[ferroequinologist]

Easiest way is to remove the safety valve and turn it upside down, I do that on my little 0-4-2 aster Baldwin and remove any domes on the boiler that may fall off first. Easy on a small engine but more difficult on a large heavy one with a tender.
Russell

 

[ferroequinologist]

I have one safety valve in the cab and the other safety valve is under the main steam dome and that is the one I remove, the steam dome is a push on fit to get access to remove the safety valve.