Big bag hanging units are used on upper frames to hold bigbags brought by overhead cranes and forklifts. A lifting cross is put over the big bag. Big bag handles or straps are fixed to the hooks of lifting cross. It is then lifted together with bigbag by crane or forklift and placed on top frame hanging unit. Spring and damper mechanism applies upwards force to lifting cross. When raw material begins unloading, this mechanism moves big bag upwards and aids product discharge. The strength of springs and dampers can be adjusted with respect to weight or bulk density of raw material. Side massaging pistons and big bag vibration motor can also be utilized to increase big bag unloading speed.
Pneumatic pistons placed on side frames of big bag unloaders are available as an option to aid unloading of bigbags. These pneumatically actuated massage cylinders apply side forces to the big bag. Massaging system is especially effective when the storage in bigbag cause problems with compressed bulk materials and where vibration aids can cause further compression and prevent uniform discharge. Piston stroke lengths, motion speeds and intervals can be adjusted by built in control panel of big bag unloading station.
The big bag platform is composed of two independent surfaces connected to pneumatic pistons. These two surfaces apply force and compacting effect from lower two sides to the big bag which aids the product move to the outlet spout of big bag.
Storage silos can be installed below the big bag unloading platform. Unloaded material is directly transferred to silo and stored for later use. In this configuration there is no need for additional storage silo and conveying equipment connected to big bag unloading system. Additionally big bags can be completely emptied and removed in one time. Different silo capacities are available depending on raw material consumption. There exist level sensors on the silo to monitor the product level in the silo. And alarm signal is generated in case of low product levels. Flow aids as air jets or vibrating bin activators are provided as an option for silos. Dust collection systems are connected to big bag unloading stations and storage silos for bulk products with high dust content.
Dust collection system of big bag unloading station is needed for preventing dust emission during big bag unloading. Dust emissions from big bags are seen during cutting or untying of bag spouts, product discharge and removal of empty big bags. Vacuum air supplied by dust collector, collects any dust in the region. A jet filter system with built in fan is used for this purpose. Collected dust is sent back to the big bag unloading unit automatically and any product loss is prevented. Vacuum air is cleaned with reverse pulse jet system and discharged to outside.
When the raw material amount in the big bag is to be monitored, big bag weighing system can be used. Big bag unloading station consists of loadcells on main frame. Weight of the big bag is continuously measured and user is informed. System can send signal to another PLC automation system or system can control other equipment connected to the big bag unloader unit.
Product discharge from the big bag can be controlled by iris valve. Big bag discharge spout passes through the iris valve. A pneumatic piston or manual handle controls the iris valve. Product discharge spout can not only be kept completely open or closed but also it can be adjusted in any level. Big bag unloading speed can be adjusted with this mechanism.
Optional cutting blades can be installed in the middle of big bag platform rubber seal. When big bag is placed on the platform, these blades cut the big bag instantly and provides faster product flow. Bulk bag cutting equipment is generally preferred in applications where high transfer rates are needed.
Big bag automation systems provide control of whole big bag and bulk material handling operations. Vibration motor, iris valve, massaging system, hoist, dust collector, big bag weighing system, conveying system etc. are connected to automation system. Depending on the complexity and configuration of big bag unloading station, different type of automation systems can be utilized. For simple big bag unloading units a small sized manual controlled electrical panel is enough. PLC controlled automation panels are preferred for big bag unloading stations with many accessories installed on. These units can also take control of other material handling systems that are connected to bulk bag unloading station like screw feeders, pneumatic conveying systems, rotary valves etc. Daily, monthly, annual reporting functions are available as an option. PLC controlled systems have option for connecting to other Scada, PC and PLC systems in production plant for better handling and monitoring of complete production process.
Time to time raw material is delivered in small bags or sacks instead of Bulk bags. Or small amount of additives are to be fed into the system. Sack tipping unit is installed on big bag discharge hopper. Operator can discharge small bags through this opening to the same place.
Bulk solids stored in FIBC bags for long time tend to be compacted because of its own weight and possible moisture in the environment and form big sized lumps. During bulk bag unloading, these lumps should be broken before entering to down stream equipment. Lump breakers are installed below big bag unloading systems to prevent any problems caused by big sized particles and lumps.
To prevent any oversized particle entrance into the production line, screen is used. Screening systems are installed at the discharge point of big bag unloading unit. Depending on bulk material properties and acceptable particle sizes different types of screens can be used. Vibrating screens are one of the most common screen type used in bulk material handling.
Foreign materials in bulk solids will lead to serious problems in production processes. Magnetic separators are used to detect metallic particles in bulk solids and separate them from main product stream. Metal detectors and separators can be installed at the outlet port of big bag unloading systems and prevent contaminations caused by metallic particles.
Food grade big bag unloaders are available on request. All surfaces that have contact with food are made of food grade materials as stainless steel, silicone etc. All parts are designed and manufactured carefully to prevent any contamination and bacterial growth. Filter bags, valves and other mechanisms are selected from food certified equipment.
Handling of explosive and flammable raw materials in hazardous explosive atmosphere need special care both in design and manufacturing of big bag unloading systems. Overheating, gas or dust leakage, static electricity and electrical spark generation should be prevented. Atex certified and ex-proof equipment are used in such working conditions.
Design and construction material of big bag unloading stations can change with respect to handled bulk material and type of application. Stainless steel body made of either AISI 304 or AISI 316 is preferred for food materials, additives, PVC, Polypropylene, Polyethylene, PET, HDPE, LDPE, painting materials etc. High carbon steel and manganese alloys are preferred for abrasive materials such as arc furnace dust, perlite, quartz, silica sand, fly ash etc. Standard steel is used for general purpose applications such as cement, calcium carbonate, activated carbon handling.
Big bag unloading systems manufactured by Polimak are designed to conform human and environment safety regulations. Being CE certified, all safety measures are taken to prevent work accidents in big bag handling systems. Mechanical and electrical locks, alarm systems exist on machinery with respect to work conditions.
Wide range of big bag unloading stations are available with respect to different applications. Big bag unloaders can be configured according to bulk solid types (powdered, granular, abrasive, food etc.) application types (silo filling, mechanical conveying, pneumatic transfer, mixer feeding etc.)
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