Sunday, December 6, 2009
The No. 14 Double Check Valve
Here is a drawing of a "No. 14 double check valve", one of many air-brake parts on the SN 1005. Many of these parts have come off 1005 for servicing. When this is done, the opportunity is also seized to paint both the parts and the piping.
In most cases, the parts are "hard plumbed" into the 1005's plumbing, which means a part comes off by following each pipe back to a union. The part comes off with an octopus of pipes attached. Here is an example of a double cutout cock, in which one handle closes two pipe circuits at once. The proximity of the ports makes piping a real challenge.
Before we are done, that part will be thoroughly cleaned externally, and overhauled internally - for this cutout cock, that means lapping the valve. And then, it will be painted - the valve will receive two coats of Awlgrip 545 primer then up to two coats of Awlgrip topcoat, "super jet black". The pipes will receive cold galvanizing compound, which will weather to the appearance of galvanized pipe.
Let's return to the No. 14 double check valve. Here you see a picture of WRM's spare unit. It is an interesting exception to the rule when it comes to "hard plumbing". As you may know, there was a major "shift in consciousness" about railcar plumbing. Now all the pipes go to a pipe bracket which is nothing but a manifold for attaching pipes. The device attaches with a gasket and a few bolts. It can easily be swapped, or carried as a unit to repair.
If you look above at the drawing, where you can see a clear separation line - above gasket #11. Is the upper piece really intended as a pipe bracket? A quick consultation of the parts list (below, off page) reveals that part #10 is indeed called a "pipe bracket". But you also see where the repairman had better know what he is doing if he means to unbolt the lower assembly from the pipe bracket - he's liable to have parts going everywhere. Clearly, pipe brackets have come a long way since.