The lining has to survive the
cycle, steel and slag.

A steel vessel charges, taps, drains and cools, then repeats the cycle, heat after heat. Molten steel sits against one face of the lining and slag against another, and each wears it differently. Specify for one without accounting for the other, and the face exposed to the material you didn’t design for wears first. Replacing the lining doesn’t change the cycle the vessel has to survive.

Three of three tap holes,
held for two years

Shinagawa was performing on two of three tap holes. The third moved to Shinagawa after a competitor’s product was affected by a raw material change. Shinagawa has since held all three, for two years.