Propane fired Mikado

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Bmalone
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Propane fired Mikado

Post by Bmalone »

I was going to see if anyone had a suggestion on Propane. I have a Mikado I am firing on propane and when my tanks are full it steams great, but as the propane in the tanks (3, 20 lb tanks in parallel) drops, they start to freeze up. This then drops the preasure in the tank. I have to keep the burners at about 7 PSI to steam well. I have 28 burners and from my best calculations burn around 151,000 BTU's.

My thoughts are to switch to 2x 40 lb horizontal tanks but they are VERY expensive. Around $500.00 for 2. I have looked up the BTU's out of those tanks and it is about 190,000 BTU at around 70 deg. I have seen suggestions about sitting the tanks in water but not completely sure that will be possible.

Anyone have any suggestions?
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Brad Malone
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Harold_V
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Re: Propane fired Mikado

Post by Harold_V »

A couple copper coils for steam wrapped around the tanks may provide the required heat to prevent icing. Worth a try. With a valve to control the steam, should work well.

Harold
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Dick_Morris
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Re: Propane fired Mikado

Post by Dick_Morris »

Is there adequate air circulation around the tanks to let the air warm them? Could you put some form of finned, clamp-on heat sink to more effectively use the air to heat the tanks?
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Re: Propane fired Mikado

Post by ccvstmr »

Brad...you didn't say what kind of burners you were using...rose bud (slotted cap), slot burners, impingement jets or other. I've said before on this forum, I get real nervous when I hear people say they run with propane pressures in excess of 5 psi. Your 7 psi propane pressure seems extreme to me. There's gotta be something else causing your operating problems. A better description of your fuel/burner set up might provide insight for other readers to offer comment. Carl B.
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NP317
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Re: Propane fired Mikado

Post by NP317 »

I agree with Carl B's comments that your propane pressure is excessive.
I have propane burners in my Allen Ten Wheeler (LocoParts made, ~98,000 Btus), and first steamings required higher propane pressures at the burner than I liked. (They were around 3 psi.) I installed an angled stainless steel arch plate that was about 2/3 the length of the firebox, with 1/2" clearance on the side sheets. That seriously increased the propane combustion path (aft, up, and around), lowering the required burner pressure to 0.5 - 2 psi max. And I can make all the steam required to climb Train Mt.'s steepest grades and still pop the safeties.

My 90-ton 2-8-2 also has a similar arch plate installed. I've not yet had the opportunity to fire that boiler, but I expect similar success.
Food for thought.
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Re: Propane fired Mikado

Post by Bmalone »

There are 28 burners from Loco parts. I am going to replace the gas line under the tender from a 1/4" to a 3/8" line which should help drop the preasure a little.
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Re: Propane fired Mikado

Post by steamup »

There are more variables than what you are figuring. Find out what pressure the burners you bought are designed to run on.

For instance , a orifice made with a #70 drill bit will pass 5470 BTUH of propane at 14" WC pressure (1/2 psi). At 5 psi, the same hole will pass over 19,000 BTUH of propane or almost 4 times the propane.

You may be over firing the Loco and wasting propane. Improper air at over firing will result in incomplete combustion and fuel not producing the heat it should. If you are getting an acrid smell out of the stack, that is a sign of over firing.

Conversely, too much combustion air and fuel will be wasted heating needless air running through the firebox and won't be used making steam.

I found a chart on the internet that states at 60 deg. F., a 25% full 20 lb cylinder will vaporize 24,000 btuh of gas before frosting. Since the surface area of the liquid touching the tank is one of the main factors in calculating vaporization rate, I am guessing at your burn rate, any time the tanks dip below 50% at full burn you can get frosting on a cool day.

One trick to prolong your run time would be to fire up a cold engine on a separate set of tanks before setting off down the track.
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Re: Propane fired Mikado

Post by NP317 »

Where are you measuring the propane pressure? We should make sure we're talking the same language here.

On my locomotives, I first set the gauge on the tank regulator for about 12 psi, and then adjust the actual propane pressure/flow at the firing valve in the loco cab. I have a pressure gauge tapped into the propane line between the firing valve and the burners, and that's where I see the actual firing pressure.
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Re: Propane fired Mikado

Post by Bmalone »

The preasure at the regulator it about 12 PSI, but the line is about 7 PSI past the regulator. I changed the line under the tender today to a 3/8 line which has greatly reduced the back preasure so I will have to see next week what kind of effect that has.

The other thing I am considering is closing in the bottom of the fire box under the burners. Right now it is wide open but I am going to try to put a temporary plate in to see if I still get a good burn. With the plate there it will hold a lot more heat in the firebox.
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NP317
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Re: Propane fired Mikado

Post by NP317 »

Bmalone wrote:The preasure at the regulator it about 12 PSI, but the line is about 7 PSI past the regulator. I changed the line under the tender today to a 3/8 line which has greatly reduced the back preasure so I will have to see next week what kind of effect that has.

The other thing I am considering is closing in the bottom of the fire box under the burners. Right now it is wide open but I am going to try to put a temporary plate in to see if I still get a good burn. With the plate there it will hold a lot more heat in the firebox.
I first installed such a bottom baffle plate around the burners in my Ten WHeeler.
I ended up removing it due to insufficient combustion oxygen, based on the smell and stinging eyes from unburned propane!
I even tried running with the fire door open to admit addition air, but that did not solve the issue.
So I now run with an "open" firebox bottom, under the burner assembly.
Again, the arch plate provided the primary improvement in performance.
~RN
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shayloco
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Re: Propane fired Mikado

Post by shayloco »

Bmalone wrote:The other thing I am considering is closing in the bottom of the fire box under the burners. Right now it is wide open but I am going to try to put a temporary plate in to see if I still get a good burn. With the plate there it will hold a lot more heat in the firebox.
You have received good advice regarding the pressure at the burners being 3 psi or less. No more than that should be required. I agree completely on the use of an arch. When I added a baffle plate below the burners I created so much heat that I melted one of the burners. I have two locos that run with the bottom wide open and just the arch. No problems, no complaints, so I am going to keep it that way.
If you have multiple tanks and they are freezing then you are drawing propane too fast. I run just one 20 lb tank and do not have a problem with freeze up with 12 Locoparts burners. If you put in the arch you may find that is all you need.
-Larry
Bmalone
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Re: Propane fired Mikado

Post by Bmalone »

Thanks for all the advice. Unfortunately the way the boiler is made, getting into the firebox to add an arch is next to impossible. I am hoping the larger gas line will help, there is now much less back preasure on the line. All I will be able to do is work from the bottom of the engine, of through the firebox door.
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