Home Tips Installing and adjusting the Kiln Burners
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Installing and adjusting the Kiln Burners.

The actual firing position and direction should be determined before installation, check the following "Kiln Floor Plan" sheet for some ideas.

For safe and efficient operation, it is important to follow these guide-lines:

MOUNTING

The burner tip should be mounted approx. 20mm away from the kiln port face. The safety probe should not be sited near the hot surface of the burner port. An amount of "secondary" air is necessary to complete combustion and this must be available around the burner tip.

Never place the burner tip inside the kiln port.

The burners should be rigidly mounted to the kiln frame or the floor if the kiln is securely fixed to the ground. The tips must fire centrally into the burner port. The usual method is to use pipe type clips.

GAS CONNECTION

The gas connections to the kiln must be undertaken by a suitably qualified person. It is important to ensure the gas supply is adequate for the amount of heat required. The gas-fitter will size the pipe according to the total loading ie. the total BTU/HOUR or MJ/HOUR. You can calculate this from the sizing chart you received at your initial query. Make sure all joints are checked for leaks with soapy water or a manometer prior to a start.

FIRING

There are critical points in the firing when the atmosphere will affect the clay body and the glaze and to obtain the best results you should have a thorough understanding of this. Until you wish to experiment during the firing the most efficient setting for the atmosphere is neutral until you commence reduction.

(The following applies to L.P.Gas burners, the main burner valves only are adjusted if using natural gas burners, please contact ACS for more details)

a) Open the main gas valve fully. If using a changeover valve, ensure the handle is pointing to the full cylinder and is fully open. A thorough check for leaks should have been performed with soapy water.

b) Set the main pressure to approx. 50 kPa. If possible the kiln door should be open to negate the risk of a build up of unignited gas in an enclosed space.

LIGHT UP

c) Depress the button of the safety unit completely and light the low setting of the main burner or the pilot burner if fitted.

Hold the button down for approx. 10 seconds, ensuring the flame is heating the tip of the probe only-Release the button slowly, the flame should stay alight, if not repeat this step. Light all burners (or pilots) and control the gas rate to the main burner/s using the burner control valve or the main gas pressure according to the firing program.

SHUT DOWN

d) Close main gas valve. Close all burner valves.

BURNER PORT SIZE

The size of the port depends on the amount of excess air required for the type of firing and the height of the flue or chimney. A reasonable guide is approx. 20mm bigger in diameter than the burner tip. The higher the flue, the greater the draw of secondary air and the smaller the port. The optimum port shape is a round hole with a 15° taper but with venturi burners this is not a critical size as the venturi burner inspirates most of the air required for combustion through the venturi throat.

FLUE SIZE AND HEIGHT

A long flue or chimney with an excessive draw is not as important for gas kilns but it is important to ensure the waste gasses exit from the workplace. A canopy is usually constructed and this is positioned above the flue termination and also serves a dual purpose by diluting the gasses. A tile can be set on this outlet for reduction but should be restricted from completely closing as a dangerous situation could occur.

The actual size of the flue is dependant on many factors and the usual method is to oversize slightly and reduce accurately with the damper. A good guide is 1 square inch per 8,000 BTU input.

PRIMARY AND SECONDARY AIR

The primary air can be increased or decreased by controlling the rotating shutter on the burner inspirator. Closing the shutter will reduce the amount of air available to mix with the gas and will produce a gas rich or reducing flame. Opening the air shutter will create an oxidising or air rich flame. The most efficient flame setting for kilns is blue without a defined cone.

Adjusting the flue damper or tile will also control the secondary air. Closing the damper will reduce the amount of air available around the burner tip. This type of burner can require up to approx. 50% of the total combustion air as secondary air. The important point is to ensure there is the correct amount of gas to the total air available for efficient mixing.

Assuming the gas quantity and primary air rate are correct, a simple method to set the secondary air rate is to fire the kiln to near top temperature and close the flue damper slowly until a small reducing flame is noticed. Open the damper slightly until the flame disappears, this will be the most efficient setting. It is easier to see the small flame in a darkened kiln room.


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