Estudo comparativo sobre o rigor e falsos positivos das principais metodologias para a obtenção do grau de estanqueidade de tanques de postos de combustíveis

Abstract

Due to the great risk of contamination by leak in underground fuel storage tanks (UST) of gas stations all over the world, the establishment of effective monitoring methods in this environment is extremely necessary. Among UST monitoring methods the tightness test is one of the most effective ones in identifying leaks, it can be done in two different ways, either a wet or a dry part test. This study aims to unfold false positives and compare the rigor and the effectiveness of the parameters used for the two types of tank tightness test allowed by the current standard. The motivation comes from the necessity of supplying reliable evidence to compare both tests, coming from experimental data (laboratory and on site tests at gas stations) and theoretical concepts. But the study has a grater range, as most countries also use the USA standard as the base for theirs, with minor local adaptations. The on site tests followed this sequence: wet part test is performed, the tank is emptied, dry part test is performed. The study showed greater rigorousness coming from the dry part test and also confirmed the great influence of the fuel’s evaporation rate on the results of the test for semi empty tanks. The results points to the immediate necessity of improvements of the methods and parameters for both types of test. Finally, it is noted that the coexistence of two methods with such a difference in rigor degree weakens the credibility of the standardizing, preventing, in specific situations, that the main goal of leak detection to avoid environmental accidents is achieved