Roger Korn on sat 19 dec 98
Chess Denman wrote:
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I thought I would post the outcome of my propane vs natural gas
enquiries.
Posts on the list were mixed in opinion. So I decided to investigate
cost.
First I telephoned a company who sell burners. Basically the man there
was
quite unwilling to offer any help on the reasonable grounds that they
make
sell and vouch for their own brand of kiln and they dont want to say
things
to enquirers which might prove untrue. So next I spoke to the proprietor
of
TRU FIRE kilns (I'll supply telephone no and address to any one who
wants
it) I had stumbled on this firm a year and a half ago and ended up
buying
all my firebrick burners etc from it chiefly because its proprietor -
originally an architect - specialises in making custom built kilns of
all
kinds including, when I was there a "walk in" size raku kiln. When I had
visited then he gave me an hour of his time and lots and lots of free
advice
with no hint of trade secret crap.
Anyway......
What he said was that I could convert to natural gas but I would need
new
burners because I was going from high pressure propane to low presser
natural gass. The orifice in the burner nib would need to be larger but
far
more important the internal bore of the burner would need to change from
1"
to 1.5". This would also mean enlarging the burner ports.
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There's another possibility here. The reason for enlarging the venturi bore
is that the velocity of the natural gas would be lower than for the higher
pressure propane, hence it would be more difficult to entrain the required
amount of air.
But you can get the gas company to increase the gas pressure from the
nominal 8" WC to 55" WC (2 psi). This means buying a $25 US regulator for
your household gas devices, but the increased pressure means that the same
burner can be used for either, merely by changing the orfice size. As an
example, an MR-750 rated at about 72000 BTU/hr at 8 psi propane w, using a
#50 orfice will put out about the same heat on 2 psi natural gas, using a
#41 orfice (experimentally demonstrated).
Some negotiation with the gasco may be required, but if there's a chance
your gas consumption will go up, they are more than happy to put in a
bigger meter (500,000 BTU/hr) and high-pressure regulator for free. It may
have helped that the gasco technician who responded to the request was an
O'Sullivan from the same part of West Clare as my mother's people, and that
his daughter was a potter.
Roger Korn
McKay Creek Ceramics
Box 436
North Plains, OR 97133
http://www.europa.com/~rkorn/pottery.html
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