Yarn dyeing equipment without pumps - using temperature and pressure variation to maintain liquor circulation

A method of dyeing or bleaching loose fibre or yarn packages which dispenses with the use of pumps to circulate the liquor and penetrate the fibre or yarn cake uses instead a controlled variation of temperature and pressure within the dyeing vessel to agitate or circulate the liquor. Steam extracted from the vessel is passed to a condenser to reduce the pressure in the vessel and maintain a slow boiling action in the pre-heated liquor, aided if necessary by additional steam-heating within the vessel. The pressure in a separate internal chamber may be varied independently of that in the outer chamber to promote a reversible flow of liquor through the material being treated.. The dyeing action is quicker and more intensive, and produces more uniform, better quality dyeings with minimum liquor movement.