A flash of LPG occurred a refinery during a transfer operation between a fixed storage tank and a tanker truck. On the day of the accident, a tanker was being loaded when the screw-type connection between the loading arm and the tanker began to leak. The resulting cloud caught fire, engulfing the driver. He was severely burned and later died of his injuries.

Analysis of the accident showed thread wear on both parts of the threaded union: on the arm, the threaded union of the brass bushing (ACME, 3¼”; female) was particularly worn (the initially trapezoidal section of the threads had become triangular). The threads on the tank’s connector were also extremely worn: the end of the union was nearly conical and the threads themselves had visible flat portions. According to the local inspectorate, this situation could have been avoided by simply observing the prevention principles: regular document-based inspections and visual inspections of the unions, including the threads. German regulations require that a visual inspection be conducted 2 times/year. Furthermore, while certain users were tightening the bushing with a hammer (an apparently common practice), the practice is prohibited at the refinery and also not recommended by the German LPG association. This type of accident is not uncommon at these types of installations and warnings have been issued to this effect. It appears that the warnings were known at the site involved.

An extensive nation-wide thread verification program was conducted in Germany and revealed that a large number were in fact worn. In the six months following the accident, the situation was vastly improved and this type of problem appears to have been solved.

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