Welding




  • Process Selection
  • Fatigue Sensitive Welds
  • Procedures & Specifications

OSG has the expertise to specify which welding processes are most suitable, considering the application. The main welding processes OSG can assist with include;

  • Onshore welding: GTAW (root and hot pass) plus SAW (fill and cap), GMAW (root and hot pass) plus SAW (fill and cap), GMAW.
  • Offshore welding: GMAW, GTAW (root and hot pass) plus GMAW (fill and cap).

OSG can help optimize the selected welding process variables and evaluate welding parameters and techniques. OSG can also prevent common welding defects such as, undercutting, excessive melt-through, incomplete fusion, incomplete joint penetration, porosity, weld metal and heat affected zone cracks, porosity, tungsten inclusions, susceptibility to magnetic effects, slag, solidification cracks and hydrogen cracking.

For recent SCR’s, the pulsed gas metal arc welding (PGMAW) process has been used because it reduces copper pick up from backing shoes and is less prone to weld defects when compared to the short arc welding process. The combination of GMAW and SAW welds, have shown poor fracture toughness and fatigue performance on recent projects. The mechanized GMAW process is the most widely used welding process currently used offshore mainly due to good process control due to mechanization, productivity, track record. Some limitations of this process include, lack of fusion (planar defects) and copper contamination from contact tips and copper backing shoes.

OSG can help prepare welding procedures and specifications to address the most stringent requirements including fatigue sensitive welds.

  • Acceptable codes and standards
  • Welding procedure specification requirements
  • Welding process selection
  • Essential variables including, process, position, diameter-wall thickness groups, joint design, welding direction, shielding gas, filler metal, electrical characteristics, time between passes, pre and post weld heat treatment, type and removal of line up clamp, cleaning/grinding of slag and spatter
  • Procedure qualification record
  • Welding procedure qualification testing including, mechanical test matrix, tensile, charpy impact, hardness, CTOD’s, macros, weld metal overmatching, sulphide stress corrosion cracking, fatigue testing, reeling requirements
  • Welder qualification/disqualification/identification
  • Welding preparation including;  surfaces, alignment and pre-heating
  • Materials and equipment for welding including,  shielding gases, handling and storage, welding machines, leads, shielding gas flow meters and analyzers
  • Inspection and testing including, inspection matrix, methods of inspection, planar/linear defects, volumetric, MPI, UT, RT, AUT, engineering critical assessment
  • Defective welds, pipe defects and allowable repair