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[SailorGreg]

After the maiden voyage of my steam launch I have attempted another couple of runs.  Although the boiler builds pressure OK when the burner is lit, as soon as I start to run the boat the pressure starts to drop and keeps dropping until everything grinds to a halt.   

First, there are no obvious steam leaks.  Plenty of gas in the tank and water in the boiler.  There are two reasons that I have come up with that might be causing the pressure drop.  Perhaps the gas jet is partially blocked, or the top-up water is cooling the water in the boiler faster than the burner can heat it.  I took the gas jet out today and as far as I can see it is clear (a bright light shines through the hole) but I have nothing thin enough to poke through the hole to check.  Should I clean it in acetone or something similar?  Regarding the top-up water, this goes through a heating loop in the chimney before going into the boiler, but it is still possible I am cooling the boiler too much.  I still need to experiment a bit more with the by-pass valve to get the flow right, but I am not increasing the volume of water in the boiler, so I am only feeding water in at the same rate it is being used, if that.

Is this a problem others have had, and if so what was the solution, or can anyone suggest something I haven't thought of?  All suggestions welcome.  Thanks in advance.

Greg

[Jerry C]

Greg.
Ref feed water, feel the clack valve when running and pumping if it's cold you need more turns on the heating coil. If it burns you it's ok.
Ref burner jet. I bought a set of three Rolson wire brushes (tooth brush size). A wire from the brass one fits the jet. I've done it for 2 years with no probs. If that doesn't improve things then your using too much steam. What size and pitch is the prop?
One further check. Look at the flame through the slot in the burner. Does the flame change when the engine starts. Sometimes the exhaust steam alters the draft at the burner. I had that so removed the exhaust from the chimney and used an external pipe.
Jerry.

[kiwimodeller]

Greg, why do you need the feed pump working on these early sorting runs? As long as the runs are relatively short you should be able to do them on the water in the boiler. With the pump disconnected you have immediately eliminated the top up water temperature as a posible cause of the problem. Cheers, Ian.

[SailorGreg]

Thanks for the responses guys.  Ian, you are quite right, I don't need the pump working as I get used to the boat and engine.  The only reason I can give is that when I did a full scale run of the whole system ashore before the maiden voyage I used the pump to top up the boiler and pressure stayed up.  Of course, I wasn't actually loading the engine, and that might make all the difference.  The steam plant is out of the boat at the moment, but my first run when everything is back together will be without any water being pumped into the boiler.  Likewise Jerry, I can't check the clack valve at the moment, but once I have a couple of successful runs without pumping water I will try again with the pump to see if the valve is hot.

And Jerry - are these the brushes you mean?

Thanks again.  Onwards and upwards!   

Greg

[Jerry C]

Greg, yes, those are they.
Jerry.

[southsteyne2]

I think Jerry is on the right track to your problem , that is not enough heat from the burner as I have pumped cold water into my boiler 4" x 8" horizontal return flu for years now and makes very little difference  to the pressure running 30 - 40 psi .I have considered preheating the feed water to get a bit more punch but too many projects on the go ,I also use the stainless gauze burner purchased from clevedon steam and propane from camp bottle hope this is helpful
Cheers
John

[Landlocked]

Greg,


Sounds like the problems I had this summer as I started sorting my system out. 


I used the "suck on the supply end of the jet" clearing method.  Haven't choked myself yet but only do it when the system has cooled down.    I'm planning on getting some spares for hot swap outs.


If you have your bypass valve fairly open, you'll just recycle the water back to the feed tank.  That's what I did on my first couple of steam ups.  I was concerned with wear on the feedpump internals if I ran it dry with no water moving through it.


Good luck,


Ken