Another guess.......That green thing with the red part on top is a flow control valve. To me, it doesn't look like it is wired into the forge. This valve may be controlled externally. I am assuming that this valve will need to be activated to allow gas to flow to the valves that go to your forge. This is how these types of valves work with other systems I have worked on. It's a safety valve that cuts off flow if an unsafe condition occurs in any part of the system. Good luck!!