Our company has two serial desalters. Wash water at pH 7-7.5 level is injected, and brine of pH 6 is released. Not long ago, Brazilian crude(Lula) was mixed at about 30 percent, and the pH dropped to 4.5. The TAN value of Lula is low at 0.3 level. I cut naphtha and checked for organic acids, but this isn't a particularly large amount. Our chemical vendor gave the opinion that this was because there were a lot of salts crystallized in the crude oil. However, even after analyzing metal and ash, there was not much. We need to analyze the cause; does someone have similar experience?