Why don't draincocks go through the blastpipe?

I was thinking the other day, and triggered to post by being reminded about this in another topic, about the cylinder cocks of locos and how they come out the front of the loco right next to the cylinders. However, would it not make more sense to route them up into the blastpipe or something like that to create more draw for the fire like the steam normally does after being ejected from the cylinders?

I'm sure there's a reason why this isn't done, or else it would have been done a long time ago. At first I thought that maybe it was because smoke and ash would get into the cylanders somehow, but with the blastpipe being there that sort of defeats that arguement. Then I thought that maybe it was something to do with the pressures, but couldn't think why.

 

The drain cocks are there to get rid of water - you'd be surprised how much - so the cocks need to be low down. Otherwise, water would remain in the pipework after the cocks were shut, and when in use everyone within a hundred yard radius would get a shower!

 

Perhaps anybody standing nearby would be showered with sooty water when a loco started off with drain cocks open?

 

Ah ha! I knew there would be some simple explanation like that. I'd just been having the same mind-block for about a week now trying to work this one out, so I thought I'd eventually post the question here, as although it seems simple now with an answer, it was really starting to bug me ](*,)

 

Water naturally runs downhill and also needs to drain off the cylinders while the loco is stationary, also while not in use. Don't forget locos also need to be moved when they are cold.

 

What comes out the blastpipe should be steam, whereas what comes out of the taps is mostly water. Steam is less effected by gravity than water in its liquid state, so would be unlikely to clear the blastpipe, let alone the chimney.

You also need to consider the reason for the taps: to get rid of liquid water which has condensed from the steam when passing through cold steam pipes, valve chests and into cold cylinders. Once the engine has been working for a short time these parts heat up, condensation ceases and the taps are closed. So you have no steam from the taps for all but a couple of minutes of a day's work.

 

Another reason not to do this is back-pressure. You need to get the condensate (water) out of the way of the piston quickly, or else you could blow the cylinder cover (B1 & Black 5 recently). So the drain pipes from the taps need to be a short as possible to reduce the resistance to the flow of the water being expelled from the cylinder when the loco first moves off from cold. In fact, IIRC some engines (GWR?) just have short elbows off the bottom of the taps rather than the 2 or 3 feet of pipe you see on most types.

 

There is also the problem of moving a loco dead, where the cylinders will be full of water, and still need draining. Ejecting up the blast pipe is not an option then!

 

In that case I completely withdraw both comments