#57 - Calibration Procedure for NOVA Model 380

The Nova Model 380 Tri-Gas Analyzer for hydrogen-cooled power generators has been mentioned in this blog before. (http://nova-gas.blogspot.ca/2011/12/45-portable-hydrogen-purity-analysis.html)

This analyzer has three analysis ranges:

Range 1 - Measures Hydrogen in Air from 0-100%.  Normally used to monitor hydrogen purity from 90-100%. 

Range 2 - Measures Hydrogen in CO2.  For use when the generator is being purged with CO2 as a blanketing gas, or when the hydrogen is refilling the generator after a shutdown. 

Range 3 - Measures Air in CO2. For use when air is displacing the CO2 blanketing gas prior to opening up the generator or when CO2 is displacing air prior to refilling the generator with hydrogen.

Calibration

We occasionally get requests to post the calibration procedure for these instruments. Because it is a simple process, it can easily be described in a blog post. So here goes:

• Range 1 - H2 in Air

1. The 380WP should be calibrated at least once a month and also checked on pure hydrogen prior to checking hydrogen purity in Range 1.
2. Using the range switch, select Range 1.  With the pump switched on, allow approximately 1 LPM of air to flow through the analyzer.  Adjust the 'AIR REF ZERO' knob located on the right side of the analyzer until the reading is zero.
3. Next, turn the pump off and allow 1 LPM of 100% hydrogen to flow through the analyzer.  Remove the top cover and adjust the top panel ‘1 H2 IN AIR SPAN’ potentiometer (pot) until the reading is 100.

• Range 3 - Air in CO2

1. Select Range 3.  With the pump off, allow 1 LPM of 100% CO2 to flow through the analyzer.
2. Adjust the knob marked 'CO2 REF ZERO' located on the right side of the analyzer until the reading is zero.
3. With the pump on, flow 1 LPM of air through the analyzer.
4. Adjust the top panel pot marked ‘3. AIR IN CO2 SPAN’ until the reading is 100.

• Range 2 - H2 in CO2

1. Select Range 2.  The zero is shared with Range 3, so it will not have to be set up again in Range 2.
2. With the pump off, allow 1 LPM of 100% hydrogen to flow through the analyzer.
3. If the reading is not 100, adjust the top panel pot marked ‘2. H2 IN CO2 SPAN' until the reading is 100.

Calibration is now complete.

Notes

For calibration, main plant sources of H2 and CO2 may be used, or two high pressure cylinders with 0-30 PSI pressure regulators. These cylinders should contain the following gases:

• 100% H2 for Range 1 and 2 span calibration.
• 100% CO2 for Range 2 and 3 zero calibration.
• Note: Range 1 will zero on air and Range 3 will span on air.

Gas cylinders can usually be purchased from a specialty gas or welding gas supplier. The gas cylinder pressures should be regulated down to approx. 2-5 PSI (14-35 kPa) and have a flow control valve to meter the gas flow into the analyzer. Flow through the analyzer should be approximately 1 LPM.

The Nova Model 380 Tri-Gas Analyzer is being used for hydrogen-cooled power generators all around the world. Maintenance staff at power utilities love the 380 because it’s quick and easy to use.

We’re Nova. We make gas analyzers for carbon dioxide, hydrogen, air, and other gases.

For information on gas analyzer systems, give Mike or Dave at Nova a call, or send us an e-mail.
1-800-295-3771
sales at nova-gas dot com
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http://www.nova-gas.com/
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