corrosion in boiler

[zanbaq]

Hi dears
there is a boiler in the factory where I work. the color of boiler water is very light and clear. but when the boiler shutdown and turn on again water of boiler is brown and red.what is the reason?
thank you

 

[metengr]

The reason is the boiler feedwater contains rust - or iron oxide (Fe203) from corrosion of steel components touched by water. You need to remove oxygen from the feedwater during off-line conditions or drain the boiler dry.

 

[zanbaq]

thank you dear
but we use oxygen scavenger!

 

[metengr]

Not enough. The water needs to be circulated for effectiveness. Plus considering the amount of surface areas it does not take much oxygen to result in rust-colored feedwater. Flash drain the boiler instead.

 

[rmw]

If by shutdown, you mean intermittent or on/off operation, then the following doesn't apply. If by shutdown you mean taken off line and laid up for a period of time, then you may want to consider blanketing the boiler with Nitrogen to keep the oxygen in the air that enters the boiler from rusting the metal that was previously protected by steam when the boiler was in operation.

rmw