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The IR section (Figure 7, Figure 8) contains CO and CO2 detectors in series, pump, tubing, and power supply. The pump pulls a split of sample gases from the oven to the IR absorbance detectors. A pressure controller in the IR unit maintains a constant gas pressure between the oven and IR detectors. The CO and CO2 detectors function as infrared detectors with maximum sensitivity set to detect the wavelengths of CO and CO2, respectively. Results from these detectors are used to determine S3 and S4 parameters.
Figure 7. CO and CO2 Detectors without Insulating Covers.
Figure 8. Internal View of the SRA IR Section.
FID Unit
The FID detector combusts pyrolysis products in a hydrogen/air flame (Figure 9, Figure 10). Both the energy released upon combustion and the temperature at which the pyrolysis products are generated reveal hydrocarbon characteristics. Results from this detector are used to determine S1, S2, and Tmax parameters.
WARNING! During operation keep the FID unit covered to avoid injuries (the FID temperature is 325°C; be careful when handling to prevent serious burns—even when the unit is covered).
Figure 9. Internal View from Side of SRA FID Unit. 
Figure 10. Internal View from Top of FID Unit.
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Routine maintenance of the SRA includes the following. Additional troubleshooting information (i.e., encountered problems) is available in the binder and log books.
Maintenance | How Often | See |
Calibrate IR detectors | Once per year | IR Calibration |
Adjust autosampler tray arm | After autosampler tray is disconnected | Autosampler Tray Arm Adjustment |
Change filter behind FID back panel | When it turns brown | FID Unit Filter |
Warm up 6 hr | After power shutdown | SRA Instrument Preparation section in the |
Calibrate with Calibration Standard | After power shutdown With each batch or 1 per day | Quality Assurance/Quality Control section in the SR Analyzer User Guide |
IR Calibration
The IR must be calibrated at least once a year. Turn the instrument on at least 2 hr before calibrating. Calibration history records are located on the side panel of the instrument. Use the following standardized gases to calibrate the SRA (method error is 5% [~500]).
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- 13X-Z8, 4A-Z8 molecular sieve, synthetic sodium potassium or calcium aluminosilicate
Archive Versions
SRA User Guide: 29th September 2022