NNSA-HAJ-0002-2019 Qualification test of welding operators for civil nuclear safety equipents
1 Introduction
1.1 Purpose
This technical document provides technical reference for employing units to conduct skill qualification of welders and welding operators for civil nuclear safety equipment on their own.
1.2 Scope
This technical document is applicable to the skill qualification of welders and welding operators for civil nuclear safety equipment conducted by employing units within their own units.
The skill qualification of welding methods, filler materials, special test coupon forms and other welding variables that are not covered in this technical document may be carried out in accordance with the design documents.
2 General requirements
2.1 In principle, the skill qualification of welders and welding operators shall be conducted based on a qualified welding procedure specification. When all relevant requirements of this technical document (such as welding method, test coupon form, weld form, filler material, welding position, welding elements, and inspection requirements) are met, the skill qualification of welders and welding operators may be conducted simultaneously with the welding procedure qualification.
2.2 The results of skill qualification for butt welds are applicable to surfacing or repair welding for increasing or restoring dimensions. For repair welding to restore dimensions, there is no minimum thickness limit for the deposited metal. The results of skill qualification for surfacing are applicable to repair welding within the surfacing layer.
2.3 The number of test coupons for the skill qualification of welders and welding operators shall meet the requirements of this technical document, and additional test coupon shall be welded for selection. The preparation, welding, and inspection of test coupons shall meet the following requirements:
(1) The surfaces to be welded and the areas within 25mm on both sides of the test coupons for skill qualification shall be cleaned to remove iron filings, oxide scale, oil, rust, dirt, and other impurities.
(2) The groove form and dimensions of the test coupons shall meet the requirements of the welding procedure specification.
(3) The covered electrodes and fluxes shall be dried as required and used as needed; the welding wires shall be degreased and derusted.
(4) Clock-hour marks of welding positions shall be made on the horizontal fixed test coupons and 45° fixed test coupons, and tack welds shall not be located at the "6 o'clock" mark; for test coupons for horizontal fixed tube vertical down position welding, the test coupon positions shall be fixed according to the clock-hour marks, and the arc shall only be struck at the "12 o'clock" mark and extinguished at the "6 o'clock" mark; for horizontal fixed tube vertical up position welding, the arc shall be struck at the "6 o'clock" mark.
(5) For the test coupons for skill qualification of welders, there shall be at least one arc stop-welding position at the root bead, where a mark shall be made. Except for cases where the welding procedure requires arc stop, no arc stops are allowed in the middle of each bead of the test coupons for skill qualification of welding operators.
(6) Run-on and run-off plates may be used during the skill qualification of welding operators.
(7) The welding position shall not be changed after the welding of test coupon for skill qualification has started.
(8) The surface weld layer of the test coupons for skill qualification shall not be ground before visual inspection. Grinding is allowed after the inspection is passed.
(9) With the consent of the skill qualification supervisor, welders may grind out minor defects, except for the surface weld layer.
(10) The welds of test coupons for skill qualification shall not be repaired.
(11) For manual welding, the plate test coupons thicker than 5mm shall not be rigidly fixed.
(12) The material thickness, wall thickness, diameter, and other dimensions shall be nominal dimensions.
(13) All inspection results shall be documented in a report according to relevant requirements.
(14) Welders, welding operators, or skill qualification supervisors shall record the actual parameters of the welding process.
3 Variables, codes and their scopes of application
The skill qualification of welders and welding operators shall be based on welding variables. This clause outlines the scope of application of each welding variable. Welding activities beyond the scope of application of these variables require a skill re-qualification.
3.1 Welding methods
3.1.1 The classification and codes of welding methods commonly used in welding activities for civil nuclear safety equipment are shown in Table 1. The various welding methods listed in Table 1 are not interchangeable. Welding methods may be performed through manual welding, mechanized welding, and automatic welding. When manual welding is employed, the welding method codes are as shown in Table 1; when mechanized welding is employed, the welding method codes are "the codes in Table 1 - M"; when automatic welding is employed, the welding method codes are "the codes in Table 1 - A".
Table 1 Classification and codes of welding methods
Contents
1 Introduction
1.1 Purpose
1.2 Scope
2 General requirements
3 Variables, codes and their scopes of application
3.1 Welding methods
3.2 Test coupon forms
3.3 Weld forms
3.4 Filler materials
3.5 Welding positions
3.6 Weld metal thickness and tube outside diameter
3.7 Welding elements
4 Dimensional specifications of test coupons
4.1 Plate test coupons
4.2 Tube test coupon
4.3 Surfacing test coupon
4.4 Stud welding test coupon
5 Inspection and acceptance
5.1 Inspection items and quantities
5.2 Visual inspection
5.3 Other non-destructive testing
5.4 Bending test
5.5 Metallographic inspection
5.6 Inspection of stud welding test coupon
6 Skill qualification of special welds
6.1 Austenitic-ferritic stainless steel and nickel-based alloy surfacing and pre-surfacing edges
6.2 Tube-plate welding for heat exchangers or steam generators
6.3 Special sealing welds
6.4 Tube socket weld
6.5 Hardfacing
7 Skill qualification item codes
7.1 Representation methods for skill qualification item codes
7.2 Examples for application of item codes
Annex Implementation of skill qualification
1 Quality assurance
2 Qualification personnel
3 Process control
4 Result evaluation
5 Report preparation
6 Report maintenance
Terms and definitions
Bibliography
Name of the preparing persons
