Integrity and service life of LPG carafes

摘要

The reliability of 10 kg liquefied petroleum gas carafes used nowadays in Argentine households is evaluated in this study. Chemical, mechanical and metallographic studies were performed to determine base metal, weld metal and heat affected zone conditions. Residual stresses were measured in both inner and outer surfaces of the carafes. Lower bound values of fracture toughness (K1c) were determined from upper shelf Charpy energy (CVN). Charpy tests at 0 ℃ were carried out. A marked increase in toughness of the base plate was found, as the date of fabrication increases. Diverse degrees of non-conformities, resulting in significant defects usually undetectable by external inspection, were found in the circumferential welds of 25% of all carafes manufactured before 1990. The number and criticality of these defects falls markedly in the carafes built after 1990. Serious errors during reconditioning, such as repairs of leaks and scratches, are indicative of a poor approach to the rehabilitation of the vessels. It is recommended to evaluate changes in the rehabilitation procedures and standards. A gradual process of substitution of the carafes built prior to I 990 is also recommended.