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We are using a Hach Series 5000 Silica Analyzer to measure the silica concentration in boiler feed water.
The analyzer was taken in service in Feb, 2010. Recently we replenished the reagents and calibrated (Auto Calibration) the device, after calibration the analyzer started showing negative readings of Silica (-400 ug/l) although the concentration of silica in water is normal [2 to 5 ug/l] (as tested by a second analyzer installed in laboratory).
We have calibrated the device, checked the stir bar, checked the lamp and found them all to be alright (as they were before). The sample flow, sample pressure, SOV and sample tubing are all fine and no alarms appear but still the value is negative.
Any idea as to what might be the problem? I would welcome any diagnostic measures or advice.
The analyzer was taken in service in Feb, 2010. Recently we replenished the reagents and calibrated (Auto Calibration) the device, after calibration the analyzer started showing negative readings of Silica (-400 ug/l) although the concentration of silica in water is normal [2 to 5 ug/l] (as tested by a second analyzer installed in laboratory).
We have calibrated the device, checked the stir bar, checked the lamp and found them all to be alright (as they were before). The sample flow, sample pressure, SOV and sample tubing are all fine and no alarms appear but still the value is negative.
Any idea as to what might be the problem? I would welcome any diagnostic measures or advice.