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How to choose full or partial radiographic or ultrasonic inspection?

How to choose full or partial radiographic or ultrasonic inspection?

The criteria for determining whether full (100%) or partial radiographic or ultrasonic inspection should be performed are outlined in section 10.3 of GB/T 150-2011 “Pressure Vessels.”

Pipe fitting ready for radiographic test

Pipe fitting ready for radiographic test

Full (100%) Radiographic or Ultrasonic Inspection

Pressure vessels and pressure components that meet any of the following conditions must undergo full radiographic or ultrasonic inspection of their Class A and Class B welded joints using the method specified in the design documents:

  • a) Category III vessels with a design pressure greater than or equal to 1.6 MPa.
  • b) Vessels subjected to pneumatic or combined pneumatic and hydrostatic tests.
  • c) Vessels with a weld joint efficiency factor of 1.0.
  • d) Vessels that require internal inspection but cannot be inspected internally after use.
  • e) Vessels containing extremely or highly hazardous toxic media.
  • f) Low-temperature vessels with a design temperature below -40°C or weld joint thickness greater than 25 mm.
  • g) Austenitic stainless steel, carbon steel, Q345R, Q370R, and their matching forgings with a weld joint thickness greater than 30 mm.
  • h) 18MnMoNbR, 13MnNiMoR, 12MnNiVR, and their matching forgings with a weld joint thickness greater than 20 mm.
  • i) 15CrMoR, 14Cr1MoR, 08Ni3DR, austenitic-ferritic stainless steel, and their matching forgings with a weld joint thickness greater than 16 mm.
  • j) Ferritic stainless steel and other Cr-Mo low alloy steel vessels.
  • k) Low alloy steel vessels with a minimum tensile strength (Rm) of 540 MPa or higher.
  • l) Vessels specified in the drawings for 100% inspection.

Note: The inspection requirements for butt joints between nozzles with a nominal diameter of DN ≥ 250 mm and nozzles or high-neck flanges are the same as for Class A and Class B welded joints in the vessels mentioned above.

Ultrasonic testing of welds

Ultrasonic testing of welds

Partial Radiographic or Ultrasonic Inspection

Vessels not covered by the above requirements should undergo partial radiographic or ultrasonic inspection of their Class A and Class B welded joints as specified in the design documents. The inspection length for low-temperature vessels must be at least 50% of the length of each welded joint, and for non-low-temperature vessels, at least 20% of the length of each welded joint, with a minimum inspection length of 250 mm.

The following areas, along with the weld intersection points, should undergo 100% inspection. The inspection lengths for areas (a), (b), and (c) and the weld intersection points can be included in the partial inspection length:

  • a) All weld joints on convex heads formed after plate assembly.
  • b) Weld joints covered by reinforcement rings, supports, pads, internal components, etc.
  • c) Weld joints within the range of the smallest distance from the center of the opening to the vessel surface, equal to the diameter of the opening, for nozzles not requiring additional reinforcement as per GB150.3-2011, section 6.1.3.
  • d) Butt weld joints between embedded nozzles and cylinders or heads.
  • e) Butt weld joints between nozzles with a nominal diameter of DN ≥ 250 mm and nozzles or high-neck flanges subjected to external loads.

Note: After the specified inspection, the manufacturer remains responsible for the quality of the uninspected portions. However, if further inspection may reveal minor pores or other non-threatening defects exceeding the standard, and if this is unacceptable, 100% radiographic or ultrasonic inspection should be chosen.

Additional Provisions

1.Inspection requirements for butt weld joints between nozzles with a nominal diameter of DN < 250 mm and nozzles or high-neck flanges should be specified in the design documents.

2.For the final circumferential closure weld of a cylinder with a diameter not exceeding 800 mm and its head, single-sided butt welds without backing that cannot undergo radiographic or ultrasonic inspection are permitted without inspection, provided that the root pass is made using gas-shielded welding.

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