Common errors in pressure vessel drawings

Thread Content

1: The technical specifications table is missing information on the material of the main compression elements, as well as data such as the filling coefficient and operating volume. 2: The inner tube is welded to the jacket; for welds between different metals (such as carbon steel and stainless steel), high-chromium-nickel electrodes are not used, only ordinary stainless steel electrodes are employed, such as A102 ； Instead, A302 or A307 should be used. Note: Since these are two different types of steel being welded together, it is even more important to control the proportion of base metal in the weld, that is, the fusion ratio. Its purpose is to reduce weld cracks. An excessive fusion ratio leads to excessive dilution of the weld, which can result in insufficient austenite content in the weld and the formation of martensitic structure, thereby causing brittle cracks in the joint. When 201 stainless steel (austenitic) is welded to low-carbon steel (pearlitic), using the commonly used A102 and A132 stainless steel electrodes will inevitably result in the formation of martensite in the weld metal, leading to cracks in the weld. By using E309 electrodes and keeping the fusion ratio of the base metal at less than 30%, an ideal austenite + ferrite duplex structure can be achieved, thereby preventing weld cracks. 3: The forging grade in the technical requirements is incorrect. 4: The medium is flammable and explosive, and the requirements for static grounding of explosion-proof motors and equipment are not specified. 5: The nozzle orientation diagram lacks positioning dimensions or positioning angles. 6: The pressure testing steps for the hydrostatic test and airtightness test are incorrect. After the hydrostatic test is successful, a gas-tightness test can be conducted if necessary. Containers with a medium toxicity level that constitutes extreme or high hazard, or those in which even trace leaks are not permitted (including those required by other drawings to undergo leak tests), shall be subjected to leak tests after passing the pressure (water pressure) test. Leakage tests include airtightness tests, as well as ammonia leak detection tests, halogen leak detection tests, and helium leak detection tests. --GB150-2011 P15 4.7 7: No anti-backflow valve is provided at the steam inlet of the jacket. 8: For equipment flanges, attention should be paid to the issue of bolt mid-span; the drawings may not show this mid-span position. 9: The cylinder thickness does not meet the minimum thickness specified for the heat exchanger. 10: For U-tube heat exchangers, it is important to ensure that the bending radius of the U-tubes is at least twice the outer diameter of the heat exchange tubes, as well as to pay attention to mechanisms to prevent short circuits. 11: Are the dimension markings complete, and are the positioning dimensions of the pipe ends complete? 12: The thickness of the partition plates does not meet the minimum thickness requirement. 13. The length of the thermometer probe is too short; it cannot go below the liquid surface. 14. The medium inside the inner cylinder is flammable and explosive; a packing seal is used for shaft sealing, and no mechanical seal is employed. 15. The drawings show non-radial nozzles, but there are no diagrams of non-radial welding joints. 16. Pipe boxes with a weight of over 30 Kg should preferably be equipped with lifting lugs.