ELAINE CARROLL on thu 29 jul 10
I have one more question about my gas kiln.=3DA0 Please don't think too har=
sh=3D
ly of =3D0Ame, I'm not really as backward as I sound sometimes and I am ver=
y =3D
grateful for =3D0Aall the valuable help I have gotten from you clayart guru=
s.=3D
=3DA0 My question is:=3DA0 I =3D0Athe Water Inches Col.=3DA0guage supposed =
to read =3D
11 inches when the kiln is on =3D0A(burning) or before it is lit. I have be=
en=3D
assuming it is before it is lit, but =3D0Athe last time I tired to use it,=
w=3D
e couldn't get it above 1400 F and then it =3D0Astarted losing a few degree=
s =3D
the go up a couple degrees.=3DA0 The the rain came and =3D0Awe cut it off.=
=3DA0 E=3D
laine
William & Susan Schran User on thu 29 jul 10
On 7/29/10 8:21 AM, "ELAINE CARROLL" wrote:
> I have one more question about my gas kiln.=3DA0 Please don't think too h=
arsh=3D
ly of
> me, I'm not really as backward as I sound sometimes and I am very gratefu=
=3D
l for
> all the valuable help I have gotten from you clayart gurus.=3DA0 My quest=
ion =3D
is:=3DA0
> I=3D20
> the Water Inches Col.=3DA0guage supposed to read 11 inches when the kiln =
is o=3D
n
> (burning) or before it is lit. I have been assuming it is before it is li=
=3D
t,
> but=3D20
> the last time I tired to use it, we couldn't get it above 1400 F and then=
=3D
it
> started losing a few degrees the go up a couple degrees.=3DA0 The the rai=
n ca=3D
me
> and=3D20
> we cut it off.=3DA0 Elaine
When there is no gas pressure - when the main cut-off valve before the
pressure gauge is turned off - there should be no pressure showing on the
gauge. There may be pressure showing if the last time the kiln was shut dow=
=3D
n
the burners were shut first then following the line back to the main shut
off being the last valve turned off.
One should ALWAYS, whether lighting the kiln or shutting it down, shut off
the main valve on the largest main line, farthest away from the kiln,
turning on or off and working towards the kiln - the burners being the last
thing to be lit or shut down. This gets all gas/pressure out of the line.
Not being able to fire above 1400F is another issue. We'd need more
information about the kiln before addressing that. First thought however
would be either too much pressure/back pressure or not enough gas pressure.
Are you firing with natural gas using residential gas pressure? Residential
usually peaks at 7wci unless you request higher pressure.
If you are firing with propane, then your gauge might show psi and if you
are firing at 11 psi, then that is way too much.
Bill
--=3D20
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
David Finkelnburg on fri 30 jul 10
Elaine,
I think Bill has answered your question, but just in case...
I am thinking the gas supply to your kiln can be thought of as follows:
----X1-------------X2--------G---------B
where the pipe is represented by the dashes, --------------
and B is the burner nozzle (outlet)
and G is your gas pressure gauge
and X1 is your valve that shuts off all the gas to the kiln. It's wide open
when you fire.
and X2 is the valve that you adjust to control the amount of fuel to the
burner. You open this more and more as the firing proceeds.
IF you had a gauge between X1 and the pressure regulator, and you use
liquid propane, you would have ~11" w.c. pressure at that point with X1
closed. For natural gas this is typically ~7" w.c.
When you first crack X2 open and light the burner(s) the gauge will
indicate the pressure drop between X2 and the burner nozzle. The pressure
at the burner nozzle, of course, is zero inches w.c. or atmospheric
pressure.
If you barely crack X2 open, you will take a lot of pressure drop across
X2 and the gauge will read very low, perhaps 1" w.c or less. However, at
the peak of the firing, if you have X2 wide open, the reading on the gauge
will approach the pressure being supplied through the regulator because all
the pressure drop will occur across the burner orifice. Thus, the higher
the reading on the pressure gauge, the more you have valve X2 opened up and
the more fuel you have going into the kiln.
EVERY kiln and gas train will differ slightly in these readings, and
every gauge will be a bit different, too.
IF your kiln temperature quits rising, AND you have plenty of fuel
available, there are two possible problems.
1. Not enough fuel is getting into the kiln. The burner orifice is
restricteded, or it's too small. With more than one burner you have to
check each burner. They should all be firing the same.
2. Not enough air for the amount of fuel. This is easy to check. IF you
cut the gas a bit and the temperature in the kiln rises, even for a few
seconds, then the problem is lack of air to burn the fuel. Opening the
burner air may help, stacking looser near the burner ports and flue outlet,
or even throughout the kiln may help.
You may want to fire the kiln completely empty just so you can focus on
the gas, air and temperature. When you know you can fire the kiln to
temperature then you can worry about firing rate, atmosphere, etc.
Good firing!
Dave Finkelnburg
http://www.mattanddavesclays.com
-----------------------------
Date: Thu, 29 Jul 2010 05:21:22 -0700
From: ELAINE CARROLL
Subject: Gas Kiln question
I have one more question about my gas kiln.=3DA0 Please don't think too har=
sh=3D
ly of =3D0Ame, I'm not really as backward as I sound sometimes and I am ver=
y =3D
grateful for =3D0Aall the valuable help I have gotten from you clayart guru=
s.=3D
=3DA0 My question is:=3DA0 I =3D0Athe Water Inches Col.=3DA0guage supposed =
to read =3D
11 inches when the kiln is on =3D0A(burning) or before it is lit. I have be=
en=3D
assuming it is before it is lit, but =3D0Athe last time I tired to use it,=
w=3D
e couldn't get it above 1400 F and then it =3D0Astarted losing a few degree=
s =3D
the go up a couple degrees.=3DA0 The the rain came and =3D0Awe cut it off.=
=3DA0 E=3D
laine
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