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Burners

The information here is a guide only to burners for gas and oil kilns. You will need to experiment with these designs to suit your own kiln configuration.

Oil Burner

The basic idea behind the oil burner is to drip a small amount of oil onto hot plates that vaporise the oil , this hot gas then combusts inside the kiln. Several important considerations are:

1. The oil can be of any grade, sump oil from cars through to kerosene can all be used, obviously the more contaminated the oil (like sump oil for instance) the more contaminates and pollution will be caused by burning the oil. Also the oil will need to be filtered to remove any particulate.

Burner

2. The metal plates require preheating in the early stages of the firing. This can be achieved with gas burners, or even a wood fire. Once the firebox has got hot the radiant heat will keep the plates hot and the burner becomes more efficient the hotter these plates become.

Burner

3. The burners require a decent amount of air flow past them to pull the vaporising and burning oil into the kiln. This can be achieved with a tall chimney or use a forced air system by incorporating a blower into the system (this latter alternative will give a more controlled and efficient burning of the oil)

burner

4. In addition to the dripping oil a small amount of water can also be dripped onto the hot plates, this is recommended only after you reach 1000 degrees and only a very small amount of water is need. The water acts in two ways, firstly it provides steam as a carrier of the oil vapour and also can be beneficial as a reducing agent inside the kiln.

Kiln burner

As with all burners a trial period is needed for the potter to come to grips with the system. It can produce vast billowing clouds of smoke if too much oil is used, similarly it can choke up the firebox with clinker is badly adjusted. But when working optimally, with the correct air, water and oil ratio it will produce a clean burning flame.

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Venturi Gas Burner

These are a form of natural draft burner, or also called atmospheric burners. They utilise a common mechanical effect called the venturi principal. This effect occurs when gas or other fluids travelling along a tube encounter a narrowing of the passage, the gasses accelerate through this narrowing creating a partial vacuum effect behind. In the case of the venturi gas burner the gas exits the jet just in-front of the constriction of the burner tube. the gasses are already under pressure and this narrowing accelerates them further. This then creates a partial vacuum behind the jet which sucks air into the burner tube. This means that the venturi burner will mix more air with the gas than a simple Bunsen or other natural draft burner. It is this increased fuel-air mixture which make the venturi burner a more efficient burner and able to generate a wide range of flame types, from oxidising to reducing. Also the shape of the burner tube after the constriction slows down the velocity of the gas, allowing the air and gas to mix more thoroughly before encountering the flame retention head. This feature, the flame retention head, at the end of the burner tube is designed to ensure that the flame doesn't burn back down the tube, or lift off from the burner head, both common problems in simple burner designs.

The wheel at the left end of the burner is the primary air control and rotates on the shaft of the gas supply. This wheel can rotate to seal against the body of the burner, stopping the air from mixing with the gas. The brass threaded rod, through which the gas flows, can be adjusted by screwing forward or backwards into the burner body. This adjustment is necessary to optimise the burner performance. If this rod is too far inside the burner then the venturi effect is lessened, similarly, if too far out side the burner the correct amount of air won't be sucked in. To set the correct position first connect up the burner to the gas supply, set the primary air disk so that there is only 1 or 2mm gap between it and the burner body and light the gas flame. Have the brass rod set so that the jet is as far outside the burner as possible, then slowly wind in the brass rod, simultaneously adjust the primary air wheel so that the gap distance remains constant. Observe the flame, as the optimal gas-air ratio is reached the flame should change from yellow to blue and the noise of the burner increases as more air is sucked into the burner. If you adjust the rod in too far then the flame will change again back into a yellow flame.

If you have any problems or require more advice (these burners can be tricky to initially set up if you are unfamiliar with this type) then please email me.

Links to sites with more information

GasKilns

Ward Burner Systems