In today’s world there are so many gadgets and appliances that we take for granted: we flick a switch and a light comes on; tap an icon and an email appears; press a button on the remote and the TV is on! From time to time, though, I stop and wonder: how does that happen?
Yesterday, while cooking dinner for the family, I had one of those moments: how does the propane that’s stored in the tank outside, come out of my cooktop burner and why does it burn blue?
When a propane-powered appliance, like a cooktop, is switched on, its intake valve is opened and propane vapor (or gas) is drawn from the outside propane tank through the tank’s outlet valve and into a regulator that converts the gas pressure so that it can be safely piped into the house.
When the propane arrives at the cooktop it passes through a venturi tube – a wide tube with a narrow section in its middle. As the gas flows into the narrow section the pressure increases but as it exits that pressure decreases and oxygen is sucked in through a small hole. The oxygen mixes with the propane gas and makes it combustible; it’s that mixed gas that finally arrives at your burner.
The mixed gas now flows out through holes in the outer perimeter of the burner and when a pilot light or spark comes into contact with the gas, it ignites and burns off. By adjusting the burner’s knob you can increase or decrease the flame simply by increasing or decreasing the flow of gas.
But why is the flame blue? Well, propane contains hydrogen and hydrogen burns blue. If the flame is orange it’s a sign that there’s not enough oxygen in the mix. Why orange? Because propane also contains carbon and since too-little oxygen in the mix results in a lower-temperature flame, the carbon will not all be burned off but will remain in the flame, giving it an orange appearance. The lack of sufficient oxygen may indicate that the venturi tube needs cleaning or adjusting. Also, a poor gas mix will reduce the burner’s efficiency and the presence of unburned carbon can cause clogging of both the burner and the intake valve. So, if you’re cooktop starts burning orange instead of blue it might be time to have a technician come take a look.