Uni-directional Scraper Pig is a common pig. It has 4 cups and a steel frame. The pig can remove soft dirt and dust from the pipeline. Its leather bowl has two functions. First, it has a good sealing performance. Therefore, it can completely separate the liquid or gas at both ends. Then a pressure difference will be formed at both ends of it, which can push it to run. Second, it can clean the sundries in the pipe and the dirt on the inner wall of the pipe.