Thanks for the clarification. We know what happens when we don't use "not propa walve".. Get the movie guys...but it still has a sad ending.....no matter how many times I watch it...
Our Otter uses a 1/2" angle globe valve as a main steam stop valve, and a strainer w/ wire mesh to remove any scale, etc, carry-over that would damage slide valves, etc.... and the throttle valve is a 1/2" angled bronze globe valve w/ a metal-metal seat. this combo works very well.
A thought, cause I like Bart's idea. Modifying the concept (and perhaps the valve handles): use the throttle valve (with a handwheel that has a short handle - like a crank) to regulate the speed and the main steam stop for quick maneuvering (off - on). If the main steam stop is within easy reach of the engineer's station - and a simple quarter turn ball valve - that might be a thought. Over 35 years in this hobby and I suddenly came up with this simple idea. What's wrong with it? Must be something.
I used a globe valve with a crank as you described.....like the one on Sabino, it can be a bit slow to open or close...even with the "Brody" knob on it...I tried out the ball valve ( 1/4 turn open to close) and I really like it...very controllable and it stays put....and can be closed in a blink.
Think I'll stick with it......at least for a while...but I'll let you know