>> This is just for the record.
>> Some of you may remember that I bought an ex-school Flamefast CM350
[quoted text clipped - 9 lines]
>propane burner to run off 30 PSI, I ended up going with a 1.00 mm jet
>size. What gas pressure are you running?
>> 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?
> Flamefast reckon 35mBar - a hell of a lot less than 30psi
> http://www.flamefast.co.uk/heat-treatment/crucible-furnaces-cm350.html
>
> 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.
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: http://ronreil.abana.org/design2.shtml#BTU
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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Duncan Munro
http://www.m0kgk.co.uk/
Charles Ping - 29 Jun 2008 17:25 GMT
>>> 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
[quoted text clipped - 20 lines]
>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....
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
Charles Ping - 29 Jun 2008 18:49 GMT
>>>> 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
[quoted text clipped - 26 lines]
>
>Charles
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
Andrew Mawson - 29 Jun 2008 19:19 GMT
> >>>> 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?
> >>
> >>> Flamefast reckon 35mBar - a hell of a lot less than 30psi
http://www.flamefast.co.uk/heat-treatment/crucible-furnaces-cm350.html
> >>> 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.
[quoted text clipped - 26 lines]
>
> Charles
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
Charles Ping - 30 Jun 2008 09:48 GMT
>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
[quoted text clipped - 5 lines]
>
>AWEM
Andrew
The CM350 is self blown (no sniggering at the back) with no seperate
air blower. The forges do have a low pressure air blower (or at least
my one did). It *might* muck up the jet hole size but assuming that
the fan is a blowing the same for both types of gas the ratio of jet
areas between propane and natural gas might be the same.
Charles
Duncan Munro - 29 Jun 2008 19:50 GMT
> 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!
Thank God for that, you had me scratching my head big time :-)

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Duncan Munro
http://www.m0kgk.co.uk/