What are double line drawings in a pneumatic schematic?

Double line drawings in a pneumatic schematic represent the piping and tubing connections in a pneumatic system. The two lines indicate the boundaries of the pipes, distinguishing them from other elements like valves or cylinders. This notation helps clarify the flow paths and connections, making it easier to understand the system's operation and design. It’s a standard practice in engineering drawings to enhance the readability and communication of system layouts.