STORAGE

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Ship unloading systems:

Figure 1: The simple design of mechanical unloaders reduces wear and maintenance costs

Mechanical Vs Pneumatic?

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or efficient unloading of grain and other bulk goods, both mechanical ship unloading systems like the BĂźhler Portalink and Portalino and pneumatic ship unloaders like the BĂźhler Portanova are employed worldwide. Each of these system types is founded on sophisticated, powerful technology and is the perfect instrument for specific areas of application. Mechanical and pneumatic ship unloaders serve the same basic purpose: to unload grain or other bulk goods as efficiently as possible. But each system possesses specific advantages that make it the preferable choice for certain areas of application. An often-used rule of thumb is that pneumatic unloaders are an excellent choice for lower unloading capacities up to 600 t/h (some experts even set the limit at just 400 t/h) and lower annual shipping volumes, while mechanical unloaders show their strengths at higher capacities. The comparison that follows is intended to illustrate the most important characteristics, advantages and disadvantages of each of these technologies. Grab systems, which are also commonly used, are not included in this analysis.

62 | Milling and Grain

by Vincent van der Wijk, Buhler

Functional principles and technical configuration

Mechanical: The Portalink/Portalino mechanical ship unloading systems transport bulk material to the pier at low speed via a high-performance chain conveyor. This is carried out using two independently run chain conveyors, one in the vertical conveying arm, the other in the boom. The boom and tower designs are standardised and can thus be manufactured economically. The advantages of this simple design principle with few wearing parts and low conveying velocity are high dependability and low maintenance requirements. The low wear also ensures a constant conveying capacity with no losses in performance over the entire life cycle. Thanks to the minimal maintenance requirement, the amount of downtime of the entire installation decreases while system availability increases. Pneumatic: The design of pneumatic ship unloading systems requires the inclusion of several components such as telescopable spouts, airlocks, filter systems and the suction nozzle. These parts require more maintenance and thus also lead to higher maintenance costs. The high conveying velocity of the bulk material also contributes significantly to the high level of wear – unexpected failures of the installation are more probable with this system. Additionally, many of the parts must be designed to be particularly resistant to wear in order to withstand great forces