GB/T 9251-2022Methods for hydrostatic test of gas cylinders (English PDF)

3.1 Testing cylinder

Cylinders to be tested or being tested.

3.2 Pressure proof test

A process of testing and verifying the safe bearing capacity of the testing cylinder after it is pressurized to its hydraulic test pressure and maintained for a specified period of time.

3.5 Special water jacket

A special equipment for measuring the volumetric deformation of the testing cylinder during the hydrostatic test by water jacket method.

3.6 Calibrated cylinder

A bottle equipment that if the corresponding relationship between the calibration pressure and the expansion value has been determined, the expansion value shall have the characteristics of repeatability and linearity, and there will be no permanent deformation under the calibration pressure. It is used to verify the accuracy of the hydrostatic test device of gas cylinders.

3.7 Calibrated gauge

A pressure measuring instrument for verifying the pressure value of the test system. Its accuracy level shall not be less than that of other pressure measuring instruments.

3.8 Reference zero point

Zero reading on water volume measuring instrument. The error shall be the larger value of ±0.1% of the total volumetric deformation value and ±0.1mL.

6.1 Basic requirements for test device

6.1.1 The testing cylinder shall be pressurized by a plunger pump, a pneumatic pump or other pressurizing device with stable pressure output. Use water as the pressurized medium.

6.1.3 Metal pipes shall generally be used for pressure-bearing pipeline. They shall be fixed. The connection with the test device and the measuring instrument shall have a good seal. The pressure-bearing capacity of the pressure-bearing pipeline shall meet the requirements of the hydrostatic test's pressure of the testing cylinder.

6.1.4 The special water jacket shall be made of stainless steel or other corrosion- resistant metal materials, with a certain rigidity. Make sure that it does not change in volume during the hydrostatic test.

6.1.5 The dimensions and materials of all associated piping of the hydrostatic test devices for water jacket method and direct expansion method shall be such that they do not deform under the weight of water.

6.1.6 The calibration of the calibrated cylinder shall comply with the provisions of

GB/T 35015.The calibration data of the calibrated cylinder shall be able to meet the test requirements of the testing cylinder (at least three pressure levels). A clearly identifiable calibration certificate and label shall be attached.

6.2 Measuring instruments

6.2.1 Pressure measuring instrument

6.2.1.1 A pressure gauge and a calibrated gauge for calibration shall be installed on the 6.2.1.3 The range of the pressure measuring instrument shall be 1.5 times to 3 times the pressure of the hydrostatic test of the testing cylinder. The accuracy level of the pressure gauge shall not be lower than level 1.0.

6.2.2 Water volume measuring instrument

6.2.2.1 Electronic balances, measuring tubes or other suitable measuring instruments can be used as water volume measuring instruments. They are used to measure the total volumetric deformation value, volumetric residual deformation of the testing cylinder in the water jacket method and the total pressurized water volume in the direct expansion method.

6.2.3 Weighing instrument

For the weighing instrument used to weigh the mass of the testing cylinder, the maximum weight shall be 1.5 times to 3 times the commonly used weighing value. The allowable error shall meet the requirements of "medium accuracy level" specified by JJG 539.

6.2.4 Temperature measuring instrument

For the temperature measuring instruments used to measure the temperatures of the test water and the ambient temperature, the minimum scale value shall not be greater than 1°C.

7.1 General

It does not need to measure the volumetric deformation for the pressure proof test. If the filling medium of the gas cylinder and the hydraulic test pressure are the same, the test can be carried out on multiple testing cylinders at the same time.

7.2 Test device process

The typical flow of the pressure proof test device is shown in Figure 1.

7.3 Test steps

7.3.1 The test device shall be calibrated by a calibrated gauge before use. The error of the displayed value of the pressure gauge shall not exceed ±2% of the displayed value of the calibrated gauge. The error of the displayed value of the pressure transmitter shall not exceed ±1% of the displayed value of the calibrated gauge.

7.3.2 Before the testing cylinder is pressurized, all the air in the cylinder and the pressure-bearing pipeline shall be exhausted.

7.3.3 When the pressure in the testing cylinder rises to the nominal working pressure of the gas cylinder, the pressurization can be suspended. Check system connections for leaks.

7.3.6 The test pressure deviation shall not exceed +3% of the specified test pressure. Relevant standards for gas cylinders shall comply with the regulations.

7.3.7 The judgment of the test results shall be carried out in accordance with the relevant standards for gas cylinders.

7.4 Test records and reports

7.4.1 Test records

The test agency shall record the relevant information and data of the test process according to the actual situation of the gas cylinder pressure proof test. The test records shall be in a file format that cannot be changed, such as pictures, PDF. Test records shall be detailed, true, accurate and traceable.

8.1 Test device process

Figure 2 shows the typical flow of the test device for water jacket method.

8.2 Test steps

8.2.1 Use a calibrated cylinder to calibrate the test device before use. Calibration shall be carried out in accordance with the provisions of Annex A.

8.2.5 The pressure in the testing cylinder rises to the specified test pressure. Hold the pressure for at least 30s or specified time.

8.2.6 Depressurize to zero. After the testing cylinder is completely shrunk, record the volumetric residual deformation value of the testing cylinder or the value indicated by the electronic balance.

8.2.9 Before and after the test, keep the water temperature in the system constant.

8.2.10 The judgment of the test results shall be carried out in accordance with the relevant standards for gas cylinders.

8.3 Calculation

Calculation of volume elastic deformation value and volume residual deformation rate of testing cylinder The volumetric elastic deformation value of the testing cylinder is calculated according to formula (1). The volume residual deformation rate is calculated according to formula (2).

8.4 Test records and reports

8.4.1 Test records

The test agency shall record the relevant information and data of the test process according to the actual situation of the hydrostatic test by the water jacket method of the gas cylinder.

8.4.2 Test reports

The test agency shall issue a hydraulic test report based on the test records.

In addition to recording the relevant information and main technical parameters of the testing cylinder, the test report shall at least include the following main contents.

9.1 Test device process

The typical flow of test device for direct expansion method is shown in Figure 3.

9.2 Test steps

9.2.1 Use a calibrated gauge to verify the test devices before use. The displayed value of the pressure gauge shall not exceed ±1.5% of the displayed value of the calibrated gauge. The displayed value of the pressure transmitter shall not exceed ±1% of the displayed value of the calibrated gauge.

9.2.4 Before the testing cylinder is pressurized, exhaust all the air in the cylinder and the pressure-bearing pipeline. It can be pressurized and relieved repeatedly within the nominal working pressure range until no air bubbles emerge in the water measuring instrument.

9.2.5 Before starting the test, close the water filling valve and the pressure relief valve.

Keep the indication value of the initial value of the water measuring instrument stable for at least 5s.

9.2.6 When the pressure in the testing cylinder rises to the nominal working pressure, suspend the pressurization and inspect it.

9.2.7 The pressure in the testing cylinder rises to the specified test pressure. Hold the pressure for at least 30s or specified time. During the pressure holding period, the actual test pressure shall not be lower than the specified test pressure.

9.2.8 Open the relief valve. Depressurize to zero. After the testing cylinder is completely shrunk, record the volumetric residual deformation value of the testing cylinder or the value indicated by the electronic balance.

9.2.11 Before and after the test, keep the water temperature in the system constant.

9.3 Calculations

Calculations of total volumetric deformation value, volumetric elastic deformation value and volumetric residual deformation value of testing cylinder

9.4 Test records and reports

9.4.1 Test records

The test agency shall record the relevant information and data of the test process according to the actual situation of the hydrostatic test of gas cylinders by direct expansion method.

9.4.2 Test reports

The test agency shall issue a hydraulic test report based on the test records.

In addition to recording the relevant information and main technical parameters of the testing cylinder, the test report shall at least include the following main contents.