Cupola Furnace working or construction

Construction and working of Cupola Furnace 
It is the constructed in the form of a hollow cylindrical vertical steel shell.It is lined from inside with a refractory material .It is generally supported on four cast iron lags mounted on a concrete base .The bottom of the furnace is closed by two cast iron doors hinged to the bed plate of the furnace .A wind box cast iron encircles to the outside of the furnace bottom .This box is connected to the furnace blower by pipe known as the blast pipe .Air which supplies the oxygen necessary to burn the fuel ,is forced through the cupola by a blower .The top of the furnace is shielded by a mesh screen and topped with a cone shaped spark arrester ,which permits the free vent of the waste gas and deflects spark and dust back into furnace.
working 

First of all ,the waste material dumped on the floor under the furnace after the previous heat must be cleared away.the cupola repair man then enters the cooled furnace and cleans out the slag and refuse on the lining and around the tuyeres from the previous run.Any bad spots or broken bricks are repaired with a refractory material to return the lining to its original shape .Then the bottom doors are swung into the position and the prop placed under them .all cracks are closed with fire clay and a layer of black moulding sand is placed on bottom .This sand is rammed down and given a slope towards the spout .The kindling material usually soft,dry pieces of wood is placed on the sand bed and a charge of coke is put in the furnace .The kinding and bed charge of coke are ignited through the tap-hole opening .As soon as the coke bed is thoroughly ignited ,the first charge of metal ,pig iron ,scrap and flux is placed on top of the bed charge of glowing coke .A weighed charge of coke is placed on top of the metal charge .After the cupola is fully charged upto the charging door ,the iron should soak in the heat for 45 mins or longer .No forced draft is used during this period .The only draft comes from tuyere peep hole and spout openings. As the charge descends in the furnace it is preheated untill it reaches the area where the melting takes place .The metal melts in small drops .Intermittently ,the tap hole is oppened ,allowing the metal to flow through the spout into the receving ladder.It is then closed again with a conical clay plug.This procedure is repeated ,until all the metal is melted and poured.