Steel chemical cleaning - When to stop? 1

[Esbirinai]

We usually performe chemical cleanings to some equipments, like pumpes, piping, vessels, in a closed circuit usually with citric or phosphoric acid. I was told that the best way to know when to stop the cleaning (if visual inspection is not possible) was to do some total iron analysis. Is this true? If so, how does the iron chart looks like?

Thank you

DL

 

[ash9144]

You want to measure total and ferric iron. The ferric iron concentration is your metal being dissolved so you want a low ferric concentration. Other iron states are deposits and corrosion products. Be certain to use some type of inhibitor to reduce metal loss. It is usually best to let a water treatment group or industrial cleaning group to handle these jobs if it is a large piece of equipment. Also be sure to have the equipment passivated after cleaning.

 

[kenvlach]

I think ash9144 meant 'ferrous' iron. Rust contains ferric iron. I strongly agree with the use of an inhibitor; after all, citric acid can be used to dissolve iron from stainless steel during passivation.

 

[JLSeagull]

What system?

You would want the lube oil and seal oil systems for your 35000 hp gas turbine compressor package to be cleaner than your crude oil separator.

 

[EdStainless]

In some cases they measure other things. If you are trying ot remove scale, tehn you should analize for those elememnts and run until they level off.
Determination of the end point is part of the original cleaning plan. This needs to be desinged into your process.

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