As you know the pH is critical to the successful operation of cooling water treatment. Not enough acid and we get scale, too much we can corrode the system.For the most part the acid feed is controlled by the pH sensor so it needs to be accurate and responsive.
When we do wet chemistry is very important that tAlk roughly match up with the pH readings. The other night we had a situation on Line6 Latte where the pH was around 6.9 (via testing) the tAlk was less than 50 ppm BUT the Walchem unit was reading in the 9s! The acid pump would have kept on pumping had we not caught it.
Lesson #1 – If when doing the tALK test you get less than 50 ppm (meaning it turns red on one drop), retest in rinsed vial and should it happen again STOP EVERYTHING and investigate. If the acid pump for that cooling tower is still on there is a problem most likely due the pH meter reading too high. Clean and calibrate the sensor right away. Then later the shift retest to prove that the calibration is working. If not, change the probe (pH probes are label WEL-pH) and re-calibrate.
Lesson #2 Below is rule of thumb for relating pH to tALK. (This is not precise, but it can give you a ballpark).
50 tAlk = 7.4 pH
100 tAlk = 7.8 pH
150 tAlk = 8.1 pH
200 tAlk = 8.35 pH
250 tAlk = 8.5 pH
300 tAlk = 8.6 pH
REMEMBER:tAlk is the heart of the wet testing for the cooling towers, if we get low or high we must know why
