Basic Air Monitoring Concepts And Use Of The Altair 4 Gas Meter.
-
Upload
emerald-sutton -
Category
Documents
-
view
224 -
download
2
Transcript of Basic Air Monitoring Concepts And Use Of The Altair 4 Gas Meter.
MSA Altair 4 Multi-Gas Meter
Explosive AtmosphereOxygen ConcentrationCarbon MonoxideHydrogen Sulfide
Photo Ionization DetectorMeter using ultraviolet light to detect vapors with low LEL’s, up to 10,000 ppm
Colorimetric TubesUsed to detect single gases
Flame Ionization Detector
Similar to the PID, but uses a hydrogen flame instead of UV light to detect vapors
Some Common Haz-Mat Terms
Vapor PressureThe amount of force applied on a container by the
vapors coming from a substance. A vapor pressure greater than 40 mmHg is considered a respiratory
hazard. Water has a VP of inbetween 17 - 25 mmHg.
Vapor DensityThe relative comparison of a material to air. This determines whether the vapors will rise or settle. Air is given a score of 1. If the density is less than one, say .8, the substance will rise. If its say 1.9,
the substance will settle.
The Metering Process
o Identification of the substanceo Placardso MSDS Sheetso DOT ERG guide (Orange Book)o NIOSH Booko Shipping Paperso History of event
Getting Started
After turning the meter on in a clean atmosphere.
1. Determine flammability/explosive potential
2. What is the flammable range of the substance you are metering ?
3. This number is usually given as a percentage.
4. What does this number mean ?
Flammable RangeLower Explosive Limit (LEL)
The smallest concentration in air of a substance that will support fire or an explosion
Upper Explosive Limit (UEL)The largest concentration of a substance that will
support fire or an explosion
Example: Methane LEL = 5 % UEL 15 %
5 % 15 %
Methane
100 %0 %
Correction FactorsLEL sensors are calibrated to a certain gas, in our case pentane. The catalytic bead LEL sensor will
respond to other gases as if they are pentane. So what do we do if we are metering something other than
pentane ?
We use correction factors ! Yeah !
What are the correction factors for our meter ?
Methane 0.5Hydrogen 0.5Propane 0.8Pentane 1.0
Take your explosive reading and multiply by the numbers on the left to get your reading.
If your meter shows 25 % of the LEL and you are monitoring methane, multiply 25 x 0.5, so the actual reading is 12.5 %
OxygenBefore entering the atmosphere to be metered, the
oxygen concentration should be in the normal range, approximately 20.8 %. Concentrations above 20.8 % and below 19.5 % should be considered dangerous
and the area left as soon as possible.
Calibration Vs. Bump Test
Calibration
Putting the meter into a ‘calibration mode’ and making sure the meter reads within a specific range of a known gas and if not, making necessary adjustments to correct.
Bump Test
Attaching the meter to a known source of gas and making sure the meter alarms with the appropriate
numbers.
Safe LEDThe instrument is equipped with a green "SAFE LED". This green SAFELED flashes every 15 seconds under the following conditions:• the SAFE LED feature is enabled• instrument is in Measurement Mode (Normal Operation)• combustible reading is 0% LEL or 0.00%CH4• Oxygen (O2) reading is 20.8%• Carbon Monoxide (CO) reading is 0 ppm• Hydrogen Sulfide (H2S) reading is 0 ppm or 0 mg/m³• no gas alarms are present (low or high)• instrument is not in Low Battery warning or alarm• CO, H2S, STEL and TWA readings are 0 ppm or 0 mg/m³.
The √ symbol will be displayed in the Measure mode for 24 hours after asuccessful Bump Test or calibration.
Instrument runtime 16 hours at 77°F (25 °C)Charging time≤ 4 hoursThe maximum safe area charging voltageUm = 6.7 Volts D.C.Temperaturerange-4 °F to122 °F (-20 °C to 50 °C) operating50 °F to 95 °F (10 °C to 35 °C) while charging battery
A combustible gas reading of "XXX” indicates the atmosphere is above100 % LEL or 5.00 % vol CH4, and an explosion hazard exists.Move away from hazardous area immediately.
Do not use the ALTAIR 4 Multigas Detector to test for combustible ortoxic gases in the following atmospheres as this may result in erroneousreadings:• Oxygen-deficient or oxygen-rich atmospheres• Reducing atmospheres• Furnace stacks• Inert environments• Atmospheres containing combustible airborne mists/dusts.
• Do not use the ALTAIR 4 Multigas Detector to test for combustiblegases in atmospheres containing vapors from liquids with a high flashpoint (above 38 °C, 100°F) as this may result in erroneously lowreadings.