Welding of Pipelines and Related Facilities PDF

WELDING OF PIPELINES AND RELATED FACILITIES 13 5.3.2.12 Cleaning and/or Grinding The specification shall indicate whether power tools or hand tools are to be used for cleaning, grinding, or both. 5.3.2.13 Preheat and Postweld Heat Treatment (PWHT) Preheat and PWHT shall be as follows: a) for prehe...

WELDING OF PIPELINES AND RELATED FACILITIES 13 5.3.2.12 Cleaning and/or Grinding The specification shall indicate whether power tools or hand tools are to be used for cleaning, grinding, or both. 5.3.2.13 Preheat and Postweld Heat Treatment (PWHT) Preheat and PWHT shall be as follows: a) for preheat, the methods, minimum temperature at the start of the weld, and minimum ambient temperature below which preheat is required shall be specified; b) for PWHT, the methods, minimum and maximum temperature, time at temperature, and temperature control methods for PWHT shall be specified. 5.3.2.14 Shielding Gas and Flow Rate The composition of the shielding gas and the range of flow rates shall be designated. 5.3.2.15 Shielding Flux The type of shielding flux shall be designated. 5.3.2.16 Speed of Travel The range for speed of travel, in in. (mm) per minute, shall be specified for each pass. 5.3.2.17 Method of Cooling After Welding If forced cooling is to be used, the specification shall designate the type of cooling after welding, such as forced cooling with water, as well as the maximum metal temperature at which forced cooling is applied. 5.4 Essential Variables 5.4.1 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 5.4.2 are changed. Changes other than those given in 5.4.2 may be made in the procedure without the need for requalification, provided the welding procedure specification is revised to show the changes. 5.4.2 Changes Requiring Requalification 5.4.2.1 Welding Process or Method of Application A change from the welding process or method of application established in the welding procedure specification (see 5.3.2.1) constitutes an essential variable. 5.4.2.2 Base Material A change in base material constitutes an essential variable. When welding materials of two separate material groups, the procedure for the higher strength group shall be used. For the purposes of this standard, all materials shall be grouped as follows. a) SMYS less than or equal to that of the material specified as API 5L Grade X42; 14 API STANDARD 1104 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 materials 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 1 The groupings specified in 5.4.2.2 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. NOTE 2 When base material with multiple grade markings is being used, the company designates, before using the material, the selected single grade to be used. 5.4.2.3 Joint Design A major change in joint design (e.g. from V groove to U groove) constitutes an essential variable. Minor changes in the angle of bevel or the land of the welding groove are not essential variables. 5.4.2.4 Position A change in position from roll to fixed, or vice versa, constitutes an essential variable. 5.4.2.5 Wall Thickness A change from one specified wall thickness range to another constitutes an essential variable. Examples of suggested groupings are shown in 6.2.2 e). 5.4.2.6 Filler Metal The following changes in filler metal constitute essential variables: a) a change from one filler metal group to another (see Table 1); b) for Groups 1 through 3 in Table 1, any change in suffix designator except within the group consisting of: — no suffix designator, — -1, — A1, — C1, C2, Ce, — C1L, C2L, C3L, — M, — P1, or P2; NOTE For example, a change in suffix designator from A1 to B3, or vice versa, constitutes an essential variable. A change from A1 to C3, or vice versa, does not constitute an essential variable. c) for any filler metals with a G suffix designator only, a change in the manufacturer or trade name; WELDING OF PIPELINES AND RELATED FACILITIES 15 d) for 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 5.4.2.2). NOTE Except as indicated items in b) and c) above, changes in filler metal within filler metal groups may be made within the material groups specified in 5.4.2.2, items a) and b). The compatibility of the base material and the filler metal should be considered from the standpoint of mechanical properties. 5.4.2.7 Electrical Characteristics A change from direct current (DC) electrode positive to DC electrode negative, or vice versa, or a change in current from DC to alternating current (AC), or vice versa, constitutes an essential variable. Table 1—Filler Metal Groups Group 1 2 3 AWS Specification AWS Classification Electrode A5.1 E6010, E6011 A5.5 E7010, E7011 A5.5 E8010, E8011, E9010 A5.1 or A5.5 E7015, E7016, E7018 A5.5 E8015, E8016, E8018 Flux c E9018 A5.17 4 a EL8 P6XZ EL8K F6X0 EL12 F6X2 EM5K F7XZ EM12K F7X0 EM13K F7X2 EM15K 5b A5.18 ER70S-2 A5.18 ER70S-6 A5.28 ER80S-D2 A5.28 ER90S-G 16 API STANDARD 1104 Table 1—Filler Metal Groups Group AWS Specification AWS Classification Electrode 6 A5.2 RG60, RG65 A5.20 E61T-GS d 7 NOTE Flux c E71T-GS d 8 A5.29 E71T8-K6 9 A5.29 E91T8-G Other electrodes, filler metals, and fluxes may be used but require separate procedure qualification. a Any combination of flux and electrode in Group 4 may be used to qualify a procedure. The combination is identified by its complete AWS classification number, such as F7A0-EL12 or F6A2-EM12K. Only substitutions that result in the same AWS classification number are permitted without requalification. b A shielding gas (see 5.4.2.10) is required for use with the electrodes in Group 5. c In the flux designation, the X can be either an A or P for as-welded or postweld heat treated. d For root pass welding only. 5.4.2.8 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. 5.4.2.9 Direction of Welding A change in the direction of welding from vertical downhill to vertical uphill, or vice versa, constitutes an essential variable. 5.4.2.10 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 for the shielding gas greater than 20 % of the nominal flow rate also constitutes an essential variable. 5.4.2.11 Shielding Flux Refer to Table 1, Footnote a, for changes in shielding flux that constitute essential variables. 5.4.2.12 Speed of Travel A change in the range for speed of travel constitutes an essential variable. 5.4.2.13 Preheat A decrease in the specified minimum preheat temperature constitutes an essential variable. 5.4.2.14 PWHT The addition of PWHT or a change from the ranges or values specified in the procedure each constitutes an essential variable. WELDING OF PIPELINES AND RELATED FACILITIES 17 5.5 Welding of Test Joints—Butt Welds To weld the test joint for butt welds, two pipe nipples shall be joined, following all the details of the welding procedure specification. 5.6 Testing of Welded Joints—Butt Welds 5.6.1 Preparation To test the butt-welded joint, test specimens shall be cut from the joint at the locations shown in Figure 3. The minimum number of test specimens and the tests to which they shall be subjected are given in Table 2. For pipe less than 2.375 in. (60.3 mm) in OD, two test welds shall be performed to obtain the required number of test specimens. The specimens shall be air cooled to ambient temperature prior to being tested. The full-section specimen shall be tested in accordance with 5.6.2.2 and shall meet the requirements of 5.6.2.3. 5.6.2 Tensile Strength Test 5.6.2.1 Preparation The full-thickness tensile strength test specimens shall be either of the types shown in Figure 4. a) The standard specimens shall be prepared as shown in Figure 4 a). They may be machine cut or oxygen cut, and no other preparation is needed unless the sides are notched or are not parallel. If necessary, the specimens shall be machined so that the sides are smooth and parallel. b) The reduced section specimens shall be prepared as shown in Figure 4 b). The weld reinforcement may be removed. 5.6.2.2 Method The tensile strength test specimens shall be broken under tensile load using equipment capable of measuring the load at which failure occurs. The tensile strength shall be computed by dividing the maximum load at failure by the smallest cross-sectional area of the specimen, as measured before the load is applied. 5.6.2.3 Requirements The tensile strength of the weld, including the fusion zone of each specimen, shall be greater than or equal to the specified minimum tensile strength (SMTS) of the pipe material but need not be greater than or equal to the actual tensile strength of the material. If the specimen breaks outside the weld and fusion zone (i.e. in the parent metal) at a tensile strength not less than 95 % of that of the SMTS of the pipe material, the weld shall be accepted as meeting the requirements. If the specimen breaks in the weld or fusion zone and the observed strength is greater than or equal to the SMTS of the pipe material and meets the soundness requirements of 5.6.3.3, the weld shall be accepted as meeting the requirements. If the specimen breaks in the weld and below the SMTS of the pipe material, the weld shall be set aside and a new test weld shall be made. If a specimen breaks outside of both the weld and the heat-affected zone (HAZ) at a tensile strength not less than 95 % of that of the SMTS of the pipe material, that specimen shall be accepted as meeting the test requirements. Any specimen that fails due to improper specimen preparation or testing may be replaced and retested. 18 API STANDARD 1104 Top of pipe Nick break Under 2.375 in. (60.3 mm) Top of pipe Root bend Root or side bend See Note 2 Nick break Top of pipe Face or side bend Tensile Nick break Root or side bend Nick break Root or side bend Greater than 4.500 in. (114.3 mm) Greater than or equal to 2.375 in. (60.3 mm) but less than or equal to 4.500 in. (114.3 mm); also, less than or equal to 4.500 in. (114.3 mm) when wall thickness is greater than 0.500 in. (12.7 mm) but less than or equal to 12.750 in. (323.9 mm) Root or side bend Nick break Face or side bend Tensile Root bend or side bend Top of pipe Face or side bend Tensile Nick break Tensile Root or side bend Face or side bend Nick break Greater than 12.750 in. (323.9 mm) Root or side bend Nick break Tensile Face or side bend Face or side bend Nick break Tensile Root or side bend NOTE 1 At the company’s option, the locations may be rotated, provided they are equally spaced around the pipe; however, specimens do not include the longitudinal weld. NOTE 2 One full-section tensile specimen may be used for pipe with an outside diameter less than or equal to 1.315 in. (33.4 mm). Figure 3—Location of Test Butt Weld Specimens for Procedure Qualification Test WELDING OF PIPELINES AND RELATED FACILITIES 19 Table 2—Type and Number of Test Specimens for Procedure Qualification Test Outside Diameter of Pipe in. mm Number of Specimens Tensile Strength Nick Break Root Bend Face Bend Side Bend Total Wall Thickness ≤ 0.500 in. (12.7 mm) <2.375 <60.3 0b 2 2 0 0 4a 2.375 to 4.500 60.3 to 114.3 0b 2 2 0 0 4 >4.500 to 12.750 >114.3 to 323.9 2 2 2 2 0 8 >12.750 >323.9 4 4 4 4 0 16 Wall Thickness > 0.500 in. (12.7 mm) ≤4.500 ≤114.3 0b 2 0 0 2 4 >4.500 to 12.750 >114.3 to 323.9 2 2 0 0 4 8 >12.750 >323.9 4 4 0 0 8 16 a One nick break and one root bend specimen are taken from each of two test welds, or for pipe less than or equal to 1.315 in. (33.4 mm) in diameter, one full-section tensile strength specimen is taken. b For materials with SMYS’s greater than the material specified as API 5L Grade X42, a minimum of one tensile test is required. 5.6.3 Nick Break Test 5.6.3.1 Preparation The nick break test specimens (see Figure 5, top) shall be approximately 9 in. (230 mm) long and approximately 1 in. (25 mm) wide and may be machine cut or oxygen cut. They shall be notched with a hacksaw on each side at the center of the weld, and each notch shall be approximately 1/8 in. (3 mm) deep and the edges shall be smooth and parallel. Nick break specimens prepared in this manner from welds made with certain mechanized and semiautomatic processes may fail through the pipe instead of the weld. When previous testing experience indicates that failures through the pipe can be expected, the external reinforcement may be notched to a depth of not more than 1/16 in. (1.6 mm), measured from the original weld surface (see Figure 5, bottom). At the company’s option, nick break specimens for qualification of a procedure using a semiautomatic or mechanized welding process may be macroetched prior to being nicked. 5.6.3.2 Method The nick break specimens shall be broken through the weld by any convenient method (i.e. pulling, bending, or striking). This does not exclude other testing methods. The exposed area of the fracture shall be at least 3/4 in. (19 mm) wide. 5.6.3.3 Requirements The exposed surfaces of each nick break specimen shall show complete penetration and fusion. The greatest dimension of any gas pocket shall not exceed 1/16 in. (1.6 mm), and the combined area of all gas pockets shall not exceed 2 % of the exposed surface area. Slag inclusions shall not be more than 1/32 in. (0.8 mm) in depth and shall not be more than 1/8 in. (3 mm) or one-half the specified wall thickness in length, whichever is smaller. There shall be at least 1/2 in. (13 mm) separation between adjacent slag inclusions of any size. The dimensions should be measured as shown in Figure 6. Fisheyes, as defined in AWS A3.0, are not cause for rejection. 20 API STANDARD 1104 Specimen may be machine or oxygen cut; edges are smooth and parallel Approximately 1 in. (25 mm) Approximately 9 in. (230 mm) Wall thickness Weld reinforcement not removed on either side of specimen a) Tensile Strength Test Specimen Length sufficient to extend into the grips for the required load At least weld cap width plus 1 ½ in. (38 mm) or as required At least ¾ in. (19 mm) Weld cap width ¾ in. (19 mm) 1 ¼ in. (32 mm) 1 in. (25 mm) R min. NOTE Dimensions are approximate. b) Reduced Section Tensile Strength Test Specimen Figure 4—Tension Test Specimen For a test weld diameter greater than 12 3/4 in. (323.9 mm), if only one nick break specimen fails, then the specimen may be replaced by two additional nick break specimens from locations near to the failed specimen. If either of the replacement nick break specimens fail, the weld is considered unacceptable. 5.6.4 Root and Face Bend Test 5.6.4.1 Preparation The root and face bend test specimens (see Figure 7) shall be approximately 9 in. (230 mm) long and approximately 1 in. (25 mm) wide, and their long edges shall be rounded. They may be machine cut or oxygen cut. The cover and root bead reinforcements shall be removed flush with the surfaces of the specimen. These surfaces shall be smooth, WELDING OF PIPELINES AND RELATED FACILITIES 21 Notch cut by hacksaw; specimen may be machine or oxygen cut; edges are smooth and parallel Approximately 1/8 in. (3 mm) 3/4 in. (19 mm) min. Approximately 1/8 in. (3 mm) Approximately 9 in. (230 mm) Wall thickness Weld reinforcement not removed on either side of specimen Approximately 1/8 in. (3 mm) Transverse notch not to exceed 1/16 in. (1.6 mm) in depth . in 9 3 /4 1 .( in )m m m Optional nick break test specimen for automatic and semiautomatic welding Figure 5—Nick Break Test Specimen and any scratches that exist shall be light and transverse to the weld. The specimen shall not be flattened prior to testing. 5.6.4.2 Method The root and face bend specimens shall be bent in a guided-bend test jig similar to that shown in Figure 8. Each specimen shall be placed on the die with the weld at midspan. Face bend specimens shall be placed with the face of the weld toward the gap, and root bend specimens shall be placed with the root of the weld toward the gap. The plunger shall be forced into the gap until the curvature of the specimen is approximately U shaped. Alternate best test fixtures with bend radii equal to or less than the radius specified in Figure 8 may be used at the discretion of the company. 5.6.4.3 Requirements The bend test shall be considered acceptable if no crack or other imperfection exceeding 1/8 in. (3 mm) or one-half the specified wall thickness, whichever is smaller, in any direction is present in the weld or between the weld and the fusion zone after bending. Cracks that originate on the outer radius of the bend along the edges of the specimen during testing and that are less than 1/4 in. (6 mm), measured in any direction, shall not be considered unless obvious 22 API STANDARD 1104 Depth Separation Length NOTE A broken nick break test specimen is shown; however, this method of dimensioning applies also to broken tensile and fillet weld test specimens. Figure 6—Dimensioning of Imperfections in Exposed Weld Surfaces 1/8 in. (3 mm) max; radius all corners Specimen may be machine or oxygen cut Approximately 1 in. (25 mm) Approximately 9 in. (230 mm) Weld Wall thickness NOTE The weld reinforcement is removed from both faces and made flush with the surface of the specimen. The specimen is not flattened prior to testing. Figure 7—Root and Face Bend Test Specimen: Wall Thicknesses Less Than or Equal to 0.500 in. (12.7 mm) imperfections are observed. For test weld diameter greater than 12 3/4 in. (323.9 mm), if only one bend specimen fails, the specimen may be replaced with two additional specimens from locations adjacent to the failed specimen. If either of the replacement bend test specimens fails, the weld is considered unacceptable. 5.6.5 Side Bend Test 5.6.5.1 Preparation The side bend test specimens (see Figure 9) shall be approximately 9 in. (230 mm) long and approximately 1/2 in. (13 mm) wide, and their long edges shall be rounded. They shall be machine cut, or they may be oxygen cut to