![Image](http://i179.photobucket.com/albums/w283/CCairns_2007/IP%20Engineering/IPM03ReplacementSafetyValveforMamodSteamLocomotive.jpg)
I do not have one of the replacement safety valves produced by Dream Steam or RWM (formerly PPS), but I assume they are of a similar construction. The one fitted to my Mike Chaney replacement boiler is not adjustable.
![Image](http://i179.photobucket.com/albums/w283/CCairns_2007/IP%20Engineering/IPEngReplacementSafetyValveforMamodSteamLocomotive.jpg)
So they have a hollowed out body, a stainless steel ball, a rod with a cup shaped to sit on top of the ball, a spring and a threaded cap which has 4 exhaust holes. These are set to about 20-25 PSI for fitting to a Mamod, but by using something like the small circlip pliers that I use into those exhaust steam holes you can screw in the threaded cap to increase the pressure to approx 40-45 PSI.
Chris Cairns.