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20.10.2016

Tire production: emptying and conveying of silica

The constantly growing diversity of products which can be seen in almost every industry sector can also be seen in manufacturing tires. Whoever thinks, “a tire is just a tire” is wrong. Even in this industry, companies are constantly working on developing formulas and procedures to provide the customer added values such as safety, durability, environment protection and energy efficiency.

Essential factors for success when developing new formula concepts are not just a company’s own innovative strength or the ingredients used and their mixture ratio. Intensive competition also forces the manufacturers in the industry to realize the cost-cutting potential in purchasing and production, for example by constantly optimizing the raw material supply to ensure a production line free of bottle necks. Here, if efficient process technology is used then productivity increases and the cost-cutting potential is realized as this current project by bulk solid specialist J. Engelsmann AG shows.

Big bag emptying systems as important links between the raw materials and production

Big bag emptying stations don’t just belong to the most complex equipment, they also play a key role in the manufacturing process in mass production as the delivered material needs to be supplied as efficiently as possible to downstream production devices. When emptying big bags, there are two essential aspects: It needs to be as easy as possible to handle and empty the containers (emptying function) as well as to convey the raw material to the production process (distribution function). And as well as all components involved in handling bulk solids, big bag devices also have to be adjusted, in terms of equipment and function, to the properties of the material being processed and the operator’s processing environment. For this, big bag device manufactures like J. Engelsmann AG draw on a broad spectrum of components such as big blasters, screw conveyors, conveyor belts, rotary feeders and other conveyors and dispensing equipment that make the delivery of appropriate “turnkey” devices from one source possible.

In this example case, a well-known tire manufacturer only bought the raw material silica in large containers. Silica is white, granulated, slightly abrasive and has a bulk weight of 0.8kg/dm3. Like many other bulk solids, silica tends to form dust when it is moved. To be more flexible with smaller batches, the manufacturer wanted to be able to use additional big bags. A combined device made from two big bag stations was planned which allowed for the limited space in the production hall and gave the operating staff enough room to be able to use the device easily and, above all, safely. The actual emptying process needed to guarantee the big bags would be emptied fully to avoid wasting materials unnecessarily. Because the product is moved to an already existing weighing container once it has been emptied out, both emptying stations in the lower outflow zone must be equipped with suitable conveyor equipment to be able to convey the material to the downstream production process in the best way possible. Due to silica’s abrasive properties, the entire device had to be protected against damage caused by the ingredients to reduce machine downtime to a minimum because of maintenance work as well as the replacement of parts. It was particularly important to the operator that the big bag emptying station and the conveyor system that is used allow the machine to be used without producing dust. Additionally, all of the components of the device had to have the appropriate CE mark.

Dust-tight design for a secure and residue free product flow

Both big bag emptying stations are next to each other on an operator platform with access stairs and a lateral landing. To be secure on the floor of the hall the supports have footing support plates. In the machine base a crane runway with a chain hoist is integrated which projects laterally over the housing so that the big bags are lifted next to the stations and can be taken to be emptied with the help of remote control in the device. Both cargo gears have four safety loading hooks to hook in the loops of the big bag. The hooks are controlled with pressure springs so that during the emptying process the containers are automatically restrained.

The emptying elements also consist of a guide funnel with a hand-operated sealed plate. In the middle of the funnel is the product guide tube for the intake or insertion of the big bag outflow which can be attached securely and dust-tight by connecting the sealed plate. A nozzle with fitted cartridge filters is built in to remove dust from the container. On the side of the funnel there is console which can be retrofitted with a roller vibrator as a flow aid if necessary. To support the emptying process, both stations are fitted with a pneumatic flexing device which ensures that the big bags are emptied quickly and without leaving anything behind.

Underneath both guide funnels each have an inclined screw conveyor attached which acts as a collecting screw. Both collecting screws convey the silica directly into a third inclined screw conveyor with enlarged drain inserts which loads the weighing container which is provided by the customer. Then the product is dispensed in the downstream processing stage. To control the flow of materials, pneumatic shut-off valves are attached to the inlet of the collecting screws and to the outflow of the third inclined screw conveyor.

The connection of the collection screws to the third inclined screw conveyor and the product inlets in the weighing container are built as a seal system to reduce dust emulsions to a minimum while the material is being transported. At the operator’s request a fill level sensor was installed on all three inclined screw conveyors which send a signal when the big bags are empty.

All components which come into contact with the product, such as the feed container, the emptying equipment and the screw conveyors are made from high quality resistant stainless steel to ensure the product is conveyed with as little residue as possible.

The big bag emptying and conveyor system is a classic turnkey solution. As well as planning and designing, Engelsmann also assembled the system on location, put it into operation and instructed the operating staff. As well as the lower coordination effort and the seamless project procedure it was the dust free and user friendly construction along with the fact that the machine solution was low maintenance that won the tire manufacturer over.