The blast pressure is usually measured in the blast box or in the ring pipe upstream of the tuyeres.
It increases with increasing blast rate . Its value depends on the fragmented size of the charge and on the furnace construction of the cupola furnace, i.e. at constant blast rate, the pressure increases with decreasing fragment size of the charge.
The resistance of small fragments in the charge is higher than of rough fragments so that pressure increases. When comparing the blast pressures of different furnaces, the furnace construction must be taken into account. Furnaces with relatively small nozzles have a higher pressure than those with larger nozzles since the pressure is measured upstream of the nozzles. Therefore, increasing pressure in the blast pipe at equal blast rate and equal charge size is a sign of pipe slagging and cross-section reduction.
Cupola furnace network diagram
Hot blast stove