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.