S6.1 Grade FP91 shall be normalized in accordance with
5.5.3 and tempered at a temperature, to be specified by the
purchaser, less than 1350°F [730°C]. It shall be the purchaser's
responsibility to subsequently temper at ,1350°F
[730°C] minimum. All mecha'nical tests shall be made on
material heat treated in accordance with 5.4.3. The certIfication
shall reference this supplementary requirement indicating
the tempering temperature applied. The notation
"86" shall be iricluded with the required marking of the pipe.