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DEMIN WATER used for Hydrotest in carbon steel tank

DEMIN WATER used for Hydrotest in carbon steel tank

(OP)
Dear Guys.
I would appreciate some help about an issue (I've seen many comments regarding DEMIN water and corrosion issues in direct contact with carbon steel material)
Our Contractor is going to water filling a tank to perform hydrostatic test. Water quality is DEMIN WATER supplied by a Thermal Power Plant close of our Project.
The time to water filling the tank is expected in 3 weeks. All internal butt welded joints are not painted.
I have a concern because I’ve heard that DEMIN water could generate corrosion even higher than fresh water or potable water.
I have received quality certificate of this DEMIN WATER, which is attached. I would like to know some opinion of you guys. This DEMIN WATER could generate corrosion in this tank considering time storage (3 weeks)?
I read API 650 which states that if test takes more than 14 days, oxygen scavengers and some chemicals should be considered to be added.
Have you had before some situation like that?

RE: DEMIN WATER used for Hydrotest in carbon steel tank

Advise the use of a corrosion inhibitor.

RE: DEMIN WATER used for Hydrotest in carbon steel tank

In addition to the oxygen scavenger, demin water used for hydrotest should also be doped with a biocide, preferably with neutral environmental effect to allow for subsequent treatment / discharge.

RE: DEMIN WATER used for Hydrotest in carbon steel tank

a corrosion inhibitor and a biocide would be good.
Since this water will be there for so long you have to expect things to start growing, which is not good.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: DEMIN WATER used for Hydrotest in carbon steel tank

You're going to need corrosion inhibitor(s) in combination with a low level of biocide. The oxygen scavenger will not work in this situation as there is too much air present. For a hydrotest or lay-up situation, an oxygen scavenger is used when there is basically no air present, like for a pipeline where they completely fill the pipeline with the water solution.

RE: DEMIN WATER used for Hydrotest in carbon steel tank

hello
if you estimate the ratio "time with corrosive demin water / lifetime of the tank" and consider a very high corrosion rate of 1mm/y, maybe you will be able to conclude that the transcient operation with demin water can be tolerated because it lasts only a very short time, if it is not a continuous corrosive service.
regards

RE: DEMIN WATER used for Hydrotest in carbon steel tank

Hello,
You should always use water soluble corrosion inhibitor for hydro-testing, because corrosion effect increases exponentially at high pressures.
Regards,

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