The NB/T 20002 Welding Code for mechanical components of PWR nuclear islands consists of the following seven parts under the general title:
——Part 1: General requirements;
——Part 2: Acceptance for welding filler materials;
——Part 3: Welding procedure qualification;
——Part 4: Qualification of filler materials;
——Part 5: Technical qualification for production workshops;
——Part 6: Production welds;
——Part 7: Hardfacing.
This is the third part of NB/T 20002.
Welding code for mechanical components of PWR nuclear islands - Part 3: Welding procedure qualification
1 Scope
This part specifies the requirements to be satisfied for the qualification of a welding procedure specification by welding procedure tests of the NI mechanical components of PWR nuclear power plants. It defines the conditions for the execution of welding procedure tests and the validity scope of the welding procedure qualification.
This part is applicable to the welding procedure qualification of carbon steel, low-alloy steel, austenitic stainless steel, austenitic-ferritic stainless steel, nickel and nickel-based alloy, simulated welding repairs, cast steel parts welding repairs, special welds, austenitic-ferritic stainless steel weld overlay cladding on carbon and low-alloy steels, nickel-based alloy weld overlay cladding on carbon and low-alloy steels, and welding of heat exchanger tube to tube plate of the mechanical components of PWR nuclear islands.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 3375 Welding terminology
GB/T 5185 Welding and allied processes - Nomenclature of processes and reference numbers (GB/T 5185-2005, ISO 4063:1998, IDT)
GB/T 16672 Welds - Working positions - Definitions of angles of slope and rotation (GB/T 16672-1996, ISO 6947:1900, IDT)
GB/T 16702 Design rules for mechanical components of PWR nuclear islands
GB/T 19866 Specification and qualification of welding procedures for metallic materials - General rules (GB/T 19866-2005, ISO 15607:2003, IDT)
GB/T 19867.1 Welding procedure specification for arc welding (GB/T 19867.1-2005, ISO 15609-1:2004, IDT)
GB/T 19869.1 Welding procedure qualification test for steels, nickel and nickel alloys (GB/T 19869.1-2005, ISO 15614-1:2004, IDT)
GB/T 25775 Technical delivery conditions for welding consumables - Type of product, dimensions, tolerances and markings (GB/T 25775-2010, ISO 544:2003, MOD)
NB-T 20002.1-2013 Welding code for mechanical components of PWR nuclear islands – Part 1: General requirements
NB/T 20002.2-2013 Welding code for mechanical components of PWR nuclear islands - Part 2: Acceptance for welding filler materials
NB/T 20002.4-2013 Welding code for mechanical components of PWR nuclear islands - Part 4: Qualification of filler materials
NB/T 20002.5-2013 Welding code for mechanical components of PWR nuclear islands - Part 5: Technical qualification for production workshops
NB/T 20002.6-2013 Welding rules for mechanical components of PWR nuclear islands - Part 6: Production welds
NB/T 20003 Non-destructive testing for mechanical components in nuclear island of nuclear power plants
NB/T 20004-2011 Physical and mechanical test methods for material used in nuclear island mechanical components of nuclear power plants
NB/T 20005 Carbon steel and low alloy steel for pressurized water reactor nuclear power plants
NB/T 20006 Alloy steel for pressurized water reactor power plant
NB/T 20007 Stainless steel for pressurized water reactor power plant
NB/T 20008 Other materials for pressurized water reactor nuclear power plants
ISO 15614-8 Specification and qualification of welding procedures for metallic materials - Welding procedure test - Part 8: Welding of tubes to tube-plate joints
3 Terms and definitions
For the purposes of this part, the terms and definitions given in GB/T 3375, GB/T 5185 and GB/T 19866 apply.
4 General
4.1 Overview
The provisions of 4.2 to 4.6 apply to all the welding procedures covered in this part.
Clause 5 is applicable to plate butt weld, pipe butt weld, fillet weld and branch joints, including steel and nickel-based alloys of all grades.
The requirements for special cases are specified in Clause 6 to Clause 11. Clause 6 is simulated welding repairs. Clause 7 is cast steel parts welding repairs. Clause 8 is special welds. Clause 9 is austenitic-ferritic stainless steel weld overlay cladding on carbon and low-alloy steels. Clause 10 is nickel-based alloy weld overlay cladding on carbon and low-alloy steels. Clause 11 is welding of heat exchanger tube to tube plate.
See relevant provisions in GB/T 5158 for the definitions of reference numbers of welding processes.
4.2 Welding repair of production welds
The welding procedure qualification used for these repairs shall be carried out in accordance with 4.1.
In some special cases, however, the weld repairs shall be simulated on the test plates subjected to welding procedure qualification (or, on a production test plate) or shall be proved by appropriate tests, in particular:
——the welding repair of austenitic-ferritic stainless steel or nickel-based alloy weld overlay cladding, buttering or welds on carbon or low-alloy steel base metal;
——the welding repair of heat exchanger or steam generator tube to tube plate;
——the welding repair carried out by another welding process to welds made by the active gas metal arc welding (MAG) (135) and flux-cored wire (136 or 114);
——the welding repair of seal welds of control rod drive mechanism (CANOPY and OMEGA type welds);
——the welding repair of plasma arc welds with or without filler material (15).
4.3 Documents to be established
Every welding procedure qualification shall be carried out in accordance with the provisions set out in an officially approved set of documents. These documents shall comply with the relevant requirements of this part and comprise the following as a minimum:
——the p-WPS (preliminary Welding Procedure Specification);
——the range of qualification;
——the tests to be carried out and the associated criteria of acceptance in relation to the qualification level;
——the sketch for sampling test specimens;
——weld pass distribution and sequence and the welding process used for each pass.
4.4 Qualification tests
4.4.1 General requirements
The preparation, execution and testing of the test plate shall take account of the conditions for the preparation, execution and inspection of production welds.
4.4.2 Number and type of test plates
The number and type of test plates subjected to welding procedure qualification and the tests to be carried out depend on the welding operation to be performed and the following factors:
——the variables impacting the range of qualifications;
——the working conditions: the circumstance of the production weld hard to access shall be taken into account in the performance of the welding procedure qualification test and in the determination of conditions for the nondestructive examination of the test plates subjected to qualification.
4.4.3 Dimensions
The dimensions of the qualification test plates shall be determined in accordance with the following factors:
——the welding process;
——the plan for the specimens for tests and retests;
——the non-destructive examinations to be performed;
——test for the simulated welding repairs (if necessary).
In any event, the width of each part (or of each section of tube) to be welded shall not be less than 150 mm or twice the thickness of the test plate, whichever is larger.
4.4.4 Acceptance of base metals and filler materials
The filler materials used for qualification shall be tested for acceptance in accordance with NB/T 20002.2.
The base metal shall undergo an acceptance test to verify its conformance with the corresponding requirements. The acceptance test for base metal is not necessary for the manufacturer if it is procured in accordance with NB/T 20005, NB/T 20006, NB/T 20007 and NB/T 20008.
The acceptance test reports relating to the base metal and filler materials and the welding consumables qualification data sheet issued by the welding consumables supplier in accordance with NB/T 20002.4 shall be available before the welding of the test plate. These documents shall be submitted to the inspector at his request.
However, the lot of filler materials used for the surfacing procedure qualification test is exempted from acceptance tests to the extent that the surfacing conditions, the inspection items and the results to be obtained satisfy the requirements of the acceptance test specifications.
4.4.5 Position and direction of welding
The basic welding positions are defined in the standard GB/T 16672.
4.5 Welding procedure qualification reports
The results of welding procedure qualification tests shall be made available to the inspector at his request.
Welding procedure qualification shall strictly control and record the actual process parameters and various inspection results of each process in detail. The welding procedure qualification report shall be prepared to contain:
——the essential conditions (both specified and actual) for the preparation of the test plate;
——the non-destructive examinations performed and the results obtained;
——the destructive tests carried out, together with the required values and the results obtained;
——the base metal and filler materials acceptance reports stipulated in 4.4.4.
The welding procedure qualification report shall be issued by the technical director.
4.6 Validity of the qualification
The welding procedure qualification is valid for an unlimited time on condition that it is not invalidated by the requirements of 9.1 and 11.3 of NB/T 20002.6-2013.
However, for welds listed in Annex A of NB/T 20002.5-2013, the manufacturer shall demonstrate that the level of skill has been maintained in accordance with the requirements defined in 2.3.2 of NB/T 20002.5-2013.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 General
5 General requirements
6 Simulated welding repair
7 Cast steel parts welding repair
8 Special welds
9 Austenitic-ferritic stainless steel weld overlay cladding on carbon and low-alloy steels
10 Nickel-based alloy weld overlay cladding on carbon and low-alloy steels
11 Welding of heat exchanger tube to tube plate
Annex A (Normative) Manual on grouping of base metals
