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.
Most process safety-related incidents involve some type of human involvement. Not only is human error a contributing factor, operating technicians are often part of the last line of defense. In the words of Trevor Kletz, “The operator is the last man on the bus.”
Consequently many hazards analyses and incident investigations generate recommendations on the following lines:
Improve operating procedures and training.
The material in this post is extracted from the 2nd edition of the book Plant Design and Operations.
Dedicated connections should be provided for sample collection. Sample take-off connections should be easily accessible and should be at ground level. The sample line should be as short as possible. If it cannot be made short then a sample loop, as described below, will be needed. Sample take-off connections should never be located at dead ends of piping.