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PD-Tanks are vertical pressure differential storage tanks used to store bulk products that can be discharged pneumatically. They are typically used to add additional store to an exisiting silo system. A PD-Tank basically a vertical guppy or pig that takes a quarter of the space. One of the many benefits of a PD-Tank verses a Guppy or Pig is that you can place four PD-Tanks in the same foot print as one guppy (pig) giving you 9000 cf of storage which is more than twice the storage capacity of one guppy. Plus with multiple PD-Tanks you can load and unload simultaneously which something you can not do with a single guppy unit.

“PD” is an acronym for “Pressure Differential” which is term used commonly to describe a pneumatic conveying technique to convey free flowing bulk products from one point to another.  Technically its the difference in pressure between two points.

Dilute phase pneumatic conveying is one of the most popular methods for moving bulk products in the cement industry.  Pneumatic conveying refers to the moving of bulk powder products suspended in or forced by a gas stream through horizontal and/or vertical pipes.  Pneumatic conveying can be used for particles ranging from fine powders to pellets and bulk densities of 16 to 3200 kg/m3 (1 to 200 lb/ft3).

There are many reasons why silos lose flow. However the most common reason is bulk materials stored can pack or settle, which can lead to “bridging” or “rat-holing”.  These events can lead to bulk materials “hanging” in the silo and cause a loss-of-flow to the discharge point. Depending on the density and flow characteristics of the bulk materials will effect how they will behave in a storage silo. There are various silo designs and systems to prevent this from happening.