Sand coating

Planning and advising, the basis for success

Schematic diagram of a sand coating plant

The world-wide use of Webac plants reflects and emphasizes the success of the concepts underpinning our installations. Our concept, which has become a philosophy, is based on the following features:

  • durability owing to the high quality of all components
  • flexibility in finding individual customer solutions
  • consistency throughout the implementation of developments
  • expert follow-up provided both in terms of advice and visits, after commissioning of the plants

Research, development and many years of practical experience have helped the basic principle of sand coating to become a tried-and-tested success. Special customer demands and a great variety of products for different tasks show the importance of designing each coating installation in a flexible way and of adapting it to specific requirements.

Our advisory service covers all kinds of details, beginning with the question of 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 of whether the sand coating plant should use one type of quartz sand, various types of sand, or even zircon or chromite sands. The same applies to resins. How many resins are required, or should it be a mixture of different resins? However the task to be solved is formulated, our installations are designed and realized so as to meet the demands of our customers in full.

Sand is a fine basic substance for obtaining fine results

Mixer with gyra screen

As distinct from other resin-bonded sands, the shell sand produced in our installations has already maintained its position on the market for many years. The advantages of the coated sand are its storage and transportation capabilities, as well as its excellent moulding properties.

Other advantages offered by coated sand are found in conjunction with thermal reclamation. Since the sand has been subjected to thermal load, a change in the volume of the quartz, due to changes in its crystal structure, can be avoided. Another positive feature with 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.

Stages of the process

Sand coating plants

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. In 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, the sand grains receive a uniform resin coating. Subsequently, hexamethylenetetramine dissolved in water is added as a hardening agent. If liquid resins are used, calcium stearate is added as the hardening agent. For additional cooling, air can be blown through the sand bed. In accordance with cooling requirements, clean water controlled by a water meter can also be additionally fed into the mixer. The immediate vaporization of the water cools the sand quickly, thus avoiding any undesirable reactions between 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 fluidity of the sand. 

When the coating process in the mixer has finished, the sand is discharged and fed on to the gyra screen. The remaining sand lumps are broken down to sand grain size and the sand is conveyed into the fluidized bed cooler. The fluidized bed cooler cools the sand to storing temperature. If required, it is possible to add a fine screen.

Job Offer