Propane Burner Arrangement

[electrosteam]

A good friend of mine is building a wooden steam launch of about 22 ft with a 3x4 inch cylinder and a propane fired water-tube boiler.
I am assisting with boiler set-up and commissioning.
The boiler has been fired twice, each time with some propane burner difficulties.

The burner system was purchased from a commercial gas supplier and it consists of a pressure reducer/regulator, isolating cock, safety valve, pilot burner with flame detector loss shut-down and a ball-valve gas regulator.
The kit is the same as that provided for use with wok cookers in asian restaurants.

The difficulties experienced centre on draft control.
The pilot cannot be reliably lit with the natural ambient temperature draft up the stack, a damper fixes that.
When the main burners ignite, the pilot is extinguished and, a few moments later, the system initiates a safety shut-down.

Initially, could the members of the forum point me towards related threads here and other resources that may be accessible, dealing with issues associated with propane burners in steam launches.
A bit of self-education will enable us to more correctly describe the particulars of this build.

Thank you all in advance for any comments or suggestions provided,
John.

[DetroiTug]

Sounds as though it needs a guard around the pilot to keep the flame on the thermocouple while the main burner is on. Some guarding or repositioning the pilot should fix that. Position the pilot so it's flame and thermocouple parallel the direction of the draft. If it's 90 degrees to it, the increased draft will pull it away. And consider using a larger orifice on the pilot for a larger flame.

-Ron

[fredrosse]

Ron has the right answers here, and try to use stainless steel for the shroud around the pilot, it will hast a long time. On cooking equipment the pilot is made as small as possible, to reduce standby losses when the burner might not be used for days or weeks. For a launch boiler, a pilot can be 100x this size, so it keeps steam up to a minimum, in addition to providing the same safety features. Hopefully the intensity of the pilot can be adjusted.

[electrosteam]

Fred and Ron,
Thanks for the responses.
The builder and I are planning to visit the burner supplier to discuss the situation and to investigate how to best install a larger pilot.
The builder is not concerned about gas usage by a larger pilot.

It seems to me that a stack damper is a 'good idea' to handle variable firing rates and assist at the initial pilot lighting.
Is this generally the case for propane fired boilers ?

I think the builder is reviewing the arrangement of the burner in the bottom of the firing casing.
Currently it is a major job to get the burner assembly out.
Is it generally better to have easy dismantling in this area ?

John.

[Lopez Mike]

Close off the stack and it will just blow fire out the firebox door. Control your fire with a valve in the propane line.

[electrosteam]

Some poor photos showing the latest build status.

The builder drilled the pilot valve out to 1 mm (thought to be about 0.3 mm before) and got a very large pilot as a result.
A pilot shield was added to direct one of the three pilot flames onto the temperature detector.
An adjustment on the safety valve reduced the pilot flame down to something manageable, and photo #37 shows the pilot in the burner chamber without any damper on the stack.

Photo #38 shows the main burners operating without any damper on the stack.
The pilot is dancing around due to the air turbulence, but not going out.

Photo #42 shows the gas safety valve.

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Thanks for all the comments, the builder and I are both learning at a fast rate.
John.