Are you sucking or blowing on the system? If sucking, then try blowing as that will not introduce extra air in the gas. Next try to determine how dry your fuel is. It needs to be dry. If you think the spiral tubing is leaking, you might try aluminum furnace tape tightly wound arount the tubing.
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I have had decent luck with flex exhaust, but I checked with soapy water after installing and I used silicone RTV where it was clamped down. The first place it will leak seems to be at the mouths.
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Hi Wes , i have some large dia exhaust pipe coming out of the back of my pellet heater and i have a carbon monoxide meter right next to it and it reads zero , now thats not to say that all flex is as well sealed as this one i have , both answers above should work well for you if you start blowing air in from where your gas normally comes out and get a spray bottle with soapy water and start covering everything from the outlet pipe all the way back to the filter and the gasifier flexi pipe , in fact spray anywhere that there is a join or coupling if no water bubbles up then move onto the next thing , i would check the filter and make sure you are not over restricting the flow ,in fact i would remove the filter and try pulling gas straight from the pipe with your fan and see if that gets a flare .
Looking at the photo of your build you have a ash clean out at the bottom don’t forget to spray around there see if you get any bubbles you can always seal up leaks with the tape that Don mentioned or use high temp silicon .
Let us know how you get on and more photo’s would be great .
Good luck , Dave
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Good to hear that 2" flexible exhaust tubing isnt my worst choice, and that it can be completely sealed with foil hi temp tape. i plan on replacing the section from cyclone separator to cooling radiator with 2" flexible metal (plastic jacketed) with sealing fittings but might hold off until i leak check again. I did find a potential air leak in my burner tank; apparently the upper limit of red silicone is exceeded inside! My burner tube/air jet assembly is welded to a half 20# propane tank and drops into a round hole inside my burner tank, and i had sealed that drop-in unit with a bead of red silicone covered in foil to contact the bottom of my burner tube tank shell to the round hole in my burner tank. when i removed the burner tube assembly to change the orifice i noticed much of the silicone was now missing, burned, flaked off, etc. ive replaced that seal with a 1" dia fiberglass rope seal joined together to form a circle that the burner assembly will sit and press down on. this might have been a source of a large air leak. maybe i should spring load it to press the seal together along with the weight (about 40 lbs) of the burner assembly?
now a bit about burn pattern inside the tube; nice white dust from just below the air jets all the way to the bottom of my 4 to 3 cone restrictor at the bottom. (i just replaced the 4 to 3 cone with a 4 x 3 flat plate located where the top of the cone used to be. total distance from air jets to flat plate restrictor is about 4".(then another 4" to bot of burn tube, and another inch to shaker grate. about 2" ash clearance below.
a clue to having inlet air leaks is evidence of charred creosote with white tips @ exit of burn tank to cyclone.
i’d really not prefer to change from a vacuum ID system (as is now) to a pressure FD system because my ultimate goal is to run gas engine; engine vacuum being the source of pull for gases theu the system.
ive replaced my 40 gal cyclone with a 20# propane tank version. although the 40 gal was giving me nice cooling, i thought it was an awful lot of volume and would take a while before any adjustment in burn would reach the flare. in addition, was suspect of cleanout door gasket and welds. im hoping it will still provide some cooling.
ive got a cheap IR termp gun to measure temps at certain points, and was making fairly cool gas @ blower outlet. temp @ burner outlet before cyclone was around 350F.
gas produced has funny color; almost yellowish-green, and turns a propane torch flame from blue to yellow but never quite burns. im using a 6" stovepipe about 16" long with my 1" gas outlet hanging in the bottom of it. gas temp @ outlet is about 100F or so.
i plan to retest either later in the week or by weekend at latest after some more tweaking, and, of course, more leak test!
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Just for testing for air leaks blow through the system and spray as soon as you find where the leaks are showing up then seal and go back to sucking .
Dave
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yes now i understand; currently i put regulated compressed air to my blower outlet to leak check. found a big one yesterday between blower motor and mounting plate. factory spot welds. there was another on my filter box cover, i had duct taped the door edges but missed a spot near the hinges. im using an electrical enclosure with baffles to separate fiberglass insulation filter media inside. the auto exhaust flex hoses seemed leak free in the spiral, and i had siliconed the joints before clamping them. new fiberglass rope between burner housing and mounting plate shows some slow leakage, nothing like the other 2 i had found. new drain plug @ radiator bottom also, there was a couple inches of condensate in there. hope to have new smaller cyclone mounted & ready for this weekend’s test
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Still no light off but seems to burn properly. Bed of charcoal in tube after cool down and blower off. Is it necessary to achieve light off before trying an engine?
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We’ve now achieved lightoff @ flare tube. Flame is nearly invisible so im guessing cooling and filtering are working well. Maintained flame for about 40 mins using about 1CF of fuel (pallet wood 1/2 x 1/2 x 3). Latest revisions were better seal below burn tube ass’y, restricted air jets a little, sealed filter box leak, added swirl plate in flare tube. Not sure which change made the difference but we weren’t far off. Now to run something with it…
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