Welding in API 6D
Welding Requirement In API 6D
Welding, including repair welding, of pressure-containing and pressure-controlling parts shall be performed in accordance with procedures qualified to ISO 15607, ISO 15609, ISO 15614-1 or ASME Section IX and 9.2 and 9.3 of this International Standard. Welders and welding operators shall be qualified in accordance with ISO 9606-1, ASME Section IX or EN 287-1.
NOTE 1 The purchaser, pipeline design standards, material specifications and/or local requirements can specify additional requirements.
The results of all qualification tests shall be documented in a PQR.
PWHT shall be performed in accordance with the relevant material specification.
NOTE 2 Some pipeline welding standards can have more stringent requirements for the essential variables of welding. It can be necessary to provide full weld test rings, in the same heat treatment condition as the finished valve, for weld procedure qualification.
Qualifications of procedures for welding include repair welding; pressure-containing parts shall meet the toughness test requirements of the applicable pipeline design standard.
As a minimum, impact testing shall be carried out for the qualification of procedures for welding on valves with a design temperature below – 29°C (- 20 OF).
NOTE Design standards and/or local requirements might require impact testing at minimum design temperatures above – 29°C (- 20 OF).
A set of three weld-metal impact specimens shall be taken from the weld metal (WM) at the location shown in Figure 15. The specimens shall be oriented with the notch perpendicular to the surface of the material.
A set of three impact specimens shall be taken from the heat-affected zone (HAl) at the location shown in Figure 16. The notch shall be placed perpendicularly to the material surface at a location resulting in a maximum amount of HAl material located in the resulting fracture.
HAl tests shall be conducted for each of the materials being joined, when the base materials being joined are of a different P-number and/or Group-number in accordance with ISO 9606-1, ISO 15607, ISO 15609, ISO 15614-1 or ASME Section IX when one or both of the base materials being joined are not listed in the P-number grouping.
Impact testing shall be performed in accordance with ISO 148-1 or ASTM A370 using the Charpy V-notch technique. Specimens shall be etched to determine the location of the weld and HAl.
The impact test temperature for welds and heat-affected zones shall be at or below the minimum design temperature specified for the valve.
Impact test results for full-size specimens shall meet the requirements of Table 8. If the material specification or the pipeline design standard requires higher impact values than those shown in Table 8, the higher values shall apply.
Hardness testing shall be carried out as part of the welding procedure qualification on pressure-containing and pressure-controlling parts in valves required to meet ISO 15156 (all parts).
Hardness surveys shall be performed on 8M, WM and HAl in accordance with the requirements of ISO 15156-2. The hardness method used shall be Vickers HV5 or HV1O.
NOTE For existing qualification, other hardness measurement methods (such as HRC or HRB) are acceptable by agreement.
Minor defects may be removed by grinding provided there is a smooth transition between the ground area and the original contour and the minimum wall thickness requirements are not affected.
Repair of defects shall be performed in accordance with a documented procedure specifying requirements for defect removal, welding, heat treatment, NDE and reporting as applicable. Repairs of fabrication welds shall be limited to 30 % of the weld length for partial-penetration repairs or 20 % of the weld length for full-penetration repairs, except the minimum length of any weld repair shall be 50 mm.
The heat treatment (if applicable) of weld repairs shall be in accordance with the applicable material standard.
Weld repair of forgings and plates to correct manufacturing defects shall be by agreement. Weld repair of castings shall be in accordance with the applicable material standard.
Figure 1 – Charpy V-notch weld-metal (WM) specimen location
Figure 2 – Charpy V-notch heat-affected zone (HAZ) specimen location
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