Chlorine in Gas Engine Oils

The X-ray Fluorescence technique is often used to detect Chlorine in landfill gas engine systems. The Chlorine comes from the Chlorinated Fluorocarbons in aerosols and other sources which have been dumped in the land fill.

This chlorine is a contaminant in the methane gas which is being extracted from the landfill to run the engines, which then produce electricity for the grid. Hence Chlorine is not normally an issue for gas engines running on natural methane gas. 

As the engine runs, this Chlorine can be absorbed into the metal surfaces. While the engine remains hot there is little or no moisture present so the Chlorine remains inert, i.e. has little if any effect on the engine’s internal parts.

However, when the engine is not running or the parts are left in the open air the chlorine can rapidly react with moisture to form Hydrochloric Acid. This can then cause metal parts to corrode and show pitting within a very short period of time. 

There have been instances where engine parts have been removed for maintenance and on first glance look perfectly ok, however after only a few hours of being exposed to air and moisture have shown signs of corrosion and/or pitting.  

The Chlorine action alert level is normally set at 1000ppm for in service oils.

X-Ray Fluorescence (XRF) Spectroscopy

This method is often used in the laboratory to determine the Chlorine level in the gas engine oil samples.

A sample of the oil is placed in a small cup which is subjected to an X-ray source. The resulting X-ray energy emitted from the sample is characteristic and unique to the chemical elements present.

In this case the required X-ray detector is calibrated specifically for Chlorine so it will determine the amount present.

With the correct detector and calibration the same instrument can be used to determine wear elements e.g. Iron, Chromium etc. 

So when should you change the oil? 

In the case of Chlorine you should consult your oil and/or equipment suppliers to ascertain the recommended levels for the equipment being used.

By testing systems regularly the Chlorine level can be determined and potential warning signs identified. This will help to reduce the potential for corrosion of engine parts, hence extend equipment life, productivity and reduce costs. 

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