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  2. Article: Screening, Dosing, Filling - Precisely Fitting System for Cramped Conditions

18.03.2020

Screening, dosing, filling – precisely fitting system for production in cramped conditions

When it comes to procuring new machines and plant, cramped space conditions at the installation location can quickly become a problem. And this is by no means just the case when an additional component is to be incorporated into an existing process. Space is also often scarce in new production halls planned from scratch. If, on top of this, many different production and process steps have to be represented and seamlessly linked to each other, plant planners quickly come up against their limits with standardized components.

This challenge was also faced by a producer from the chemical industry, who was looking for a suitable system unit for the production hall they were planning. The task: Different chemical products were to be freed from coarse particles at the end of the manufacturing process and then placed in dosed amounts in big bags. Because it was already in use in other places in production, the operator wanted to use the vibration screening machine JEL Konti from J. Engelsmann AG here as well. Because the bulk solids experts from Ludwigshafen also offer individually designed system units as well as individual screening machines and big bag emptying and filling stations, not only the screening machine is commissioned from Engelsmann but the entire small system.

Process section no. 1: the removal of coarse particles

In this special use case the vibration screening machine is to be installed, raised, on the ground of the first floor – the big bag filling station is on the ground floor under that. The screened coarse fractions were to be directed via the coarse material outlet into an on-site collection container next to the filling station. In order to be able to reach this container at all, the coarse material outlet of the JEL Konti had to be modified and inclined at 30°.

Because the individual products also have different bulk solid properties, the screen had to be flexibly adaptable – an ideal application for the JEL Konti. Many parameters of the Konti can be adjusted, such as for example the screen inclination, oscillation amplitude and even the tilt angle of the vibration motors. This means that several products can be screened without any problem. Because other sieve layers are often used when the product is changed, it is definitely an advantage to be able to change the inserts quickly. Thanks to JEL Konti’s special drawer system this can be carried out within seconds, with just a few flicks of the wrist. Most screening machines first have to be separated from the product feed, so that the machine cover and the individual screen deck can be dismantled and removed from the machine from the top. With the JEL Konti, only a front-side machine cover has to be taken off and then the screen insert can already be pulled from the screen housing like a drawer. Separation from the product feed and discharge is not necessary in this case. Just as important as flexible adaptation possibilities and simple handling is the equipment’s thorough cleanability – because it should be ensured that the different bulk solids do not mix with each other, especially when the product has to be frequently changed. Here too the JEL Konti offers advantages: The rectangular screening trough is constructed with larger radii. This means that the interior trough is free from corners and edges in which product residues can stick. Interior seals can be reached easily and can be removed, cleaned and then installed again quickly and without the use of tools. This reduces the need for cleaning work to a minimum.

Process section no. 2: dosing

After the screening stage the product must be conveyed in dosed quantities into the big bag filling station. There is a problem with this: If a full big bag is tied off and a new one is brought into the station, the screening machine must be switched off so that the product does not get congested in the conveying elements. This not only costs time but above all also valuable throughput. To avoid this, Engelsmann suggests incorporating a collection container as buffer storage between screening machine and filling station. This way the operator can change the connected big bag without the manufacturing and/or screening process having to be stopped. Not much space was available for this intermediate step however, because the big bag filling station already took up a great deal of space with its planned height of 3.10m. The collection container therefore had to be constructively modified to fit exactly into the remaining space between the big bag filling station and the screening machine. In this case this also meant that the upper part of the collection container was set directly into the floor beneath the vibration screening machine JEL Konti.

The collection container is equipped with two level indicators which monitor the minimum and maximum level. Here too, it was important to the operator to be able to adapt the equipment to various products and process properties. Because these are also spread around the container in different ways. In the case of dry, easy-to-pour products, measurement of the level is unproblematic, because they accumulate in an even material column in the container. With products with less favorable flow properties, measurement is somewhat more difficult, because they form steeper or flatter debris cones under the inlet. The ambient temperature also influences the behavior of a bulk solid. For the full indicator, the operator therefore decided to have an oscillating fork with tube extension, in which the fork can be fastened to any desired point on the tube. In addition, the collection container is equipped with a screw sampler. This makes it possible for the operator to remove samples from the ongoing product flow. The dusty air displaced by the product flow can escape out through a dust extraction filter.

Just like the screening machine, it should also be possible to clean the container as quickly and simply as possible. The cover has therefore been designed to screw in and out, so that the operator gains access to the inside of the container with just a few flicks of the wrist and can clean it easily.

The dosed material discharge from the collection container into the filling station is controlled with a vibrating metering flap at the outlet of the container. Vibrating metering flaps have two main advantages over conventional flaps: Better product flow without the forming of bridges and very precise dosing. When standard metering flaps are opened again after a long time, the product often does not flow at first. The main reason for this is bridges with compressed material which frequently form when a bulk solid has not been moved for a long time. If the vibration function is activated before the flap is opened, the vibration is transferred to the material column lying above it which sets the mass flowing once again. Control of the opening angle of the metering flap also allows very precise dosing in the product discharge. Using the mounted control system, the operator chooses the desired set weight; dosing from the container then takes place automatically. The flap’s vibration function can be switched on and off as required.

Process section no. 3: filling

Coming from the collection container, the product flows via a flexible compensator directly into the big bag filling station and/or the big bag connected to it. For the weighing of the package, the filling station is equipped with a weighing frame, which is built upon four weighing cells. The compensator is in this case not just purely a connecting element between the collection container and filling station, it also uncouples the scales so that only the connected big bag is weighed. It is extremely easy to connect an empty big bag: Using a platform, the operator can conveniently hang the big bag on the station’s hooks. The big bag inlet is then fastened to the filling head and the inflatable sleeve is pneumatically activated. Due to the inflation of the sleeve, the big bag is firmly clamped in this position and can now be safely filled. On the side suction connection, an on-site dedusting system can be connected which ensures that the filling process is dust-free. Because the customer wanted to operate the emptying station via an already existing platform and uses relatively large big bags (2m high), the filling frame is also a special construction conceived specially for this application. Because the installation location is an ATEX area subject to explosion hazards, the entire filling station is constructed with earthing.

The bottom line: The integration of production equipment requires a high degree of flexibility: especially if the space conditions at the installation location are difficult. Often production can only be operated cost-effectively through exact adaptation to the process world of the client. Due to the precisely fitting integration of the system unit, the customer in this case was able to make optimal use of the limited space and even integrate an additional process step. Thanks to the collection container acting as an intermediate buffer, the operator was able to maximally utilize the throughput performance of their production process.