Liquid Petroleum gas

[Fred Graham]

Hi folks,

I'm what I believe you call a 'newbie' on this site so I hope I can get to grips with finding my way round. As a visitor I have already found a lot of interesting stuff so I was eager to 'get aboard'

My interest is steam and up till now has been 'straight running' boats but I have started trying to get into R/C. The straight running boats have almost invariably been run with boilers fired by parafin or petrol blowlamps, my own included. The more popular centre flue boilers typicaly available in the model market use mostly LPG. I have always thought that they would not provide enough steam to power larger engines especially as when demand for more gas causes the fuel tank to cool (even freeze) performance falls off.

I have been playing around with this problem and exchanged letters with Martin Ranson (who has written articles for Model Engineer and Model Boats) who uses a heat shunt to warm his fuel tanks. I have a series of articles by Peter Arnott, another M/Boats writer, who advocates using vaporising to avoid cans cooling and I have managed to utilise his idea and heat my centre flue boiler using avaporising coil. This means that neat liquid fuel is fed to the burner via a couple of coils of copper pipe round the entry to the centre flue. The system seems to work OK and I wondered if there are other users of this method with long experience with it who can advise me of any problems which I may encounter with this firing method. I noticed at Harrogate exhib. there was a boat which seemed to use this method but he was not available to chat.

There seems to be a lively steam fraternity on this site so I lookforward to comment, hopefully especially critical.

All the best, Fred Graham

[Dinosaursoupman]

Hello Fred,

I would like to welcome you to the site. I have absolutely no experience with steam but there are plenty members here who do.

One thing all of us particularly enjoy are pictures. You obviously already have a knowledge of steam vessels and your knowledge can help those of us with little or no experience. Posting pictures of your work and areas in question not only give a clearer idea of what is being discussed but helps to educate those of us who expect someday to try a steam powered vessel. Of course, pictures are not mandatory to post, but as they say, "they are worth a thousand words".

Anyhow, welcome and we look forward to hearing more from you,

Randy

[Fred Graham]

Hi Randy,

Nice to get a welcome so quickly. I'm no expert on steam (or anything else for that matter) but I spend quite a lot of time in my workshop playing with ideas and making stuff.

I agree about pictures but and still feeling my way here as I'm a very new newbie. I tried to put a picture on my post but I failed to manage it. I have also tried to put something on the site about what I'm interested in etc but am still looking for the 'register' icon so that I can do so. Ive sent an email to the admin guys to get clear how it's done and will add pics etc. when they educate me!

All the best and thanks for your response, Fred Graham

[Tug--Kenny]

Hi Fred.

Welcome to Paddleducks. It's nice to have a steam 'engineer' on board.
                     

Like Randy, I too would love to see any 'steam' pictures you might care to put up on here.  I am just thinking of getting into steam and know absolutely nothing about them, except that they do look graceful when on the water, and I do admire the workmanship involved.

Working 'this forum' board couldn't be easier. You'll soon be up and running. I'll leave the explanations to the experts.

All the best

ken

[Red_Hamish]

Hi there Fred, welcome aboard the frendliest Paddle baot site on the web. Anything you want to know about posting then just ask. To post photos try resizing a copy of the pic down to 640x480 and then when you have saved the smaller copy and know where the file is, simply either post a new topic or in the reply box there is a line called additional options "click" on that line and an option to post a pic appears if you want to add another one at the same time on the right of that line is another add more pics again click on that tag and another box will appear and add it there. Any more questions Fred or anyone then ask away

cheers

Jim 

[Dinosaursoupman]

Hello Fred,

As far as telling us about your interests; From the Main Menu in the upper left hand corner, click on the Forum button. Below the "Welcome" section is the "General" section. The first section of the "General" section is the "Introduce Yourself" section. Start a new topic there telling us all about yourself. And even if you get lost as to where to put a topic, the administrators can move it to the right section (although we try not to make a practice of this, as Eddy puts a lot of time in here as it is).

Now getting back to the topic; Although I have no experience in steam, I do however have years of experience in using propane. In my profession of waterproofing, I have to use it to liquefy the tar (pitch, asphalt, bitumen, whatever you call it in your neighborhood) to around 400 degrees Fahrenheit. The 100 lb./25 gallon tank I use sits upright. By law, there is an 80% valve in the outlet valve of the tank. This allows the tank to only be filled to 80% capacity, assuring that liquefied gas is never allowed into the gas-line and for heat expansion. The outlet valve is at the very top of the tank to allow only propane in a gaseous state to flow through the lines. I would have to assume that in steam modeling, similar practice would be implemented. You don't want liquid propane flowing through the lines as it is very unstable as it exits the burner and will only burn after it has vaporized.

It is common for ice to build up around my propane bottle, but this only occurs on humid, cold days when the bottle is below 10% full, and only to the level of the propane in the tank.

Now when you talk of using petrol, I assume you are talking about what we Yanks call gasoline, the stuff that costs so much to run our automobiles? I think it would be very dangerous to use in this capacity. Propane, if it were to leak and catch fire would simply explode, and depending on how much propane had escaped before said explosion, would be a strong indicator of how much and how far the shards of your vessel and it's machinery would fly. Bad enough in itself. But gasoline, on the other hand, would continue to burn everything it touches and is very difficult to put out especially if it's spreading out over the water where your vessel once stood. Now if you are not talking about gasoline, disregard everything I said in this paragraph.

Adding pictures is a snap. Next time you go to reply or start a new topic, look to the lower left corner of the comment box and "+ Additional Options..." is just outside the box. Click it and you'll see an "Attach" box with "Browse" at the other end. If you know the file, type it in, if you need to find it, hit browse.

Randy

[Fred Graham]

Hi folks,

I wasn't expecting such a response so quickly and thanks for making me feel welcome.

I have been messing about with LPG and the problem of cans cooling especially on cold days and the filling problem which seems difficult using the lighter filling valve. I am never sure that the tank is full. I have also discussed these issues on Model Boats Forum.

It would appear that a common solution is to provide a means of keeping the can warm by passing the exhaust steam through a pipe surrounding the can or using what has been described as a 'heat shunt' which takes the form of a copper strip connected to the can and the the back flange of the ceramic housing of the burner. The latter has been written up by Martin Ranson in Model Boats (July 2008) and we have corresponded together about his method which is apparently very reliable. Martin also described his method of filling which connects supply can and tank to be filled via valves with a venting valve to see when the tank is full. I have used this method and find it very reliable.

Another contributor, Mr Peter Arnott, proposed an LPG vaporising method which uses a fuel tank which has dual feed pipes to the burner. One pipe feeds gas in the usual way and this is used to start the firing of the boiler. As the burner heats up it conducts some heat to the entry end of the centre flue. By wrapping a couple of copper coils round the entry region and then to the jet, gas which is fed as liquid is vaporised and burns in the normal way.

I have tried this and it seems to work very well. I have a pressure gauge fitted in the supply line and the initial pressure with gas from the tank is typically 25 -35 psi. Once the gas has heated the burner, the second valve is opened and this feeds liquid fuel via the vaporising coil to the jet. the valve has a pipe which projects to the bottom of the tank and thus liquid is forced out of the tank by the gas expanding on the top of the tank. Since the gas is not using the ambient air to vaporise it the tank does not cool. The gas feed valve is now closed and the burner continues to burn without any change to the flame and the pressure remains the same on the gauge.

When Peter Arnott proposed this and described it in his article I was sceptical but I managed to locate a resarch chemist in Australia via the internet who advised me that the idea was sound and some high altitude camping stoves use vaporisors. The same guy does research papers for Coleman who are stove and gas suppliers. I have sent pictures of my arrangements to this guy and he assures me that so long as plumbing is sound and tank tested all should be well. My tank was hydraulically tested to 340 PSI and the plumbing is all bubble tested with soapy water.

I make no claim for originality in my tank/burner/boiler combination as it is a hybrid of ideas by Peter Arnott and Martin Ranson helped along by the research chemist but it seems to work well and in essence is comparable to the old fashioned Primus blowlamp arrangement.

Given the foregoing, I expect now to discover that this method is in common use and everyone is well aware of it. If this is so I will be pleased but I have had some difficulty finding other users who would tell me about it.

There is, however, much satisfaction in finding out for oneself.

My next steps are to try to understand the mysteries of radio control, batteries and chargers and how invisible forces make things move about under remote Conrail.

Incidentally I took a 'Steam long Weekend' trip to Scotland which included trips on Waverly and Sir Walter Scott. The Paddle engine on Waverly is a sight to behold.

All the best to all and thank again for the welcome.

Fred Graham

[kiwimodeller]

Fred, what we use from camping gas  cylinders is a Propane/Butane mix, not strictly what is marketed as Liquified Petroleum Gas (LPG) but it reacts the same. I deal with LPG at work and it gives the same problem. What happens is that if we draw gas off rapidly it drops the temperature and ices up the surface. The three ways to deal with this are to raise the temp as you have discussed or to reduce the draw off. My small steam boat has what is best described as a "lazy" burner that does not have to be roaring to give off enough heat and it runs fine on one cylinder with no heating. My large paddler on the other hand constantly used to ice up with a consequent gradual reduction in flame strength. The third method of solving the problem which is what we use at work is to join two cylinders together to double the surface area and so halve the rate of draw off from each one. Voila - no icing and it also doubles the run time. Of course you do need to have room in the boat for two cylinders and the sqat fat ones are better than tall small diameter ones. Hopefully there is a picture attached. Hope this helps, regards, Ian.

[Fred Graham]

Hi Ian,

Thanks for the idea, Startling glimpse of the obvious really when I engage brain but I'll need a bigger boat for that solution.

On reading my thread I see I've managed to duplicate my picture, doh!. I'll have another go and try to add the correct one on here

Meantime thanks again, Fred Graham