Standard for pressure test of HDPE pipe.

- Feb 23, 2019-

1. General requirements for hydraulic testing of HDPE pipes:



1. The pipe shall be filled with water and soaked for no less than 12h before pressure test.

2. The hydrostatic pressure of the hydrostatic test shall not be less than 1.5 times of the working pressure of the pipeline, and the test pressure shall not be less than 0.80mpa, and the pneumatic test shall not replace the hydraulic test.

3. The length of the hydraulic test shall not be more than 1000 meters. For the pipe segment with accessories in the middle, the segment length of the hydraulic test shall not be more than 500 meters. Pressure test should be carried out for pipes with different materials in the system.

4. The end support baffle of the pressure test section shall be checked for its firmness and reliability. During the pressure test, its support facilities shall not be loosened or collapsed. Valve shall not be used as sealing plate.

5, pressure should be used with mechanical equipment measuring device, when the use of spring pressure gauge, its accuracy should not be less than 1.5 class, the range should be 1.3 to 1.5 times the test pressure, dial diameter should not be less than 150mm.

6. The HDPE pipe pressure test section shall not include water hammer eliminator, outdoor fire hydrant and other types of valves contained in the pipe accessory system, which shall be in full open state.

Method of hydraulic test: divided into pre-test stage and main test stage.

1. In the pre-test stage, the following steps shall be followed and the following provisions shall be complied with: Ensure that air does not enter the pipe during the period. (2) slowly increase the pressure of the pipe to the test pressure and stabilize the pressure for 30min. During this period, if the pressure drops, the pressure can be supplemented by water injection, but not higher than the test pressure. Check whether there is leakage at the pipe interface, fittings, etc. When there is leakage, the pressure test should be stopped, and the cause should be found out and the corresponding measures should be taken before the pressure test. (3) stop filling pressure by water injection and stabilize for 60min. If the pressure drops to more than 70% of the test pressure after 60min, the pre-test phase will end. When the pressure drops below 70% of the test pressure after 60min, the pressure test shall be stopped, and the cause shall be found out and the corresponding measures shall be taken before the pressure test is organized.

2. In the main test stage, the following steps should be followed and the following provisions should be complied with: During the period, accurately calculate the amount of water discharged by depressurization, and set it as V(L). Vmax(L) Vmax=1.2VP{1/Ew+di/(en·Ep)} where V -- total volume of pressure test pipe (L); P -- reduced pressure (MPa); Ew -- volume modulus of water (MPa). Ew in different water temperatures is shown in table 1. Ep -- elastic modulus (MPa) of the pipe, which is related to water temperature and pressure test time, as shown in table 2; Di -- pipe diameter (m); En -- nominal wall thickness of pipes (m). Stop the pressure test when V is greater than V Max. After the pressure relief, the excess air in the pipe shall be removed, and then the retest shall be started from step (2) in the pre-test stage. (2) the residual pressure of the pipe should be recorded every 3 minutes for 30 minutes. When the residual pressure of the pipe has an upward trend within 30 minutes, the hydraulic test result is qualified. (3) if there is no upward trend of the remaining water pressure in the pressure test pipe within 30min, it shall be continuously observed for another 60min. When the pressure drop does not exceed 0.02mpa in the whole 90min, the hydrostatic test results are qualified. (4) when the above two conditions cannot be met in the main test stage, the results of the hydrostatic test are unqualified. The reason should be found out and the corresponding measures should be taken before the pressure test is organized.