Flame detector is one of instrument with a sensor which can detect intensity and frequency of fire at burning process in combuster at gas turbine unit. Working principle Flame detector uses optical methods that work like UV (ultraviolet) and IR (infrared), fire visual imaging, as well as spectroscopy that serves to identify sparks or flame. Intense reactions of fireinducing materials can be marked from UV rays, emissions of carbon dioxide, and radiation from infrared. Flame Detector is also able to distinguish between false alert with real burning fire through system components designed with the function of detecting the absorption of light that occurs in certain waves. Problems found in the flame detector one of them is the dirty glass flame detector in the form of burning coal inside the combuster covering the glass surface. This resulted in the indicator pointer fault even there is no pointer at all and cause in turbine gas unit trip. Flame detector in PLTGU Block 1- 2 uses UV sensor type D40-41 fireeye series with UV sensor. This study aims to analyze the causes of sediment deposition on the flame detector glass in PLTGU Block 1-2 and find a solution to prevent the occurrence of dirt deposition on the flame detector glass. Method of problem solving in the form of observation, research and interview with related parties. So it can be concluded that the failure of flame detector reading in PLTGU Block 1-2 one of them due to the dirty flame detector glass that inhibits the flame reading sensors. Precipitation of dirt on flame detector in PLTGU block 1-2 is caused by several things, namely: HSD fuel composition, non-continuous operation pattern, and incomplete combustion triangle.