Flamefast CM350 update

Jun 29, 2008 7 Replies
C

This is just for the record. Some of you may remember that I bought an ex-school Flamefast CM350 furnace from Manchester. After passng through many hands in a transport process it arrived with me in Suffolk. The furnace was natural gas and I wanted to run it on propane. Flamefast supplied new jet for £24. However for anyone else doing this I've just meausred the two jets. Small holes are difficult to measure (for me, anyway) but the natural gas one is 0.090 mm and the propane one is 0.065mm.



Charles


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D

Charles, that sounds like very small holes indeed. When I knocked up my propane burner to run off 30 PSI, I ended up going with a 1.00 mm jet size. What gas pressure are you running?

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C

Flamefast reckon 35mBar - a hell of a lot less than 30psi

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So either yours is one big old burner that will melt iron and keep Gazprom's profits high or the Flamefast furnace is very efficient. Possibly something in the middle.

Charles

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D

LOL! I'll think of Chelsea buying another player every time I fire the burner up ;-)

I had a look at the flamefast link, it shows 29000 BTU/hr or about a quarter of the output of the burner here, but I'm still curious about the massive difference in jet sizes.

Here's a link to play with:

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Scroll down to "BTU calculator" and there's an excel spreadsheet you can download which works out BTU, jet size, flow, etc. If you key in your jet size (it's imperial so 0.065mm is about 2.5 thou) and even with 30 PSI, there's not a lot coming out....

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C

OK, so you've conclusively proved that I measured the hole wrongly! What I'll do is search for some wire that *just* fits in the jet and try again.

Charles

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C

Doh! It's imperial not metric

0.090" and 0.065" Why didn't I spot that a the jet wasn't thinner than a human hair!

Charles

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A

knocked up my

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efficient.

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My Flamefast ceramic chip forge uses a venturi to suck the gas through the jet. Forced air from a blower enters the venturi which ceates the negative pressure and sucks in the gas through a special demand valve. No blowing gives no gas so it's fail safe. However I would assume that this set up mucks up jet size calculations as the set gas pressure on the regulator is not the pressure difference that the jet sees. Maybe yours is similar?

AWEM

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D

Thank God for that, you had me scratching my head big time :-)

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