yesterday at the shop in spencer, several of us were admiring the Porter 0-6-0T that came to us from a N.C. gravel pit (W.R.Bonsal near Lilesville) and originally from the army. the engine is getting a cosmetic restoration; we were noticing that she has a check valve on top of the boiler for introducing water from the injectors. i recall seeing a similar top mounting on some canadian engines; i suspect this has something to do with the circulation of water in the boiler but i was wondering if someone might explain it here and if anyone knows the origins of the check valve on top. <p><br>



Wrinnbo@aol.com

Jim,<p>I think the check valve on some of the tank engines was simply there so give good access to close the valve manually or in case it needed to be serviced. If I remember right the 0-6-0T we had at Wilmington and Western which was later sold to Queen Annes RR had the same configuration.<p>That little 0-6-0T was a great little engine to run and fire. I sure do miss her. The picture of her is a little dark but is one of my favorites.<p>Tom Gears<br>

thanks guys; all of those seem to be plusses, and i'm amazed the railroads didn't think of doing it earlier or spread the practice more widely;<p>love the picture of the 3, tom; where is she now that QA is out of business? <br>



Wrinnbo@aol.com

Jim, Robert has it right. I recently read a very fine piece on this subject in an old reprint of an issue of Railway Mechanical Engineer from the early 1940's. According to this article, top checks came along about the same time as general acceptance of feedwater heaters.<p>Tests showed that side-mounted checks did a good job when the engine was working hard. This was due to the fact that while the engine was working hard, there was a terrific amount of turbulence in the water inside the boiler, so the cooler, incoming water was thoroughly mixed with the hotter (no, not Hooter) water that was already in the boiler. However, when the locomotive was drifting or was standing (which locomotives did most of the time), the cooler incoming water tended to move to the bottom of the boiler and not mix with the hot water. This led to some substantial variations in water temperature indise the boiler, which, in turn and over time, would lead to uneven stresses on the boiler shell and sheets, and THAT, in turn, led to cracks, wastage, and higher repair costs. Top mounted checks eliminated or greatly reduced these problems. <p>Thus, top mounted checks began to show up on new power and on a number of rebuilt locomotives. <br>