[Steam-engine] relief valves

[Ted Knack]

I agree with alot of whats being said about lifting the pressure relief
valve.Its not made to be a pressure regulater.And over the years I have
seen many operaters doing just that.The worse I ever seen was a Advance
Rumley plowing a field that was 1/2 mile long.The plow was 8 bottoms,and
the engine had a 175 psi pop valve.The engineer was burning coal and as
soon as the engine started to plow,the safety valve released.And that
engine poped off all the way across the field pulling the 8 bottom
plow.Can you imagine the fire in the fire box.He never used the damper
door. He left it open. That evening in the dark me and another engineer
look inside the firebox of that engine.And we counted 21 stay bolts
leaking with a flashlite.End of story.

Ted Knack, retired, 80 HP CASE STEAM ENGINE owner, concertina player. 
http://community.webtv.net/tksteam/TedsSteamandHobby