Welding of Pipelines and Related Facilities PDF

WELDING OF PIPELINES AND RELATED FACILITIES 63 11.4.3 Ultrasonic Testing Personnel Requirements An NDT Level III in the ultrasonic method shall develop the application technique and prepare and approve the testing procedure. Only Level II or III certified personnel shall calibrate equipment and in...

WELDING OF PIPELINES AND RELATED FACILITIES 63 11.4.3 Ultrasonic Testing Personnel Requirements An NDT Level III in the ultrasonic method shall develop the application technique and prepare and approve the testing procedure. Only Level II or III certified personnel shall calibrate equipment and interpret the test results. NDT Level II or III personnel in ultrasonics shall perform the test and evaluate the results per the acceptance/rejection criteria. The ultrasonic testing personnel shall perform examinations in accordance with qualified and approved procedures (see 11.4.4). Personnel responsible for testing shall be capable of determining the acceptability of circumferential butt welds in accordance with the acceptance criteria as listed in 9.6. The company has the right, at any time, to require personnel to demonstrate their capabilities to perform to the requirements of the qualified procedure. 11.4.4 Demonstration of the Testing Procedure Prior to final written approval, the company shall require the contractor to demonstrate the application of the procedure and ultrasonic systems. A procedure demonstration report shall be generated and the results documented prior to use on actual field welds. The demonstration process shall be as follows. a) Welds containing defects and acceptable imperfections shall be prepared from actual production pipe material samples utilizing an approved welding procedure specification. Changes in wall thickness, bevel design, acoustic velocity, welding process, repair welds, and other variables that can have an effect on the detectability and resolution of the system shall require additional demonstration welds from other corresponding approved welding procedures. Welder qualification welds may be used. b) Radiographs shall be made of the welds and the results documented. c) The ultrasonic testing procedure shall be applied, within the detailed temperature ranges, and the results documented and compared with the radiographs. d) Differences in detection results shall be documented. (Differences in detectability and resolution between ultrasonics and radiography shall be noted.) If required by the company, destructive testing of the weld sample shall be made to discover or confirm the results. e) Use of the ultrasonic testing procedure on production welding shall be based on the capability of the implemented ultrasonic testing method/technique/systems to: 1) circumferentially locate, 2) size for length, 3) determine depth from OD surface, and 4) axially (weld cross section) locate required imperfections/defects in the test samples. In addition, the procedure shall accurately determine the acceptability of welds in accordance with the criteria listed in 9.6 and 11.4.7. 11.4.5 API Sensitivity Reference Standard Manual ultrasonic testing sensitivity shall be based on a two or three point reference level (i.e. DAC or TCG) derived from an N10 notch introduced into a sample of the pipe to be inspected (see Figure 27 and Figure 28). The highest point of the DAC/TCG shall not be less than 80 % of full screen height. The reference standard shall also be used to determine the actual sound beam velocity, refracted angle, and sound path distance in the pipe material to be 64 API STANDARD 1104 inspected. Unknown velocity and refracted angle shall be determined when welds in pipe of different chemistry specifications, wall thickness, diameter or from more than one pipe and rolling or piercing manufacturer are to be inspected. This may be accomplished by using two probes of the same nominal angle and frequency with the probes directed toward one another (see Figure 29). When a difference is noted in velocity, angle, or sound path distance, another reference standard shall be made from the different pipe material. B N Notch Block Side View t A N C D E End View R2 E R1 R3 Dimensions t Specified pipe wall thickness N Notch depth = 10 %T ± 10 % of notch depth A 2 in. (50 mm) minimum length B 0.125 in. (3.2 mm) maximum notch width C 11.35T + 2 in. (50 mm) minimum length D 3.1 in. (80 mm) minimum width E 1 in. (25 mm) minimum notch length R1 Outside radius of pipe R2 Radius of inside notch = R1 – 0.9T Figure 27—Reference Block for Manual Ultrasonic Testing A B Position the transducer in line with the outside notch at double the distance used to peak up the inside notch (Position B). Verify that the outside notch echo peak is at or near zero depth reading. This will establish that refracted angle and velocity settings are sufficiently accurate. Figure 28—Establishing Distance, Refracted Angle, and Velocity For automatic ultrasonic testing and when required by the company for manual ultrasonic testing, flat bottom holes shall be machined into a sample of the pipe to be inspected. This sample shall be used as calibration reflectors in addition to the N10 notches at the inside and outside surfaces. The diameter of each flat bottom hole should be approximately equal to the thickness of one welding fill pass. The flat reflecting surface of each hole shall be installed WELDING OF PIPELINES AND RELATED FACILITIES 65 Using two transducers of equal angle and frequency, one transmitting and the other receiving, maximize (peak up) the echo received. Measure the surface distance between the transducer exit points. Half the surface distance divided by measured wall thickness equals the refracted angle tangent. Without changing instrument settings, repeat this process on pipe with unknown velocity, refracted angle, and attenuation to determine any differences. Figure 29—Transfer Procedure at the same angle and position as the weld joint preparation for each fill pass required by the welding procedure. Additionally, planar reflectors or flat bottom holes shall be installed at the weld centerline position with their flat reflecting surfaces vertical to the weld. All reflectors should be spaced apart so that no two will be within the beam spread of one probe simultaneously. For testing on other than new construction, a pipe sample of the same grade, wall thickness, and OD as the pipe to be inspected shall be used to make the reference standard. A transfer technique using probes of the same nominal angles and frequencies to be used for inspection shall be carried out to determine actual full skip distance, actual refracted angle, and attenuation in the material to be inspected (see Figure 29). 11.4.6 Parent Material Ultrasonic Testing After completion of the circumferential butt weld, but prior to its ultrasonic testing, a compression wave test of the parent material on both sides of the weld (minimum distance = 1.25, the longest surface skip distance to be used) shall be performed. All interfering partial and full beam reflectors shall be noted (datum location and distance from the weld edge) and recorded on the examination record. The company may elect to waive this requirement in lieu of lamination checks performed by the mill. 11.4.7 Scanning and Evaluation Level 11.4.7.1 Parent Material Ultrasonic Testing Manual compression wave testing of parent material shall be performed with the second backwall echo from the reference standard (see Figure 27) adjusted to at least 80 % of full screen height. Automatic ultrasonic testing of the parent material shall be performed by using the same calibration method and evaluation level as that used for manual compression wave or by a different technique if demonstrated to be equal to or better than the manual method. 11.4.7.2 Manual Ultrasonic Weld Testing Manual ultrasonic weld testing shall be performed at a scanning sensitivity of DAC/TCG reference sensitivity plus 6 dB minimum. All indications that exceed 50 % of DAC/TCG screen height shall be evaluated. Evaluation sensitivity for manual ultrasonic weld testing should be DAC/TCG reference sensitivity plus 6 dB with an evaluation level for all indications at 50 % of DAC/TCG screen height. 66 API STANDARD 1104 After the reference sensitivity, scanning sensitivity, and evaluation sensitivity and levels have been established, they shall be qualified and then incorporated into the final procedure and in the final qualification report. 11.4.7.3 Automatic Ultrasonic Weld Testing Automatic ultrasonic weld testing should be performed at a scanning sensitivity of 80 % screen height reference sensitivity plus 4 dB when using the pulse-echo technique. Evaluation sensitivity should be the same as scanning sensitivity. Evaluation level screen height (recording threshold) should be 40 % of full screen height using the automated pulseecho technique. Other automated techniques, reference reflectors, reference sensitivities, scanning sensitivities, evaluation sensitivities, and evaluation levels may be used if demonstrated to be equivalent to the pulse-echo technique for the detection and evaluation of weld imperfections. 11.4.8 Production Ultrasonic Testing Ultrasonic technicians shall report to the company all defects unless the company requires that all observed (evaluation level and above) indications be reported. The company shall determine the final disposition of the weld. 11.4.9 Identification of Reported Indications The ultrasonic testing report of inspected welds shall include the weld number, datum location, length, depth from the OD surface, and defect classification (linear, transverse, or volumetric) of all reported indications. 12 Mechanized Welding with Filler Metal Additions 12.1 Acceptable Processes Mechanized welding shall be performed using one or more of the following processes: a) submerged arc welding, b) gas metal arc welding, c) gas tungsten arc welding, d) flux-cored arc welding with or without external shielding, e) plasma arc welding, f) the use of a manual or semiautomatic process combined with one of the mechanized processes listed in this section. 12.2 Procedure Qualification Before production welding is started, a detailed welding procedure specification shall be established and qualified to demonstrate that welds with suitable mechanical properties (such as strength, ductility, and hardness) and soundness can be made by the procedure. Two pipe lengths, full joints or nipples, shall be joined by following all the details of the welding procedure specification. The quality of the weld shall be determined by both destructive and nondestructive testing and shall meet the requirements of 5.6, except nick breaks (5.6.3) shall not be required, and Section 9, respectively. Should a welding procedure qualification utilize a manual weld or semiautomatic pass as outlined in 12.1, the nick break test in 5.6.3 shall be required as part of the procedure qualification. These procedures shall be adhered to except where a change is specifically authorized by the company, as provided for in 12.5. WELDING OF PIPELINES AND RELATED FACILITIES 67 12.3 Record The details of each qualified procedure shall be recorded. This record shall show complete results of the procedure qualification test. Forms similar to those shown in Figure 1 and Figure 2 should be used. This record shall be maintained as long as the procedure is in use. 12.4 Welding Procedure Specification 12.4.1 General The welding procedure specification shall include all the information that is pertinent to setting up and maintaining the proper operation of the equipment, as well as other information specified in 12.4.2. 12.4.2 Specification Information 12.4.2.1 Process The specific process or combination of processes used shall be identified. This shall include the type of welding technology and a description of the equipment to be utilized. 12.4.2.2 Materials The materials to which the procedure applies shall be identified. Materials may be grouped (see 5.4.2.2), provided that the qualification test is made on the material with the highest SMYS in the group. 12.4.2.3 Diameters The range of specified ODs over which the procedure is applicable shall be identified. 12.4.2.4 Wall Thickness Group and Number and Sequence of Beads The range of specified wall thicknesses over which the procedure is applicable shall be identified, as shall the range of number of beads required for the thicknesses and the machine used for each bead. 12.4.2.5 Joint Design The specification shall include a sketch or sketches of the joint that show the type of joint (e.g. V or U), the angle of bevel, and the size of the root face and root opening. If a backup is used, the type shall be designated. 12.4.2.6 Filler Metal and Flux The size and AWS classification number of the filler metal and flux, if available, shall be designated. For any filler metals with a G suffix designator only, the manufacturer and trade name shall also be designated. 12.4.2.7 Electrical Characteristics The current and polarity shall be designated, and the range of voltage and amperage for each size or type of electrode used shall be specified. 12.4.2.8 Position The specification shall designate roll or position welding. 68 API STANDARD 1104 12.4.2.9 Direction of Welding For position welding only, the specification shall designate whether the welding is to be performed in an uphill or downhill direction. 12.4.2.10 Time Between Passes The maximum time between the completion of the root bead and the start of the second bead, as well as the maximum time between the completion of the second bead and the start of other beads, shall be designated. 12.4.2.11 Type of Lineup Clamp The specification shall designate whether the lineup clamp is to be internal or external or if no clamp is required. 12.4.2.12 Cleaning The specification shall describe the joint end and interpass cleaning required. 12.4.2.13 Preheat The methods, width to be heated, minimum temperature at the start of the weld, and minimum ambient temperature below which preheat is required shall be specified. 12.4.2.14 PWHT The methods, width to be heated, minimum and maximum temperature, time at temperature, and temperature control methods for PWHT shall be specified. 12.4.2.15 Shielding Gas and Flow Rate The composition of the shielding gas and the range of flow rates shall be designated. 12.4.2.16 Shielding Flux The AWS classification number, if available, or the brand number of the shielding flux shall be designated. 12.4.2.17 Speed of Travel The range for speed of travel, in in. (mm) per minute, shall be specified for each pass. 12.4.2.18 Method of Cooling After Welding The type of cooling after welding, such as air cooling or forced cooling with water to expedite nondestructive examination and joint coating, as well as the maximum metal temperature at which forced cooling is applied. 12.4.2.19 Other Factors Other important factors that may be necessary for proper operation of the process or that may affect the quality of the work produced shall be designated. These may include the location and angle of arc for submerged arc welding, the contact-tube-to-work distance, and the oscillation width and frequency. WELDING OF PIPELINES AND RELATED FACILITIES 69 12.5 Essential Variables 12.5.1 General A welding procedure shall be reestablished as a new welding procedure specification and shall be completely requalified when any of the essential variables listed in 12.5.2 are changed. Changes other than those listed in 12.5.2 may be made in the procedure without the need for requalification, provided the welding procedure specification is revised to show the changes. 12.5.2 Changes Requiring Requalification 12.5.2.1 Welding Process A change from the welding process established in the welding procedure specification constitutes an essential variable. 12.5.2.2 Materials A change in material constitutes an essential variable. For the purposes of this standard, all carbon steels shall be grouped as follows: a) SMYS less than or equal to that of the material specified as API 5L Grade X42; b) SMYS greater than that of the material specified as API 5L Grade X42 but less than that of the material specified as API 5L Grade X65; c) for carbon steels with a SMYS greater than or equal to that of the material specified as API 5L Grade X65, each grade shall receive a separate qualification test. NOTE The groupings specified above in 12.5.2.2 do not imply that base materials or filler metals of different analyses within a group may be indiscriminately substituted for a material that was used in the qualification test without consideration of the compatibility of the base materials and filler metals from the standpoint of metallurgical and mechanical properties and requirements for preheat and PWHT. 12.5.2.3 Joint Design A major change in joint design (e.g. from V groove to U groove) or any change beyond the range established in the welding procedure specification for such factors as spacing, root face, and angle of bevel constitutes an essential variable. 12.5.2.4 Wall Thickness A change in specified wall thickness beyond the range established in the welding procedure specification constitutes an essential variable. 12.5.2.5 Pipe Diameter A change in pipe specified OD beyond the range established in the welding procedure specification constitutes an essential variable. 12.5.2.6 Filler Metal The following changes in filler metal constitute essential variables: a) a change from one filler metal group to another (see Table 1); 70 API STANDARD 1104 b) for any filler metals with a G suffix designator only, a change in the manufacturer or trade name; c) for pipe materials with a SMYS greater than or equal to that of the material specified as API 5L Grade X65, any change in the AWS classification of the filler metal (see 12.5.2.2). NOTE Except as indicated in item b) above, changes in filler metal may be made within the groups specified in 12.5.2.2, Items a) and b). The compatibility of the base material and the filler metal should be considered from the standpoint of mechanical properties. 12.5.2.7 Size of Filler Metal Wire A change in the size of the filler metal wire constitutes an essential variable. 12.5.2.8 Time Between Passes An increase in the maximum time between completion of the root bead and the start of the second bead constitutes an essential variable. 12.5.2.9 Direction of Welding A change in the direction of welding from vertical uphill to vertical downhill, or vice versa, constitutes an essential variable. 12.5.2.10 Shielding Gas and Flow Rate A change from one shielding gas to another or from one mixture of gases to another constitutes an essential variable. An increase or decrease in the range of flow rates established for the shielding gas also constitutes an essential variable. 12.5.2.11 Shielding Flux Refer to Table 1, Footnote a, for changes in shielding flux that constitute essential variables. 12.5.2.12 Speed of Travel A change in the range for speed of travel constitutes an essential variable. 12.5.2.13 Preheat A decrease in the specified minimum preheat temperature constitutes an essential variable. 12.5.2.14 PWHT The addition of PWHT or a change from the ranges or values specified in the procedure shall each constitute an essential variable. 12.5.2.15 Electrical Characteristics A change in electrical characteristics constitutes an essential variable. WELDING OF PIPELINES AND RELATED FACILITIES 71 12.5.2.16 Orifice Diameter or Orifice Gas Composition For plasma arc welding, a change in orifice gas nominal composition or a change in orifice diameter. 12.5.2.17 Method of Cooling After Welding An increase in the maximum weld temperature prior to forced cooling. A change in the method of cooling after welding resulting in a higher rate of cooling also requires requalification of the welding procedure. 12.6 Qualification of Welding Equipment and Operators 12.6.1 General Each welding operator shall be qualified by producing an acceptable weld using the qualified welding procedure. The completed weld shall be tested by destructive methods, nondestructive methods, or both, and shall meet the requirements of 6.4 through 6.7 except nick breaks (see 6.5.4) shall not be required. Should a welding procedure qualification utilize a manual or semiautomatic pass as outlined in 12.1, the nick break test in 5.6.4 shall be required as part of the welding operator qualification. The tensile strength tests shall not be replaced by nick break tests (see 6.5.2) and thus omitted. Prior to the start of welding, each welding operator shall have received adequate training in the operation of the welding equipment. If the welding procedure involves more than one operation, welding operators shall be qualified on the type of welding equipment that will be used in production welding. Changes in the essential variables described in 12.6.2 require requalification of the welding operator. 12.6.2 Changes Requiring Requalification Changes in the following essential variables require requalification of the welding operator. a) A change from one welding process, mode of transfer, polarity or method of application to another welding process or combination of processes (e.g. short arc, pulse arc, spray arc, gas tungsten arc, etc.). b) A change in the direction of welding from vertical uphill to vertical downhill or vice versa. c) A change in the filler metal type (solid wire, metal core, flux core). d) A change from one specified OD group to another: 1) OD less than 12.75 in (323.9 mm), 2) OD equal to or greater than 12.75 in. (323.9 mm). e) Welding operator shall qualify on the heaviest specified wall thickness that the welder/operator will weld in production. f) A change in position from that for which the welder/operator has already qualified (e.g. a change from rolled to fixed or a change from vertical to horizontal). A welder who qualifies in the fixed position shall also be qualified to perform rolled welds within the essential variables qualified. g) A change in welding bug manufacturer or model. h) A change in the method of applying the root bead (e.g. external root versus internal root). i) A major change in joint design (e.g. from a V groove to a U groove or J groove) or any change beyond the range established for such factors as spacing, root face, and angle of bevel constitutes an essential variable. 72 API STANDARD 1104 j) At the option of the company, welders/operators whose work is limited to specific weld passes in a multipass butt weld shall qualify by demonstrating their ability to weld those specific passes in accordance with a qualified welding procedure specification, with the other weld passes necessary to make complete welds being made by others. Welders shall be qualified if all tests are acceptable. 12.7 Records of Qualified Operators A record shall be made of the tests required by 12.6 and of the detailed results of each test. A form similar to that shown in Figure 2 should be used. (This form should be developed to suit the needs of the company but must be sufficiently detailed to demonstrate that the qualification test meets the requirements of this standard.) A list of qualified operators and the procedures for which they are qualified shall be maintained. An operator may be required to requalify if a question arises about their competence. 12.8 Inspection and Testing of Production Welds Production welds shall be inspected and tested in accordance with Section 8. 12.9 Acceptance Standards for NDT The acceptance standards for NDT shall be in accordance with Section 9 or, at the company’s option, Annex A. 12.10 Repair and Removal of Defects Repair and removal of defects shall be in accordance with Section 10. 12.11 Radiographic Testing Radiographic testing shall be in accordance with 11.1. 12.12 Ultrasonic Testing Ultrasonic testing shall be in accordance with 11.4. 13 Automatic Welding Without Filler Metal Additions 13.1 Acceptable Processes Automatic welding without filler metal additions shall be done using the flash butt-welding process. 13.2 Procedure Qualification 13.2.1 Procedure Before production welding is started, a detailed welding procedure specification shall be established and qualified to demonstrate that welds with suitable mechanical properties (such as strength, ductility, and hardness) and soundness can be made by the procedure. At least two welds shall be made by joining pipe lengths, full joints, or nipples and by following all the details of the welding procedure specification. The quality of the weld shall be determined by both destructive and nondestructive testing and shall meet the requirements of 13.2.3 and 13.9. These procedures shall be adhered to except where a change is specifically authorized by the company, as provided for in 13.5. 13.2.2 Radiography Prior to Mechanical Testing Each procedure qualification weld shall meet the requirements of 13.9 prior to being submitted for mechanical testing.