Which piping arrangement is not recommended for a pipeline that conveys condensable vapours?

In a pipeline designed for conveying condensable vapours, the arrangement that is least advisable is a bull headed tee. This is due to the design characteristics of a bull headed tee, which can lead to areas of turbulence and potential pooling of condensate. In systems that transport condensable vapours, it's essential to maintain a smooth flow to prevent any accumulation of liquid that could lead to blockages or operational issues. The configuration of a bull headed tee creates changes in direction and velocity that can impede the flow characteristics of vapours, increasing the risk of condensation along the pipeline.

In contrast, a crossover pipe, long radius elbow, and a straight run of pipe are generally more conducive to maintaining the integrity of the vapour flow. These options tend to provide smoother transitions and less opportunity for vapour to condense, thus reducing risks associated with condensate build-up.