（解説文要約）
明治から大正の初期、坑内の排水ポンプの動力は蒸気でした。

地上から蒸気を鉄のパイプで送り込み、ポンプを作動させて排水します。
このパイプを管理する作業員を修繕方（しゅうぜんかた）と呼びます。
描かれているように、パイプのつなぎ目の修理をするときなどは蒸気を止めますが、

長時間蒸気を止めると、パイプが冷えて色々なところに負担がかかります。
素早く作業を終えなくてはいけません。暑さとの戦いでした。

 

Around 1900, steam engines were the main power source for coal mine drainage pumps.
Built up steam was pumped underground through pipes, to draw out the water.
The men who repaired these pipes were known as Shuzenkata. They also saw after pump maintenance.
As you see in the illustration, the workers need to stop the billowing steam in order to repair the pipe. 
However, the longer it takes to fix the problem the greater the chance of damage because of cooling. 
The Shuzenkata needed to be quick and efficient workers, especially because they battled temperature of up to 45 degrees Celsius.