The purpose of this procedure is to provide a guideline, prior to welding and during the welding process for controlling structural distortions induced by welding heat that may generate non-uniform expansion and contraction of the weld metal.
This procedure covers all aspects of welding work for prefabrication and assembly of structural steel that involves material preparation weld edge preparation and the use of fabrication aids such as strong backs or clamps or fixtures in order to maintain fit-up alignment.
- AWS D1.1 – 2020: Structural welding code – steel
- AWS: American Welding Society
- SAW: Submerged Arc Welding
- SMAW: Shielded Metal Arc Welding
- FCAW: Flux Cored Arc Welding
- WPS: Welding Procedure Specification
- The construction Manager has overall responsibility for ensuring that adequately facilities, resources; personnel are available and shall oversee and monitor the welding work.
- It is responsibility of the Welding Inspector or Welding Supervisor to brief monitor and allocate welders in accordance with this procedure for the welding work.
- The welders shall be responsible for to weld in accordance with an approved welding sequence.
- Weld edge preparation shall be in accordance with shop fabrication drawings and WPS(s).
- Material preparation shall be cut to size in accordance with the approved shop fabrication drawings and edges shall be ground smooth to sound metal. Any material imperfection identified after cutting may be repaired by welding and regrinding.
- Strong backs, clamps and fixtures will be utilized during fit-up and welding to maintain alignment with acceptable tolerances. Temporary supports shall be placed at the strategic locations to ensure that the members are fully supported. Location of temporary support and/or fairing aids shall comply with the requirements of the relevant company specifications.
- Fit-up assembly
- Pre-setting technique shall be applied to assemble members where feasible. The approach requires a considerably experienced or skilled and welding supervisor.
- Fit-up configuration shall be as per drawing and approved WPS. Assembly dimension of the structural component shall also consider expected weld shrinkage upon cooling of the welded joint.
- Preheating shall be applied as required in accordance with the approved WPS using propane gas heating or other approved method prior to tacking and welding. The minimum pre-heating temperature shall be uniformly established over a minimum area of 3” ( 76mm ) on both sides of the weld groove. It shall be through thickness.
- Strong backs shall be utilized to maintain alignment during the welding process. The shall be removed after the weld is completed. Strong back weld marks shall be ground smooth, after removal and shall be tested by visual or MPI if require.
- Temperature control, Welding supervisors and welders shall be equipped with thermo sticks ( Tempilstick ) for constantly checking the minimum preheating temperature and inner pass temperature prior to and during the welding operations until completion.
- Welding sequence shall be posted or displayed at side and shall be referred to ensure all necessary preparation, precaution, equipment ect… have been satisfied to avoid possible reworks. Welding of structural part/component shall be started from member(s) with high degree of shrinkage towards member(s) with lesser shrinkage. Sequence shall include member and location of welders at each stage of assembly, sketches and other information as necessary. The welding progression on a member shall be from pints where the parts are relatively fixed in position with respect to each other toward points having a degree relative freedom of movement.
- The welding sequence is detailed as follows:
- Welding sequence for plates, stiffener and longer weld (See Appendix I).
- Cooling rate – all weld joints shall be allowed to naturally cool to ambient temperature. Water cooling shall not be allowed.
- Number of welders required shall be determined by the joint and welding sequence ( see Appendix I).
- Where more than one weld is involved on a specific joint, these welders shall commence welding at the same time.
- All welders performing welding work shall be qualified to the recognized standards. Welder qualification positions depend upon joint configuration and shall be in according with the recognized standards.
- All welding parameters, amperage, pre-heating, type and size of electrodes shall be in accordance with the relevant approved welding procedure.
- In preparation for bad weather, weather protection and wind shield shall be provided prior to welding operations commencing.
- Welding Inspector/ Welding Supervisors shall be responsible in filing all relevant reports.
- All quality records shall be properly filed and retained.
- The approved welding procedure specifications shall be display at side.
Appendix I: welding sequence for flat guide assembly.