Simple Solutions That Work! Issue 8

quicker for the ladle manufacturer to do this, it does have a number of disadvantages, both to the foundry and ironically, to the ladle manufacturer. Bolt-on Trunnions What do we mean by bolt-on trunnions? The ladle shell has machined trunnion mounting pads, faced and bored for accuracy, and the trunnions fix to these pads. Each trunnion has a large diameter machined spigot that locates in a matching hole in the pad, which takes the shear load, and the trunnion plate is then bolted, using high tensile bolts, to the machined trunnion mounting pad. The big advantage to the foundry is if a trunnion gets damaged at some later date (collision of the ladle with an inanimate object being a popular choice), it is relatively simple for the foundry to replace the trunnion, using its own maintenance crew and without the need to send the ladle to a machine shop (which would be the case when replacing a welded on trunnion). Having the machined trunnion mounting pad means that accuracy and alignment of the replacement bolt-on trunnions is automatically maintained. A secondary advantage to the foundry is that the trunnion mounting pads are set off the ladle shell, creating an air gap behind the trunnions and greatly reducing heat transference from the ladle to the sidearms and gearbox assembly. The big advantage to having bolt- on trunnions, as I’ve mentioned, that it makes it easy to transport ladles dismantled, knowing that the foundry’s own maintenance crew can easily reassemble them. Therefore, if a ladle needs to be dismantled for transport it will be typically shipped with both the side arms and the lifting bail removed, each as complete assemblies. The trunnions are kept mounted in the side arms and the gearbox is fully assembled and attached to the geared sidearm. So reassembly is just a case of putting the trunnions back onto the ladle and then refitting the lifting bail assembly. This begs the question then why would it be necessary with regard to ladles to send for an engineer to supervise the installation, and, in most cases, it isn’t. However sometimes either, due to the size and design of the ladle or due to the nature of the customer, site supervision is requested. Case Study 50-65 Ton Ladles We supplied a 50 ton capacity motor drive ladle to the Rolls Royce Naval Marine facilty in Mississippi and two 65 ton capacity ladles to the Naval Foundry and Propeller Center in Philadelphia. In both cases, although dismantled, due to size they had to be transported using special carriers. While both customers were more than capable of reassembling the ladles without supervision, they each wanted to ensure that there were no “grey areas.” The ladles supplied to both facilities had motor driven gearboxes with radio remote control. Radio remote control ladles was something new to both foundries, therefore they appreciated our presence for their maintenance crew to receive on-site training in the operation and maintenance of the new ladles. As I’ve mentioned, with site supervision, you only get an engineer – equipped with all relevant manuals and drawings etc., but no tools. Due to the difficulty in bringing tools, a list of tools and lifting equipment required for the re-assembly of the ladle, plus a set of instructions are sent in advance of the visit. While most of the tools are standard to any foundry, we do use metric fastenings and therefore need the necessary metric spanner sizes. Or, as experience has taught us, “Wrench sizes.” (Yes, it’s that language issue again.) Open-end wrench = open ended spanner box wrench = ring spanner, socket wrench set = socket spanner set and monkey wrench = not something an engineer uses. My time on-site is usually constricted by the need to fit in with a pre- arranged travel schedule. So I’m always keen to make best use of the time spent with the customer. As usual communication is the key. Nobody will deliberately put obstacles in the way but, when priorities do differ, unintentional ones may arise and having a clear path of communication is the best way to deal with it, especially when the foundry is part of much larger organization. With respect to both case studies, the ladles were reassembled and commissioned within the allotted time, giving me chance to carry out some sightseeing before having to fly back home. Contact: STEVE HARKER [email protected] 23