Head jointing
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Under what circumstances cannot end caps be joined together, and why? What should be noted when splicing?
For smaller diameters, the available plate size is sufficient, allowing for production in whole plates; for larger diameters, the available plate size is not enough, so piecing together the plates is necessary. There are requirements regarding inspections for such piecings, and the standards in JB/T4746 can be referred to
Generally, those with smaller diameters are manufactured as single pieces; for larger diameters, to save material, they can be assembled by splicing. The welds are subject to 100% radiographic inspection as per Class A standards, and the internal welds must be ground to be level with the base material
Except in cases of special requirements or when the diameter is small, end caps are generally constructed by splicing； If the diameter is too large, a melon-segment design will be considered; each melon segment is pressed together first and then welded into shape. When welding the end caps, attention should be paid to the requirements regarding misalignment variations. After welding, 100% RT testing must be carried out in accordance with the drawing specifications, and the acceptance standard is the same as that for Class A and Class B welds. In the case of overall compression, it is required that the inner surface of the weld be ground to be level with the base material. Appropriate inspections are carried out after molding; RT testing should be performed on the welds at the head’s arc sections to assess the quality of those welds
If the diameter is greater than 2100 mm, welding is generally required; for flaw detection, JB/T4746 can be followed
When the nominal diameter is greater than 2000, welding is required; the corresponding welds must be inspected in accordance with GB4730 \"Non-destructive Testing of Pressure Equipment\"