The objective of this article is the presentation of a method to evaluate the productivity impact factors in the welding of industrial welded carbon steel pipes with the shielded metal arc welding process. The methodology used is based on Monte Carlo simulation and productivity data collected at Petrobras managed works at the Duque de Caxias Refinery (REDUC, acronym in Portuguese). The tool used is the software @Risk6.1 (2013), adapted for evaluation of productivity. This "software" has a resource for the elaboration of the tornado chart, through which the sensitivity analysis is performed, allowing the detection of activities and events with the greatest impact on productivity. The results obtained demonstrate the feasibility of using the method, both for the evaluation of the impact factors on the productivity of the welding procedure, which is called intrinsic productivity, and for the overall productivity, which also considers the unproductive times, where welding is paralyzed as a result of some event. The methodology adopted allows evaluating which activities have the greatest impact on welding productivity, allowing the selection of actions that should be prioritized with a view to their improvement.