22 which are not compatible with external moisture and will result in scrap cores. AIR FLOW Air flow to the blow tank should always be adjusted to the minimum necessary to keep the system operating properly. Check the manufacturer's operating manual for recommended settings. Excessive air flow in a dense system can cause just as much damage as a dilute phase system. Turning up the air flow does not always give higher throughput. In fact it may cause just the opposite and result in high shock waves in the pipe line, damage to pipe supports, premature pipe wear and degradation of the sand. These air settings should be verified every month as part a a companies preventive maintenance system. PIPE CONNECTIONS All pipe connections must be tight and pressure tested. Leaky pipe joints change the system design conditions and may stop sand flow completely. When properly designed the run and size of the pipe line is matched to the required system performance. Changing pipe diameter or layout of an existing pipe run may have unexpected results. As a rule of thumb pneumatic conveying can be expressed as a ratio of capacity to a given length of run. The shorter the system run—the higher the capacity. This means if the system is designed for 10 tons per hour at 250 feet, extending the run to 300 feet will correspondingly reduce the capacity. When considering the pipe line layout vertical runs should always be located within the first one-third of the run length. Pipe runs should be laid out with minimum change in direction and have a maximum of straight sections. PIPE BENDS Pipe bends and risers near the end of a line should be avoided. Minimize the number of bends in the pipe line. A maximum of three bends will satisfy most installations. The fewer the number of bends the better will be the conveying capacity. Receiving bins should have plenty of "disengaging" height. The force of the compressed air and of the sand slug entering the receiver is considerable and must be allowed to dissipate. If not properly sized, the turbulence generated will push a lot of good sand into the dust collection system. Once a new system has been placed into operation and works satisfactorily, keep a record of the operating parameters and if something should go wrong at a later date - maybe because someone changed the settings, you can cross check operating data and make necessary corrections to the system. Pneumatic conveying, when chosen and operated correctly can have a profound impact on material handling in your foundry. Your correct choice can eliminate or reduce potential problems with dust collection and maintenance of conventional material handling systems. Understanding the details will help you to optimize your system for the highest results. Well there you have it folks, Chris’s recipe for success with pneumatic transport systems. Understanding the details is only part of the equation. Knowing how and why the system works will enable you to communicate on a higher level, to get exactly what you need. Contact: JIM GAULDIN [email protected]
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