How do you operate an UpDraft Gas Kiln?

OPERATING AN UPDRAFT GAS KILN

Once the kiln is hooked to a gas source, each burner may be ignited with a fire stick and the primary air-adjusted for each of the air mixers or burners. Before attempting to adjust burners, loosen the locking screw. The locking screw is not re-tightened unless the kiln is moved.

Air adjustment is accomplished by revolving the adjustment shutter plate up or down below the air mixer. The recommended starting point for natural gas is 1/4” and for propane 3/8” – 1/2”.

The air adjusting plate is locked between the burner orifice and the burner. To move this plate the burner must be loosened slightly from the brass orifice which threads into the center of the burner. Air adjustment is very important and should be accomplished with care. After loosening the locking screw and the burner from the orifice, rotate each plate to ensure it will move freely. Next position each air adjustment plate so the air inlets are 50% open. The kiln may be ignited while fine air adjustments are being made.

A properly adjusted kiln will have all flames uniform in appearance with the transition from the candle flame to intense flame occurring at the same time for each burner as the gas valve is opened. The kiln operates most efficiently when the intense flame has a bright blue color. Propane gas will not generate as intense blue color flame as natural gas. If the flame tends to blow out when the gas valve is opened the air inlet should be closed slightly. The air adjustment of the burners is not be changed once the optimum settings are obtained; however, reduction firing in the kiln may be accomplished by closing the air inlets. The easiest and most reproducible reduction is obtained by placing a damper (kiln brick, kiln shelf ) over the vent hole in the lid.

If you plan to use natural gas with your kiln, a large burner is necessary when used on natural gas pressure, you will need 6-8 inches of the water column. If you order your kiln for household natural gas use, it will be equipped this way. The natural gas pipeline that connects to the kiln needs to have a 3/4" inside diameter. If you plan to use propane gas, your tank must have a low-pressure regulator like those on a camper trailer. If an adjustable regulator is being used, about 1/2 pound pressure is necessary. The gas pipeline needs to be a hard line with a ¾” inside diameter. The line should run 20 – 40 ft. long from the propane tank. The larger the tank the better; however, a five (5) gallon tank is the minimum size for the 1827G or 18 Raku, and a 15-gallon tank is the minimum size for the 2327G/23 Raku and 2827G/28 Raku kilns. Due to gas flow, the propane tank may tend to freeze solid. If ice is observed forming on the outside of the tank, water can be run over it to help keep it melted. The tank can also be lowered into a large bucket of warm water. When portable tanks are used for rakuing, keep gas tanks at a safe distance from the kiln.

 

PYROMETER OPERATION

The first option is to use witness cones and an analog or digital pyrometer. Using a pyrometer requires the
kiln operator to be with the kiln during the entire firing process. Analog or Digital pyrometers display a kiln’s
inside temperature but do not have any control over how the kiln fires or have the capability of turning the
kiln off. The pyrometer is not installed directly on the gas kiln but needs to hang on a wall nearby.

 

Olympic Torchbearer and Raku gas kilns have an exposed area on
the stainless-steel skin usually positioned in the rear of the center of
the kiln where the thermocouple of the pyrometer will be inserted.
The thermocouple only needs to be inserted into the kiln about 1
½”. If hole is not pre-drilled use a ½” drill bit to create hole.
Hang wall mount pyrometer away from the kiln to prevent damage
to the instrument. The lead wire from the instrument to the
thermocouple is 6 feet. If calibration of an analog pyrometer is
required, adjust the set screw located on the plate of the instrument
with a screwdriver.

KILN SITTER WITH TIMER OPERATION

A kiln sitter may be ordered with your Torchbearer gas kiln or added later. If the kiln is installed with a kiln sitter, the kiln sitter electrical box on the kiln plugs into a standard 120-volt outlet. The electric valve plugs into the receptacle on the kiln sitter box.

Gas kiln sitter systems may be retrofitted after the purchase of the kiln. To add a kiln sitter to a Torchbearer kiln, drill a 1” hole in the exposed brick area of the kiln for the kiln sitter tube assembly to go through. Mount the kiln sitter electrical box to the kiln and secure to the kiln body with #6 sheet metal screws. Screw the electric valve to burner manifold, paying attention to the gas flow direction embossed on the valve. The kiln sitter with timer is a mechanical device that  will shut the kiln down once it reaches temperature. Pyrometric cones are inserted into the kiln sitter’s cone supports and once the kiln reaches temperature the cone will bend and mechanically shut down the kiln. The timer is usually set 30 minutes beyond the estimated firing time and will shut down the kiln if the cone in the kiln sitter does not. During the firing the kiln operator will open the gas valve in 45 minute increments from low to medium to high to reach the desired temperature. When firing a gas kiln with a kiln sitter it is a good idea to have a pyrometer to know the temperature inside the kiln and witness cones on shelves to determine accurate firings.Kiln Sitter manuals come with the kiln sitter.