Thanks a lot, Renee!
Added small pipes for the valves on the boiler.
Firstly, added the small valve handles.
The air valves at the right hand side. I think it is controlling sandbox (forward and backward selectively).
Added the relatively thinner pipes for the valves.
I guess the compressed air comes from tank. And the sandbox valves are opened selectively (break aid, forward or backward)
Seen through the opening at the back