Hydraulic testing, pneumatic testing, leak testing

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Hydraulic testing: 1. Clean water is generally used. When conducting hydraulic testing on austenitic stainless steel pipes, or on pipes connected to such pipes or equipment, the chloride content in the water must not exceed 0.005%. If this level poses a negative impact on the pipes or the process, other suitable non-toxic liquids can be used. When flammable substances are used for testing, their flash point must be at least 50℃； 2. The liquid temperature during testing must be no lower than 5°C, and higher than the brittle transition temperature of the corresponding metal material ； 3. For pipes subjected to internal pressure, in addition to meeting the requirements of item (5) herein, the hydrostatic test pressure at any point in the system must not be less than 1.5 times the design pressure. When the design temperature of the pipe is higher than the test temperature, the test pressure must not be lower than the value calculated using Equation (1). If the test pressure PT generates stresses exceeding the yield strength of the pipe material at the test temperature, the test pressure PT shall be reduced to the maximum pressure that does not exceed the yield strength.
4. For pipes subjected to external pressure, the test pressure shall be 1.5 times the difference between the design internal and external pressures, and must not be less than 0.2 MPa ； 5. When the pipeline and the container are subjected to a hydraulic test as a single system, and the test pressure for the pipeline is less than or equal to that of the container, the test shall be conducted at the pressure specified for the pipeline. If the test pressure for the pipeline is greater than that of the container, and it is not possible to separate the pipeline from the container, while the test pressure for the container is greater than or equal to 77% of the pipeline’s test pressure calculated in accordance with item (3) of this clause, then, with the approval of the design unit, the test may be carried out at the pressure specified for the container ； 6. The test pressure for the inner pipe of a jacketed pipe shall be determined based on the higher value between the internal and external design pressures; the test pressure for the outer pipe of the jacketed pipe shall be determined in accordance with item (3) of this article ； 7. The pressure is increased slowly during the test; once the test pressure is reached, it is maintained for 10 minutes. Then the pressure is reduced to the design value, and this level is held for 30 minutes. The test is considered successful if the pressure does not drop and there are no leaks ； 8. During testing, the gas in the pipes must be completely removed. If a leak is detected during the test, it must not be repaired while under pressure; when draining the liquid after the test, care must be taken to prevent the creation of negative pressure. Pneumatic testing (I): The gas used for testing is dry and clean air, nitrogen, or other non-flammable and non-toxic gases ； (II) It is strictly prohibited to bring the test temperature close to the metal’s brittle transition temperature ； (III) During testing, the equipment shall be equipped with an overpressure relief device, the set pressure of which shall not be higher than 1.1 times the test pressure or the test pressure plus 0.34 MPa (whichever is lower) ； (IV) The test pressure for steel pipes subjected to internal pressure as well as non-ferrous metal pipes is 1.15 times the design pressure ； (5) A preliminary test must be conducted using the test gas before the actual test, with a test pressure of 0.2 MPa ； (VI) During the test, the pressure should be increased gradually and slowly. When the pressure reaches 50% of the test pressure, if no abnormalities or leaks are detected, the pressure should be increased further in steps of 10% of the test pressure until the test pressure is reached. After that, the pressure should be reduced to the design pressure for inspection; a pass is considered to be achieved if no leakage is detected using a foam detector. It is strictly prohibited to tighten bolts while the pressure is still high during the test. Leakage tests shall meet the following requirements: Pipelines transporting extremely hazardous, highly hazardous fluids, and flammable fluids must undergo leakage tests. (1) The test shall be carried out after the pressure resistance test is successful; air is preferably used as the testing medium, but according to the provisions in the design documents or relevant standards, halogens, ammonia, or other sensitive gases may be used for sensitivity leakage tests at lower test pressures ； (II) The key points of inspection for leakage tests are the valve stuffing box, flange or threaded connections, vent valves, exhaust valves, drain valves, etc ； (III) For the leakage test, the pressure is increased gradually step by step. Once the test pressure is reached and the pressure is held constant for 10 minutes, all sealing points are inspected by applying a neutral foaming agent; no leakage is considered acceptable.