Ribble Enviro - Model GFM435 -Truly Universal Landfill Gas Analyser

• 5 gas analysis as standard (CH4, LEL(CH4) C02, 02, CO and H2S) - 2 further optional gas channels.
• Borehole flow, borehole pressure and atmospheric pressure measurements.
• Optional temperature and velocity measurement
• All gas and flow channels MCERTS certified.
• Hexane equivalent measurement of hydrocarbon vapours from common liquid fuel and oil spills.
• Display of PID compensation factors for accurate operation of PID sensors in CH4 rich atmospheres.
• Intrinsically safe EEx ib MB T1

HEXANE Channel
With the GFM435 when and if the methane sensor shows an over-range signal or abnormally high value ( a good indicator that other hydrocarbons are present in a borehole) the hexane value will remain valid and in range up to 2.000% allowing standarised monitoring of other hydrocarbon vapours expressed as a percentage of hexane vapour equivalent.

PID Compensation Factor
The PID (Photo lonisation Detector) is the standard instrument used to characterise hydrocarbons other than methane in a borehole. However, the presence of methane attenuates the UV light of the   PID quenching its signal and consequently de- sensitising its response. The effect can be catastrophic. Only a few percent of methane can make the indicated PID signal inaccurate by factors of 1/1 Oth or more.

The GFM435 PID Compensation Factor is a figure derived from extensive testing of a range of common PID instruments. Its value (1-10) must be used to multiply the PID reading to give an accurate measure of the total hydrocarbons in the borehole when methane is present.

Borehole Flow Measurement
The built-in flow transducer is very robust. The transducer is calibrated up to 100 l/hr full scale measurement range but is tested at four times this flow rate. This allows unexpected short bursts of over-range flows to be tolerated without instrument damage.