Pneumatic unloading: Staying ahead of the surge
If your plant uses a pneumatic unloading system to transfer material from pressure differential railcars and trucks, you're probably concerned about a phenomenon called the "surge." This is a large surge of air that can overwhelm your unloading system's receiving vessel and lead to other problems as well. This article discusses safe, reliable, and robust methods you can use to control surge effects.
As a pressure-differential railcar or truck compartment becomes nearly empty during pneumatic unloading, an air surge that's significantly larger than the airflow required for transferring your material will deluge the unloading system's receiving vessel [typically, a bin or silo with a dust collector such as a bin vent or baghouse]. This large surge is due to the compartment's sheer volume and can overwhelm the receiving vessel's dust collector. Commonly, the result is a dusty operation. In an extreme case, the surge can overpressurize the receiving vessel and cause it to fail. [Editor's note: For basic information on pneumatic unloading systems and how they operate, see "A practical approach to improving your pneumatic unloading rate" by Keith Solimar in Powder and Bulk Engineering, May 1994, pages 67- 74.]