[N&W] Re: Steam questions

[nw-mailing-list at nwhs.org]

1. Simple means each of the four cylinders is fed steam direct from the
boiler and said steam is used only once before going up the exhaust stack.
Compound means steam is fed from boiler into rear cylinders at
high-pressure; steam is then used there, loses some pressure in the process
and is fed into pipes that carry it to forward, low-pressure cylinders that
are larger in size to accommodate a greater volume of steam (since it's now
at lower pressure) to do the same work. Steam is then exhausted from
low-pressure cylinders after having, in essence, worked twice...

2. Blowdowns are valves that vent steam from the boiler, normally to help
blast away scale that accumulates therein or, as we used to do on the 1522
at the end of an operating season, to purge the boiler of steam/water before
shutting down for the winter ... made quite a show, taking about 20 minutes
to drain the boiler. Never stand near one of these when they open BTW ...

3. An exhaust steam injector uses exhaust steam (energy that would otherwise
be wasted) to drive water into the boiler as needed. Injectors have to use
steam to overcome the boiler pressure and force water past check valves and
into the boiler. Steam engines had to have at least two methods of putting
water into a boiler BTW...

Andre Jackson and/or Lisa Burrows