The fluids flowing through many pipelines are two phase, i.e., a mixture of liquid and gas. Ideally the two phases separate out with the liquid at the bottom section of the pipe. The two phases flow together to a processing facility that separates the two phases. In practice, however, the two phases often travel at different rates which means that they can form slugs whereby the composition of the stream at different sections is almost all liquid or almost all vapor.
This Safety Moment discusses a case where a hazards analysis found that there was no operating manual for a very critical operation. When the manual was located it was noted that following the instructions as written would cause a serious incident. The material provided here is extracted from the ebook 52 Process Safety Moments.
Safety Moments are short stories or anecdotes that illustrate some aspect of personal or process safety. Generally they feature a near miss or foolish event that had the potential to be much worse than it was. They can be used to start a meeting or a task assignment.