Innovation with ACO Moisture Measurement Systems

Problem description

If the clay has a too high moisture content, the dimensions of the roof tiles will not be consistent, also the tile will stick on the gypsum mould. If the moisture content is too low, the tile can crack in the dryer and the gypsum plaster will be worn out. For this reason Wienerberger searched on the market for an appropriate solution: a cooperative solution between Wienerberger and ACO.

Application

The first solution ACO brought was an automatic moisture measuring system in their plant for special shaped tiles. In this plant, special roof tiles are made. Due to the shapes of the tiles, a higher moisture content is required (22 till 24%). The clay will be moisturized in a circular screen feeder. A part of the clay is coming from the (indoor) storage, a part is return clay coming from the special shaped tile department. Here lays the problem. The return clay has a higher moisture content compared to the stored clay. The moisture measurement will prevent the clay getting too moisturized due to the return clay by reducing the water adding.

The moisture measurement system TFM1

ACO developed a compressing device, to reduce the influence of the density variations. This patent pending clay moisture measuring device type TFM1 has been developed especially for the ceramic and brick manufacturing industry. It can measure the moisture of critical materials such as clay, limestone, special ceramics and sand. Due to the difficult structure of these materials, the moisture measurement is depending on constant pressure conditions on the material. This electromechanical device is compressing the material always with the same (adjustable) pressure, so you get repeatable readings of the moisture sensor. The output signal of the sensor is a signal of 0-10VDC or 0/4-20mA and is averaged (filtered). It can directly be hooked up to any PLC controllers or command circuitries. The target of this equipment is to get a constant moisture in the production process, which is fed to the extruders or tools, which will last much longer. Finally the quality will be increased.

How does this solution fit into the Wienerberger application

The clay comes out of the circular screen feeder. It falls as round strips on to a swivel plate, where a metal plate beams the clay into the TFM1. With a timer the plug is hydraulically pushing the clay over the sensor. Due to the fact that this happens with a constant pressure, Wienerberger gets reproducible and accurate results. This solution has been operating for over 4 years.

Application

The second solution was a new idea offered by Wim van Gelder of the Engineering & Product Development.: place the digital moisture sensor behind a ceramic window directly into the press head.

The digital moisture sensor

The ACO digital moisture sensors are developed for the toughest applications and for industrial use. They are developed after experiences from the practice for permanent use, they function according the principle of HFC-FFM principle (High Frequency Capacitive + Field Frequency Modulation) and without a lot of difficulties anywhere - also additional - to be placed in the process. By using the norm signal output or the Profibus DP interface (RS232). the sensor can be connected to every SPS or controller without additional software. Only for the configuration of the sensor PC-software is required.
Advantages of these moisture systems for Wienerberger are an easier controlling of the plant and the quality of the tiles by the press operators.