... . As a result, we'veacquired many national patents. The production line was designed using highdensity polythene (PE) as its main material ... to return it. Its outsidewall is neat and smooth. This line outputs pipes in specifications ranging indiameters of 400 to 2 ... materiallike cement, cast iron, porcelain and ceramic. They are widely used for sewers,bridges, building, sports fields, mines and farms.