Porin Teollisuusputki Oy was involved in the new sulphuric acid plant project of Suurteollisuuspuisto industrial park as a contractor of cooling water tower piping. Major problems arose during the project: cracks and other welding defects were found in the welds of the special steel (Sandvik SX) used inside the factory. Since PTP had experience with this material, design was started to ensure the quality of the welding.

The welding instructions were prepared on the basis of existing PTP procedure tests, while taking into account the specificity of the repair measures, as the welds were not always repaired in their entire circumference. Ensuring traceability was also very important. The data of existing welds had to be transferred to the documentation, where applicable, at the same time as the repair measures were added to the material and the inspections of the areas to be repaired were carried out.

Repair welding was carried out at PTP’s production facilities in Pori to ensure the highest quality and occupational safety, after which the parts were installed in Harjavalta. The project can be considered a success, as all of the approximately 400 welds requiring repair were completed without any welding defects that would have led to rejection in the inspections carried out (100 per cent PT, RT, VT and pressure test).