Upper expansion is using on bell less top of blast furnace, it is matching with the lower expansion.
The upper inflating corrugated pipe ( upper expansion joint): there is anti-friction bush in the corrugated pipe, which is used for compensating the temperature distortion of machine. Wave 1-2.
The lower inflating corrugated pipe (lower expansion joint): there is not anti-friction bush in the corrugated pipe, which is easy to realize a smooth combination of receiving hopper and charging bucket. Wave 3-4
Blast furnace top spare-upper expansion