Dust Control Handbook for Industrial Minerals Mining and Processing

these operations, the dust concentration within the clean filtered air of the OASIS remained3under 0.04 mg/m .When the OASIS is used with standing workers, it can be advantageous to place clear plasticstripping down the sides of the device. This allows the workers to recognize the boundary of theclean air zone and the inability to be protected once exiting the physical barrier of the plasticstripping.An additional benefit provided by the OASIS is a general improvement to the overall mill airquality. This occurs because the OASIS is drawing air from the plant environment, filtering it,and then blowing this clean air down over a worker. After flowing over the worker, it thenbecomes part of the general mill air again. At one site using the OASIS, there was a 12 percentreduction in respirable dust levels throughout the entire mill building [Volkwein et al. 1986].The volume of clean air delivered by the OASIS is variable based upon the size of the unit, but itis normally in the range of 6,000 to 10,000 cfm. Other studies have also shown the benefit ofrecirculating air back into a plant after it has been cleaned [Godbey 2005]. The OASIS isgeneric in design and can be fabricated and installed in-house or through any local engineeringcompany that handles ventilation and dust control systems.Automated Bag Placer and Filling SystemsMany manufacturers provide automated bagging systems that eliminate the operator fromperforming the bagging task manually. These systems normally include both a mechanical bagplacer and a product filling system. For most automated systems, a worker is only required toplace empty 50- to 100-pound bags on a storage rack. From this point forward, the systembecomes automated. Normally some type of robotic arm using suction cups takes the unfilledbags from a storage rack and places them on the individual fill nozzles of the bag filling unit.When the bag is in place, the filling process starts and continues until a sensor indicates that thebag has reached the correct weight. The bag saddle then actuates to eject the loaded bag fromthe fill nozzle/fill station. Figure 6.13 shows an example of a bag storage area and an automateddevice to place the bag on the fill nozzles.For open-top bags, typically a semi-automated bagging system places, fills, and weighs the bagsof product, then a worker manually feeds the bags through a closer device. For fully automatedsystems, all tasks are performed automatically and the operator/worker only needs to monitor thesystem's performance.There are many different factors to evaluate when an operation is considering some level ofautomation (semi-automatic to fully automatic) [White 2006]. For facilities only bagging oneshift per day, semi-automated systems are more commonly used. When operations bag manydifferent product types, the cleanout or change over between batches is also easier with semi-automatic systems. Automated bagging systems require more care and maintenance thannonautomated systems. It is also important to stock some spare parts for these systems,especially if the vendor is not located nearby. There are fewer parts necessary for semiautomatedsystems; thus a smaller inventory of these critical parts is necessary.172 Bagging