Reversing/Throttling Steam Valve Pictures

Gies Reversing Gear

Here are some pictures of a reversing/throttling steam valve that controls a drum winch, like for a marine railway.  The handle will rotate about 45 deg with the center being off or closed.

   The seemingly apparent problem with this is the D-valve would try to unseat itself in reverse.  This is taken care of in a few different ways.  One is the valve is captive on the seat by the steam box cover.  Not a very good way, but effective.  Another way is to hold the D valve in place by a balance disc on the back of the valve.  Both of these ways are effective, but not very efficient.  Obviously, with a piston valve this type of reversing valve arrangement works much better.

The two slippers are held out from the stem by a spring in the center to keep them in contact and seated with the bore of the valve.  The interior 'cavities' of the slippers are the low pressure sections, or exhaust, which also forces the slippers against their seats.

Final exhaust is from the bottom of the valve body.

This is a Gies Reversing gear.  They were found in marine use quite often.  The design is still popular today for industrial reversing gear.