Vacuum Conveying Easy Powder Handling Thanks to Advanced Vacuum Conveying Technology

Editor: Dominik Stephan

Transporting powders, dusts, and granules requires reliable, clean and safe solutions that allow for flexible and gentle conveying processes — especially in hazardous environments. But there is a simple solution to this complex challenge: vacuum conveyors.

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Automatic loading of a mixer with paracetamol powder; previously this task was done manually with a hand scoop. (Picture: Volkmann)
Automatic loading of a mixer with paracetamol powder; previously this task was done manually with a hand scoop. (Picture: Volkmann)

Fine dye powders, coarse shavings, heavy ferric powders, or chemicals like titanium dioxide — some materials are especially challenging in terms of transport. But also operation flexibility, different setup possibilities and dust-free conveying are much sought after qualities in a conveyor system. A simple solution to this complex task is the use of vacuum. There are many complicated large-scale vacuum units, but the functional principle of Volkmann’s multiple-stage compressed air driven ejector Multijector is not only revolutionary but also effective.

It is based on simple physical correlations: The driving gas enters the pump’s casing and flows through the first stage of de Laval nozzles. As the compressed air enters the nozzle it is highly accelerated, reaching the speed of sound at the nozzle’s smallest diameter. As the stream of compressed air leaves the first nozzle it is captured by another, larger ejector. This second nozzle performs a similar task as the previous, smaller one; but also increases the total amount of air in the stream. The subsequent three or four nozzle stages utilize the existing high energy air flow in order to multiply the suction capacity of the pump without the need of any additional energy. The resulting airstream velocity, as well as the immense pressure drop, provide the vacuum necessary for the plug-flow conveying, providing a level of efficiency that was previously thought unachievable.

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However, vacuum pumps with Multijector technology also have other benefits: Multijectors have no moving parts, therefore no lubrication is necessary, no heat is generated during operation, making mechanical breakdowns impossible. Therefore, Multijector pumps can achieve life spans much longer than conventional pumps or ventilators.

Tough, Quiet and Flexible – Vacuum Conveying

With the help of computerized flow simulations and long-standing empirical methods, new nozzle designs, which decrease compressed air consumption and increase suction capacity, could be developed. Innovations have also led to a much improved silencing system, although the technology is already relatively quiet to mechanical vacuum pumps. The use of new materials for pump construction and the avoidance of plastic parts provide a long lifespan of Multijector units even under rough plant conditions.

It seems there is no other form of conveying that is as versatile as vacuum. Vacuum conveyors can transport anything from fine powders, such as powdered sugar or dye pigments, to bulk items, such as seashells and bottle caps, and everything in between.

Save and Dust Free Conveying

Product change, and the risk of cross contamination, are critical steps in the processing of fine bulks. Therefore, the modular design of the new conveyors allows an easy disassembling of all parts that come in contact with the product. The resilient materials of the filter unit even withstand pressurized wet or ultrasonic cleaning — abilities that are especially important for applications in the pharmaceutical and food industries.

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