Pressure inside the tank - Demineralize water tank

[Syahar1975]

Good morning guys,

I have demineralize water tank. According to the tank data sheet the tank need to be design based on 20 mBar pressure.

My question why we need to maintain that pressure inside the tank ?

Best regards,

Syah

 

[JStephen]

Why- I can't help there.
But will point out that it is not uncommon for tanks to be specified with a design pressure higher than it needs to be- if it seems unreasonable, confirm with the person that wrote the data sheet that it is correct.

 

[LittleInch]

Is it gas blanketed?

Or is there some sort of vent with pressure?

A demin tank could be either.

20 mbar is a very low pressure so not a big issue.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mk3223]

IMO, the water tank is open vent tank and the design pressure is for the venting of the roof deck limitation.

 

[bimr]

Demineralized water will absorb carbon dioxide from the atmosphere which will tend to increase the corrosivity of the demineralized water. Pure demineralized water without oxygen content is not corrosive.

Ultrapure water applications will add a nitrogen blanket to the air space of the demineralized water storage tank to prevent contact of the demineralized water with atmospheric air.

 

[Syahar1975]

Dear all,

Thanks for the respond.

These tanks have PVSV and anchor bolts as well. Each tank has 3 PSVS 12" size.

We will have pneumatic test at 1.25 x Design pressure on these tank.

BMR,

Do you mean if we just put goose neck vent like fire water tank, this demineralized water will absorp CO2 easily ?

Thanks and regards,

Syah

 

[LittleInch]

Syarhar,

I assume you mean you will add this pressure when the tank is completely full of water for the test. 25mbar (20 x 1.25) is equivalent to about 10" / 250mm of water only.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Syahar1975]

Little inch,

Yes that is what we are going to do.

We will follow API 650 appendix F.7.5.

Syah

 

[bimr]

Do you mean if we just put goose neck vent like fire water tank, this demineralized water will absorp CO2 easily ?

Correct. Demineralized water has a good affinity to absorb carbon dioxide and oxygen from the atmosphere, and both lead to metal surfaces corrosion.

https://books.google.com/books?id=J...for their destruction like corrosion.&f=false

This may or may not be a problem for your application, but is a common problem for high purity water.

 

[MFJewell]

You can add a CO2 scrubber if you want to prevent carbonic acid accumulation.