Limited room for steam.

[Emfinger]

I managed to get my 2-4-2 oil eater working. It took some time learning how to control the burner, but I got it...sort of.
As it turns out I have very little room for steam. If I add water the steam gets wet and blows water out the stack. The throttle valve is in the dome. My question is can I make the dome taller and move the valve to the top? If so what would be the best way to raise the dome?
Thank you
Tom Emfinger

[NP317]

I face a similar situation with a high crown sheet and limited steam volume.
In my Build log there is a discussion of solutions builders have made:

http://www.chaski.org/homemachinist/vie ... 8&start=12

Look at the lower half of that page and beyond for some pictures and drawings of "water shedding" methods at the steam intake on the dome.
Hope this gives you some ideas.

I have yet to fully address priming with my new Mikado. I've been unable to get it on the tracks during the past year so it's only run about 1 mile total!
Almost a criminal situation.
Next year, however... Test, evaluate, resolve.
RussN

[Emfinger]

Thanks, I think I need to make the dome taller....somehow.

[Glenn Brooks]

Some pictures and dimensions of your boiler would be helpful to assess possibilities for altering your steam dome and throttle valve.

Generally boilers have a lot of froth and sloshing when steamed up to operating pressure. Eng. Porta, of the Argentine Railway’s Lempor exhaust system fame, described water levels in boilers as similar to boiling milk in a sauce pan - lots of thick bubbles and mineral froth constantly rolling around, exploding and disturbing the surface layer, splattering froth to and fro. If your water level is so high that you are priming the throttle vale, then you have no room for steam reserve in the boiler. So generally the answer is to lower the water level, to the point where you protect the crown sheet, and keep it constantly replenished.

You may be better off putting your time into fine tuning and/or rebuilding your front end. If you achieve maximum evaporation rates you will readily replenish what you use during operation. If you have noticeable stack talk, you are wasting significant quantities of steam. A properly constructed front end will lower steam consumption, lower backpressure on the cylinders, and correspondently deliver higher horsepower and tractive effort on the drive side of the cylinder stroke. Sort of a win-win all around.

Another common solution for high Crown sheets, is to add a mechanical water pump that outputs a small constant flow of water into the boiler. You can then run the loco with consistently lower water levels over the crown sheet- giving you more reserve steam capacity in the boiler with more consistent inflow and evaporation. These things complement each other, and make the loco much easier to run.


Glenn

[Emfinger]

Got it
Thank you.
Tom

[Fred_V]

I face a similar situation with a high crown sheet and limited steam volume.
In my Build log there is a discussion of solutions builders have made:

http://www.chaski.org/homemachinist/vie ... 8&start=12

Look at the lower half of that page and beyond for some pictures and drawings of "water shedding" methods at the steam intake on the dome.
Hope this gives you some ideas.

I have yet to fully address priming with my new Mikado. I've been unable to get it on the tracks during the past year so it's only run about 1 mile total!
Almost a criminal situation.
Next year, however... Test, evaluate, resolve.
RussN

Russ, new boilers will often prime for awhile until all the oil gets out from rolling flues. Do a lot of blow downs and injector filling to flush it out.

[NP317]

FredV:
I agree on your New Boiler assessment. Multi washouts were done before first rail tests were made.
The boiler for my Mikado definitely has less steam room above the crown sheet (at least 1 inch less) compared to the Ed Perry-built boiler in my Ten Wheeler.
So I have s good comparison to deal with.

The Mikado boiler did not prime much, but it did exhibit sensitivity to water level (wet safety valve output) which the Ten Wheeler boiler does not.
This may primarily (joke...) be an issue of me learning how to fire it.
Like prototype locomotives, every one is different with it's own character.
RussN

[Kimball McGinley]

I believe boilers don't need "room for steam" since steam is released from the hot water to maintain pressure.

What is needed is enough height between the bubbles on top of the water and the throttle opening so that only steam goes to the cylinders. Full-size locos measure this distance in feet, us LS guys in a few inches at best...

And yes, make sure that new boiler is clean.

[Bill Shields]

look at a NYC Niagara boiler some time....if you want to see low overhead...

many of the ideas to 'keep water out of the dry pipe' really don't scale down well...

perforated baffles, stainless steel wool...and all that may help against a random droplet...but think about waves inside the boiler.

Water splashing around, rolling waves front to back cause a lot of carryover...and there is little you can do to prevent waves by way of anything inside the steam dome.

[NP317]

ASTEAMHEAD (on this discussion board) has a functional design for a steam intake in the dome that sheds water intake.
It uses the heavier water momentum to bypass the intake openings. Pretty smart design based on physics analysis.
He provided drawings on my Build log on the link I posted above.
I am considering this design as a solution if I can't resolve carryover in my Mikado boiler.
RussN

[Bill Shields]

full-size locos used a centrifugal separator...unfortunately it cannot be scaled down...but is something I have looked at long and hard before I just 'raised the dome'.

[Glenn Brooks]

I believe boilers don't need "room for steam" since steam is released from the hot water to maintain pressure.

What is needed is enough height between the bubbles on top of the water and the throttle opening so that only steam goes to the cylinders. Full-size locos measure this distance in feet, us LS guys in a few inches at best...

And yes, make sure that new boiler is clean.

Just had a fascinating discussion with a 1:1 railroad guy. He talked to a west coast railway shop manager about the steaming issues on my Ottaway. Consensus was do what Kimball said - try running with a full glass (nearly full boiler). This was the operating technique full size steam engineers commonly used in the old days. So I tried it on my loco, and was surprised it steamed better than with half boiler full. So learned something new. (Also used a lot more cut off than before)

Apparently the theory is with a full boiler, at operating pressure, the latent heat stays resident in the water until it’s needed, when you advance the throttle- then the top surface flashes into the steam once it contacts the dry area of the steam dome. When you open the throttle, the boiler water vaporizes fairly instantly on contact with the heated steam dome, and away you go.

Seemed to work for me, so will be doing some more extensive trials next week.

Only cravat - make sure you don’t suck water into the cylinder, or you risk Hydraulic lock and damage to the steam chest and cylinder.

Sounds like this means limited steam space in the boiler shouldn’t be a worry - except for drowning the dry pipe...

Glenn