6 replies to this topic

[nishadagarkar]

Can anybody please tell me in detail regarding the effects of chloride contents in water used for Hydrostatic test in SS pressure vessels.

Regards,

[breizh]

Hi ,
Corrosion pitting will occur in case of CL- is in contact with SS .
Corrosion may occur in case of combination of Cl-+ high temperature .

I would advise you to do some goole work .

Regards
Breizh

[ankur2061]

Nisha,

Chloride Induced Stress Corrosion Cracking is caused by the presence of chlorine salts in austenitic & martensitic stainless steels.

A maximum of 5% chloride concentration is allowed for both these types of stainless steels as per Norsok Standard M-001. Other standards/company practices may have different guidleines for maximum chloride concentration.

For hydrostatic testing the chloride content of the water should be checked before use. In case you have availability of demineralized (DM) water or water from Reverse Osmosis (RO) plant this can be used for hydrostatic test although an expensive option. I have used DM water for hydrostatic testing and after the test I have recycled the water to the DM water unit instead of draining it to the sewer to reduce costs.

Hope this helps.

Regards,
Ankur.

Edited by ankur2061, 22 April 2010 - 02:55 AM.

[Zauberberg]

If there is a Service/Fire Water system in your location (I hope there is one), you can normally use it for hydrotesting purposes - if the water comes from a nearby river. In case there is only a saline water supply: hydrotest is a fairly short-duration activity so maybe you can go with higher chloride levels for a few hours - check with your Material Expert on this subject.

According to SS 304/316/317 specification sheet from one steel company, these are the chloride limits for continuous service:

304: 100ppm
316: 2,000ppm
317L: 5,000ppm

Further, it says: "Although the alloys 316/317 have been used with mixed success in seawater (19,000 ppm chloride), they are not
recommended for such use."

[terryc]

There might be another possible danger. Even if initially the water has a low chloride content, then if it is allowed to dry out the chloride concentration increases and could cause localised pitting. I seem to recall cases where water with a low chloride concentration has wetted insulated pipework and the concentration effect described above has caused severe corrosion of the underlying piping.

Is my memory correct?

[iyer]

Ankur, 5% looks like a high number. I have seem a max of 50ppm limit being imposed and addition od Sodium Nitrate to reduce chloride levels. So do you have any literature on the 5% number?

Edited by iyer, 22 April 2010 - 08:41 PM.

[Zauberberg]

Ankur, 5% looks like a high number. I have seem a max of 50ppm limit being imposed and addition od Sodium Nitrate to reduce chloride levels. So do you have any literature on the 5% number?

Ankur has quoted NORSOK standard for material selection: http://www.sveis.no/...der/M-001_0.pdf

See the Note #2 for martensitic steels.