You do not even imagine what problems people had in the past. For example, how to clean the uppermost part of the tunnels after hundreds of steam locomotives were passed? Soot deposits are not so safe as it seems - it consists carbon, and one spark can suffice to turn a tunnel into the mouth of a volcano.
Understanding this important problem Walker Bros. (Wigan) Ltd., a leading company of ventilation equipment for mines and tunnels, designed this auto-scraper for the ceiling of ventilation tunnels on the chassis of the Pagefield truck. It worked in Liverpool.
