Looking at the tourist locomotive at the following link (sorry, being a local source I don't thnk the link will light up, probably have to copy and paste)
http://cs.trains.com/trn/b/observation-tower/archive/2020/09/17/building-a-world-class-tourist-railroad.aspx
I see three streams leading from the engine.. An exhaust stream leading from the main flue, what I'm guessing is a whistle stream of steam due to the crossing...
But what is the third stream? An overpressure relief valve of some sort?
You'll get much better views of #110 here:
https://m.youtube.com/watch?v=9uo4wVbXoVU
This is a thoroughly modern engine as logging locomotives go, built by Baldwin in 1928. It is hard to make out in the picture you linked but there are two upright safety valves on top of that dome, and it appears the crew makes use of them fairly often. They will be set a couple of psi apart (I think on 110 the left one before the right one) both for redundant safety and so you can avoid blowing off a huge mass of steam through a big valve when only a relatively slight overpressure is developed.
Note in some of the shots that the engine has a turbogenerator (with an angled exhaust pipe) up on the top right front of the boiler and this is likely what produces the visible plumes at the front in some of the distance shots (but not in your crossing shot)
Overmod It is hard to make out in the picture you linked but there are two upright safety valves on top of that dome, and it appears the crew makes use of them fairly often. They will be set a couple of psi apart (I think on 110 the left one before the right one) both for redundant safety and so you can avoid blowing off a huge mass of steam through a big valve when only a relatively slight overpressure is developed.
So, is that a fairly routine occurrence while operating one of these engines? Somehow I always envisioned a safety relief valve as something that was just there to avert disaster subsequent to an oversight, mistake, or malfunction.
A good fireman would try to maintain boiler pressure just a few pounds below the safety valve setting. A slight overpressure would cause a feather of steam from the safety valve, which was good advertising for the fireman.
Convicted OneSomehow I always envisioned a safety relief valve as something that was just there to avert disaster subsequent to an oversight, mistake, or malfunction.
Factor of safety in these boilers was 4:1 and is now 5:1 (hence the controversy over PRR K4 1361's boiler repairs) and even regular hydro testing is to a far higher pressure than 'safety' valve relief.
In a sense the 'logical' place to set a "safety" valve would be, as in a furnace, a few, perhaps more than a few, psi above working pressure -- particularly when vented steam carries a high price both in terms of water mass and the heat involved in making it high-pressure steam. Instead, on locomotives, it is set -- I think in provisions of the 1911 boiler law as amended -- to start at rated pressure, and the release then gets used as a convenient audible and visible indication that full rated pressure is available from the boiler.
In practice, when the first pop lifts it's the signal to the fireman that it's injector time (or feed time on a FWH equipped engine) This can very quickly take the overpressure down, compared to the essential impossibility of arranging this via firing (for a variety of significant reasons!) Unfortunately if the boiler is already 'full' and you are having to work steam, you are stuck: more water would mean carryover, which is a Really Bad Thing especially with treated water, so you run with a feather and sometimes more than a feather of steam to have full pressure available all the time.
Now in practice, on a tourist railroad using a twelve-coupled articulated, I'd be more inclined to use sliding-pressure firing and trade more steam mass flow for pressure. But that presumes the pressure-cycling has lower boiler-maintenance consequence than thermal cycling does -- and even Tuplin's data never really established this.
Where there are multiple valves they are not all 'redundant safety devices' set to the same pressure. They are provided so the aggregate area will safely vent any overpressure mass flow of steam even full firing would produce -- as on an ascending grade if the engine were suddenly stopped. On N&W for example there were four physical valves, the first set at 300psi and the others about 2psi apart, so that at 306 psi the last one would pop open. Then as the pressure falls they just as progressively pop closed... if you want something to worry about it would be to see all four open and blowing for more than a few seconds... (Incidentally setting these had to be done manually, with a wrench on the valve and no warning of impending actuation, with the boiler at full steam pressure as monitored by calibrated gauge ... while fat violet MHD sparks crawl all over everything during release... not a job I'd like to have!)
If you want an uncomfortable 'parallel' in safety devices, take that great scam the Nathan drop plug. Supposedly if you overheat the crown, the solder in these will melt and the core will drop out opening the whole bore to steam. Which will then (presumably) dampen the fire, establish to the fireman 'how badly he screwed up', and -- not incidentally -- start relieving the boiler pressure. In theory.
The problem is that -- and the actual formula in their own ads says as much -- the required relief would require more than the ~5 plugs usually fitted, for any modern size firebox. And to get mass action from the 'proper' number of drops would involve so much high-pressure steam into the firebox... displacing both incandescent combustion plume and burning fuel toward any pressure exits such as the fire door or secondary-air ports in the cab... that crew survival might be questionable particularly in a vestibule cab.
On 110 the safety valves do not appear to be 'popping' as modern ones do, which means opening immediately to their full capacity and nearly as quickly closing -- these look to me as if they are proportional relief valves that only open enough to balance pressure. That they stick up to be so visible indicates they were intended as a 'substitute' pressure indicator as much as a "safety assurance" device.
In practice, isn't the fusible crown-sheet plug more of a warning device, that the sound of the plug blowing warns the fireman to either work the drop grate to dump the fire as quickly as possible and the engineer to work as much steam as possible as well as stop the train, and if not possible, to evacuate the locomotive cab?
There was an article in the Steam Glory series where the crew took those precautions, but it was from a burst "security circulator" (one of the firebox tubes with the dual function of holding up the crown sheet and supposedly aiding water circulation in the firebox walls?) and not an incipient crown-sheet failure, thank goodness.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Paul MilenkovicThere was an article in the Steam Glory series where the crew took those precautions,
"A Niagara Falls," from Classic Trains "Steam Glory 3," published in 2012. Great special issue! It's one that never made it to the recycle bin, I've still got it.
Per Overmod's mention of 4:1 and 5:1 safety factors, I've got a video of C&O 614's return to steam in the 1990's. In it Ross Rowland (during the safety valve setting segment) said that 614's boiler was built to stand a theoretical pressure of 1000 PSI, but "Obviously we don't want to find out if that's true!"
Paul MilenkovicIn practice, isn't the fusible crown-sheet plug more of a warning device, that the sound of the plug blowing warns the fireman to either work the drop grate to dump the fire as quickly as possible and the engineer to work as much steam as possible as well as stop the train, and if not possible, to evacuate the locomotive cab?
The originals were 'fusibles', like threaded tubular fittings filled with solderlike material with relatively high braze strength. As long as there was water on one side, these would stay solid, but if not the solder would melt and steam pressure progressively blow it out of the tube to full opening. This was great for steamboats and relatively small American-type locomotives at ~60psi, but for a variety of reasons including corrosion to refractory oxide many of the original types proved less than satisfactory; hence the innovation of the drop type where the plug is tapered to fall out easily and only a thin film of solder holds it in. The catch is that when either there is a large radiant area or a large reserve of high-pressure water in the boiler, very many more than a few of these need to open to practically relieve pressure to levels "safe" in a major 'rapid unanticipated disassembly' process... at which point the vented steam causes its own bad effects in the firebox, where you do NOT want overpressure when the fire is between it and the door.
Complicating this is that you do NOT respond to the usual drop by injecting any water... unless you try and get away with it. Likewise once you drop the fire, you're not getting it back... and on a large engine you now have considerable problems with where that much fire goes... and thermal expansion of a large firebox abruptly cooled is not exactly a happy contributor to safe or timely depressurization.
If you had to stay with the engine you might open the throttle and put the reverse as far in the corner as balance would stand (compression being an issue) the problem there being the fire you dropped will still happily 'draw' from its new forgelike configuration in the ashpan, and we also know that a real fast way to rip out staybolts is to combine a rapid drop in pressure with high draft -- PRR 6200 being a particular poster child. So you'd pull the cylinder cocks and probably any blowdown valves you have... but these are steam at a very high volume compared to the overcritical water remaining -- the fireless-cooker principle arises to bite you.
Circulator failures are grim because they represent unpatchable leaks very low in the boiler structure, usually designed by 'thermodynamicists' who have cross-connected the rest of the arch tubes so 'flow to the blow' is high. This promises to expose at least part of the crown very quickly, so it is a sort of race and crapshoot together to see if the fire drowns before the crown heats beyond tolerance. Here at least -- once the fireman recognizes the problem, which might not be easy to see past the clouds of incandescent blowback -- full injector and FWH feed will be valuable both in keeping water up and pressure 'lowering'.
Another kind of steam engine ejecta :
Same me, different spelling!
Is that a CLINKER that I see??
Yep, dat's a one big clinker!
Becky was kind enough to show it to us on the "Classic Trains" Forum a while back. Or the "Classic Toy Trains" Forum. I forget the site, but I never forgot the clinker!
Hopefully she'll come back and tell us the story of how she got it.
Imagine that falling in some dry grass near the track, still glowing red... ......no wonder coal-burners started so many fires!
Greetings from Alberta
-an Articulate Malcontent
SD70Dude Imagine that falling in some dry grass near the track, still glowing red... ......no wonder coal-burners started so many fires!
Ah! But it was! It was thrown by the 765 during the Steel City Express runs in 93. I chased between Akron and Youngstown and a friend did Pittsburgh to the Ohio/Pa line. It was my last chase, and I kicked it around in a puddle a bit till it was cool enough to put in my car. Hey, souvenirs are good! Wish I had the photos though. I was taking them to be developed when the rolls fell out of my purse while I was eating pizza at the mall and an overzealous sweeper must have just scooped them up and put them in the trash! Oh well, I have my VHS footage!
Hell of a souvenir! 765 must have thought you were someone special to thrown a "custom memento" at you!
With the way my luck runs I'm surprised it didn't bounce off my noggin!
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