Welding of Pipelines & Related Facilities PDF

WELDING OF PIPELINES AND RELATED FACILITIES 43 c) linear indications are evaluated as IF and exceed 1 in. (25 mm) in total length in a continuous 12 in. (300 mm) length of weld or 8 % of the weld length. Rounded indications shall be evaluated according to the criteria of 9.3.9.2 and 9.3.9.3, as ap...

WELDING OF PIPELINES AND RELATED FACILITIES 43 c) linear indications are evaluated as IF and exceed 1 in. (25 mm) in total length in a continuous 12 in. (300 mm) length of weld or 8 % of the weld length. Rounded indications shall be evaluated according to the criteria of 9.3.9.2 and 9.3.9.3, as applicable. For evaluation purposes, the maximum dimension of a rounded indication shall be considered its size. NOTE When doubt exists about the type of imperfection being disclosed by an indication, verification may be obtained by using other NDT methods. 9.4.3 Base Material Imperfections Imperfections in base material detected by magnetic particle testing shall be reported to the company. The disposition of these imperfections shall be as directed by the company. 9.5 Liquid Penetrant Testing 9.5.1 Classification of Indications Indications produced by liquid penetrant testing are not necessarily imperfections. Machining marks, scratches, and surface conditions may produce indications that are similar to those produced by imperfections but that are not relevant to acceptability. The following criteria shall apply when indications are evaluated. a) Any indication with a maximum dimension of 1/16 in. (2 mm) or less shall be classified as nonrelevant. Any larger indication believed to be nonrelevant shall be regarded as relevant until reexamined by liquid penetrant or another NDT method to determine whether or not an actual imperfection exists. The surface may be ground or otherwise conditioned before reexamination. After an indication is determined to be nonrelevant, other nonrelevant indications of the same type need not be reexamined. b) Relevant indications are those caused by imperfections. Linear indications are those in which the length is more than three times the width. Rounded indications are those in which the length is three times the width or less. 9.5.2 Acceptance Standards Relevant indications shall be considered defects should any of the following conditions exist: a) linear indications are evaluated as crater cracks or star cracks and exceed 5/32 in. (4 mm) in length, b) linear indications are evaluated as cracks other than crater cracks or star cracks, c) linear indications are evaluated as IF and exceed 1 in. (25 mm) in total length in a continuous 12 in. (300 mm) length of weld or 8 % of the weld length. Rounded indications shall be evaluated according to the criteria of 9.3.9.2 and 9.3.9.3, as applicable. For evaluation purposes, the maximum dimension of a rounded indication shall be considered its size. NOTE When doubt exists about the type of imperfection being disclosed by an indication, verification may be obtained by using other NDT methods. 9.5.3 Base Material Imperfections Imperfections in the base material detected by liquid penetrant testing shall be reported to the company. The disposition of these imperfections shall be as directed by the company. 44 API STANDARD 1104 9.6 Ultrasonic Testing 9.6.1 Classification of Indications 9.6.1.1 General Indications produced by ultrasonic testing are not necessarily defects. Changes in the weld geometry due to alignment offset of abutting pipe ends, changes in weld reinforcement profile of ID root and OD capping passes, internal chamfering, and ultrasonic wave mode conversion due to such conditions may cause geometric indications that are similar to those caused by weld imperfections but that are not relevant to acceptability. 9.6.1.2 Linear Indications Linear indications are defined as indications with their greatest dimension in the weld length direction. Typical linear indications may be caused by, but are not limited to, the following types of imperfections: IP, IPD, ICP, IF, IFD, ESI, cracks, EU, IU, and HB. 9.6.1.3 Transverse Indications Transverse indications are defined as indications with their greatest dimension across the weld. Typical transverse indications may be caused by, but are not limited, to the following types of imperfections: cracks, ISIs, and IFD at start/stops in the weld passes. 9.6.1.4 Volumetric Indications Volumetric indications are defined as three-dimensional indications. Such indications may be caused by single or multiple inclusions, voids, or pores. Partially filled voids, pores, or small inclusions at start/stops in weld passes may cause larger indications in the transverse direction than in the weld length direction. Typical volumetric indications may be caused by, but are not limited to, the following types of imperfections: IC, BT, ISIs, porosity, and CP. 9.6.1.5 Relevant Indications Relevant indications are those caused by imperfections. Relevant indications shall be evaluated at the evaluation level given in 11.4.7 to the acceptance standards given in 9.6.2. NOTE When doubt exists about the type of imperfection being disclosed by an indication, verification may be obtained by using other NDT methods. 9.6.2 Acceptance Standards 9.6.2.1 General Indications shall be considered defects should any of the following conditions exist: a) indications determined to be cracks, b) individual indications with a vertical height (through-wall) dimension determined to be greater than one quarter of the wall thickness, c) multiple indications at the same circumferential location with a summed vertical height (through-wall) dimension exceeding one quarter the wall thickness. WELDING OF PIPELINES AND RELATED FACILITIES 45 9.6.2.2 Linear Surface (LS) Indications LS indications (other than cracks) interpreted to be open to the ID or OD surface shall be considered defects should any of the following conditions exist: a) the aggregate length of LS indications in any continuous 12 in. (300 mm) length of weld exceeds 1 in. (25 mm), b) the aggregate length of LS Indications exceeds 8 % of the weld length. 9.6.2.3 Linear Buried (LB) Indications LB indications (other than cracks) interpreted to be subsurface within the weld and not ID or OD surface connected shall be considered defects should any of the following conditions exist: a) the aggregate length of LB indications in any continuous 12 in. (300 mm) length of weld exceeds 2 in. (50 mm), b) the aggregate length of LB indications exceeds 8 % of the weld length. 9.6.2.4 Transverse (T) Indications T indications (other than cracks) shall be considered volumetric and evaluated using the criteria for volumetric indications. The letter T shall be used to designate all reported transverse indications. 9.6.2.5 Volumetric Cluster (VC) Indications VC indications shall be considered defects when the maximum dimension of VC indications exceeds 1/2 in. (13 mm). 9.6.2.6 Volumetric Individual (VI) Indications VI indications shall be considered defects when the maximum dimension of VI indications exceeds 1/8 in. (3 mm). 9.6.2.7 Volumetric Root (VR) Indications VR indications interpreted to be open to the ID surface shall be considered defects should any of the following conditions exist: a) the maximum dimension of VR indications exceeds 1/4 in. (6 mm) or the specified wall thickness, whichever is less; b) the total length of VR indications exceeds 1/2 in. (13 mm) in any continuous 12 in. (300 mm) length. 9.6.2.8 Accumulation Any accumulation of relevant indications shall be considered a defect when any of the following conditions exist: a) the aggregate length of indications above evaluation level exceeds 2 in. (50 mm) in any 12 in. (300 mm) length of weld, b) the aggregate length of indications above evaluation level exceeds 8 % of the weld length. 9.6.3 Base Material Imperfections Imperfections in the base material detected by ultrasonic testing shall be reported to the company. The disposition of these imperfections shall be as directed by the company. 46 API STANDARD 1104 9.7 Visual Acceptance Standards for Undercutting 9.7.1 General Undercutting is defined in 9.3.11. The acceptance standards in 9.7.2 supplement but do not replace visual inspection requirements found elsewhere in this standard. 9.7.2 Acceptance Standards When visual and mechanical means are used to determine depth, undercutting adjacent to the cover or root bead shall not exceed the dimensions given in Table 4. When both mechanical and radiographic measurements are available, the mechanical measurements shall govern. Table 4—Maximum Dimensions of Undercutting Depth Length >1/32 in. (0.8 mm) or >12.5 % of pipe wall thickness, whichever Not acceptable is smaller >1/64 in. (0.4 mm) but ≤ 1/32 in. (0.8 mm) or >6 % but ≤ 12.5 % of pipe wall thickness, whichever is smaller 2 in. (50 mm) in a continuous 12 in. (300 mm) weld length or one-sixth the weld length, whichever is smaller ≤1/64 in. (0.4 mm) or ≤ 6 % of pipe wall thickness, whichever is smaller Acceptable, regardless of length 10 Repair and Removal of Weld Defects 10.1 General Weld defects may be identified during visual or nondestructive testing, or during the company’s review of nondestructive testing results. 10.2 Authorization for Repair 10.2.1 Company Authorization Company authorization is required for crack repairs, back weld repairs, and double repairs and as otherwise noted in 10.2. Company authorization is not required for any repairs that do not involve the application of heat or weld metal, such as grinding, filing, etc. 10.2.2 Crack Repairs Cracked welds shall be cut out unless permitted by 9.3.10 or repair is authorized by the company. When a crack repair is authorized: a) a cracked butt weld or branch weld may be repaired by complete or partial removal of the weld provided the length of a single crack or aggregate length of more than one crack in a single repair area is less than 8 % of the weld length using a qualified repair procedure; b) a cracked fillet weld may be repaired by complete or partial removal of the fillet weld using a qualified repair procedure; c) a butt weld or branch weld that contains multiple repair areas with crack(s) may not be repaired unless the total accumulated repair length is less than 8 % of the weld length and a qualified repair procedure is used; d) a double repair of a crack is not permitted. Additional cracking in any weld after repair shall require a cut out; WELDING OF PIPELINES AND RELATED FACILITIES 47 e) shallow crater cracks or star cracks found and contained completely in internal or external weld reinforcement may be repaired by grinding (i.e. abrasive methods) without a qualified repair procedure. If the grinding exceeds the internal or external reinforcement, the reinforcement shall be replaced using a qualified weld procedure. 10.2.3 Repairs of Defects Other Than Cracks Defects other than cracks in the root, filler, and finish beads may be repaired with prior company authorization. A qualified repair procedure shall be required whenever a repair is made by welding when: a) using a welding process, combination of welding processes, or method of application or filler metals different from that used to make the original weld; or b) repairs are made in a previously welded repaired area; or c) required by the company. 10.2.4 Grinding Repairs Grinding repairs may be used to remove defects in the reinforcement of root beads and cover passes provided: — there is a smooth transition free of undercutting and other imperfections between the ground area and the original weld, and — pipe surface contour and the minimum wall and weld thickness requirements are not violated. If the minimum wall/weld thickness is not known, the grinding depth is limited to the excess root bead penetration or external reinforcement. The grinding repair length and number of grinding repair areas is not limited. Grinding repairs do not require use of a qualified repair procedure. 10.2.5 Back Weld Repairs When back weld repairs are permitted by the company, a repair procedure shall be qualified in accordance with 10.3. 10.2.6 Welded Double Repairs A double repair requires prior company authorization. For repair procedure qualification purposes, this is a partial thickness or full thickness repair that tests a HAZ that has received three full thermal cycles from welding. A grinding repair is not considered to be one of the thermal cycles. NOTE Subsequent repair of a double repair weld is not permitted unless specifically authorized by the company and repaired with a qualified repair procedure appropriate for the number of thermal cycles used. A qualified repair procedure for a double repair may be used for a single repair with prior company authorization. 10.2.7 Repair Area Length 10.2.7.1 Large Diameter Pipe For pipe with a specified OD greater than or equal to 2.375 in. (60.3 mm), the length of an individual repair area or total length of accumulated repair areas within a completed weld for a partial thickness or full thickness repair shall not exceed a percentage of weld length determined by the company. The length of an individual repair area or total length of accumulated repair areas determined by the company should be based on sound welding practice and/or engineering analysis of the installation stresses (i.e. combined axial and bending) and repair sequence for segmented repairs. 48 API STANDARD 1104 10.2.7.2 Small Diameter Pipe For pipe with a specified OD less than 2.375 in. (60.3 mm), all repairs require company authorization. 10.2.7.3 Limit Increases An increase in the specified individual or accumulated repair area length limits are subject to the discretion of the company. 10.2.8 Minimum Deposited Repair Weld Length All repair welds shall have an individual deposited repair weld length of at least 2 in. (50 mm) or as otherwise specified by the company. 10.3 Repair Procedure 10.3.1 General When a repair procedure is required, the procedure shall be established and qualified to demonstrate that a repair weld with suitable mechanical properties and soundness can be produced. The repair weld shall meet the minimum requirements of the production weld or as otherwise specified by the company. 10.3.2 Types of Repair Procedures Types of repair procedures may include, but are not limited to, the following: a) full thickness repair, b) internal partial thickness repair, c) external partial thickness repair, d) cover pass repair, e) back weld repair. 10.3.3 Qualification Repair procedures shall be qualified by visual and destructive testing. NDT may be required at the discretion of the company. For repair procedure qualification, sample preparation and destructive and nondestructive testing shall not commence until the repair weld has been allowed to cool to ambient temperature. The minimum total number of specimens and the types of destructive tests to which each repair procedure shall be submitted are shown in Table 5. At the discretion of the company, additional types and number of tests may be required. When the production welding procedure was qualified with Charpy impact testing, Charpy impact testing shall also be performed to qualify partial thickness and full thickness repair procedures. As noted in Table 5, when wall thickness is over 0.500 in. (12.7 mm), the side bend tests shall be substituted for face bend or root bend tests. NOTE Dependent on pipe material or welding process, the company may require additional cooling time prior to destructive and nondestructive testing. WELDING OF PIPELINES AND RELATED FACILITIES 49 Table 5—Type and Number of Butt Weld Test Specimens per Repair Type for Repair Procedure Qualification Repair Type Tensile Strength Nick Break Root Bend Face Bend Side Bend Macro/ Hardness b Total (Minimum) Charpy Impact Full thickness 1 1 1a 1a 0 1 5 Note c Internal partial thickness 1 1 1a 0 0 1 4 Note c a 0 1 4 Note c External partial thickness 1 1 0 1 Cover pass 0 0 0 1a 0 1 2 0 Back weld 0 1 1a 0 0 1 3 0 a Side bend tests are substituted for face bend or root bend tests when wall thickness is over 0.500 in. (12.7 mm). b The hardness survey is made on the macrosection test specimen. c When required by the company. 10.3.4 Specification Information A repair procedure, as a minimum, shall include the following. a) Location and method for exploration of the defect(s)—identify excavation location at either weld centerline and/or fusion line. b) Method of defect removal—including method of inspection by which the repair groove shall be examined to confirm complete removal of the defect. c) Requirements for preheat and interpass temperature—temperature (minimum/maximum), method of application, location, and extent shall be included. d) Welding processes and other specification information contained in 5.3.2. e) Requirement, if any, for interpass NDT. f) Methods (i.e. storage, handling, usage) to control filler metals, fluxes, and shielding gases when hydrogen control is required per the manufacturer’s recommendations. g) Repair type and repair procedure limitations. h) Time delay before final inspection, when required. 10.3.5 Essential Variables 10.3.5.1 General A repair procedure shall be reestablished as a new repair procedure and shall be requalified when any of the essential variables listed in 5.4.2 or the following are changed. Changes other than those given in 5.4.2 or below may be made without the need for requalification, provided the repair procedure is revised to show the changes. 10.3.5.2 Location of Excavation Location changes requiring requalification are as follows: a) a change from centerline to fusion line location for excavation of partial thickness repairs, b) a change from centerline to fusion line location for cover pass repairs. 50 API STANDARD 1104 10.3.5.3 Type of Repair Any change from a repair type listed in 10.3.2 to another, except when changing from a full thickness repair to either an internal or external partial thickness repair. 10.3.5.4 Preheat and Interpass Temperature A decrease in the specified minimum preheat temperature used during repair procedure qualification. The addition or change in the interpass temperature requirements used to weld the test joint. 10.3.6 Welding of Test Joints Repair procedures shall be qualified on a test weld completed following the details of the production welding procedure specification. The repair procedure shall be qualified in the fixed position on a segment of a fullcircumference test weld for each repair type to be qualified in the location(s) specified by the company. The repair weld shall be a minimum of 8 in. (203 mm) in length to provide the necessary weld deposit length for destructive testing without Charpy impact tests. A single test joint may be used to qualify more than one type of repair procedure. Details for each repair procedure shall be recorded with the complete results and circumferential location of each repair. Qualification of repair procedures may be required in the presence of the company. 10.3.7 Testing of Repair Welds 10.3.7.1 Tensile, Nick Break, and Bend Tests The test specimen preparation, test method, and acceptance requirements in 5.6 or 5.8 are appropriate for repair welds, except that test specimens shall be cut from the joint at each of the repair area locations. Weld reinforcement on tensile test specimens shall not be removed for cover pass repairs. 10.3.7.2 Macrosection/Hardness Tests 10.3.7.2.1 Preparation Transverse sections shall be cut suitable for visual examination of the weld and adjacent base metal, and for a hardness survey. The transverse macrosection test specimens for hardness tests should be at least 1/2 in. (13 mm) wide. They may be machine cut, or they may be oxygen cut oversized and machined by a nonthermal process to remove at least 1/4 in. (6 mm) from the side(s) that will be prepared. For each macrosection test specimen, at least one face should be ground and polished to at least 600 grit finish and etched with a suitable etchant, such as Nital, ammonium persulfate or dilute hydrochloric acid to give a clear definition of the weld structure. 10.3.7.2.2 Visual Examination The macrosections shall be visually examined with lighting that will sufficiently reveal the details of the weld soundness. The use of optical devices or dye penetrants is not necessary. A visual examination of the macrosections shall show that the repair weld portion of the completed weld is completely fused to the adjacent base metal and/or weld metal at the root and between weld passes and is free of cracks. Any defects shall be within the applicable individual size limits specified in Section 9. If a cross section shows defects that are not associated with the repair weld portion of the completed weld, an additional cross section shall be evaluated. If the additional cross section contains other defects, the qualification test is unacceptable. 10.3.7.3 Hardness Testing Macrosection test specimens shall be prepared for hardness testing in accordance with ASTM E384. The minimum required number of indentations shall be made using a Vickers indenter and a 10-kg load, or less at locations shown WELDING OF PIPELINES AND RELATED FACILITIES 51 in Figure 21 through Figure 26, or made at locations otherwise specified at the discretion of the company. HAZ hardness impressions shall be entirely within the HAZ and located as close as possible to the fusion boundary (between the weld metal and HAZ). If subsequent repairs (e.g. double repair) are qualified, the company shall provide hardness test locations. Maximum hardness values for repair welds shall not exceed those given in Table 6 unless otherwise specified by the company. NOTE When hardness testing is required, chemical analysis is performed to determine the carbon equivalent of the base materials. 5 /64LQí1/64 in. PPíPP 3 /64 in. PP 5 /64LQí1/64 in. PPíPP 127( +HDWDIIHFWHG]RQH +$= KDUGQHVVLPSUHVVLRQVPXVWEHHQWLUHO\ZLWKLQWKH+$=DQGORFDWHG DVFORVHDVSRVVLEOHWRWKHIXVLRQERXQGDU\ EHWZHHQWKHZHOGPHWDODQG+$=  Figure 21—Hardness Locations for Full Thickness Repair Procedure Qualification 5 /64LQí1/64 in. PPíPP 3 /64 in. (1 mm) NOTE Heat-affected zone (HAZ) hardness impressions must be entirely within the HAZ and located as close as possible to the fusion boundary (between the weld metal and HAZ). Figure 22—Hardness Locations for Partial Thickness Repair Procedure Qualification at Weld Centerline 52 API STANDARD 1104 5 /64LQí1/64 in. PPíPP 3 /64 in. (1 mm) NOTE Heat-affected zone (HAZ) hardness impressions must be entirely within the HAZ and located as close as possible to the fusion boundary (between the weld metal and HAZ). Figure 23—Hardness Locations for Cover Pass Repair Procedure at Weld Centerline 3 /64 in. (1 mm) 5 /64LQí1/64 in. PPíPP NOTE Heat-affected zone (HAZ) hardness impressions must be entirely within the HAZ and located as close as possible to the fusion boundary (between the weld metal and HAZ). Figure 24—Hardness Location for Back Weld Repair or Internal Partial Thickness Repair Procedure at Weld Centerline 10.3.7.4 Impact Tests 10.3.7.4.1 General When required by 10.3.3, Charpy impact testing shall be performed at locations in the weld as specified by the company. 10.3.7.4.2 Preparation For each repair procedure, both the weld metal and the HAZ shall be tested. Each test (of weld metal or HAZ) shall consist of at least three valid specimen tests performed at or below the minimum design temperature. The exact size of the specimens depends on the weld thickness but the largest possible size shall be selected. The specimens shall be machined, notched, and tested in accordance with ASTM E23. The notch shall be oriented in the throughthickness direction.