In MARK 6 TRPG, there are two parameters for Flame Detector Threshold, namely FlameLimitHI and FlameLimitLOW. I do understand it is the lowest number of counts of pulses generated due to presence of flame intensity that would be considered as Flame ON. But what is the difference between High and Low limit thresholds?

 

M. Ali,

I believe this is "legacy" (or, left-over) programming/configuration from early DLN-I days and Mark V control systems. There was the ability to program one rate for detecting "solid" flame (the high threshold, if I remember correctly), and another ability for preventing false flame detection (the low threshold, if I remember correctly). For the limits to be used, there has to be some application code (sequencing; logic) in the Mark V to enable/disable the different thresholds depending on combustion mode.

Some units equipped with DLN-I combustors may still use this configuration capability when Mark VI turbine control systems are used, but for units with conventional combustors or DLN-2/2.n combustors it's usually not necessary or used.

Hope this helps!

 

Thank you CSA.