I am suggesting the butterfly valves as a e-stop and not a primary throttle valve replacement.

Slamming the throttle shut happens on the road and everyone survives the dark cloud that ensues.

You can set air operated butterfly valves up for any speed of closing by the solenoid size and porting/restriction you choose. In electric generation, Golden Anderson/ Gimpel piloted poppet valves are faster, which is desirable in critical steam turbines- the emphasis being on reaction time (<.3 sec) to prevent overspeed and to hell with what happens upstream. The butterfly valve fits in a biscuit, about 4-6" thick and you could fabricate branch pipes which were shorter in case one wanted to swap it back.

When dealing with an old prime mover that you are running for profit, my preference is to have as much off the shelf, in-production, cost effective equipment as possible. I think some of the later throttle designs would be great, but the issue is cost and having another weird, unsupportable system. My experience with old throttles of all types reminds me that there has to be a better way today- but I could say that of many locomotives I've worked on, too.

An air-operated butterfly valve might be a way for the average dome throttle locomotive to be compliant for the least cost.

IF you -HAVE- to go for cutting the power on a steam engine, forget the main throttle. Cut the oil or cut the steam to the stoker engine. IF your crew has really all gone THAT brain dead you need to consider they may also be running low on water. Chop the 'energy input' at the source and minimize the energy in the system. Plus the devices and valves needed to do that would be much smaller and simpler. Yes, I am aware you have a lot of stored energy in the boiler that could cause issues for a very long time.

[quote="Pegasuspinto"]IF you -HAVE- to go for cutting the power on a steam engine, forget the main throttle. Cut the oil or cut the steam to the stoker engine. IF your crew has really all gone THAT brain dead you need to consider they may also be running low on water. Chop the 'energy input' at the source and minimize the energy in the system. Plus the devices and valves needed to do that would be much smaller and simpler. Yes, I am aware you have a lot of stored energy in the boiler that could cause issues for a very long time.[/quote]

Cutting the oil or stoker doesn't cut the power to the engine. 5,000 gallons of water at 400F has a lot of potential energy that will keep the engine moving for a few miles.