Abstract: Taking EO spherical tanks as example, this paper analyzes the difficulties and problems occurred when outlet nozzles are set at the top crown. It puts forward the preventive measures that can be taken when the inlet and outlet are set at the bottom crown of spherical tanks with extremely or highly toxic medium. According to the common problems appeared in projects and the successful experience of projects at home and abroad, the paper presents the idea that even if the spherical tanks contain highly or extremely toxic medium, it is feasible to set the inlet and outlet nozzles at the bottom crown of the spherical tanks as long as appropriate precautions are taken in designing. Meanwhile, it puts forward some suggestions on the revision of relevant standards and specifications.

Key words: extremely, highly, toxic medium, spherical tank, exit position+discussion