Thread Content
The pressure test of pressure vessels is divided into two types: hydraulic test and pneumatic test. When the materials used for each component of the pressure vessel (cylinder, head, nozzle, flange and fasteners) are different, the smallest material/t ratio of each component should be used to calculate the pressure test. 1. Pressure resistance test requirements for jacketed pressure vessels (1) Jacketed pressure vessels whose inner cylinder design pressure is less than the jacket design pressure ； Jacketed glass-lined equipment with a volume of less than or equal to 1000L can be exempted from the inner cylinder hydraulic test with the approval of the technical director of the manufacturing unit and the consent of the user, but the jacket hydraulic test cannot be exempted. (2) For jacketed glass-lined equipment with a volume between 1000L and 5000L, after 30 consecutive hydraulic tests of the same specification equipment, with the approval of the technical director of the manufacturing unit, every 15 units can be divided into a batch, and one unit from each batch can be selected for hydraulic testing (except for special requirements of the user). If it fails, the hydraulic test must be resumed one by one. Jacketed glass-lined equipment with a volume greater than 5000L should undergo a hydraulic test for each unit. The pressure of the pressure test should comply with the design drawing requirements and not be less than the value calculated by the following formula: pr=ηp where p——the design pressure of the liquefied petroleum gas storage tank (for pressure vessels in use, it is generally the maximum working pressure, or the maximum allowable working pressure specified on the nameplate of the pressure vessel), MPa ； pr——pressure test pressure, MPa ； η——pressure coefficient of pressure test ； ——Allowable stress of material at test temperature, MPa ； t——allowable stress of material at design temperature, MPa. 2. During the pressure test, the circumferential film stress value of the pressure vessel shell should meet the following requirements: (1) During the hydraulic test, the product of 90% of the material yield point at the test temperature and the welding joint coefficient of the cylinder shall not be exceeded. (2) During the air pressure test, the product of 80% of the material yield point at the test temperature and the welding joint coefficient of the cylinder shall not be exceeded. When checking the pressure of the pressure test, the wall thickness taken should be deducted from the additional wall thickness, and the pressure taken for the hydraulic test should also be included in the static pressure of the liquid column. For tube-and-tube heat exchangers where the shell-side pressure is lower than the tube-side pressure, the corrosion allowance does not need to be deducted. (3) Before the pressure test, the fastening bolts of each connection part of the liquefied gas storage tank must be fully assembled and tightened properly. The pressure gauges used for testing should comply with regulations. At least two calibrated pressure gauges with the same range should be used, and should be installed on the top of the vessel being tested in a position that is convenient for observation. (4) The pressure test site should have reliable safety protection facilities and be inspected and approved by the unit’s technical director and safety department. During the pressure test, no work unrelated to the test is allowed, and irrelevant personnel are not allowed to stay at the test site.