Detailed analysis suggested that the 8-inch pipe had failed due to "creep cavitation" at a high temperature while the pipe was under pressure. The metal of the pipe would have experienced hard-to-detect deformation, microscopic cracks, and structural weakness as a result, increasing the likelihood of failure. Failure had been accelerated by contact with molten zinc; there were indications that an elbow in the pipe had been at significantly higher temperature than the rest of the pipe. The hot elbow led to a non-return valve held between two pipe flanges by twelve bolts. After the disaster, two of the twelve bolts were found to be loose; the inquiry concluded that they were probably loose before the disaster. Nypro argued that the bolts had been loose, there had consequently been a slow leak of process fluid onto lagging leading eventually to a lagging fire, which had worsened the leak to the point where a flame had played undetected upon the elbow, burnt away its lagging and exposed the line to molten zinc, the line then failing with a bulk release of process fluid which extinguished the original fire, but subsequently ignited giving a small explosion which had caused failure of the bypass, a second larger release and a larger explosion. Tests failed to produce a lagging fire with leaked process fluid at process temperatures; one advocate of the 8-inch hypothesis then argued instead that there had been a gasket failure giving a leak with sufficient velocity to induce static charges whose discharge had then ignited the leak.