Re: Moist Air

On a locomotive the air system can in certain instances have quite a bit of moisture in it. This comes from compressing atmospheric air which contains a good deal of moisture, then having it cool in the air tanks and the lines where the moisture condenses out. Some of the moisture may also enter the system at the piston packing on the air pump. If the packing on the steam side above is leaking a lot and the air side which is below is also not tight, some of the moisture from the leaking steam ends up in the air side of the pump. On steam engines with some improvements, the moisture is given as much opportunity as possible to condense out before it get to appliances. The condensing coils on the side of an engine are the first step, and they have a condensate drain. The air then goes to the first air resevoir as on SVRy 19, where it has a chance to dry out some more and moisture collects at the bottom of this tank, then the air flows to the resevoir on the opposite side of the engine, giving more chance for moisture to collect rather than pass into systems. On 19 there is very little condensed water to drain out of the second resevoir. Many smaller engines and I am no authority, but have experienced this first hand with our #3, which has no condenser coil, and only one air tank, that the air getting to the brake components and it would be the same for the sanders can be quite moist. The moisture combined with oil can really gun up the feed valve on the brake stand. I imagine moist air might create problems with sand clogging up the sanders as well. For this reason, I can imagine that on the Grande's smaller motive power which may have experienced the same scenario with moist air, a remedy was found to provide really dry hot air to the sanders. Also moist sand left in the sanders could freeze in cold weather making them inoperable when they are needed most.