Moisture will affect the performance of the materials used in the production of PE pipes, so it is generally necessary to dry the materials before use to reduce some factors that may affect their use during the production of PE pipes.
The polyethylene material currently in use is not easily hygroscopic, and the water content of newly produced materials is generally only a few tens of parts per million; However, during long-distance transportation and storage, the surface of the material is prone to absorbing some moisture, and black materials are more severe. Water layers and even dripping can be found on the inner surface of the material bag. So, after the materials enter the factory, the analysis of the trace water content of the materials is very important. It can not only check the quality of the materials, but also determine the drying process based on this. If the water content is low, materials from South Korea and domestic countries with closer transportation distances can be used directly without drying; But when using black materials or materials with different batch numbers, they need to be dried before use to avoid wall thickness fluctuations in the pipe due to fluctuations in extrusion volume and load. There are two types of drying equipment for materials, namely hot air dryer and dehumidification dryer. The principle of a hot air dryer is to use hot air to blow away the moisture in the material, with a temperature range of 80-100 ° C and a drying time of mostly 40-60 minutes; The hot air dryer is an open system that can only remove moisture from the surface of materials. The principle of a dehumidification dryer is to replace the moisture in the hot air with molecular sieves, and then blow away the moisture in the material with drying air. This method can reduce the moisture in the material to below 0.1%. The drying temperature is generally between 80-100oc, and the drying time is generally between 2-3 hours. A stable dryer can lower the dew point of the drying air to below -30 ℃; If the moisture content in the material is greater than 0.08%, it is necessary to use a hot air dryer for pre drying.
During the production of PE pipe materials, extrusion operation is required. If the water content in the material, that is, the moisture content, is relatively high, the extrusion operation will also encounter problems. Therefore, the drying operation before use is necessary, which is also a good way to remove the moisture content of the product.