Small blue flame ignition sensing problem


Thread Starter

Dan Mc

I have tried several optic flame sensors, but none of them work because the intensity of the light emitted by the flame is to small. The sensors I have tried work with an orange flame but not the small blue flame. I have been
thinking about using bare thermocouple wire and a temp control that can be configured to give a discrete output on temp rise. Anyone know of any device that will do this? I could amplify the thermocouple signal and go to an analog card, but that would require a PLC upgrade. Looking for a cheaper, easier solution.
You can get a simple control from a gas furnace company. My home model has a T/C stuck in the pilot light. This generates power which controls the thermostat - in other words - we could loose power but the control would still run the- because it gets it power from the T/C.

Another model is available from hardware stores for about $10.00 T/C sensor as well. I use that type in another furnace we happen to have.

If that dosen't work - we can build you a T/C with a 4 - 20 out or most any custom.

Thanks Bob Hogg go to "temperature controls"

Curt Wuollet

Is flame rectification an option? Or UV optical? I would think technology from home heating controls should work with even a small flame. It's cheap too, compared with automation stuff.
Try Honeywell or Robertshaw or White-Rogers.


The application you note is often used to detect ignited flange leaks in LPG and LNG bulk loading loading facilities. Temperature detectors such
as T/C and RTD are wrapped around piping flanges. Then if escaping gases ignite, the "blue-flame" fire is detected, and a water deluge system is actuated!

Phil Corso, PE
(Boca Raton, FL)

James D Walsh

I know of two ways of doing this. One is by UV sensor, but it sounds like you may have tried this already.

Another way is to use metal probe, similar to the the type used in Gas Boilers, they sit in the blue pilot light and detect ignition by
measuring the flame current.

A company that specialses in flame detection and combustion is a company called Pactrol controls.
Hope this is of some help