Boiler plant operators are becoming increasingly aware of the importance of their steam condensate systems. These systems can be the source of energy-wasting leaks, wasted energy caused by malfunctioning steam traps, and as a result, excessive maintenance costs. Unexpected downtime can also be a costly result of condensate line neglect.
Since most of the iron in condensate is in suspended form it can be identified by the use of membrane filters. Iron in the condensate shows up on filters through which the water has been filtered. Condensate streams that have very little iron leave only a slight color on the filter. Streams that are heavily contaminated with iron leave a very dark circle in the center of the filter. The darker the circle, the more iron that is present in the sample. This is a very visual method of evaluating the performance of your condensate return line corrosion control program.
Once return line problem areas have been identified, corrective measures can be taken. These may include the feed of neutralizing or filming amine corrosion inhibitors, dosage changes, or even changes in the feed point for these products. Solutions may also involve dealkalization or oxygen scavenger feed changes. Any changes in the pretreatment system or in the chemical treatment can be monitored by using membrane filters.
In the past, attempts were made to measure the amount of suspended iron in the condensate by comparing the filter discs with standard color charts for this type of test and the type and quantity of iron found in a sample of condensate or feedwater. However, it was frequently difficult to find a color standard that matched the test sample. Even with these shortcomings it has been found that the filter discs are useful without the necessity of assigning a quantitative number to the amount of iron in the condensate sample.
Best use is made of this method when samples are checked over a period of time and a history is taken of each sample point. Mounting the filter disks in a notebook provides a historical record that can be useful. The condensate sample does not have to be drawn cool as when running a pH test, but excessive flashing can cause greatly increased solids and iron in the sample. Handling will also be more difficult with a very hot sample - the sample should be cooled before testing.
What equipment is needed to perform these checks? In our blog next week, we will go over the equipment needed as well as a procedure to take these samples.