Boilers that use an oxygen treatment method (OT) for water treatment have the risk where
the growth of powder-like scale consisting of eluted iron in feedwater equipment causes heat
transfer inhibition and leads to problems such as tube leakage. For this reason, it is necessary to
control the iron concentration of boiler feedwater to 2 μg/L or less to maintain stable boiler
operation. However, the conventional analysis technique of minute amounts of iron is subject to the
environmental effects and has the problem of ensuring analysis accuracy. This time, we developed
a double filter concentration method that simultaneously uses a membrane filter and an
iminodiacetate type chelate filter as a method to analyze minute amounts of iron easily and
inexpensively. This paper presents the developed method. This method is adopted in the JISB8224
Boiler Feed Water and Boiler Water Testing Methods revised and published in March 2016.
