The NORSOK standards are normally based on recognised international standards, adding the provisions deemed necessary to fill the broad needs of the Norwegian petroleum industry. Introduction The reference document for grade specifications is the August edition of EN The main changes in Rev. Latest issue of the references shall be used unless otherwise agreed. Other recognized standards may be used provided it can be shown that they meet or exceed the requirements and guidelines of the standards referenced below. Normative references are given in the individual data sheets. The reference document for grade specifications is the August edition of EN
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The holding time and temperature shall be as recommended by the steel manufacturer. The temperature difference between different parts of the structure during soaking time shall not exceed 30 qC within the heated area. Double sided heating shall be used as far as possible. The temperatures shall be continuously and automatically recorded on a chart. Grinding tools, direction, surface roughness and final profile shall be specified.
Reference samples for typical joints and sections may be prepared and used for acceptance of treated welds. Typical examples for requirements for grinding of joints are given in A. Tools for grinding and peening, surface roughness and profile of grinding as well as peening shall be specified.
Tools for check and measurements shall be described and shall be available during operations. Documentation of correct performance shall include macrophotography. Typical examples of requirements for peening of joints are given in A.
Production tests Production tests shall be selected on weldments in critical regions to verify that the specified requirements have been meet. Minimum one test coupon is required from each applied welding process. Test coupons shall be welded in a manner which realistically simulates the actual production welding, normally as extension of the production weld, and meet the requirements for welding procedure approval tests.
CTOD testing is not required for production testing. If a production test fails, the reason for the failure shall be determined and remedial action implemented. Fabrication tolerances Fabrication tolerances shall be in accordance with Annex E, unless otherwise specified on drawings. Non-destructive testing NDT 9. Final inspection and NDT of structural steel welds shall not be carried out before 48 h after completion except where PWHT is required. Prior to fabrication start-up, contractor shall implement a system for recording of weld defect rates.
The defect rates shall be recorded on a weekly basis for VT, MT, PT, UT and RT from each production area geographically split in production areas at the same yard and shall be reported together with the accumulated defect rate.
The defect rate statistics shall be used as a tool in weld quality control. Causes for defects shall immediately be investigated and corrective actions shall be taken to prevent further occurrence.
The defects shall be reported with reference to the numbering system according with ISO At a weekly high defect rate or at repeated occurrence of planar defects, two trigger levels apply for extended NDT for welds in inspection category B, C and D. Two steps of actions apply within trigger level 2.
The increased NDT extent shall cover welds of the same inspection categories, welded in the same period of time by the specific welder s and WPS when the high defect rate was produced, to assure that the weld quality is maintained also with the lower extent of NDT. A low defect rate may be used as basis for a reduction in the extent of NDT for inspection categories B, C and D, provided that a correct defect rate identification is prepared for each weld method, each NDT method b and each production area, see Table 3, table footnote.
Defect rate shall be based on at least 5 welds or 1 m tested weld length. NDT after repair shall not be included when calculating the defect rate. NDT personnel performing visual inspection of welded joints shall be qualified in accordance with EN , VT rd level 2 or equivalent 3 party certification scheme. NS latest revision may be used.
Ultrasonic operators performing inspection of welds in duplex stainless steel material shall be specially rd trained and qualified for the purpose according to EN or equivalent 3 party certification scheme When testing of castings or forgings, the NDT operator shall document experience with forged and cast products. Design drawings may show areas of welds where testing is mandatory. Testing performed shall be representative for the weld quality. Partial NDT shall normally be planed for on all shop drawings.
Ultrasonic testing to reveal the presence of possible weld metal transverse cracking shall be included for butt welds with thickness more than 25 mm.
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