1939_DNVGL-RU-SHIP_2016-07_Book.pdf

1939_DNVGL-RU-SHIP_2016-07_Book.pdf - Intended application...

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Unformatted text preview: Intended application Steel type/grade Deformation degree for which heat treatment may be waived All ≤ 5% Pressure vessels operated at ambient temperatures or feedstock temperatures down to -10°C VL 3.5Ni Pressure vessels operated at charging media temperatures below -10°C, as well as gas tanks with design temperatures below 0°C VL 5Ni ≤ 5% VL 9Ni C and C-Mn Alloy(other than above) ≤ 3% 3.2.4 For manufacturers performing hot/cold forming and/or heat treatment on hot/cold formed parts an appropriate manufacturer approval of the process is required. 3.3 Heat treatment of tubes after bending 3.3.1 Tubes shall be heat treated after bending when required in Ch.6 Sec.10 [3]. 4 Testing 4.1 Extent of non-destructive testing (NDT) 4.1.1 For pressure equipment designed with a joint efficiency of v > 0.85 non-destructive testing shall be carried out as follows: a) b) c) d) e) f) All longitudinal butt welded joints in drums, shells and headers shall be subjected to 100% radiographic testing. 25% of the length of circumferential butt welded joints in drums, shells and headers shall be subjected to radiographic testing. 10% of the total number of circumferential butt welded joints in pipes and tubes shall be subjected to radiographic testing. For set-in flat plates the cylindrical shell shall be ultrasonically tested for lamellar tearing in way of the circumferential weld to the flat plate. For shell plate thickness 15 mm and less the extent of testing shall be at least 10% and for greater thickness at least 20% of the total length of the weld. The internal fillet weld shall be 100% magnetic particle tested for surface flaws. For standpipes and branches with outside diameter exceeding 100 mm, all weld connections to shell and reinforcement rings shall be subjected to magnetic particle testing. For outside diameters 100 mm and less, spot testing shall be carried out. The magnetic particle testing is also to cover weld joints between reinforcement rings and shell. All welded joints shall be subjected to visual inspection. 4.1.2 For pressure equipment designed with a joint efficiency of v = 0.85, non-destructive testing shall be carried out as follows: a) b) Longitudinal butt weld joints in drums, shells and headers shall be subjected to radiographic testing at the rate of 20% of the length. All crossings between longitudinal and circumferential joints shall be included in the testing. All welded joints shall be subjected to visual inspection. Rules for classification: Ships — DNVGL-RU-SHIP-Pt4Ch7. Edition October 2015, amended January 2016 Pressure equipment DNV GL AS Page 117 Part 4 Chapter 7 Section 7 Table 3 Conditions where heat treatment after cold forming may be waived a) b) c) 10% of the length of longitudinal butt welded joints shall be subjected to radiographic testing. 10% of the length of circumferential butt welded joints shall be subjected to radiographic testing. 25% of the length of T-welds and corner welds shall be subjected to ultrasonic testing. 4.1.4 For non-ferromagnetic materials or materials with changes in magnetic permeability penetrant testing replaces magnetic particle testing in [4.1.1]. 4.1.5 For carbon and carbon-manganese steels of grades given in Pt.2 Ch.2 Sec.3 Table 3 with thickness less than 38 mm, the radiographic and ultrasonic testing may be carried out before post-weld heat treatment. Magnetic particle or penetrant testing shall be carried out when all heat treatment has been completed. Ultrasonic testing may be used in lieu of radiographic testing for thicknesses equal to or above 10 mm, and shall be carried out as specified in written procedures established in compliance with Class Guideline DNVGL CG-0051 as a minimum. 4.1.6 The requirements for NDT of welded joints for thermal oil piping can be found in Ch.6 Sec.10 [1.5]. 4.2 Performance of non-destructive testing (NDT) 4.2.1 For carbon and carbon-manganese steel with thicknesses greater than 30 mm and for alloy steels the non-destructive testing is normally to be carried out not earlier than 48 hours after completion of the welds in question. For carbon and carbon-manganese steels with thicknesses 30 mm and less the time limit may be reduced to 24 hours. 4.2.2 All testing shall be carried out by qualified and certified personnel. The NDT operators and the supervisors shall be certified according to a Third Party certification scheme based on EN ISO 9712 or ASNT Central Certification Program (ACCP). SNT-TC-1A may be accepted if the NDT company`s written practice is reviewed and accepted by the Society. The Certificate shall clearly state the qualifications as to which testing method, level and within which industrial sector the operator is certified. NDT operators shall be certified Level 2 in the testing method and industrial sector concerned. Supervisors shall be certified Level 3 in the testing method and industrial sector concerned. 4.2.3 Radiographic testing shall be carried out according to procedures that as a minimum comply with relevant parts of Class Guideline DNVGL CG-0051. For radiographic testing, X-ray source shall be used whenever possible. Gamma-ray sources may be used when qualified through examination by the Society. RT may be replaced by ultrasonic testing and vice versa, when methodologically justifiable and in agreement with the Society. Processing and storage shall be such that the radiographs maintain their quality throughout the agreed storage time. The radiographs shall be free from imperfections due to processing. 4.2.4 For ultrasonic testing the following apply: The welded connections in question shall be tested for laminations, transverse and longitudinal defects in accordance with procedures that as a minimum comply with Class Guideline DNVGL CG-0051. UT shall not be carried out on welds with thickness < 10 mm if not qualified and accepted down to 8 mm. 4.2.5 For magnetic particle testing the following apply: The welded connections in question shall be tested in accordance with procedures that as a minimum comply with Class Guideline DNVGL CG-0051. The object may be directly or indirectly magnetised. AC yoke or prods shall be used. Care shall be taken to avoid local heating of the test surface. Prods shall be of the type «soft prods», lead tipped or aluminium alloy. Use of permanent magnets is not permitted. Rules for classification: Ships — DNVGL-RU-SHIP-Pt4Ch7. Edition October 2015, amended January 2016 Pressure equipment DNV GL AS Page 118 Part 4 Chapter 7 Section 7 4.1.3 For furnaces and fireboxes non-destructive testing shall be carried out as follows: The testing on each area shall be performed with the magnetic field shifted in at least two directions approximately perpendicular to each other. 4.2.6 For penetrant testing the following apply: The welded connections in question shall be tested in accordance with procedures that as a minimum comply with Class Guideline DNVGL CG-0051. Colour contrast penetrants shall be used for welds in as welded condition. For smooth (flush grinded welds) fluorescent penetrants may be used. The surface temperature during testing shall be within the temperature range 10 to 50°C, if not, a procedure qualification test using ASME comparison blocks shall be carried out. The penetration time shall be at least 15 minutes. 4.3 Acceptance criteria for non-destructive testing and repair of defects 4.3.1 As the test methods differ in their limitations and/or possibilities of recording and documentation, special acceptance criteria are given for each method where necessary. Alternative evaluations ensuring an equivalent level of quality may in special cases be considered. 4.3.2 Acceptance criteria for welds in pressure vessels see Table 4: Table 4 Acceptance criteria Testing method Acceptance level 1) Visual testing EN ISO 5817 – Level B Magnetic particle testing EN ISO 23278 – Level 2x Penetrant testing EN ISO 23277 – Level 2x Radiographic testing EN ISO 10675 – Level 1 Ultrasonic testing 2) EN ISO 11666 – Level 2 1) except for imperfection types as follows, for which level C may apply: excess weld metal, excess convexity, excess throat thickness and excessive penetration 2) All imperfections from which the reflected echo amplitude exceeds the evaluation level shall be characterized and all that are characterized as planar, e.g. cracks, lack of fusion, incomplete penetration, shall be rejected. 4.3.3 NDT shall be reported as required and specified in Class Guideline DNVGL CG-0051 and all essential control parameters shall be given. 4.3.4 Defects which exceed the acceptance limits shall be completely removed and repaired according to an approved repair procedure. Magnetic particle testing is normally to be used to ensure complete removal of defects prior to repair welding. 4.3.5 When unacceptable defects are found in areas with less than 100% testing, the extent of testing shall be doubled compared to the initial area. If this increased testing reveals more unacceptable defects, the entire area of the weld shall be tested. Rules for classification: Ships — DNVGL-RU-SHIP-Pt4Ch7. Edition October 2015, amended January 2016 Pressure equipment DNV GL AS Page 119 Part 4 Chapter 7 Section 7 Required magnetic field strength: ...
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