Large lumps of clay on constantly moving conveyor belts are accurately weighed so Strøjer Tegl can produce bricks of the highest quality. New weighing electroncis from Siemens ensures that the mixing of clay is precise. The solution is the first in the world with the new SIWAREX WP341 weighing card.

At Strøjer Tegl, they have combined one of the world's oldest production methods with some of the most modern weighing technology you can get today. 
The brickworks in Assens has been producing bricks since the mid-1800s. Back then, it was seasonal work, but today it's an almost fully automated process that produces bricks from 555 tons of clay per day, seven days a week. 
The star of this story is in the hall where the raw clay is automatically shoveled onto conveyor belts and starts the journey from clay to brick. The star is only 20 millimeters wide, sits safely and securely in the electrical panel and bears the name SIWAREX WP341. 
Behind that name is a weighing electrconics that is pre-wired to scales under each conveyor belt and is also fully integrated with the SIMATIC S7-1500 PLC/CPUs and ET 200SP nodes that Strøjer Tegl uses to control production. The full integration brings many benefits, especially in the communication between the different devices.

Compensating for the partner 
The bricks are produced from two different types of clay, red clay and blue clay, and the mixing ratio affects the color of the bricks, among other things. Therefore, it is important to know how much of each type of clay the bucket puts on the conveyor belt. 
It sounds simple enough, but clay tends to settle in clumps, so a look at the monitoring shows fluctuations of several hundred kilograms almost every second. 
"If one conveyor belt has to deliver 80 percent of the clay and produce 50 tons per hour, our old system could ensure this by increasing and decreasing the speed of the belt. But the old system couldn't compensate for the other conveyor belt, and the new one can. So, if one conveyor is dosing more or less, the other one compensates and turns it up or down, and this ensures a much more homogeneous mix of the clay." 
This part will be especially important in the next stage of the project. While a test is currently being run at a smaller production plant, the second stage will be at the main plant, where the scales must also be able to dose the addition of sand and sawdust. 
"Sand is the most important factor besides the clay, and the amount must be adjusted according to how wet the clay is, among other things. Producing bricks is a craft where the most skilled craftsmen can actually taste the clay to determine how much sand and sawdust to add. With our new system, it's much easier to dose automatically because we can fine-tune the amount of clay and know exactly how much clay is coming through at all times," says Ulrik Lei.