Simple Solutions That Work! Issue 18

JIM GAULDIN Chief Sales Engineer Klein Palmer Inc. ARTICLE TAKEAWAYS: • Advantages and disadvantages of common mixer types • Using Single or dedicated mixers in core rooms T here are a number of considerations that should be addressed when installing a new multiple core machine project, or improving efficiencies in an existing core room. In older plants many times the core machines are added in a somewhat sporadic manner as the company grows and production increases. Typically, this results in a core room with the core machines having no particular relationship to the others, the mixed sand supply, or the flow of the finished cores to the molding area. It’s very easy to look at a layout and realize it’s obviously not the optimum design for current needs, but you need to realize that plants kind of grow up around themselves. Many times, equipment is installed wherever there is room at that time, with the old adage that “we’ll fix it later,” and as we all know, later never comes. At best the core room is inefficient, at worst, it’s dangerous. For purposes of this discussion, we will assume a core room with 2 or more core machines using PUCB resins and a standard gas generating system and fume Understanding Sand Mixer Types For Cold Box Core Room Applications collection scrubber. And, while there are a number of different ways to mix sand, this is a general discussion of the most popular methods. The most common process design is to have a mixed sand surge hopper above the core machine blow chamber valve, where the level indicator on the hopper tells the batch or continuous mixer when to cycle. If a dedicated mixer is used for each core machine, a bulk transfer system (BTS) should be specified where the chemicals are in a location remote from the core room usually in a temperature controlled, fireproof room. A properly designed BTS will keep the day tanks at each mixer full with a small amount of resin. This day tank sizing is normally determined with the in- house safety and environmental personnel, insurance carrier, and plant engineers. A general rule of thumb is to have ½ a shift of chemical close to the mixing system. In normal operation, the resin is heated in the temperature controlled fireproof room, and pumped to the day tanks. The day tanks will have a low watt density heat blanket wrapped around them to maintain room temperature. MIXER SELECTION: BATCH OR CONTINUOUS One of the primary drivers for core machine layout is the type and number of sand mixers selected. As in any manufacturing process, the introduction of raw materials Continued on next page 39 HOW TO ISSUE