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Multi-Gas Detector Calibration in Techmaster.
The multi-gas detector can detect harmful gases such as CO, H2S, LEL (LOWER EXPLOSIVE LIMITED – short for explosive gases) and oxygen concentration. These gases, if exceeded, will cause unsafety at work, dangerous to human health. This is a device that helps to ensure the safety of users when working in the environment of mines, manhole, tanks, …
The multi-gas detector is equipped with highly sensitive sensors for precise gas and oxygen concentration determination. So multi-gas detector need to be calibrated periodically.
1. What is multi-gas detector ?
The multi-gas detector is used for the detection of flammable gases, oxygen depletion and an extensive range of toxic gases meeting the safety monitoring requirements of a broad range of different industries.They are commonly used for the following gases, Hydrogen Sulphide, Carbon Monoxide, Oxygen and combustibles (%LEL). This equipment is extremely important when working in environments: mines, manhole, tunnels, tanks, …. These are environments that often generate many harmful gases that affect health. The multi-gas detector will issue an audible warning and a flashing light if an excess gas leak is detected.
2. Multi-Gas Detector Calibration Process
2.1 Why Multi-Gas Detector Calibration?
Multi-Gas Detector is an important measuring device that requires high accuracy. Therefore, calibration of this device is extremely necessary. As it will help ensure stability and accuracy for related operations. Besides, the calibration also helps to detect equipment failures (if any) early for timely correction and repair.
2.2 Calibration instrument
– Standard gas mixture.
– Gas detector, with calibration cap supplied with equipment (if available)
– Regulator.
– Gas tubing.
2.3 Environment conditions
– Temperature: (20 ÷ 25) ºC
– Relative Humidity: (20 ÷ 65) %RH
Note: environment conditions above apply for Techmaster inhouse laboratories. Outside this bound conditions will be considered with customer for uncertainty and measurement results.
2.4 Preparation Multi-Gas Detector Calibration
– Ensure UUT is clean and error free.
– Battery and Flash can be checked, if damaged, replace when necessary.
– Place the UUT and standard gas in calibration area for a minimum of 4 hours.
– Visual inspection to determine the conformity of the measuring instrument, with the requirements specified in the technical documents in terms of shape, size, display, used power source, brand, adjustment mechanism, condition normal operation and accessories included.
– Turn on UUT and warm up according to the user manual.
2.5 Perform Multi-Gas Detector Calibration
– Almost gas detector shall be calibrated at 2 points, in there the zero point is correspond with clean air.
– For oxygen sensor, reading value should be approximately 20.9% at clean air. Or use pure nitrogen cylinder (>99.99%nitrogen) to perform zero point calibration.
2.5.1 Zero calibration
– Follow manufacturer’s manual to perform calibrate or adjust for zero point. Ensure that calibration environment does not contain gases that could interfere with UUT
2.5.2 Span calibration
Select standard gas cylinder suitable for gas type of UUT.
– If UUT is single gas detector, use single standard gas for calibration.
– If UUT is multi-gas detector, use mixture gas cylinder with concentration follow manufacturer requirement.
– If UUT is Total Violent Organic Compound meter, use isobutylene standard gas cylinder with 10ppm or 100ppm concentration.
– Attach regulator to cylinder and tubing. Open valve at a moderate level and wait for about 3-5 seconds and then close the valve, so that inside regulator and tubing are fulfill with calibration gases. This is done before attaching tubing end to UUT.
– The UUT should be fitted with a suitable calibration cap.
– Refer to the UUT manual for measuring or adjusting according to this 2nd point.
– Attach tubing to UUT to connect with gas cylinder.
– Open the gas connection valve so that the gas in the cylinder enters to UUT.
– Wait for the value on the UUT to stabilize, record the 5 readings of the gases.
– Same as above, change the standard gas mixture tank to calibrate different values if any.
– Compare the measurement results of the concentrations of the gases H2S, CO, CH4, O2, NH3 with the concentrations of the gases in the standard gas mixture.
– Turn off the machine and clean the used equipment.
