A companion flange is a type of flange used in piping systems to connect two separate sections of pipe or equipment together. It consists of two flanges that are bolted or welded together, creating a secure and rigid connection. The companion flange typically has identical hole patterns on both flanges, allowing it to be easily aligned and attached to matching flanges on the pipe or equipment. It provides a convenient means of joining pipes or equipment that have different end connections, such as a flanged pipe to a threaded pipe or a flanged pipe to a piece of equipment. They ensure a strong and leak-free connection, allowing for the smooth flow of fluids or gases through the piping system.