AutoPIPE Vessel team decided to not apply the Annex C7.A9 for sliding tubesheet because this chapter is not sufficient.

There is no rule to determine the thickness of the tubesheet, so we decided to follow the same rules as floating tubesheets; like the other codes (ASME, EN) do.

This is a conservative approach to be sure that the thickness of the tubesheet is sufficient.

By the way, the behavior of a sliding tubesheet is similar to the one of a floating tubesheet.