Puff back spring tension strength

Hi Guys!
Just curious how strong puff back springs should be. I have a valve spring on my lid, but shaved a lot of metal off to reduce the tension. Any thoughts as to spring tension in terms of pounds of force?

This is my first build. How loud are these puff backs typically on a typical gasifier?

Just enough tension to keep it from smoking right after shutdown I’d say. I’m using the springs that hold brake shoes against the backing plate. The less spring you have and the bigger the opening the quitter it will be.


I use Jeep CJ hood latches, McMaster P/N#1344A21:

and have never had a failure even on my propane tank machine.



I’m with Marvin .

Just enough to keep it from smoking .

I use screen door springs cut in half . . ( one spring cut so it will make two ) Total of 8 halves .

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not a lot… I use an electric fence gate handle thingy… just enough spring to keep some tension on it… but thats all

Should the hay filter or heat exchanger have any springs, AND my hopper door is 15" and hopper is 24"square,And 18" Tall,is the door enough opening for fuff back.THE hopper is getting built today,the metal is cut.ITS TIME TOO BBB STEEL.THANKS

I forgot the second question. My worst “sneeze” on a gasifier would rival a 12ga shotgun going off. The Victorias typically “Phfft!” instead of bang(!)


Hello Kevin .

Several years back ( 2008 ) I used a puff lid on the heat exchanger but it caused problems and I discontinued

No puff lids on hay filter or heat exchanger now .

Nice! My neighbors will love that ; )

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Any changes in your gas production with these changes?

These look strong. Interesting.

I’m going the light tension seal route.

Ill echo what is said, you want just enough to create a seal during shut down. If you have no leaks the vacuum under operation will pull those lids shut.

I use a puff back on all hoppers and also at my media filter. The spring tension is enough to initiate the seal and maintain it during shut down.

Ive had puff backs that have destroyed lids on the media filters. A puff back or flash back is really dependant on volatility of the gas and how well the oxygen is mixed.

To prevent hopper flashbacks during shut down. Cap off the intake to your gasifier first before relieving a vacuum. What happens is when you relieve the vacuum on the system the hopper pulls back the gases. If your intake is open then the O gets sucked into the hearth and mixed with the ready made high volatile gas. This all mixed up in the high temp in your hearth can cause your puff backs. I have never had a puff when shut down this way. I hope this helps.


Thanks Wayne on the testing,i thought it might be too hard to reseal on puff back on the move,I am welding angle iron around my hopper outer and around the car rim seal areas top side.and some center braceing, i may need one more scales too weigh it,should be good traction for winter time any way.

HI STEPHEN A, I had one of them on my first gasifier that tom C was helping on, Then he said couldent beat DOW plans, so i went ahead and got the have wood will travel BOOK and internet support,I was fiddeling with empty hot hoppers with lid off and on,when char hit fan.I was surprized how little ashh made it out, with no puffback door,just a snug fit lid that poped off.Even then it was mostly ,starteling ,and smoke, as i could not find any hot char .

HI matt ,i dont understand what you mean by releiveing a vacuem,i know how too shut off incomeing air.and some gassers are venting the hopper at shut down too releive back psi.or is that what you meant.

The spring tension should be relative to the lid size. for example a drum lid would be about 380 square inches. So for example if the total spring tension was 10 pounds you would pop off at .026 pounds per square inch. Now if you were relying on a tennis ball valve on a 2" coupler. you have only 3 square inches and would need a spring of only .078 pound tension for the same release.
NOW, the question I have about this is the size of pop off valve needed to accommodate the volume of escaping gasses.

I use an 1840 vintage carriage seat spring for my puff lid …I have home made turnbuckles to adjust the tension on the ends … I caught a blast in the face while I was poking through the restriction the other day … Didn’t lose any hair … current gasifier is on the studebaker right now … I’ll try to post a video or pictures in a bit … Mike … puff is something you learn … too many factors to figure in …

Boy, It’s taking me a while to use this linux along with Steve U’s defective computer :o) … Look at it wrong and it types all kinds of extra stuff even when you have your hands behind your head … Hope the 2 pictures go through … Thanks for the camera Jeff !!! Mike

Ha! Ha! Just goes to show “that no good deed goes unpunished”
Mike I gave it to you so’s you could have the satisfaction of slamming it up against a brick wall. High blood pressure relief!
I’d hoped that wiping off the Windows system and all of thats collected spam and spyware would cure it. Not it seems. Seems to be a ahrdware issue.
Just junk it out anytime as a freebie with no regrets Mike.
I’ll cheer.

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