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[Underpressure]

Here's one for you guys, and before anyone gets into tanks freezing up and such, I have been running steam plants in model boats since 1990 and have NEVER had a gas tank or gas feed pipe FREEZE. Cold yes, freeze no.

So, to the question. I am currently (slowly) building a Mountfleet River Queen, into which I am installing a little SVS plant. Layout dictates that the gas tank is going to be in front of the boiler (towards the bow) and the burner is at the back of the boiler (near the stern). I have a choice of three possible pipe runs to get the gas to the burner: 1) Under the boiler. (2) Alongside the boiler (3) Over the top of the boiler. All of these could impart some heat / warmth to the gas pipe, depending how close I run the pipe to the boiler, but which will be the most beneficial and are any likely to be detrimental, causing the gas to vaporize and possibly lock?

Your thoughts please gentlemen.

Neil

[Bunkerbarge]

I don't ever actually remember seeing any comments about tanks freezing, I think you would have problems long before that happens.

However tanks cooling enough to affect the saturation vapour pressure and hence the burner performance, I've seen that happen.

Just a thought and no more, one concern with the under the boiler route I would have would be that I wouldn't be able to see the pipe to inspect it's condition.

[Underpressure]

BB, good point about the pipe.

I have suffered plenty of occasions of tank / pipe cooling. The easiest fix for that is just to the turn the gas down a little, as the slower the flow of liquid, the less the cooling effect. I only mentioned freezing as I have seen it mentioned a couple of times recently on different threads and I wanted to avoid yet another outbreak of over emphasis. 

Neil

[Bunkerbarge]

Completely agree Neil.

Something else I thought of earlier was accessibility of the rest of the plant so going over the top of the boiler may be restrictive. 

I have a Pintail set up with the gas tank quite close to the burner at the front and the pipe and tank do get noticably warm when in use.  I'm just wondering whether the heat going into the pipe from the burner may be more than the pipe can pick up radiated from the boiler so it may be the better option to lag the pipe and reply on conduction along it.  Only experimentation will help I'm afraid but it's an idea.

[derekwarner]

Neil-BB.....I posted in a different thread on Mayhem a few days ago displaying my wooden planked insulation to my gas tank.....but acknowledging with the higher temperatures in OZ & we insulate for the opposite reason ....to keep the tank cooler  

However in colder [UK] temperatures, it is the 70/30% butane/propane mix changing from a liquid state to a gaseous state & the resultant endothermic reaction which draws heat from the atmosphere & results in the "icing" of the tank externals & to a lessor extent the gas line to the burner [the only critical internal icing point is the orifice in the needle valve at the gas tank discharge]

In Paddleducks we have spoken   about the combined gas equation P1V1/T1= P2V2/T2....in this case it is the minimisation in the ratio between T1 > T2 that we are attempting to achieve  

So I agree...insulate both the gas tank & lag the gas line ...cosmetically a bonus too  

I do note that the respected modeler Bernhard uses a form of steam coiled heating around the OD of the gas tank for the same purpose   - Derek