process; take strict precautions against erosion from rain and chemicals.

7.5 Storage

7.5.1

Indoor temperature shall be maintained at -15°C ~ 40°C during product storage;

relative humidity shall be between 50% ~ 80%.

7.5.2

Products shall be laid flat during storage; stacking height shall not exceed 1.0 m;

tipping during storage shall be on a quarterly basis.

7.5.3

Other contents follow the provisions of GB/T 9576 and GB/T 9577.