Splicing of the coiled tubes inside the reaction vessel
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The coils inside the reaction vessel need to be joined together; what non-destructive testing requirements should be imposed on these joints? How should pressure and medium be determined?
We generally follow the method of splicing heat exchange tubes. Of course, factors such as medium toxicity also need to be taken into consideration additionally.
Yes, generally, the splicing of heat exchange tubes is referred to GB151, but reaction vessels are always a bit concerning.
:) There’s actually no need to worry; there aren’t that many coil connectors to start with. Of course, don’t use short pipes for the connections: lol. In the case of containers of type three, it’s not a waste to conduct flaw detection on all the connectors.
This is mainly in accordance with the requirements of 6.3.3 in GB151, as follows: 6.3.3 When joining heat exchange tubes, the following requirements shall be met: a) A welding procedure qualification shall be carried out for the butt joints. The number, dimensions, and testing methods of the test specimens shall comply with the provisions of JB 4708 ； Welded joints of aluminum, copper, and titanium can be referenced accordingly ； b) For the buttwelds of the same heat exchange tube, there shall be no more than one such weld on straight sections ； There shall not be more than two U-tubes ； The minimum tube length shall not be less than 300 mm ； There shall be no welds at the joints within the U-shaped bend section, which must include at least 50 mm of straight pipe section ； c) The pipe end groove shall be machined mechanically and cleaned thoroughly before welding ； d) The misalignment at the joint shall not exceed 15% of the wall thickness of the heat exchange tube, and shall not be greater than 0.5 mm ； The straightness deviation shall be such that it does not prevent smooth pipe insertion ； e) After alignment, a ball test should be conducted on the welded joint by selecting an appropriate steel ball diameter as specified in Table 50; the joint is considered qualified if the steel ball passes through it: Table 50 – Steel ball diameter based on outer diameter of heat exchanger tube: d ≤ 25: 0.75d; 25 < d ≤ 40: 0.8d; d > 40: 0.85d. Note: d refers to the inner diameter of the heat exchanger tube. i— f) The butt joints shall be subjected to radiographic inspection; the number of samples inspected shall be no less than 10% of the total number of joints, and at least one sample per joint, with grade III according to JB 4730 considered as acceptable ； If one item is found to be non-compliant, random inspections should be doubled ； If non-conformities occur again, a 100% inspection should be carried out ； g) The heat exchange tubes after alignment shall be individually subjected to a hydraulic test, with the test pressure being twice the design pressure.