Jon Pettyjohn on wed 11 aug 99
Hi,
A few of here are getting ready to build new kilns and
I'm wondering about what pressures to use for hard
or soft brick down-drafts using propane gas and
Venturi type burners.
The older books like Olsen's for example strongly
recommend very low gas pressures because they promote
longer flames and more even firing in addition to
being somewhat safer. Olsen likes 11 WCI in fact
which is just a fraction of 1 PSI.
I've seen some recent catalogs that are selling systems
that use much higher pressures, even up to 10 PSI
and I seem to get the impression that the higher pressure
might be more efficient. Also some of the new Fiber
kilns seem to use fewer burners and higher pressures.
So I'm very curious about what the current thinking on
this is, if there are any kiln builders out there with
opinions, we'd appreciate your thoughts very much.
Hope Ward reads this too.
Thanks,
Jon Pettyjohn
Mt. Makiling
Philippines
jon@mozcom.com
Marc Ward on thu 12 aug 99
hey Jon,
<<might be more efficient.>>>
Generally speaking, with the average burner that a potter uses, as pressure
increases, efficiency decreases because flame velocity increases. The flame
enters and leaves the kiln quicker thus having less time to radiate it's
energy to the kiln and ware. But, these inefficiencies may not be enough for
the average potter to worry about.
<<this is, >>>
There is no pat answer other than "it depends".... what gas you are using,
how many burners you want, what the max pressure you can have, what the kiln
is made of, firing temps, firing times, ect., all are variables that will
affect which way you go.
Marc Ward
Ward Burner Systems
PO Box 333
Dandridge, TN 37725
USA
423.397.2914 voice
423.397.1253 fax
wardburner@aol.com
M. R. W. on thu 12 aug 99
Hi Jon,
Please be careful with that propane pressure!!
11 inches of water column (11 wci) is the standard
working pressure for propane and you had better be
specially setup for anything higher than that. The
10 pounds of pressure you refer to probably comes
from the normal two stage system where the 100 psi
(approx) in the propane storage tank is reduced to
10 psi by the first regulator at the tank and this
pressure is delivered to a point near the use site.
At this point a second stage regulator is used to
again reduce the pressure to the 11 wci. It is now
ready to use in the normal manner. Again, be very
careful with pressures higher than that-be sure
your system is setup for it. ALWAYS check with your
propane supplier and have him check that system for
safety. --Reg Wearley
Big Arm, MT
--- Jon Pettyjohn wrote:
> ----------------------------Original
> message----------------------------
> Hi,
>
> A few of here are getting ready to build new kilns
> and
> I'm wondering about what pressures to use for hard
> or soft brick down-drafts using propane gas and
> Venturi type burners.
>
> The older books like Olsen's for example strongly
> recommend very low gas pressures because they
> promote
> longer flames and more even firing in addition to
> being somewhat safer. Olsen likes 11 WCI in fact
> which is just a fraction of 1 PSI.
>
> I've seen some recent catalogs that are selling
> systems
> that use much higher pressures, even up to 10 PSI
> and I seem to get the impression that the higher
> pressure
> might be more efficient. Also some of the new Fiber
> kilns seem to use fewer burners and higher
> pressures.
>
> So I'm very curious about what the current thinking
> on
> this is, if there are any kiln builders out there
> with
> opinions, we'd appreciate your thoughts very much.
>
> Hope Ward reads this too.
>
> Thanks,
>
> Jon Pettyjohn
> Mt. Makiling
> Philippines
> jon@mozcom.com
>
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