Video: Rapidox 5100

Video transcript

What this portable analyser measures, why it calculates the energy of the gas on site, and how to sample, calibrate and export the data. Biogas and syngas change by the hour, and their composition decides how much energy the plant is producing. A laboratory result arrives long after the gas has changed. The measurement has to be made where the gas is. So this is a laboratory instrument in a case: up to 6 gases at once, their calorific value,

more than 8 hours on battery, and an IP 66 case. Two versions cover most of the work. Biogas: methane, carbon dioxide, oxygen and hydrogen sulphide. Syngas: methane, carbon monoxide, hydrogen, oxygen and carbon dioxide. Anything else is built to order. The calorific value is a thermodynamic calculation from the measured composition, following IS 069 76, corrected for temperature, pressure and water. Just tell it whether the gas is saturated or dry.

Six sensors in one box raise a real problem: sensors react to gases they are not meant to measure. Hydrogen sulphide, for example, drives a chlorine sensor below zero. That is why each configuration is designed and calibrated around these effects. Opened, it is all on one panel: touchscreen, printer, gas ports, flow knob, power switch and battery light. Setting up: the earth point to the site earth, the probe with its water trap on GAS IN,

and a 6 millimetre tube on GAS OUT, vented away from you. The USB stick takes the data, and mains only charges it, while it keeps measuring. Before the first job: the fuse is shipped removed, to isolate the lithium battery. Fit it, then charge with the lid open, until the light turns from red, through orange, to green. Switch on, and readings appear after about a minute. Start the pump, set the flow so the ball floats mid-gauge, and let it settle. From a pressurised source, switch the pump off:

the gas flows through on its own. Continuous mode shows live readings, with an average over up to an hour. Timed mode samples for a set time and holds the result. Either way, a location name travels with the data. To calibrate, zero in fresh air, or with zero air for carbon dioxide. Then apply a certified span gas, enter its value, wait for a flat line, and press Cal. A wrong gas triggers a warning.

Everything is logged, all the time: Four gigabytes, about a year of monitoring. Any date range goes to a USB stick, as a file that opens in Excel. Alarms can be set on every gas, and on flow, pressure and temperature. Screen brightness costs battery, so set it sensibly. And lock the menus with a password, changing the defaults when it is commissioned. Keep water from condensing inside it, vent the outlet with toxic gases, and never use it in a hazardous area.

A periodic zero and span calibration keeps the results repeatable. Biogas and anaerobic digestion, syngas and gasification, fermentation, and combustion and gas quality checks. Gas analysis, from Amperis.