How to Consider Lifetime Costs for Powder And Bulk Conveying

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Volkmann GmbH

Keeping Dust Under Control

The use of vacuum helps to avoid contamination of the environment, because any leaks result in atmospheric air being drawn in. Leaks in a positive pressure conveying system, in contrast, mean that dust is released. Vacuum conveying is therefore the preferred choice for harmful powders and pharmaceutical active ingredients. Special vacuum conveyors are used in production areas requiring an OEB (Occupational Exposure Band) of 4 and OELs (Occupational Exposure Limits) of 1–10 µg/m³.

Once the conveying air has done its job, however, it is still necessary to filter it before discharge to the atmosphere. The drop in velocity as the material enters the receiver causes most of the powder to collect just above the discharge valve. Tangential suction modules with internal cyclones further clean the air stream, and a high-performance filter just below the vacuum pump removes any remaining fines. The filter system is easy to clean and largely maintenance-free, yet provides effective protection for particle sizes down to 0.2 µm and meets hygiene regulations in the pharmaceutical and food industries.

Filters are generally cleaned using reverse pulses of compressed air, and optionally by vibration. In food and pharmaceutical applications, solid filters made from polymers or stainless steel are often used. These can be cleaned with hot water or steam, and are often durable enough to last for two years or more.

* The author is Sales Manager with Volkmann Vakuum, Soest/Germany.

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