This paper presents a case study of the defects that occurred during the construction of a Bellmouth. Boca de Sino is a submarine equipment, whose central body is built with USI SAR 80T steel. In order to carry out the welding of this equipment, welding procedures were qualified from USI SAR 80T steel plates, with the requirements required by the AWS D1.1 standard. The submerged arc process (SAW) was selected for welding. In the qualification of the welding procedure, a preheating and no postheating was performed, and no defects occurred during the qualification. After the qualification of the procedures, the construction of the equipment was carried out in an analogous way and during the penetrating liquid examinations the occurrence of cracks was verified.As a proposed solution to the problem, a post-heating heat treatment was carried out, maintaining the temperature between 280 ° C and 300 ° C for 180 minutes with slow cooling. In this way the occurrence of cracks after welding was eliminated.