FID based total hydrocarbon analyzers are real LTA's (Low Trace Analyzers) and measure concentrations in the ppm (Parts Per Million) range. The highest care should be taken to keep FID analyzers up and running. The user should always strictly follow the manufacturer's instructions and recommendations.

To understand how sensitive a FID-analyzer really is, consider the following: One ppm is the equivalent of about a one ounce shot glass full of contamination in a typical 10,000 gallon railroad tank car filled with water.

Since FID analyzers measure THC's (Total HydroCarbons) on a hot & wet basis, these hydrocarbons tend to condense on the walls of sample the lines in the analyzer and the lines upstream of the analyzer too. Therefore, the feeding of sample should be done at the highest possible temperature. All sample lines and the analyzers need to be maintained at temperatures around a maximum of 204°C (400°F, 673K).

Carefully step up the temperatures of the whole sampling train in 10° F increments, starting from the probe towards the analyzer. Whenever possible separately heat or, at least carefully insulate all cold spots. JUM's heated analyzers (excludes Model 3-200), including our heated sample filters ans sample sequencers allow the heated lines to be coupled inside of the oven and therefore are cold spot free.

The minimum requirement to keep the sample stream clean is the use of a fine-enough, heated sample filter at the stack probe. Such filters typically are change filters from various sintered materials and need to be replaced quite often. While the stack probe filter is replaced frequently, the question is who cares about the hydrocarbon contamination (hang up) in the heated sample line (and sample probe)? May be someone sometimes, but in fact a heated line should be cleaned as often as the stack probe filter is changed. Such hydrocarbon hang-up easily becomes permanent over time and generates much higher THC readings than they are in the actual sample.

All of our FID analyzers are equipped with an internal fully heated permanent 2µ stainless steel sample filter which is cleaned by high-pressure back purge with dry compressed air or nitrogen. A stack probe mounted sample filter is not necessary in this case, because the whole sample train is always automatically back purged also when the sample filter is purged.

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