Hydraulic test, pneumatic test, leak test
Thread Content
I. Hydrostatic testing 1. Clean water is generally used; when conducting hydrostatic 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 media 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 the requirements specified in item (5) of this section, the hydrostatic test pressure at any point in the system shall be not less than 1.5 times the design pressure. When the design temperature of the pipe is higher than the test temperature, the test pressure shall not be lower than the value calculated using equation (1). If the test pressure causes stresses in the pipe material that exceed its yield strength at the test temperature, then the test pressure 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 shall 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 tube of the jacketed tube shall be determined as the higher of the internal or external design pressure, while the test pressure for the outer tube of the jacketed tube shall be determined in accordance with item (3) of this clause ； 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 negative pressure from forming. II. Pressure Test (1) The gas used for the test shall be 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) The test setup 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 prior to the actual test; the test pressure is 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 agent. It is strictly prohibited to tighten bolts while the pressure is still high during the test. III. Leak Test The leak test shall meet the following requirements: Pipelines transporting extremely hazardous, highly hazardous fluids, as well as flammable fluids, must undergo a leak test. (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 a leak test at lower pressures to assess sensitivity ； (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.
A hydraulic test refers to the process of applying internal liquid pressure to pipes or equipment. Clean water is commonly used as the testing medium for hydraulic tests, but for austenitic stainless steel pipes or equipment, the chloride content in the water must not exceed 0.005%. If other liquids are used for testing, non-toxic and harmless liquids should be selected, and the flash point of flammable substances must be no lower than 50°C. During the hydraulic test, the liquid temperature must be no lower than 5°C and above the brittle transition temperature of the metal material. The test pressure for pipes subjected to internal pressure is generally not 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 also be calculated using a specific formula. The test pressure for pipes subjected to external pressure shall be 1.5 times the designed internal and external pressure difference, and shall not be less than 0.2 MPa. During the hydraulic testing, when pipes and containers are tested as a single system, it is necessary to determine which pressure to use for testing based on the relationship between the testing pressure for the pipes and that for the containers. The test pressure for the inner tube of the jacketed tube is determined based on the higher of the design pressures on the inside and outside, whereas the test pressure for the outer tube of the jacketed tube must be set in accordance with the requirements of the pipe that is subjected to internal pressure. The hydraulic test should involve a gradual increase in pressure; once the test pressure is reached, it should be maintained for 10 minutes. After that, the test pressure should be reduced to the design pressure and held at that level for 30 minutes. A successful hydraulic test requires no drop in pressure and no leaks. During the testing process, the gas in the pipes must be emptied; pressure should not be applied in the event of a leak, and negative pressure must be prevented at the end of the test. A pressure test refers to the process of applying internal gas pressure to a pipeline. For pressure testing, dry and clean air, nitrogen, or other non-flammable and non-toxic gases are used as the testing medium. During pressure testing, the test temperature should be kept away from the metal’s brittle transition temperature. During testing, an overpressure relief device must be installed, with its set pressure not exceeding 1.1 times the test pressure or the test pressure plus 0.34 MPa, whichever is lower. The test pressure for steel pipes and non-ferrous metal pipes subjected to internal pressure is 1.15 times the design pressure. Before the pressure test, a preliminary test using the test gas is required, with a test pressure of 0.2 MPa. During the test, the pressure must 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. Then the pressure is reduced to the design pressure for inspection, and no leakage is considered acceptable. It is strictly prohibited to tighten bolts under pressure during the pressure test. A leak test is the process of detecting leaks in pipes. Leakage tests are generally carried out after the pressure resistance test is successful. Air is usually used as the testing medium; however, in accordance with the specifications in the design documents or relevant standards, halogens, ammonia, or other sensitive gases may be used for leakage tests at lower test pressures to assess sensitivity. The key areas to be inspected during a leak test include valve stuffing boxes, flange or threaded connections, vent valves, exhaust valves, drain valves, etc. During the leak test, pressure is increased gradually and slowly. Once the test pressure is reached and the pressure is held for 10 minutes, all sealing points are inspected by applying a neutral foaming agent; no leaks are considered acceptable. .
Many of them are incorrect; for those needed, go and check the relevant standards directly.