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Old 06-13-2016, 03:27 AM   #8
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Join Date: Jan 2008
Location: Massachusetts
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Originally Posted by NorthWest View Post
Looks like 6029 might've 'found' a few people while blowing down.
FWIW, the photo looks more like a spectacular start, with the cylinder cocks open for an extended period of time vs. a blow-down. Unless the blow-down valve is aimed straight down (which some of them are), a blow-down usually features a well-defined and extended horizontal plume of super-heated water flashing to steam.

This is a blow-down:
Image © Kevin Madore
PhotoID: 575525
Photograph © Kevin Madore

With respect to how far away you'd need to be to avoid being scalded, it depends on a number of factors. There is so much evaporative cooling going on in that plume that you don't have to be all that far away before you just get soaking wet (vs. scalded). In the case of the small locomotive pictured above, it is very likely that if you were at the extreme left edge of the frame, you would probably not be harmed. Higher boiler pressure and/or a larger blow-down valve would probably increase the danger zone.

Most locomotive crews are pretty good about clearing the areas around the blow-down valves, and yelling "CLEAR!" before opening the valves. While out on the line, blow-downs are often done on bridges, where there is no danger to pedestrians.

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