Simple Solutions That Work! Issue 13

True to the various definitions of defects prevention mentioned above, it was soon realized that a totally different approach to the elimination of the problems of current sand transfer systems was necessary rather than build on existing technology. The driving force for the development of a better and more efficient sand transfer system was to eliminate the inherent defects of the “old systems” and provide a system that can be “install and forget.” To start, an investigation of different sizes of pressure vessels or blow tanks was initiated, which showed that small units with a fast sequence of operation and short cycle times not only offered advantages with respect to size and cost, but also with respect to energy requirements. A new conveying system was subsequently developed, as an extension of the Dense Phase concept, operating between 15-90 psig air pressure, sand velocities in the pipeline of only 100 to 450 FPM and using up to 45 percent less compressed air than conventional Dense Phase systems. This meant that sand velocities in the piping were as much as 6 to 10 times lower than in conventional Dilute and Dense Phase systems, pipeline wear was drastically reduced, sand degradation practically eliminated and operating costs slashed to the bone. A major difference between the newly developed conveying system and the conventional conveying systems was the reduction in cycle time for the batch operation. Because of the comparatively large size of the pressure vessels of conventional systems, a complete cycle included the approximately 90 seconds fill time required to refill the pressure vessel with sand, which took up a large portion of the overall cycle and temporarily stopped the flow of sand in the pipeline. The newly developed conveying system utilized a much smaller pressure vessel with a total cycle time for fill and blow of only about 14 seconds, resulting in an almost continuous flow of sand into the pipeline. The required individual cycle functions were also simplified so that fewer control components are needed, resulting in additional cost savings. The advantages of a pneumatic sand conveying system with proper defects prevention built-in: 1. You don’t need fluidization! This means: - 40% lower compressed air consumption - fewer parts to install and maintain - less compressor energy required - lower operating cost - standard schedule 40 pipe can be used - no need for heavy duty pipe 2. You don’t need boosters! Again, this 4. Lower sand degradation because of lower velocities! Resulting in: - less dust generation - less waste material - savings in resin consumption (excessive dust in the sand soaks up resin like crazy) - more efficient operation - improved house cleaning 50 Contact: JIM GAULDIN [email protected] means: - lower compressed air consumption and elimination of the extra booster piping and fittings - smaller dust collectors - reduced installation labor - fewer parts to install - minimal maintenance - a less complicated system 3. Much lower velocities! Translating into: - considerable less pipeline wear! - fewer costly repairs - less waste of compressed air; (leaks in the pipe line waste a lot of compressed air) And what can we expect regarding sand quality with a system designed to prevent problems because of sand defects? To determine the feasibility of such a system a number of tests were performed to assure consistency of results. Shown below is typical test data and proof that recognizing problems in a process or equipment and systematic follow-up to eliminate defects is realistic and brings desired results.