2022

Setting time during gypsum board production

Regardless of the gypsum board production line or the gypsum line equipment, gypsum powder is used, but different gypsum products have different setting times due to temperature, raw materials, product thickness and other aspects. If the setting time process of gypsum board or lines will directly affect its production capacity, today we will take a look at the setting time problem in the production process of gypsum board.

The setting time includes initial setting time and final setting time. The initial setting time is the time from when the gypsum powder is sprinkled into the water until the gypsum slurry loses its fluidity and starts to thicken under the standard water consumption (standard consistency); The time elapsed between when the gypsum slurry is sprinkled into the water and when the gypsum slurry solidifies. According to relevant standards, the setting time of qualified gypsum powder should be: under the standard consistency, the general initial setting time is not less than 7min, and the final setting time is not more than 30min.

Setting time is an important technical parameter in the manufacture of gypsum board production lines. Appropriate setting time is a prerequisite and necessary condition for normal use in the production of gypsum powder. In production, we need the setting time of gypsum powder "not too short for the initial setting and not too long for the final setting", or "the initial setting time is longer and the final setting time is shorter". Because the initial setting time is too short or the final setting time is too long is not good, will affect the production. If the initial setting time is too short, less than 7min, it is manifested as barrel injection during production, which delays production; if the final setting time is too long, far greater than 30min, it is manifested that the slurry is too thin and easy to run off when the gypsum line is installed, or even the gypsum slurry does not solidify. also affects production. In large-scale production, taking into account various factors such as operation, the initial setting time should be controlled at about 12 minutes, and the final setting time should be controlled at 25-30 minutes. The length of setting time (initial setting and final setting) is mainly related to the ratio of gypsum powder and water (cream-water ratio). The larger the paste-to-water ratio, the shorter the setting time.

The detection of setting time in production does not necessarily have to be carried out under the standard consistency of water consumption, but should be carried out with the ratio of large-scale production paste to water, which has more practical guiding significance.

Determination method: At present, the detection methods include the cutting test cake method (scratch method) and the Vicat instrument method (similar to the cement industry detection). We often use the simple method of scratching and testing the cake (scratch method).