GB/T 17926-2022Compressed natural gas cylinder valves for vehicles (English PDF)

5.1 Design requirements

5.1.1 The connection thread specification of the air inlet of the valve shall be PZ

27.8 taper thread or M25×2 ordinary thread.

5.1.5 The excess flow device shall be designed with a bypass channel.

5.1.6 The valve shall specify the design service life. Valves are designed for at least one cylinder inspection cycle.

5.2.2 Non-metallic seal material

5.2.2.1 Oxygen aging resistance The non-metallic seals shall be kept for 96h continuously in oxygen with a temperature of 70°C±5°C, a test pressure of 2MPa and a purity of >=99.5%, and there shall be no visible cracks and damages.

5.3 Process requirements

5.3.1 The valve body shall be forged. There shall be no defects such as cracks, wrinkles, inclusions, porosity, shrinkage holes, and underfills on the surface that would impair valve performance. When the shot blasting process is used on the surface of the valve body, the size and depth of the pits on the surface shall be uniform.

5.4.1 Valve performance

5.4.1.1 Open and close At the nominal working pressure, the valve shall be able to fully open and close according to the temperature and test torque specified in Table 1.

5.4.1.2 Excess torque resistance The threads connecting the inlet and outlet of the valve to external parts shall bear the following excess torque.

5.4.2.1 Extrusion resistance After holding the pressure for 30 minutes at

1.2 times the nominal working pressure, increase the pressure to

2.25 times the nominal working pressure at a rate of 0.5MPa/s, and the fusible alloy of PRD shall not be extruded.

5.4.3.2 Pressure pulse Apply the nominal working pressure to the air inlet and air outlet of the excess flow device respectively and perform 100 pulses each, which shall meet the requirements of 5.4.3.3.

5.4.3.3 Flow limiting When the pressure difference between the two ends of the inlet and outlet of the excess flow device exceeds

0.65 MPa, the excess flow device shall be able to act and restrict the flow. When the pressure difference reaches 10MPa, the bypass flow of the excess flow device shall not be greater than 0.05m3/min (under the standard state).

6.1 Test conditions

6.1.1 Test environment Unless otherwise specified, the tests specified in this document are carried out at an ambient temperature of 15°C~30°C.

6.1.4 Test flowmeters and pressure gauges The accuracy of the test flowmeter is 0.5.The accuracy of the pressure gauge shall not be lower than level 1.6.The range of the pressure gauge shall be

1.5 to 2 times the test pressure.

6.2 Mechanical properties test and chemical composition analysis of metal parts materials

6.3 Material performance test of non-metallic seals

6.3.1 Oxygen aging resistance test Place 3 non-metallic seal test pieces in the aging test device. Remove air from the device. Fill with oxygen with a purity of >=99.5%. Make the pressure reach 2MPa. Warm up to 70°C±5°C. Keep 96h and take out. Visually inspect its changes, which shall meet the requirements of 5.2.2.1.

6.3.4 Medium compatibility test

6.4 Valve body appearance inspection The appearance of the valve body shall be checked by visual inspection, which shall meet the requirements of

5.3.1 and 8.1.1.

6.5 Inlet and outlet thread inspection The connection thread of the air inlet of the valve shall be checked with a gauge manufactured in accordance with GB/T 8336 or GB/T 3934.It shall comply with the provisions of 5.3.2.

6.6.1 Opening-closing test

6.6.1.1 Opening-closing test at room temperature Install the valve on the test special device. Keep the valve closed. Charge the air source from the valve air inlet to the nominal working pressure. Block the air outlet. Open the valve according to the torque specified in Table 1.

6.6.1.2 Opening-closing test at low temperature Install the valve on the test special device. Place in a temperature-controlled box at - 40°C. Keep the valve closed. Charge the air source from the valve air inlet to the nominal working pressure. Block the air outlet. Open the valve according to the torque specified in Table

1.The valve shall be able to open fully. Then close the valve according to the torque specified in Table

1.The valve shall be able to close and comply with the provisions of 5.4.1.1.

6.6.2 Excess torque resistance test Use a nut or plug to screw the air outlet of the valve. Then tighten the nut or plug with 150% of the installation torque, respectively. The applied torque shall be maintained for more than 15min. Then remove the nut or plug.

6.6.4.1 Type test air tightness

6.6.5 Vibration resistance test Install the valve on the test special device. Block the air outlet. Open the valve. Fill the valve with air source to the nominal working pressure.

6.6.7 Stress corrosion resistance test Pour ammonia water with a relative density of 0.94 (specific gravity) into a glass container with a lid. The ratio of the added ammonia water to the container volume is

21.2 ml/L (for example, 636mL of ammonia water is added to a 30L glass container).

6.8.3 Flow limiting test Install the valve with the excess flow device on the test special device. Access with air source. When the pressure difference of the incoming gas exceeds

0.65 MPa, the excess flow device shall be able to act and restrict the flow.

7.1 Enter-factory inspection of materials and parts

7.1.1 There shall be a batch product quality certificate for the materials and parts when they enter the factory.

7.1.2 The mechanical properties and chemical composition of metal raw materials shall be re-examined according to the batch number of the factory entered, which shall comply with the provisions of 5.2.1.1.

7.2 Enter-factory inspection

7.2.1 Inspection one by one Valves shall be inspected one by one before leaving the factory. The inspection items are specified in Table

4.During the inspection process, if one item fails, the valve shall be rejected.

7.2.2 Batch inspection The batch inspection of valves shall be selected from the continuously produced products that have passed the inspection one by one in each batch (shall not exceed 5000 pieces).

7.3.1 Type test principles

7.3.1.1 The valve shall be type-tested by an inspection agency with type-test qualifications in accordance with the relevant regulations and technical specifications.

7.3.1.2 When the material and sealing structure of the valve are the same, the type test can be carried out according to the following principles.

7.3.1.3 Valves that have been type-tested in accordance with

7.3.1.2 may be type-tested according to the following principles when their local design conditions change.

7.3.2 Documents provided by type test The manufacturer shall provide the following technical documents during the type test.

7.3.3 Type test items The type test items of the valve are shown in Table 5.

7.3.4 Random inspection method and determination Valves for type test shall be extracted from products that have passed the exit-factory inspection.

8.1 Marks

8.1.1 The valve shall have the following permanent marks.

8.1.2 The valve shall carry an electronic certificate in the form of a QR code and shall contain at least the following contents.

8.2 Packaging

8.2.1 Moisture remaining in the valve shall be removed before packaging. Keep the valve clean when packing. Inlet and outlet threads are not damaged. Packing list, user manual and batch product quality certificate shall be attached in the packing box.

8.2.2 There shall be the following signs on the packing box.

8.2.3 The packing list shall indicate the following.

8.2.4 User manual shall include the following.

8.2.5 The batch product quality certificate shall indicate the following contents.