# Fuel Pressure in Gauge 1 Loco's -- Test Results



## xo18thfa (Jan 2, 2008)

During recent construction of a Gauge 1 live steam locomotive, I fabricated my first butane fuel tank. Since butane containers are pressure vessels, I decided to pressure test the fuel tank the same as a copper boiler by pressurizing to twice the maximum operating pressure. I found two charts on the Internet that show the vapor pressures of butane-propane mixes based on temperature. From these I could determine the test pressure for the fuel tank.


The first chart comes from EngineeringToolBox.com. The second comes from Algas-SDI Comapny in Seattle, makers of natural gas equipment for utilities. 


The data shows that a mix of 70% butane/30% propane, which is common camp stove fuel, produces 93 PSI pressure at 110 degrees F. I used a pressure of 200 PSI to test the fabricated tank. The test was successful.


To verify the scientific data I did an experiment with the fuel tank to measure the actual pressure in the tank. I conducted the experiment with two different fuels: Coleman brand camp stove fuel and Ronson brand "Ultra Butane", both off-the-shelf from Walmart.












This is the test set-up. 












The fuel tank is a three-inch length of medium wall copper plumbing pipe, one-inch nominal diameter (1.125" OD, 1.025" ID). The end plates are 1/8" thick copper plate. Bushings for the fill adapter and gas valve are bronze. Silver solder construction throughout. The tank’s capacity is 35ml. The pressure gauge is 0-160 PSI. The valve to the left of the gauge is to release fuel after the test is over.


The test started by chilling the tank in ice water and filling with fuel in the usual fashion. The test set-up was placed in a pan of ice water and into the freezer for the first measurement at 30 degrees F. Thereafter, ice was removed from the pan and replaced with warm water. Pressure readings were taken at 10 degree F intervals to 120 degrees F. Each temperature was maintained for 15 minutes before reading the pressure to ensure the fuel was chilled/warmed throughout.


These are the pressure gauge readings:












And here is how the pressures charted out












Conclusion: The measurements I took are very consistent with the scientific data. A test pressure of 200 PSI on a fabricated fuel tank would be sufficient for operating temperatures up to 110 degrees F.


I always thought that Ronson/Zippo lighter fuel was pure butane. It does not appear to be. The test showed it might be a mix of 80% butane and 20% propane. Coleman fuel appears to be 70% butane and 30% propane as advertised.


I also did a very abbreviated test on these two brands of fuel I got at a "Chinatown" grocery store.









The pressures indicate they are probaby 70/30 mix as well.


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## Steve Shyvers (Jan 2, 2008)

Bob, 

Your report is very nicely done and provides useful data. Interesting that one could use this type of test to estimate probable fuel mixtures. Have you gathered any data to determine typical fuel tank temperatures in operating locomotives? 

Steve


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## Mike O (Jan 2, 2008)

Bob, 

that is useful information. Thanks for doing the actual tests and posting both the data and test results. 

Mike


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## Two Blocked (Feb 22, 2008)

Please see http://www.southernsteamtrains.com/notes/bestfuelgas.htm for more information. At the Summer Steamup (Sacramento) I demonstrated a homemade gas pressure sampling gauge/device that was simply made from a Bunton liquid butane decanter device (available in camping stores) that was mated to a 0-100 psig Accucraft steam pressure gauge. It works well to check the pressure of any screw-on type butane container and readily shows the difference in vapor pressures between brands and their proprietary liquid fuel mixtures. During a show-n-tell I measured the ambient pressure of a "Snow Peak" brand container (with no stated liquid fuel mixture percentage) at 80 psig and then rapidly discharged a small portion of its contents. The container cooled as it vented, and the internal pressure dropped to 29 psig in a heartbeat. The Accucraft gauge may be accurately calibrated, but it is not traceable, and so I think that the relative numbers are instructional, but not not absolute. There is one thing in our gauge one hobby that is absolute, and that is this: if you don't have at least 30 psig in your locomotive's butane fuel tank upon trying to light off your small scale steamer, you will have one hard time doing it successfully. Because at any lower pressure you will not be able to entrain sufficient combustion air through the burner's mixer to support a reliable flame. Butane tank pressure, even during the run, is the key to good performance.


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## Jerry Barnes (Jan 2, 2008)

Very interesting, especially about the oriental cans. Thanks!


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## Charles (Jan 2, 2008)

Posted By Two Blocked on 28 Aug 2010 04:15 PM 
Please see http://www.southernsteamtrains.com/notes/bestfuelgas.htm for more information. At the Summer Steamup (Sacramento) I demonstrated a homemade gas pressure sampling gauge/device that was simply made from a Bunton liquid butane decanter device (available in camping stores) that was mated to a 0-100 psig Accucraft steam pressure gauge. It works well to check the pressure of any screw-on type butane container and readily shows the difference in vapor pressures between brands and their proprietary liquid fuel mixtures. During a show-n-tell I measured the ambient pressure of a "Snow Peak" brand container (with no stated liquid fuel mixture percentage) at 80 psig and then rapidly discharged a small portion of its contents. The container cooled as it vented, and the internal pressure dropped to 29 psig in a heartbeat. The Accucraft gauge may be accurately calibrated, but it is not traceable, and so I think that the relative numbers are instructional, but not not absolute. There is one thing in our gauge one hobby that is absolute, and that is this: if you don't have at least 30 psig in your locomotive's butane fuel tank upon trying to light off your small scale steamer, you will have one hard time doing it successfully. Because at any lower pressure you will not be able to entrain sufficient combustion air through the burner's mixer to support a reliable flame. Butane tank pressure, even during the run, is the key to good performance. 
Kevin
Once again you offer fellow live steam hobbyists a key insight to make a successful steamup. Ryan and I found the workshop you gave at NSS very valuable and time well spent in better understanding the fundamentals of butane firing. Hopefully, Bing will apply the lessons learned from the insights your shared.


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## xo18thfa (Jan 2, 2008)

Posted By Steve Shyvers on 27 Aug 2010 10:23 PM 
Bob, 

Your report is very nicely done and provides useful data. Interesting that one could use this type of test to estimate probable fuel mixtures. Have you gathered any data to determine typical fuel tank temperatures in operating locomotives? 

Steve 


Hi Steve. No, I have not. Temps would be interesting to see. In fact, it might be a worthwhile experiment to see how temperatures and pressures drop while the burner is running. Maybe weight the tank at the start, time the burn, weight it at the end, come up with a rate of discharge. Monitor temp and pressure throughout.

Maybe it's time to make a more versitile test tank.


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## xo18thfa (Jan 2, 2008)

Posted By Two Blocked on 28 Aug 2010 04:15 PM 
.
.
.
. There is one thing in our gauge one hobby that is absolute, and that is this: if you don't have at least 30 psig in your locomotive's butane fuel tank upon trying to light off your small scale steamer, you will have one hard time doing it successfully. Because at any lower pressure you will not be able to entrain sufficient combustion air through the burner's mixer to support a reliable flame. Butane tank pressure, even during the run, is the key to good performance. 


I wonder what happens if there is secondary air. All the commercial models draw all air thru the mixer holes.


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## David BaileyK27 (Jan 2, 2008)

When developing our Gas Pressure Regulating valve I also set up a similar test, with a pressure gauge on the tank, I got similar pressures for Butane and Butane/Propane mix when filling the tank.
Our regulator will deliver a constant pressure of 8 PSI at the burner and I found that the burner will still light with only 10PSI in the tank, this is with a Ceramic burner, our valve will not work with a Poker type burner, so I have no data for that type of burner.
David Bailey http://www.djbengineering.co.uk/


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## jfrank (Jan 2, 2008)

Bob, I use the Korean gas cans like the Gas One you have a pic of. Everytime I buy another case the can is a different color and name, but they all say butane and all are made in Korea. I also occasionally use the Primus(get this at Diamondhead) or Brunton Isobutane mix. I have noticed a substantial difference in pressure using the Isobutane mix vs the Korean butane cans. I can actually just hear the difference in the burner noise and the engine heats up quicker and runs hotter. So there is a difference. I have never had a problem with any of them as far as jet clogging or excess pressure. However, there was a post on here some time back where this guy on a cold winter day, fueled his engine in the kitchen then poured boiling hot water over the fuel tank in the tender and took his time taking the engine out to the track. When he got it out there he discovered the fuel tank had split. My K27 engine has a safety valve on the fuel tank. It did blow off one really hot day when I delayed in getting the engine running as the hot sun was directly effecting the fuel tank. Now days I always vent the tanks immediately after fueling(by depressing the filler valve) until there is no liquid coming out of the filler valve. It's a trick that Dave Hottman taught me.


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## xo18thfa (Jan 2, 2008)

Hi Frank. While doing the fuel pressure experiment, I tried to do some research on butane to see what this mixes are. The manufactures don't publish the mixes. Coleman used to print it on the can, but the last one I got did not have it. I use the imports fuels mostly. Whatever they put in them works.

Safety valve on a fuel tank. That's a good idea. Our June and September runs here get very hot. I might incorporate that in the next tank. And a stay too for extra strength.

Bob


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## SteveC (Jan 2, 2008)

I know this is most likely a really dumb question, but just how would a safety valve on the fuel tank be a good idea? Wouldn't you be releasing a cloud of flammable gas into the air in close proximity to an already ignited burner?


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## xo18thfa (Jan 2, 2008)

I am often prone to dumb comments.


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## xo18thfa (Jan 2, 2008)

I was thinking in terms of the tank sitting in the sun, burner off.


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## Semper Vaporo (Jan 2, 2008)

Posted By SteveC on 04 Dec 2010 01:45 PM 
I know this is most likely a really dumb question, but just how would a safety valve on the fuel tank be a good idea? Wouldn't you be releasing a cloud of flammable gas into the air in close proximity to an already ignited burner?



A controlled release of gas through a safety valve might produce a flame like a cigaretter lighter produces... maybe a bit longer, depending on the actual pressure behind it. But a catastrophic failure of a seam (most likely failure point) or a bushing (2nd most likely) or a split in the base metal (least likely) would be a ball of fire, being spread by a liquid vaporizing as it flowed.

Besides, at a certain level of dispersment the gas cloud would not be able to generate and maintain a flame. It only burns in a certain limited (yet wide) set of concentration levels. Too heavy (liquid) and there is not enough oxygen to support rapid combustion and too thin and there is not enough fuel to spread the combustion to more fuel. In between those extremes, too little oxygen and too little fuel, and you have a roiling fire ball. Somewhere I have a lovely photo of a friend experiencing a smokebox full of gas released as a fireball toward his face... Not sure if it singed his eyebrows but it certainly did surprize him! If I can find it _and get his permission_ I will post it.


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## SteveC (Jan 2, 2008)

*Bob:*
I didn't mean my comment/question as a negative on your idea, just trying to understand. There's a great deal that I don't know.









*CT:*
Yes I understand that a controlled release would be semi-preferable to a catastrophic failure.

However, the first question that bubbled up when I considered the proposed idea was, if this is such a good idea then why is it that as far as I know (granted my experience and knowledge is very limited) there isn't one of the commercial manufacturers of live steam locomotives that provide this feature on their fuel tanks. You'd think that considering their natural sensitivity to safety and liability, if it were a viable idea then it would seem to me to be a very common feature.


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## xo18thfa (Jan 2, 2008)

Posted By SteveC on 04 Dec 2010 05:04 PM 
*Bob:*
I didn't mean my comment/question as a negative on your idea, just trying to understand. There's a great deal that I don't know.









*CT:*
Yes I understand that a controlled release would be semi-preferable to a catastrophic failure.

However, the first question that bubbled up when I considered the proposed idea was, if this is such a good idea then why is it that as far as I know (granted my experience and knowledge is very limited) there isn't one of the commercial manufacturers of live steam locomotives that provide this feature on their fuel tanks. You'd think that considering their natural sensitivity to safety and liability, if it were a viable idea then it would seem to me to be a very common feature.



In my glee I failed to remember that burning gas could be near by. Steve, I am so thankful you keep me straight.


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## Michael Glavin (Jan 2, 2009)

Temperature-pressure relief safety valves are mandatory on ALL propane BBQ type tanks and the like. Generally they are spring loaded and re-set after discharge, smaller disposable tanks use soft plugs if I recall. Since the need is recognized herein, perhaps its a consideration that has some merit with our low pressure butane fired toys... 

Michael


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## SteveC (Jan 2, 2008)

Right you are Michael.

After digging a bit further, even the common ubiquitous disposable propane torch/camp stove type cylinders have spring loaded safety pressure relief valves in addition to their fill/use valves. Just goes to prove once again (in my case at least) the old adage '_familiarity breeds contempt_.' Makes one wonder why there's seemingly no requirement on gas fired live steam device fuel tanks, simple oversight or maybe volume related... ????


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## Michael Glavin (Jan 2, 2009)

I suspect the lack thereof TPRV (temperature pressure relief valve) of our model trains is relative to the diminutive volume and operating pressure herein, 100% Butane @ 100*F is about 38 psi while propane is 178psi… 

John F suggested his K27 had a relief valve on the fuel tank? 

As I recall my AML 0-6-0 has no relief valve nor does my Accucraft GS4. BUT I don’t have them in front of me presently. Perhaps the fill valve doubles or works as a relief valve… 

Michael


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## jfrank (Jan 2, 2008)

The only safety valve on locomotive fuel tanks I know of was the first run of the Accucraft K27's. Mine is serial number 11 and has the safety valve.


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## Semper Vaporo (Jan 2, 2008)

Posted By SteveC on 05 Dec 2010 05:04 AM 
Right you are Michael.

After digging a bit further, even the common ubiquitous disposable propane torch/camp stove type cylinders have spring loaded safety pressure relief valves in addition to their fill/use valves. Just goes to prove once again (in my case at least) the old adage '_familiarity breeds contempt_.' Makes one wonder why there's seemingly no requirement on gas fired live steam device fuel tanks, simple oversight or maybe volume related... ????


















I don't believe those are "Safety" valves... those look like a large "Schrader" valve for filling only (just like on your automobile or bike tires). They seal tigher when the pressure is increased on the inside, and do not let gas/air flow in the opposite direction.

That cap just at the top of the pin shape on the end opposite the threads (reddish on the one on the right in the image) covers the opening completely and only pressure on the nailhead (on the threaded end of the body) will push the cap off the seat. The blue band around the middle is the seal where the body meets the bushing the valve screws into.

(I don't know what the black "O"-ring is for nor where it goes.)


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## Charles (Jan 2, 2008)

Posted By SteveC on 04 Dec 2010 01:45 PM 
I know this is most likely a really dumb question, but just how would a safety valve on the fuel tank be a good idea? Wouldn't you be releasing a cloud of flammable gas into the air in close proximity to an already ignited burner?

SteveC
As per the experience at the NSS with the Aster C62. Ryan had filled the tank and then went about his business to prepared the engine for a steam up. As he went to light the engine there was a huge flash due to the venting of the safety valve (no indicator at the time). At the same time Ryan was lucky though his was head first in the cab/tender area looking at the lit flame in the boiler he only lost all his facial hair (thus not having to shave). We still cannot figure out why the gas tank vented but thankful no serious inquiry (e.g. eyes).


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## Dr Rivet (Jan 5, 2008)

Michael 

I know my K-27 had a relief valve because I caused it to go off ONCE by putting warm water in the tender on a day when it was about 40 degrees F. If your flame is in the burner where it belongs, there is not much hazard from that engine. But if there had been an alcohol fired locomotive close by there MIGHT have been a minor "flash fire". This is why only the careless refill their gas fuel tanks on the track while alcohol burner are zipping by. The late Rick Runyon demonstrated that with a GS-4 one night during a Diamondhead meet many years ago. Some risk.. yes. High risk.. probably not. 

Regards


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## SCSteamer (Jul 24, 2009)

The Aster Climax butane tank has a relief valve. I'd much prefer a valve venting than a split tank.


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## Two Blocked (Feb 22, 2008)

Catastrophic failure? Has any one of you ever seen, first person, a catastrophically failed, either brass or copper with silver filler brazed joints, gauge one sized pressure vessel, be it round, square, or some other odd shape? If so, I have a bottle of Laphroaig Single Malt that I would willingly exchange for a couple of clear JPGs of the wounded puppy along with a clearly written "diary" of how it all came to be. Actually I'm thinking that all this talk of "catastrophic failure" is the result of active 45mm live steaming being put on hold by the very cold winter weather [29F in Lakeland Florida last night!!!], and the ensuing retreat to the BarkerLounger, accompanied by an adult beverage or two, that then leads to the doomsday hous-abouts that I just read. You know the line about "idle hands are the devil's workshop" and such? I think that it applies to idle minds too. 
All the information about butane gas pressures derived from different fuel mixtures have been in the public domain for over ten years, and this information is still posted at southernsteamtrains.com under the heading "Notes From Unit Shop"; "What Fuel Should I use in my Small Scale Live Steamer". In the ensuing years Boyle's laws of gas physics have not changed, and so the data is still current. 
Over the years I have tested a good number of small scale live steamer boilers and fuel tanks to destruction. Some were brass and some were copper and one was monel [Russian manufacture] , and none, repeat, none, failed catastrophically. What they did do was to distort their original shape and try to make themselves into some kind of equally radius-ed shape on the way to becoming a sphere. Somewhere in this high pressure morphing process one of the silver filler-ed braze joints would [and still will] fail with a whimper of a water leak [hydrostatic test always] and the test is finished. Upon inspection the failed joint always revealed that the "parent materiel" [brass, copper, and monel] tore away from the silver filled eutectic joint. This makes worlds of sense because the parent materials were all annealed to their butter soft state during the brazing operations that fabricated them, and their tensile strengths were at all time lows depending on their original alloys while the silver based filler materiel retained all of its original mechanical properties. 
I built many of the original Cricket boilers and I tested two of them to failure just because. All two boilers failed in the 180 psig to 200 psig range by one tube sheet tearing away from the boiler shell at one end or the other. The size of the failure was never more than a .100" tear right at the braze line just at the edge of the eutectic joint in the copper parent materiel. I repaired the tested boilers and re tested them to 100 psig before sending them off to Mike O'Rourke for final assembly. Mike has never had a cricket boiler fail [leak] in service. Well ........ there was the one time when the owner tried to drill through the "smokebox" in order to mount a headlight! He found that that particular boiler was an early "L" flued type that featured a wet front end! Mike felt sorry for the guy, and fixed him up for gratis. 
Early butane fired Aster locomotives did indeed have gas pressure relief devices on their gas tanks. As I remember [it was a long time ago] my Big Boy's device was a fractured diaphragm type that just sat there like a bump on a log until some unknown internal gas pressure would be reached. At that point a frangible disk in the device would rupture, and the whole one pound of liquid butane in the gas tank would burst into the atmosphere in one, uncontrolled, eruption! Not a good idea. I replaced it with a two step venting valve that allowed me to only load a half a pound of fuel, or the full pound if I chose to. This was back in my running with propane [120 psig @ 70F] phase. Yes, I actually did run BB, using the stock Aster built fuel tank, on propane. No, vessel pressure was not a problem, but decanting the liquid propane into the tender tank was a PITA. Since then I only use fortified butane liquid for BB operation 
A last note. I have first observed, and then intentionally tested, butane gas filler valves [Ronson type] as pressure relief devices. Yes, definitely, a Ronson type gas filler valve will relieve excess gas tank pressure, but at very low relief flow rates. This phenomena is not a design feature of the valve, but under sufficient excess pressure the valve will back flow to the atmosphere. This venting most commonly happens when a gas tank is filled beyond 15% of it's total cold capacity, and then as the cab mounted gas tank heats up, the butane fuel expands in liquid volume and creates a hydrostatic lock in the tank. At this point the Ronson valve will relieve the tank's internal pressure by releasing boiling liquid butane to the loco's cab interior. Usually there is no fire or explosion, but the boiling liquid/gas will alter the air mixture being drawn into the burner's mixing body and thus extinguish the burner.


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## xo18thfa (Jan 2, 2008)

I reiterate that the main purpose of my test was to confirm that 200 PSI is adquate to test a fuel tank. To do that I wanted to measure the tank pressure at temperature intervals and compare the results to published data. I am satisfied, for my purposes, that 200 PSI is a good test value.

Having said that, gas fuel tanks and boilers are pressure vessels. Therefore respect them and the operation of the engine in general.


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