Simple Solutions That Work! Issue 12

15 BACK TO BASICS The problem here is the handing of the tun-dish. It will have significant weight and obviously be very hot, possibly with bits of slag dripping from the underside. Small treatment ladles would often have the loose tun-dish lifted off by operatives but, again for obvious reasons, this is best avoided with a forklift truck or crane being a better option. The ladle design must take this into account, with extended sidearms to give the necessary clearance, suitable lifting points on the tun-dish etc. It’s not good practice to have the ladle on the ground and to rotate the lifting bail clear of the top of the ladle, as it puts a reverse load on the ladle gearbox. If this has to be done the side arms might need counter weights fitting. SLIDING TUN-DISH The sliding tun-dish has the tun-dish mounted on a frame within the lifting bail, so that the tun-dish can be raised and lowered by the crane that picks up the ladle. Basically, as the loose tun-dish but here the tun-dish cover is part of the ladle assembly and doesn’t require an independent means of handling. We were quite impressed with ourselves when we first came up with this design as it solved a lot of handling problems. However, we quickly realised that there is very little that is new and that variations on this type of ladle were already in use in foundries around the world. If anything, it showed that when faced with the same problems, the same solutions will often present themselves. There is a simple option where the tun-dish moves up and down and a “locking” option, where the tun- dish can be either locked down, on the top of the ladle, or locked in the up position clear of the ladle. This helps if the ladle needs to be filled while suspended in the air and then prepared for the next treatment cycle whilst on the ground. Acetarc has manufactured loose tun- dish ladles in capacities from 100 Kg (220 lb) up to 12,000 Kg (26,400 lb) and sliding tun-dish up to 6000 Kg (13,200 lb). However practical factors do start to kick in. With the locking sliding tun-dish cover, there is a need to remove the locking pins and this gets more difficult as the ladle gets taller. The locking pins are located in the ladle lifting bail and you don’t really want to be climbing up a ladder to remove the locking pins when the ladle is in operation. Conversely, with small ladles there can be a stability problem as the ladle has a lot of weight high up, when the sliding tun-dish cover is locked in the up position. These are points that need to be considered and discussed with the foundry. The tun-dish does add significant weight and the crane SWL needs to be checked so that it isn’t exceeded. In both cases the seal is dependent on the underside of the tun-dish cover sitting flush on the top of the ladle. As the ladle is used this “face to face” seal is likely to become affected by a build-up of detritus and the ladle will become less efficient., but it still should give better results than the open top deep treatment process. There is another trick that can be done with the loose and sliding tun- dish ladles. That is to make the tun- dish the full length of the cover and divide it into two, effectively creating two tun-dishes. From the ladle manufacturer’s perspective this helps keep the tun-dish cover balanced. From the foundry’s perspective it allows the additives to be put into the other side of the ladle halfway through the working shift so that the original reaction chamber can be “washed out” with metal. Continued on next page