Testing Boiler Condensate
Steam condensate is like money in the bank for boiler owner-operators. It has already been purchased and treated, making it most desirable for reuse as feedwater. The more condensate returned to the boiler, the less make-up water needed. Its heat content, when recycled back to the boiler, generates energy savings. Reusing such higher-purity water also means reduced boiler blowdown/higher cycles of concentration (based on feedwater), with less water going to the sewer. Clearly, boiler condensate is a valuable resource.
But it is not without problems. Condensate is low ionic strength water and typically contains dissolved gases, notably CO2. Left untreated, the carbon dioxide will form carbonic acid that will attack copper and iron in piping and equipment. Chemical treatment to prevent corrosion in the condensate system may be one or more neutralizing amines or a filming amine.
Neutralizing amines raise the pH of the condensate to counteract any carbonic acid in the water. Testing the pH of low ionic strength condensate can be difficult. If you use a pH meter, you should use an electrode specifically designed to test low ionic strength samples. The electrode must be kept in pristine condition for accurate test results. Many find they must replace these expensive probes annually or even more frequently due to malfunction or breakage. A relatively undemanding alternative is Taylor’s Long Viewpath™ (LVP) color-matching method. The K‑3232 for condensate pH employs an extra-large-volume test cell with a long viewpath of 15 cm. Using this test cell provides accurate results because only a small amount of indicator is added to the sample, which prevents the pH of the indicator itself from affecting the pH of the condensate. Once the indicator is added to the condensate sample, pH is determined by comparing the color that develops in the test cell to the nine liquid-color standards in the LVP comparator to find the closest match. The K-3232 offers a range from 6.0 to 9.2 pH units in 0.4 increments.
The type and level of neutralizing amine used to treat steam is regulated for many applications, particularly with food processing and where steam is used to humidify air in buildings. Our K‑1682 drop-test kit can be used to analyze the concentration of cyclohexylamine (CHA), diethylethanolamine (DEEA, also known as diethylaminoethanol, or DEAE), monoethanolamine (MEA), methoxypropylamine (MOPA), morpholine (MOR), or triethanolamine (TEA) in a condensate system. The residual is determined with an acid-base titration. Note that this test is not specific to neutralizing amines. Rather, it is a sensitive alkalinity test. Carbonates and other alkaline materials from boiler carryover or leaks in a condenser or heat exchange can interfere. The test cannot be used to detect neutralizing amines outside a condensate system.
Filming amines actually create a physical barrier to protect the metal surfaces in a condensate system. When fed correctly, the very thin film they form does not allow carbonic acid or oxygen to reach the metal and cause corrosion. If overfed, the system risks being fouled by "gunk balls." These accumulations of filming amine can lodge in traps, valves, and other equipment. As with the neutralizing amines, there are instances where the maximum concentration of filming amine is dictated by regulatory agencies.