Refractory lance assembly and refractory lance tube

A refractory lance assembly to be utilised with an optical sensing system to optically probe a melt, the refractory lance assembly comprising:

• an immersion tube having an immersion tip immersible within the melt and an extension tube coupled at an opposed end thereof to form a longitudinally extended composite tube defining an optical path therein for optical alignment with the optical sensing system, wherein said longitudinally extended composite tube is injectable, in use, with an inert gas to form an immersed melt surface within the melt via said immersion tip so to optically probe said immersed melt surface as exposed to said inert gas via said optical path;
• and
• a shroud longitudinally encasing said longitudinally extended composite tube to define an encasing volume therebetween, wherein coupling of said extension tube with said opposed end of said immersion tube is encased within said encasing volume whereas said immersion tip extends longitudinally therefrom for immersion within the melt, wherein said encasing volume is injectable with said inert gas to mitigate fluid contamination of said longitudinally extended composite tube and immersed melt surface via said coupling.