What are the key points in the inspection and testing of non-standard pressure vessels?
Release Time : 2025-11-18
Due to the unique design, manufacturing, and usage scenarios of non-standard pressure vessels, their inspection and testing must focus on five core aspects: structural integrity, material reliability, welding quality, safety accessory performance, and operational stability. Multi-dimensional testing methods are employed to ensure safe operation.
Structural integrity testing should focus on the geometry and connection methods of non-standard pressure vessels. Design differences in non-standard equipment often lead to stress concentration risks at the connection between the cylinder and the head, and in areas with openings and nozzles. A combination of macroscopic inspection and non-destructive testing is necessary to identify defects such as cracks, deformation, or undercut. For example, for transition areas of irregularly shaped heads and edges of reinforcing rings, penetrant testing (PT) or magnetic particle testing (MT) should be used to check for surface cracks, while ultrasonic testing (UT) or radiographic testing (RT) should be used to check for internal embedded defects. Furthermore, settlement, tilting, and support damage of the equipment foundation must also be included in the inspection scope to prevent structural instability caused by external loads.
Material reliability verification requires analysis of both chemical composition and metallographic structure. Non-standard equipment may face the risk of material deterioration due to special material selection or complex operating environments. For example, pressure vessels containing high-temperature media need to be checked for creep or spheroidization, while cryogenic equipment requires verification of material toughness. During testing, spectral analysis is needed to confirm material composition, hardness testing to determine if temper embrittlement or sensitization has occurred, and metallographic examination to observe microstructural changes when necessary. For pressure vessels with linings or weld overlays, it is also necessary to check for bulging or peeling of the lining and the good bonding condition of the weld overlay.
Welding quality control is paramount in the testing of non-standard equipment. The welding process of non-standard equipment may contain hidden defects such as incomplete fusion and incomplete penetration due to structural complexity. During testing, all welds must undergo surface quality inspection, with a focus on fillet welds, repair welds, and porosity, slag inclusions, and cracks in stress concentration areas. For critical welds, non-destructive testing (UT) or refining (RT) should be performed, paying particular attention to T-joints, cross welds, and areas with original manufacturing defects. For high-pressure or thick-walled pressure vessels, phased array ultrasonic testing (PAUT) or time-of-flight diffraction ultrasonic testing (TOFD) should be added to improve the defect detection rate.
Performance testing of safety accessories is the last line of defense for ensuring safe equipment operation. Non-standard equipment may be equipped with customized safety accessories due to the special nature of the media. During testing, it is necessary to verify whether their specifications and models match the design requirements, whether the installation position is reasonable, and whether they are within the valid calibration period. For example, safety valves need to be checked to see if the discharge capacity meets the pressure relief requirements, rupture discs need to be confirmed to operate under the specified pressure, and the indicating accuracy of pressure gauges and level gauges needs to meet the standards. In addition, the functional testing of interlocking alarm devices cannot be ignored; it is necessary to ensure that they can trigger protective actions in a timely manner under abnormal operating conditions such as overpressure and overtemperature.
Operational stability assessment needs to combine historical data of the equipment with real-time monitoring results. Non-standard equipment often faces the risk of fatigue damage due to fluctuations in process parameters or frequent start-ups and shutdowns. During testing, it is necessary to analyze corrosion rate, remaining life, and strength verification results. For example, wall thickness reduction is calculated using thickness measurement data, and the remaining service life is predicted based on media corrosiveness. For areas with alternating stress, the likelihood of fatigue crack propagation needs to be assessed. Simultaneously, equipment operation records must be checked to confirm the presence of over-temperature, over-pressure operation, or improper handling, providing a basis for subsequent maintenance.
Inspection and testing of non-standard pressure vessels must be risk-oriented, with differentiated testing plans developed based on their unique design characteristics. A comprehensive inspection of the structure, materials, welding, safety accessories, and operating status can promptly identify potential hazards and implement remedial measures, thereby ensuring the safe and reliable operation of the equipment throughout its entire lifecycle.