These pipes are produced by steel lamina S235 JR which is shaped progressively in order to shape roll and are stacked with the technique of Electric resistance welded in utmost of the lamina which has already the form of pipe without the use of additional adhesive material. Afterwards the area of welding is cleaned exteriorly and internally and is checked with ultrasounds so much for the control of welding what for the diameter, the thickness and the total of the surface of the pipe. In all the stages of productive process, the pipes are submitted in a line of trials and controls, so that are ensured completely the quality of manufacture and their reliability, according to the international models of quality. The controls are held with ultrasounds, mechanic, chemical and hydraulic trials. The pipes of gas are produced with the strictest specifications and controls of quality. Attention in any supply by the purchase of gas pipes it is searched for labeling CE and the certificate of conformity. In these pipes in utmost exists groove for the placement of special element for their assembly.