Hydro test Water PH for SS, SDSS, DSS and CS material 5

A) Anything the owner specifies.

B) NORSOK L-CR-004

C) Would you hydrotest with acidic water?

Steve Jones
Materials & Corrosion Engineer

In general the lower the pH of the fluid wetting ferrous materials the more likely you are to get corrosion -- in general we like to stay above 9.0 pH when formulating coolants and cutting fluids for use on ferrous metals

You should request potable water quality for a hydro test. With potable water, you will be allowed to discharge the water without environmental permitting problems.

The secondary standard for potable water is a pH of 6.5 to 8.5 units.

Some metals many have lower limits for certain water quality parameters. Potable water quality for hydrotest of Stainless Steel Tanks shall be "maximum 50 ppm of Chloride" in Appendix S of API 650 (Atmospheric Tank Standard).

Quality of hydrotest water is typicalluy specified in ther client and/or process licensor specifications. Typically, the Cl content in the hydrotest waterwill be explicitly addressed in these specifications.

Certain material of construction like austenitic stainless steels grades 304/304L/316/316L etc., are suceptible to chloride stress corrosion cracking due to the chloride content in the hydrotest water. For this reason we limit it sometimes to very low values (as low as 2 ppm).

I have seen this requirement of very low ppm Cl content in a certain project for vessels whose MOC was austenitic SS. The problem is not a concern for carbon steel vessels where the Cl content could be as high as 100-150 ppm.

Hope this helps.

-jehan

The specs SHOULD specify the quality of the hydro water.

I wouldn't worry too much about pH, but I would worry about "dirty river water containing lots of organics", especially for a stainless steel system, and also for CuNi systems. Hence, "potable quality fresh water" may be specified.

The specs should also specify requirements for AFTER the hydro, i.e., drain within X hours, perhaps flush with xxxx, etc.

The problem I've seen is leaving "dirty fresh water" in a piping system, leaing to pitting and MIC.

Here is a piece information in industrial codes & standards.

Chloride Limitation in Hydrotest/Rinsing Water

Codes and STD / Paragraph / Limitation / Remark

1. API 560 (Fired Heater) / 14.5.1.3 / Max. 50ppm for ASS / Hydro Test Water
2. API RP573 (Inspection for Fired Boiler and Heater) / 8.4.1 / Max. 50ppm for ASS / Hydro Test Water
3. API 650 (Storage Tank) / S.4.10.1 / Max. 50ppm for SS / Hydro Test Water
4. API 650 (Storage Tank) / S.4.9.2 / Max. 200ppm at T<40C and
Max. 100ppm at 40C<T<65C / Rinsing Water for Cleaning /Pickling
5. API 661 (Air Cooled H/EX) / 10.3.3 / Max. 50ppm for ASS or Ni-Cu Alloys / Hydro Test Water
6. API 660 (Shell & Tube H/EX) / 10.3.4 / Max. 20ppm for ASS / Hydro Test Water

*** Legends;
ASS: Austenitic Stainless Steels
SS: Stainless Steels

Hope this helps,

Thomas

bmoorthy,

From I the above posts, i would like to add 2 points.

1] As mshimko pointed out organic matter is detrimental. the reason for this is MIC (microbiological induced corrosion)

2]Where stringent ppm limits on the chloride content (example 2 ppm) have been impossed by client/ process licensor spec, SOMETIMES the client/ process licensor may give a partial waiver.
For example- "Cl content of the hydrotest will be done using water whose chloride content does not exceed 25 ppm PROVIDED POST HYDROTEST RINSING OF THE VESSEL IS DONE USING WATER WHOSE CHLORIDE CONTENT DOES NOT EXCEED 2 PPM."

can you please inform me how can i, very easily without difficoult additives to use, decrease the ph value?
the demineralized water i have been supplid have a value of 46 ppm and the acceptable value for testing (SS) is 30 ppm.

pls. send you solution to:
aironyx@hotmail.com

Thanks

It is right to be more concerned about MIC than Cl levels. As a SS guy I would would suggest low Cl, 20ppm is a reasonable number. You also have to know how the water was sanitized.
We have one customer that requires 2% H2O2 be added to all hydro test water.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

Methyl isocyanate (MIC)it's not present in the demi water i have.
I just need to know how can i decrease the ph value from 46ppm to 30ppm (client spec).
Who can advise?

aironyx,
The PH is not measured in ppm (parts per million), read the chemistry book on PH values (normal is around 6-7, acidic is below 6 and alcaline is above 7). To decrease the PH value, you could add some lemon juice to it.
The contamination of the demineralised water you have mentioned to be 46 ppm, is unacceptably high and you should send it back to whoever sold that to you. You could further filtrate the demin water, but the costs will blow you out of your office or you could buy a good size still and boil the water again 'till you remove the contaminants...
gr2vessels

aironyx,

I think MIC here is microbiologically-induced corrosion, no?

My company specifies 200 ppm chloride for hydrotesting of stainless steel (300 series) pipelines. Apart from API 650, what other code/reference that allow that level (200 ppm chloride)?

Thank you in advance.

Yep, we have a defacto pH standard for hydrotesting, which is stipulated in the form of "use potable water". That set's the pH in the area of 7 +-some margin.

50ppm Chloride limits are specified for stainless steel materials, with signficantly higher limits for CS... can't remember what it is since our town potable water is ~5ppm chlorides and so it's never an issue.


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