TECHNICAL TOOLBOX ISSUE 33 Like for any project, system specifications should first be prepared describing the planned system in detail and outlining operating requirements. For a pneumatic sand transporter system we start with the basics such as: – Type of sand to be transferred – Bulk density (pounds per cubic foot) – Particle size distribution (AFS number) – Temperature (Deg. F) – Moisture content (%) – Free flowing (Yes/No) – Capacity required (tons/hour) – Layout of pipe run: to establish the pipe run, specify location of the transporter blow tank, the location and number of receiving bins and the shortest practical distance of horizontal and vertical connecting pipe sections. Note: In laying out the actual pipe run utilize only horizontal and vertical pipe sections connected with long centerline radius (40 inch) pipe bends. Long radius bends are preferred because they have a lower pressure drop than short radius bends. Changes in elevation of the pipe run should consist only of vertical pipe sections with 90 degree pipe bends. To prevent premature pipe wear from excessive abrasion do not use inclined pipe sections. JIM GAULDIN Chief Sales Engineer Klein Palmer Inc. ARTICLE TAKEAWAYS: • Understanding the differences between dense and dilute phase conveying • Proper layout of pipe Continued on next page DESIGN TIPS FOR PNEUMATIC SAND TRANSPORTER SYSTEMS Most every foundry has to move tremendous amounts of sand as part of their daily operation and to handle and distribute such amounts effectively can sometimes grow into an ongoing major material handling battle. How much more practical would it be if the foundry engineer could develop a data base assuring the most practical data utilization and a knowledgebase to fall back on before trouble starts raising its ugly head. Belt conveyors and elevators are used many times to distribute the sand but air conveyors or pneumatic transporters are probably most widely accepted as a means to move sand around the foundry. Pneumatic transporters are practical because of their simplicity and flexibility; however, because of their operating characteristics certain design and operating details should be followed to achieve a reliable system with minimum cost of operation. Unlike most mechanical equipment in a foundry pneumatic transporter systems require compressed air as their motive force and producing compressed air is expensive. Therefore, it only makes sense to try to minimize the amount of compressed air required to keep operating costs as low as possible while at the same time optimizing the air requirements to minimize abrasion of the pipeline from the moving sand. Pneumatic transporter systems in general can be divided into two broad categories. Dilute phase conveying and dense phase conveying. Dilute phase conveying, mostly used for powdery materials such as iron oxide and bentonite, works by vacuum or low pressure air and high velocities (4000 FPM and higher), while dense phase conveying works by medium to higher pressure air and lower velocities (2800 - 4000 FPM). For sand, which can become very abrasive at higher velocities, special low velocity systems (400- 1500 FPM) can be designed which should be used exclusively.
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