Why Test Polymer Levels in Boiler Water?
Back in my previous life as a water treater I was surveying a food plant. Everything was in order except for my last stop, which was at the boiler room. The management told me that after decades of no problems they just had to acid wash the boilers. I found this very unusual for a facility showing great signs of control. So what changed?
The previous year the treatment chemical was changed from a phosphate program to a polymer program. Improved treatment results were expected, but they experienced the direct opposite. So my next step was to review the operator’s log sheets to see the history of operating conditions. I was surprised to see no “active polymer” test results. Previous log sheets showed regular phosphate testing, but no test results once the change to polymer was made. Even the treatment company’s service reports never reported a polymer test result. So what could have happened?
Since boiler water polymer treatments are composed of organic molecules, they are susceptible to thermal degradation at high cycles of concentration, especially over 50 cycles. But these boilers were only running about 30 cycles. Polymer treatments are also subject to degradation by oxygen at the temperatures experienced in boiler systems. Could this have been the root cause?
A further survey found the polymer chemical being fed into a deaerator, which was not functioning properly. Additionally, the catalyzed oxygen scavenger was also being fed from the same tank as the alkalinity booster (caustic). The high pH in the chemical feed tank removed the catalyst from the chemical feed, further hindering the oxygen removal. So there were high oxygen residuals in the feedwater, which degraded the polymer to the point where there was not enough active polymer in the feedwater to handle the softener hardness excursions they were also experiencing. The result: scale in the boiler.
Unfortunately, too many water treaters and boiler owners do not regularly test for the polymer residual. Instead, they rely on mass-balance calculations to control the chemical feed. This can be a costly mistake, as evidenced in the case study above.
Several active polymer tests exist; one test does not require an electronic meter (colorimeter). These tests are easy to do and provide results which can be the difference between a successful program and a failed program. Successful programs provide enhanced fuel efficiency and decreased downtime. The trouble and expense for acid cleaning or repairing failed boiler tubes are also avoided. Each of which, of course, contributes to all of the “green initiatives” we’re all interested in supporting!
Do you want to sleep better while feeding a polymer program in your boilers? Implement a regular program of testing the active polymer. You do not want to be surprised at your next boiler inspection!
