How to Control Corrosion in Chillers

Take a water sample in the small beaker from the loop and test it for the presence of sodium nitrite. The concentration of sodium nitrite should be between 800 and 1200 parts per million (ppm). Also test the pH of the water. The pH should be between 7.5 and 8.5.

Calculate the amount of corrosion inhibitor (containing sodium nitrite, borate buffer and tolytriazole) that needs to be added to the loop. The volume of the loop should already be known from the engineering data spec sheets. Multiply the volume of the loop in liters times 0.0001 to achieve an increase of 100 ppm. Divide the product of that calculation by the fraction of sodium nitrite in the treatment solution. For example, if the loop volume is 2000 liters, the product of the first calculation is 0.2 liters. If the treatment solution has 30 percent nitrite, then you need to add 0.2 L / 0.30 = 0.67 liters to the loop to achieve the 100 ppm increase.

Close off the valves on each side of the pot feeder and open the lid. Open the drain valve to drain enough loop water to accommodate the required amount of treatment solution. Close the drain valve and then add the corrosion inhibitor with the 1-liter beaker. If air space remains at the top of the pot feeder, open the lower valve and let it fill to the top before closing the lid. Then open both valves that allow flow through the pot feeder. Shunt the loop flow through the pot feeder with the valve in the loop located between the pot feeder pipes.

After 10 minutes, open up the shunt valve and close the valves to the pot feeder. Wait another 10 minutes and test the loop nitrite level and pH again. If the levels are below the target concentrations, add more inhibitor and re-test afterward.