Safe Removal Of Scale With Mineral-Acid-Based Cleaners

Improving waterside heat transfer in boilers and cooling towers by removing calcium carbonate scale and other mineral deposits is a critical part of efficient boiler chemical management. Even minor deposition may cause a 10%–15% increase in fuel requirements. Severe scale can cause an efficiency decrease of 40% or more. When done as part of an annual maintenance regime, controlling scale situations will improve treatment performance at existing customer locations and help you gain new customers.

Based on recent conversations with our customers about their concerns about the energy-robbing effect of waterside mineral deposits, interest is renewed in inhibited mineral-acid-based cleaners. Even though pH tests are done on the isolated system water after adding a cleaning formulation and frequently during the cleaning process, customers are still concerned about the potential for acid damage.

Taylor Technologies has many tests that are treatment-specific beyond pH analysis. As an added safeguard against equipment damage, you can also monitor the strength of the cleaning solutions themselves. Taylor has two acidity tests for this purpose. For muriatic acid (hydrochloric acid) formulations, use the K-1547 drop test kit. It measures the percent concentration of the active deposit remover as muriatic acid. For sulfamic acid formulations, use the K-1548 drop test kit.

Periodic pH testing during the entire deposit-removal procedure is still required. The use of either the K-1547 (muriatic acid) or the K-1548 (sulfamic acid) test is an additional diagnostic tool. At the completion of the cleaning you will also want to make sure that all the mineral-acid solution has been flushed out and suitably neutralized to a nonaggressive pH 7.0.

For accurate pH testing that does not involve pH meters, our colorimetric kits that contain liquid-color standards are an excellent option. Slide™ comparators are designed to compensate for color and turbidity in the water sample. Midget™ comparators may be used when color and turbidity are not concerns. Because you are comparing the water sample to another liquid, the reading is very accurate. For clear water samples or after filtering turbid samples, you could use the K-1285-1 long range (pH 3–10 in 1.0 increments) or the K-1285-4 bromthymol blue (pH 6.0–7.4). Both employ Midget comparators.

Why is it advantageous to test for the specific mineral-acid percent concentration in addition to testing pH? To achieve optimum results, most industrial-strength, mineral-acid-based, deposit-removal formulations have a very specific target percent concentration (e.g., 8%, 1.0%, or higher). Underdosing could fail to remove the deposit and could be detrimental to the equipment being cleaned. And, of course, it’s wasteful. Just adding the chosen acid until you reach the desired pH will not necessarily tell you when you have the best cleaning concentration expressed as a percent.

If you need to test for sulfamic acid cleaning concentrations, take a look at our K-1548 Acidity Drop Test Kit. With this kit you can measure sulfuric acid and phosphoric acid as well as sulfamic acid concentrations. The kit instructions come with conversion factors for all-three mineral acids. Drop equivalence for sulfamic acid varies depending on the sample size that is being tested.