42 designs which work straight from the off. The current units may benefit from a bit of fine tuning to meet each location’s particular conditions but, if it is necessary, it is a case of minor adjustment, rather than the full site commissioning that used to often be needed with the early models. Pressure gauges form part of the design so that both the foundry and we can tell exactly what is happening and how the unit should perform. All gas valves now used are industry standard, unlike early units that used a complex array of special gas valves to achieve the same result Safety is front and centre, with gas and air pressure monitoring as standard, as is a flame failure system. Flame ignition is via the control panel (no buring pieces of paper required). If required the controls can enable the burner profile to be adjusted and so on. All the units now automatically run through a purge cycle before ignition so there are no unexpected pops nd bangs caused by unignited gas. The flame failure system also shuts off the gas supply should the flame be unexpectedly extinguished. Having said that, I’m not now sure as to what a preheater’s principal purpose now is is. This may seem a strange comment but reflects the changing working practices. What do foundries want from their preheater? Is it to preheat the ladle, before it recieves the first fill, or is it to prepare the refractory lining, and maximize the refractory life? The ladle lining is an increasingly important part of the ladle operation and I’m more and more convinced that both the ladle and the lining should be viewed as a whole. The development of the ladle preheater has been driven by the changing requirements of the refractory linings. REFRACTORY LININGS Back when most UK foundry’s melted using cupolas, it was typical to fill a ladle with the first melt. A process that I think was refered to as “washing” the ladle. Then to let it stand for about 10 minutes before pigging off the metal. The ladle was then considered up to temperature and ready to use. The ladles would be lined with either fire bricks or a fire clay. It seemed pretty tolerant to thermal changes. I was told that the purpose of the preheating was to stabilize the ladle /metal temperature and thereby to reduce metalurgical fuctuations, especially with regard to the first pour when compared to subsequent pours. I was also told that the first “tap” from the cupola was metalugically variable so was
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