Welding Of Pipelines And Related Facilities PDF

WELDING OF PIPELINES AND RELATED FACILITIES 33 7.8 Position Welding 7.8.1 Procedure All position welds shall be made with the parts to be joined secured against movement and with adequate clearance around the joint to allow the welder or welders space in which to work. 7.8.2 Filler and Finish Bead...

WELDING OF PIPELINES AND RELATED FACILITIES 33 7.8 Position Welding 7.8.1 Procedure All position welds shall be made with the parts to be joined secured against movement and with adequate clearance around the joint to allow the welder or welders space in which to work. 7.8.2 Filler and Finish Beads For position welding, the number of filler and finish beads shall allow the completed weld a substantially uniform cross section around the entire circumference of the pipe. At no point shall the crown surface fall below the outside surface of the pipe, nor should it be raised above the parent metal by more than 1/16 in. (1.6 mm). Two beads shall not be started at the same location. The face of the completed weld should be approximately 1/8 in. (3 mm) wider than the width of the original groove. The completed weld shall be thoroughly brushed and cleaned. 7.9 Roll Welding 7.9.1 Alignment At the company’s option, roll welding shall be permitted, provided alignment is maintained by the use of skids or a structural framework with an adequate number of roller dollies to prevent sag in the supported lengths of pipe. 7.9.2 Filler and Finish Beads For roll welding, the number of filler and finish beads shall be such that the completed weld has a substantially uniform cross section around the entire circumference of the pipe. At no point shall the crown surface fall below the outside surface of the pipe, nor should it be raised above the parent metal by more than 1/16 in. (1.6 mm). The face of the completed weld should be approximately 1/8 in. (3 mm) wider than the width of the original groove. As the welding progresses, the pipe shall be rolled to maintain welding at or near the top of the pipe. The completed weld shall be thoroughly brushed and cleaned. 7.10 Identification of Welds Each welder shall identify the welder’s work in the manner prescribed by the company. 7.11 Preheat and PWHT Preheat and PWHT practices as listed on the qualified welding procedure specification shall be followed when materials or whether conditions make either or both treatments necessary. 8 Inspection and Testing of Production Welds 8.1 Rights of Inspection The company shall have the right to inspect all welds by nondestructive means or by removing welds and subjecting them to mechanical tests. The inspection may be made during the welding or after the weld has been completed. The frequency of inspection shall be as specified by the company. 8.2 Methods of Inspection NDT may consist of radiographic testing or another method specified by the company. The method used shall produce indications of imperfections that can be accurately interpreted and evaluated. The welds shall be evaluated 34 API STANDARD 1104 on the basis of either Section 9 or, at the company’s option, Annex A. In the latter case, more extensive inspection to determine the imperfection size is required. Destructive testing shall consist of the removal of completed welds, sectioning of the welds into specimens, and the examination of the specimens. The specimens shall be prepared in accordance with and shall meet the requirements of 6.5. The company shall have the right to accept or reject any weld that does not meet the requirements for the method by which it was inspected. The welder who makes a weld that fails to comply with the requirements may be disqualified from further work. Operators of nondestructive inspection equipment may be required to demonstrate the inspection procedure’s capability to detect defects and the operator’s ability to properly interpret the indications given by the equipment. Trepanning methods of testing shall not be used. 8.3 Qualification of Inspection Personnel Welding inspection personnel shall be qualified by experience and training for the specified inspection task they perform. Their qualifications shall be acceptable to the company. Documentation of these qualifications shall be retained by the company and shall include but is not limited to the following: a) education and experience, b) training, c) results of any qualification examinations. 8.4 Certification of NDT Personnel 8.4.1 Procedures NDT personnel shall be certified to Level I, II, or III in accordance with the recommendations of ASNT SNT-TC-1A, ASNT ACCP, or any other recognized national certification program that shall be acceptable to the company for the test method used. Only Level II or III personnel shall interpret test results. 8.4.2 Record A record of certified NDT personnel shall be maintained by the company. The record shall include the results of certification tests, the agency and person granting certification, and the date of certification. NDT personnel may be required to be recertified at the company’s option or if any question arises about their ability. All levels of NDT personnel shall be recertified at least every five years. 8.4.3 Vision Examinations 8.4.3.1 Near Distance All NDT personnel shall be examined to ensure that they have natural or corrected near-distance acuity in at least one eye such that each individual is capable of reading Jaeger Number 1 test chart or equivalent at a distance of not less than 12 in. 8.4.3.2 Color Vision NDT personnel for all methods shall demonstrate the ability to differentiate among the colors used in the method. WELDING OF PIPELINES AND RELATED FACILITIES 35 8.4.3.3 Frequency Near vision examinations shall be administered at least annually. Color differentiation examinations shall be repeated at least every five years. 9 Acceptance Standards for NDT 9.1 General The acceptance standards presented in this section apply to imperfections located by radiographic, magnetic particle, liquid penetrant, and ultrasonic test methods. They may also be applied to visual inspection. NDT shall not be used to select welds that are subjected to destructive testing in accordance with 6.5. 9.2 Rights of Rejection All nondestructive test methods are limited in the information that can be derived from the indications they produce. The company may therefore reject any weld that appears to meet these acceptance standards if, in its opinion, the depth of an imperfection may be detrimental to the weld. 9.3 Radiographic Testing NOTE All densities referred to in 9.3.1 through 9.3.13 are based on negative images. 9.3.1 Inadequate Penetration Without High-low (IP) IP is defined as the incomplete filling of the weld root. This condition is shown schematically in Figure 13. IP shall be considered a defect should any of the following conditions exist: a) the length of an individual indication of IP exceeds 1 in. (25 mm), b) the aggregate length of indications of IP in any continuous 12 in. (300 mm) length of weld exceeds 1 in. (25 mm), c) the aggregate length of indications of IP exceeds 8 % of the weld length in any weld less than 12 in. (300 mm) in length. NOTE One or both root faces may be inadequately filled at the inside surface. Incomplete filling at root Figure 13—Inadequate Penetration Without High-low 9.3.2 Inadequate Penetration Due to High-low (IPD) IPD is defined as the condition that exists when one edge of the root is exposed (or unbonded) because adjacent pipe or fitting joints are misaligned. This condition is shown schematically in Figure 14. IPD shall be considered a defect should any of the following conditions exist: a) the length of an individual indication of IPD exceeds 2 in. (50 mm), b) the aggregate length of indications of IPD in any continuous 12 in. (300 mm) length of weld exceeds 3 in. (75 mm). 36 API STANDARD 1104 Incomplete filling at root on one side Figure 14—Inadequate Penetration Due to High-low 9.3.3 Inadequate Cross Penetration (ICP) ICP is defined as a subsurface imperfection between the first inside pass and the first outside pass that is caused by inadequately penetrating the vertical land faces. This condition is shown schematically in Figure 15. ICP shall be considered a defect should any of the following conditions exist: a) the length of an individual indication of ICP exceeds 2 in. (50 mm), b) the aggregate length of indications of ICP in any continuous 12 in. (300 mm) length of weld exceeds 2 in. (50 mm). Figure 15—Inadequate Cross Penetration 9.3.4 Incomplete Fusion (IF) IF is defined as a surface imperfection between the weld metal and the base material that is open to the surface. This condition is shown schematically in Figure 16. IF shall be considered a defect should any of the following conditions exist: a) the length of an individual indication of IF exceeds 1 in. (25 mm), b) the aggregate length of indications of IF in any continuous 12 in. (300 mm) length of weld exceeds 1 in. (25 mm), c) the aggregate length of indications of IF exceeds 8 % of the weld length in any weld less than 12 in. (300 mm) in length. Bond is absent; imperfection is surface connected Figure 16—Incomplete Fusion at Root of Bead or Top of Joint WELDING OF PIPELINES AND RELATED FACILITIES 37 9.3.5 Incomplete Fusion Due to Cold Lap (IFD) IFD is defined as an imperfection between two adjacent weld beads or between the weld metal and the base metal that is not open to the surface. This condition is shown schematically in Figure 17. IFD shall be considered a defect should any of the following conditions exist: a) the length of an individual indication of IFD exceeds 2 in. (50 mm), b) the aggregate length of indications of IFD in any continuous 12 in. (300 mm) length of weld exceeds 2 in. (50 mm), c) the aggregate length of indications of IFD exceeds 8 % of the weld length. Cold lap between adjacent beads NOTE Cold lap between weld bead and parent material The cold lap shown is not surface connected. Figure 17—Incomplete Fusion Due to Cold Lap 9.3.6 Internal Concavity (IC) IC is defined in 3.1.13 and is shown schematically in Figure 18. Any length of IC is acceptable, provided the density of the radiographic image of the IC does not exceed that of the thinnest adjacent parent material. For areas that exceed the density of the thinnest adjacent parent material, the criteria for BT (see 9.3.7) are applicable. Root bead is fused to both surfaces, but center of root pass is slightly below the pipe’s inside surface Figure 18—Internal Concavity 9.3.7 Burn-through (BT) 9.3.7.1 General A BT is defined as a portion of the root bead where excessive penetration has caused the weld puddle to be blown into the pipe. 38 API STANDARD 1104 9.3.7.2 Large Diameter Pipe For pipe with a specified OD greater than or equal to 2.375 in. (60.3 mm), a BT shall be considered a defect should any of the following conditions exist: a) the maximum dimension exceeds 1/4 in. (6 mm) and the density in any portion of the BT’s image exceeds that of the thinnest adjacent parent material; b) the maximum dimension exceeds the thinner of the specified wall thicknesses joined and the density in any portion of the BT’s image exceeds that of the thinnest adjacent parent material; c) the sum of the maximum dimensions of separate BTs whose image density for any portion of the BTs exceeds that of the thinnest adjacent parent material and exceeds 1/2 in. (13 mm) in any continuous 12 in. (300 mm) length of weld or the total weld length, whichever is less. 9.3.7.3 Small Diameter Pipe For pipe with a specified OD less than 2.375 in. (60.3 mm), a BT shall be considered a defect when any of the following conditions exists: a) the maximum dimension exceeds 1/4 in. (6 mm) and the density in any portion of the BT’s image exceeds that of the thinnest adjacent parent material; b) the maximum dimension exceeds the thinner of the specified wall thicknesses joined and the density in any portion of the BT’s image exceeds that of the thinnest adjacent parent material; c) more than one BT of any size is present and the density in any portion of the BT’s image exceeds that of the thinnest adjacent parent material. 9.3.8 Slag Inclusions 9.3.8.1 General A slag inclusion is defined as a nonmetallic solid entrapped in the weld metal or between the weld metal and the parent material. Elongated slag inclusions (ESIs)—for example, continuous or broken slag lines or wagon tracks—are usually found at the fusion zone. Isolated slag inclusions (ISIs) are irregularly shaped and may be located anywhere in the weld. For evaluation purposes, when the size of a radiographic indication of slag is measured, the indication’s maximum dimension shall be considered its length. 9.3.8.2 Large Diameter Pipe For pipe with a specified OD greater than or equal to 2.375 in. (60.3 mm), slag inclusions shall be considered a defect should any of the following conditions exist: a) the length of an ESI indication exceeds 2 in. (50 mm), NOTE Parallel ESI indications separated by approximately the width of the root bead (wagon tracks) shall be considered a single indication unless the width of either of them exceeds 1/32 in. (0.8 mm). In that event, they shall be considered separate indications. b) the aggregate length of ESI indications in any continuous 12 in. (300 mm) length of weld exceeds 2 in. (50 mm), c) the width of an ESI indication exceeds 1/16 in. (1.6 mm), d) the aggregate length of ISI indications in any continuous 12 in. (300 mm) length of weld exceeds 1/2 in. (13 mm), WELDING OF PIPELINES AND RELATED FACILITIES 39 e) the width of an ISI indication exceeds 1/8 in. (3 mm), f) more than four ISI indications with the maximum width of 1/8 in. (3 mm) are present in any continuous 12 in. (300 mm) length of weld, g) the aggregate length of ESI and ISI indications exceeds 8 % of the weld length. 9.3.8.3 Small Diameter Pipe For pipe with a specified OD less than 2.375 in. (60.3 mm), slag inclusions shall be considered a defect should any of the following conditions exist: a) the length of an ESI indication exceeds three times the thinner of the specified wall thicknesses joined, NOTE Parallel ESI indications separated by approximately the width of the root bead (wagon tracks) shall be considered a single indication unless the width of either of them exceeds 1/32 in. (0.8 mm). In that event, they shall be considered separate indications. b) the width of an ESI indication exceeds 1/16 in. (1.6 mm), c) the aggregate length of ISI indications exceeds two times the thinner of the specified wall thicknesses joined and the width exceeds one-half the thinner of the specified wall thicknesses joined, d) the aggregate length of ESI and ISI indications exceeds 8 % of the weld length. 9.3.9 Porosity 9.3.9.1 General Porosity is defined as gas trapped by solidifying weld metal before the gas has a chance to rise to the surface of the molten puddle and escape. Porosity is generally spherical but may be elongated or irregular in shape, such as piping (wormhole) porosity. When the size of the radiographic indication produced by a pore is measured, the maximum dimension of the indication shall apply to the criteria given in 9.3.9.2 through 9.3.9.4. 9.3.9.2 Individual or Scattered Porosity Individual or scattered porosity shall be considered a defect should any of the following conditions exist: a) the size of an individual pore exceeds 1/8 in. (3 mm) in diameter or 25 % of the specified wall thickness, whichever is less; b) the size of an individual pore exceeds 25 % of the thinner of the specified wall thicknesses joined, but no more than 1/8 in. (3 mm) in diameter; c) the distribution of scattered porosity exceeds the concentration permitted by Figure 19 or Figure 20. 9.3.9.3 Cluster Porosity (CP) CP that occurs in any pass except the finish pass shall comply with the criteria of 9.3.9.2. CP that occurs in the finish pass shall be considered a defect should any of the following conditions exist: a) the diameter of the cluster exceeds 1/2 in. (13 mm); b) the aggregate length of CP in any continuous 12 in. (300 mm) length of weld exceeds 1/2 in. (13 mm). 40 API STANDARD 1104 Assorted Large Medium Fine Aligned (three or more) 4t 2t 2t 1t Figure 19—Maximum Distribution of Gas Pockets: Wall Thickness (t) Less Than or Equal to 0.500 in. (12.7 mm) 9.3.9.4 Hollow Bead (HB) Porosity Hollow bead porosity is defined as elongated linear porosity that occurs in the root pass. HB shall be considered a defect should any of the following conditions exist: a) the length of an individual indication of HB exceeds 1/2 in. (13 mm); b) the aggregate length of indications of HB in any continuous 12 in. (300 mm) length of weld exceeds 2 in. (50 mm); WELDING OF PIPELINES AND RELATED FACILITIES 41 Assorted Large Medium Fine Aligned (three or more) 4t 2t 2t 1t Figure 20—Maximum Distribution of Gas Pockets: Wall Thickness (t) Greater Than 0.500 in. (12.7 mm) c) individual indications of HB, each greater than 1/4 in. (6 mm) in length, are separated by less than 2 in. (50 mm); d) the aggregate length of all indications of HB exceeds 8 % of the weld length. 9.3.10 Cracks Cracks shall be considered a defect should any of the following conditions exists: a) the crack, of any size or location in the weld, is not a shallow crater crack or star crack; b) the crack is a shallow crater crack or star crack with a length that exceeds 5/32 in. (4 mm). 42 API STANDARD 1104 NOTE Shallow crater cracks or star cracks are located at the stopping point of weld beads and are the result of weld metal contractions during solidification. 9.3.11 Undercutting Undercutting is defined as a groove melted into the parent material adjacent to the toe or root of the weld and left unfilled by weld metal. Undercutting adjacent to the cover pass (EU) or undercutting adjacent to root pass (IU) shall be considered a defect should any of the following conditions exists: a) the aggregate length of indications of EU and IU, in any combination, in any continuous 12 in. (300 mm) length of weld exceeds 2 in. (50 mm); b) the aggregate length of indications of EU and IU, in any combination, exceeds one-sixth of the weld length. NOTE See 9.7 for acceptance standards for undercutting when visual and mechanical measurements are employed. 9.3.12 Accumulation of Imperfections Excluding incomplete penetration due to high-low and undercutting, any accumulation of imperfections shall be considered a defect should any of the following conditions exist: a) the aggregate length of indications in any continuous 12 in. (300 mm) length of weld exceeds 2 in. (50 mm), b) the aggregate length of indications exceeds 8 % of the weld length. 9.3.13 Base Material Imperfections Imperfections in the base material detected by radiographic testing shall be reported to the company. The disposition of these imperfections shall be as directed by the company. 9.4 Magnetic Particle Testing 9.4.1 Classification of Indications Indications produced by magnetic particle testing are not necessarily imperfections. Magnetic and metallurgical variations may produce indications that are similar to those produced by imperfections but that are not relevant to acceptability. The following criteria apply when indications are evaluated. a) Any indication with a maximum dimension of 1/16 in. (1.6 mm) or less shall be classified as nonrelevant. Any larger indication believed to be nonrelevant shall be regarded as relevant until reexamined by magnetic particle 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. 9.4.2 Acceptance Standards Relevant indications shall be considered defects should any of the following conditions exist: a) linear indications evaluated as crater cracks or star cracks exceed 5/32 in. (4 mm) in length, b) linear indications are evaluated as cracks other than crater cracks or star cracks,