Welding is a vital part of many construction projects, and the welders and welding machines used must be up to the task of the job. High-density polyethylene (HDPE) pipes are a popular material for piping solutions in industrial, commercial, residential and agricultural applications. In order to weld HDPE pipes, specific welding machines designed to weld polyethylene must be used, and there are a few different types of welding machines available.