Stack valve

While shooting for a photographic essay that might appear here (if it really comes together), I took a shot of a piece of equipment just so when I got home I could read the "nameplate" information and determine exactly what it was.

But when I brought it up with my viewer while "running the dailies", I was somehow struck by the overall image. So here it is, ex camera:


This is a stack vent valve on a large storage tank for liquid mercaptan, a chemical introduced into natural gas so it can be detected by smell (as in the case of a leak). This valve releases the pressure from the tank should it become excessive. Won't that smell great in the neighborhood!

I was very taken by the wonderful subtle greenish-bronze color, which we often see on matte-finish cast aluminum objects of its era, probably from a zinc dichromate surface finish used to resist corrosion. On smooth parts (like carburetor bodies or relay mounting plates in electromechanical telephone switching equipment) it has a wonderful "iridescent" appearance.

Hi Doug
a nice catch and interesting (smelly?) intro.
I had cropped it vertical though to eliminate some of the trees on left and right, to focus on the valve… sometimes context ain't needed!