![]() Powders can be fine, cohesive, or floodable. In the plastics industry, there are many different bulk material characteristics, particle shapes, and sizes. It is important to know the demands of the process in order to properly size the system to determine the conveying rate.Ĥ. This is the difference between 2000 lb in 5 min vs. For example, if a process requires conveying 2000 lb/hr of product, but the batch process requires conveying 2000 lb every 5 min for 1 hr, this really amounts to 24,000 lb/hr. Additionally, define whether the process is batch or continuous. When calculating conveying rates, it is important to know how many pounds or kilograms per hour will be conveyed. For this scenario, it is important to design a “line-clearing valve” to make sure that the vertical leg is clear before the batch process stops. If vertical vacuum conveying runs exceed 12-15 ft in batch mode, the material in that line will stop conveying and fall back down. Powders do not flow like liquids, and vacuum conveying systems should minimize the number of back-to-back elbows. ![]() Reducing the number of elbows in your system should be an important goal. For example, 20 ft vertically plus 20 ft horizontally and two 90° elbows equals at least 80 ft of conveying distance. It is important to keep in mind that one sweep elbow is equivalent to 20 ft of linear tubing. ![]() “Sweep,” in general, refers to a large centerline radius that is typically 8-10 times the diameter of the tube itself. It is important to know the number of 45° or 90° sweep elbows. A typical “up-and-in” system offers a vertical lift from floor-level, conveying up to a receiver over an extruder or loss-in-weight feeder. Higher-bulk- density materials require faster transport velocity.Ĭonveying distances comprise both horizontal and vertical factors. Bulk density of the material is also a factor in calculating the size of the conveying line, which in turn determines the vacuum producer and conveying velocity. For example, lighter-weight powders need larger receivers in order for the material to fall out of the air stream. This is a key factor in calculating the size of the vacuum receiver. ![]() This is typically described in pounds per cubic feet (PCF) or grams per cubic centimeter (g/cc). To properly design a pneumatic conveying system, it is important to define the following 10 key criteria in your process:Īs a first step, it is important to know more about the powder that is being conveyed, specifically its bulk density. ![]()
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