Section 10 Repair and Removal of Weld Defects- CWI Part C

Read Carefully and Take a Test

Section 1 0: Repair and Removal of Weld Defects

0.1 General

Paragraph 1 0.1 states that weld defects may be identified at any time.

1 0.2 Authorization for Repair

Paragraph 1 0.2.1 states that company authorization is required for crack repairs, back weld repairs, and double repairs. Company authorization is not required for any repair that does not require the application of heat or weld metal, such as grinding or fling.

Paragraph 1 0.2.2 gives the conditions under which company-authorized repairs can be made to cracked welds. In general, if the length to be repaired is less than 8 % of the weld length, the repair is permitted if a qualified repair procedure is used.

Paragraph 1 0.2.3 addresses repair of defects other than cracks and states that these defects in the root, filler and finish beads may be repaired with prior company authorization. A qualified repair procedure is required for repair welds when using a welding process, method of application, or filler metal different than that used for the original weld, or when repairs are made in a previously repaired area, or when required by the company.

Paragraph 1 0.2.4 permits the use of grinding to remove defects in the reinforcement of root beads and cover passes, as long as contour, minimum wall, and weld thickness requirements are not violated.

Paragraph 1 0.2.5 permits the repair of back welds as long as a qualified repair welding procedure is used and the company permits the repair.

Paragraph 1 0.2.6 requires prior company authorization for double repairs. Further repair of a double repair is only permitted with company authorization and when the repair procedure to be used has been qualified by replicating the number of thermal cycles that the pipe will have seen after the repair.

Paragraph 1 0.2.7 places limits on the lengths of repairs. For pipes having a specified OD of 2.375 inches and greater, the limit on the length of repairs shall be established by the company. For pipes having a specified OD of less than 2.375 inches, all repairs require prior company authorization.

Paragraph 1 0.2.8 establishes a minimum required repair length of 2 inches unless the company
authorizes a shorter repair.

1 0.3 Repair Procedure

This section provides detailed requirements for qualifying repair welding procedures. Repairs are categorized as full-thickness repairs, internal partial-thickness repairs, external partial-thickness repairs, cover pass repairs, or back weld repairs, and the type and number of test specimens required for each type of repair procedure are given in Table 5 on page 49, with detailed instructions in paragraph 1 0.3.3. The tests required are fewer in number to, and different than, the tests required to qualify a butt weld procedure in Table 2. This table adds macro sections and hardness tests for all of the repair procedures but Charpy impact specimens are only required if the original production welding procedure was qualified with Charpy impact tests and when specified by the company.

Paragraph 1 0.3.4 lists the information required to be on a repair welding procedure and includes:

(a) Location and method for exploration of the defect.
(b) Method of defect removal and subsequent inspection for verification of removal.
(c) Requirements for preheating and inter-pass temperature.
(d) Welding processes and all of the other specification information required in paragraph 5.3.2.
(e) Requirements for inter pass NDT, if applicable.
(f) Methods for filler metal control or storage, including electrodes, fluxes, and/or shielding gases
when hydrogen control is recommended by the manufacturer.
(g) Repair type and procedure limitations.
(h) Time delay before final inspection, when required.

Paragraph 1 0.3.5 adds three new essential variables to the list in paragraph 5.4.2: (1 ) the location of excavation in paragraph 1 0.3.5.2, (2) type of repair in paragraph 1 0.3.5.3, and (3) the preheat and inter pass temperature in paragraph 1 0.3.5.4

Paragraph 1 0.3.6 addresses the welding of the test joint and specifies a minimum length of 8 inches. In addition, multiple repair procedures may be qualified in a single test joint.

Paragraph 1 0.3.7 addresses the testing of the weld joints and provides specific requirements for visual examination and the hardness tests to be conducted on the macro sections. Hardness tests are required for both the deposited weld metal and the heat-affected zones of the macro sections at the locations specified in Figures 21 through 26 on pages 51 through 53, depending on the type of repair. Hardness tests shall be conducted per ASTM E384 using a Vickers indenter and a 1 0 kg load. Maximum hardness values shall not exceed those listed in Table 6 on page 54, but the company can specify other maximum hardness values if they choose to do so. When hardness testing is required, chemical analysis is also necessary to determine the carbon equivalent of the base metal.

Charpy impact testing shall also be performed when the production welding procedure was qualified by Charpy impact tests and shall be performed at locations specified by the company. The company shall specify the minimum design temperature at which the specimens shall be tested and the minimum required absorbed energy for those tests.

1 0.4 Repair Welder Qualification

This subsection lists the rules for qualifying welders who perform repair welds. Welders performing repair welds must have an existing qualification to subsections 6.2 or 6.3 in addition to the requirements in this subsection. The welder must then make an additional qualification weld using the applicable repair welding procedure and the number and type of test specimens required are provided in Table 7 on page 54 for the specific type of repair welding procedure.

Paragraph 1 0.4.3 gives the changes in essential variables that would require the requalification of repair welders. They are:
(a) Any change from one repair type to another except qualification on a full-thickness repair qualifies all partial-thickness repairs.
(b) A change in filler metal groups as defined in Table 1.
(c) An increase in depth of the repair area greater than twice that deposited in the qualification weldment.
(d) A change in position from that for which the repair welder has already qualified.

1 0.5 Supervision

Repair welds shall be made under the supervision of an individual experienced in repairs who is acceptable to the company. Inspection of repairs and the qualification of those conducting the inspections shall be as specified by the company. Repairs shall be documented and the records maintained by the company.

1 0.6 Acceptance Criteria

Repaired areas shall be inspected by and evaluated in accordance with the same NDT methods and acceptance criteria as used for the original weld. NDT of a repair weld must include the entire length of the repair plus the greater of 2 inches or 1 0 % of the repaired length on both ends of the repair.

Click here to Start Course-Section 11: Procedures for Nondestructive Testing (NDT)