Automatic control apparatus for soaking pit furnaces

Claim 1

An automatic regulating device for pit furnaces of the type including a pair of burners, walls enclosing a furnace space, for heating metal ingots and a waste gas off-take leading from the furnace space, wherein the power of the pit furnace burners is controlled by at least two temperature sensors, at least one of the temperature sensors responding to the temperature of the furnace space walls and controlling the burners in the heating-up period of the heating operation, at least one additional temperature sensor disposed in the waste gas off-take of the furnace close to the furnace space responding to the temperature of the combustion gases and controlling the burners in the soaking period of the heating operation, said pair of burners being disposed coaxially around one another and each having a fuel supply pipe and an air supply pipe, whereon on the one hand the fuel supply pipes and on the other hand the air supply pipes of both burners are connected through respective fuel and air manifolds to a common fuel blower and air blower respectively, and both the fuel and air supply pipes of one burner and the fuel and air manifolds common to the two burners are provided with respective throttle elements, of which the throttle element in the air supply pipe of one burner and the throttle element in the air manifold are controlled through a control device by temperature sensors responding to the temperature in the pit furnace, while on tHe other hand the throttle element in the fuel supply pipe of the aforesaid burner and the throttle element in the fuel manifold are controlled by a controller maintaining an adjusted ratio of fuel to air wherein the furnace wall temperature sensor controls the throttle element in the air supply pipe of the one burner and the combustion gas temperature sensor controls the throttle element in the air manifold common to the two burners.