Differences between hydraulic testing, pneumatic testing, airtightness testing, pressure resistance testing, and leakage testing

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Pressure test: After the pressure vessel is manufactured, a pressure test should be conducted. Pressure resistance tests are divided into three types: hydraulic testing, pneumatic testing, and combined gas-liquid pressure testing. The types of voltage withstand tests, pressures, media, temperatures, etc., are specified by the designer in the design documents. 1. Hydrostatic testing is generally used for voltage resistance tests, and the testing fluid shall meet the requirements of GB150.4 or relevant standards. 2. For containers that are not suitable for hydraulic testing, pneumatic testing or a combination of pneumatic and hydraulic testing can be used. Containers subjected to pressure tests or gas-liquid combined tests shall meet the requirements of GB150.4 or relevant standards. 3. When a gas-liquid combined test is used, the liquid and gas used in the test must meet the requirements of the above two points respectively, and the test pressure shall be in accordance with the regulations for gas pressure tests. 4. Pressure vessels under external pressure are tested for pressure resistance using internal pressure. 5. For multi-chamber containers consisting of 2 or more pressure chambers, the test pressure for each chamber is determined based on its design pressure, and each chamber is subjected to a pressure resistance test separately. a) Verify the stability of the common components under test pressure; b) If the stability requirements are not met, a leak check should be conducted first, and only after that can the pressure resistance test be carried out. During the pressure resistance test, a certain pressure should be maintained in adjacent pressure chambers so that at any moment throughout the entire test process (including pressure increase, pressure holding, and pressure release), the pressure difference between the various chambers does not exceed the allowable value. This requirement together with the allowable pressure difference value shall be specified in the drawings; c) If it is necessary to increase the test pressure in a particular chamber, the regulations regarding stress verification for pressure resistance tests must be satisfied. Leak test: After passing the pressure resistance test, leak tests shall be conducted on pressure vessels that contain media with an extremely high or high degree of toxicity, or those for which minor leaks are not permitted according to their design. Depending on the testing medium, leak tests are divided into airtightness tests, as well as ammonia leak detection tests, halogen leak detection tests, helium leak detection tests, and others. 1. The degree of medium toxicity is determined in accordance with the relevant provisions of the \"Safety Technical Inspection Regulations for Fixed Pressure Vessels\". 2. It shall be specified in the design drawings whether a pressure vessel required to undergo a pressure test according to the design requirements also needs to undergo a leak test. 3. When a cast pressure vessel is used to contain gaseous media, requirements for a leak-tightness test shall be specified in the design drawings. For pressure vessels equipped with overpressure relief devices such as safety valves and burst discs, if a gas-tightness test is specified in the design, the designer shall provide the maximum allowable operating pressure for that pressure vessel. 4. Ammonia leak detection tests can employ various methods such as the ammonia-air method, the ammonia-nitrogen method, and the 100% ammonia method. The ammonia concentration, test pressure, holding time, etc., are specified by the designer in the design documents. 5. Halogen leak detection test: For the halogen leak detection test, the required vacuum level inside the pressure vessel, the type of halogen gas to be used, the test pressure, the holding time, and the test procedures are all specified by the designer in the design documents. 6. Helium leak testing: For helium leak testing, the required vacuum level inside the pressure vessel, the concentration of helium gas, the test pressure, the holding time, and the test procedures are specified by the designer in the design documents.