Tube cleaning is the process whereby the boiler tubes of steam locomotives are cleaned out, removing soot and ash in order to ensure the effective generation of the draught for the fire.
This was often done with steam lances or compressed air and accompanied by brushing as required.
During the 1930s some UK locomotives were fitted with steam operated tube-cleaning guns, sometimes referred to as anti-carbonisers.
It was possible to direct sand, under steam pressure, to any part of the rear tube plate from a lever in the cab.
Illustrated Encyclopedia of World Railway Locomotives (2001 republication ed.).