• Steam Boiler pressure relief valve

  • Discussion of steam locomotives from all manufacturers and railroads
Discussion of steam locomotives from all manufacturers and railroads

Moderators: slide rules, Typewriters

  by BobLI
I was watching a video of steam power used on fan trips and I noticed a lot of steam escaping from the pressure relief valves on top of the boiler.
Then when looking at some old photos of steam power it seems you dont see much steam escaping from the valves. Was it frowned upon in the old days to waste steam by having too much boiler pressure?
Was it an "art" to keep the boiler pressure at just the right amount and not waste the steam? if so how was it done?
  by Steffen
Yes, it was an art!

I am fireman, and still, it's the problem: One shovel to less, the boiler pressure will drop, one to much, and the safety valves are lifting. We use safeties named Ackermann. When they open, it's a load smashing noise and then you hear load swoosh of steam through the escape channels... very disturbing. Consider it this happens in a station... most passengers and usually children run in scare - and running away is often a serious danger, as one could drop and fall, or more critical, lose orientation and drop onto the tracks...
Thus we firemen try not to blow the safeties... we try to keep maximum pressure, but not to much. But it's diffucult, as we miss the daily task and the experience, which comes from this daily duty on the footplate.
Also all the steam escapes is coal, you shoveled into the fire... and this is lost... thus you have done yourself a back draw, and you'll have to do it again, so you will do the work twice, also it's wasting energy, water and fuel...

So if you know the engine, are team with the driver and know the track with all the curves, slopes and stations, you can maintain the fire properly, you know when and how much to put onto the fire, and the safties won't lift, and you maintain maximum pressure... so as you see, it's all experience...
  by Cactus Jack

What locomotives do you fire ?
Are you a regular driver as well ?

  by johnthefireman
In South Africa we're supposed to let the safety valve lift twice to test it, once in the depot before departing and once when we are outside the depot in service. As Steffen says, letting them lift too often is frowned upon. It's a waste of coal, a waste of water and a waste of the fireman's muscle power. It's also very noisy. However, sometimes you have no real choice, eg when you get stopped unexpectedly at a red signal just as you've built the fire up for a steep climb, or when you're just about to pull away from the station and the guard suddenly decides to wait for some late passengers to board. Immediately you put on the injector to reduce the pressure in the boiler, but you can't do that if the boiler is already full and at some point you just have to grin and bear it.
  by Steffen
Cactus Jack wrote: What locomotives do you fire ?
Are you a regular driver as well ?
Well Jack,
I have fired german locomotives only - yet...
these were series 50 (a decapod) and 52 (decapod, war type series modification of series 50). I fired series 01, a pacific, but only on short distances and light engine.
Regulary I fired a prussian G8 an eight wheeler, as our little ELNA type 6 - a eight wheel switcher, also I have good experience on regulary tasks on our series 23, a Prairie engine for regional passenger trains build in the fifties...

Certain videos you'll find on my youTube channel...
  by ricebrianrice
I have a small setup, that I use to boil sap, and make Maple Syrup. Every spring when I am doing this, I have a greater
appreciation of firing a steam locomotive.

Keeping a good boil going is very hard!!!!

When adding more fuel to the fire, it cools down, and the boil stops.
Adding more cold sap to the pan, cools the pan, and the boil stops.

There is a very fine line of not adding to much fuel, and not adding to much liquid at a time to keep a good boil.

It truly is an art! My hat is off to anyone who has fired a locomotive.
  by johnthefireman
ricebrianrice, thanks for the reference to maple syrup. A couple of weeks ago I was in Vermont and upstate New York (via Amtrak, of course) and was fascinated to see the maple syrup process. Keep up the good work!
  by GSC
In steam service at the museum I volunteered at, we tested the safeties at least once a day, as required by our rules. Run up the pressure - slowly - and let the vales pop. We kept our safeties on three locomotives at about 130 and 132 psi, two pop valves on each loco. We avoided letting them go at random times as best we could. Most of the seasoned firemen knew the engines, so scaring the patrons didn't happen too often. It just takes practice.
  by Steffen
in germany the rules of the ferderal railways says, that any fireman at beginning of his shift has to check the water gauges, the water pumps, watch the fire, the ashbox and smokebox sprinklers. And after this he should draw the check of the safeties, just to ensure they open well and close sharply - ensuring they work properly.
Only if those things are done, he should start his duty - if something fails, he should call a local inspector to check if the engine will go further in service or withdrawn from service - which means, find out if the problem can be fixed or not.

So popping the safety valves is a need on regular schedule of the fireman at the beginning of his shift.
  by GSC
That we did at the beginning of our "shift" as well. The locomotive ran for one operating session each day, about 8 hours, and then was put to bed. Therefore, the safeties were tested at least once each shift, as per the rules.