The Runarsson hydraulic pusher is designed for supplying solid fuels such as bark, wood chips and shavings. The fuels are fed through a duct, which can be cooled with water, directly on the combustion grate. The amount of fuel is controlled by the dosing bin. The rate of fuel delivery is regulated by the speed and piston feed frequency. This type push feeders can be equipped with a fire damper and a sprinkler system to protect against possible fires.