Planning and advising, the basis for success
The world-wide use of Webac plants reflects and emphasizes the success of the concepts with our installations. Our concept which has come a philosophy bases on the following features:
- Long life through quality of alle components
- Flexibility with individual customer solutions
- Consistency with practice-related developments
- Competence with advising and attendance also after commissioning of the plants
Research, development and many years of practical experience helped the basic principle of sand coating to become a perfectly proven success. Special customer demands and a great variety of productin tasks show the importance of designing each coating installation in a flexible way and of adapting it to the specific requirements.
Our advising service covers all kinds of details beginning with the question whether to have a new construction building or to use existing halls, continuing with different types of processes and procedures for different sands, and finishing with the question if the sand coating plant is to use one type of quartz sand, various types of sand or even zircon or chromite sands. The same applies with resins. How many resins or a mixture of different resins are required? No matter how the task to be solved may be formulated: In any case, our installations are designed and realised to fully meet the demands of our customers.
Sand is a fine basic substance to obtain fine results
Apart from other resins-bonded sands, the shell sand produced in our installations has maintained its position on the market already for many years. The advantages of the coated sand are its storing and transporting abilities as well as its excellent forming characteristics.
Other advantages offered by coated sand are found in conjunction with thermical reclamation. Since the sand suffered from thermic load, a volume change of the quartz due to changes in its cristal structure can be avoided. Another positive feature in respect to economy is the useful combination of reclamation plant/coating plant, as the heat required for the reclamation can be used with the coating process.
The flow of process
First of all, the raw sand is heated in the sand heater to reach its process temperature. Here, the sand heater works in time with the mixer. This way, the sand reaches its process temperature as soon as the mixer is ready to take a new batch.
Sand and resins are fed into the mixer to be uniformly mixed within a few seconds. In the course of this process, the resin takes heat from the sand and starts melting. With the hot coating process, sand grain is provided with a uniform resin coating. Subsequently, hexamethylene-tetra-mine dissolved in water is added as hardening agent. In case of using liquid resins, calcium stearate is added as hardening agent. For additional cooling, air can be blown through the sandbed. In accordance with cooling requirements, clean water controlled by a water meter can be additionally fed into the mixer. The immediate vaporization of the water cools the the sand quickly and thus avoids any undesired reactions of the resin and the hardening agent Before the sand is discharged from the mixer, calcium stearate is automatically added in accordance with the preselected recipe. This improves the flow characteristics of the sand.
When the coating process in the mixer has been finished, the sand charge is fed onto the gyra screen. Existing sand lumps are disintegrated to sand grain size and the sand is conveyed into the fluidised bed cooler. The fluidised bad cooler cools the sand to storing temperature. If required, it is possible to add a fine screen.