Pump body for Sour Water Service

[ShabsRBI]

We are looking for Pump body for Sour water service having 60ppm Cl ( Chloride) and Design Temperature of 150 Deg C. Pump vendor has offered SS316L but due to high Chloride and high temperature use of SS316L is not a preferred option. Another option the Pump Vendor is offering is SS316L body with Halar coating. We don't have any experience of any pump body with Halar coating and little reluctant in accepting that option.
We are recommending options like Monel or Super Duplex SS for this application.
Are we over killing the issue asking for material like Monel or Super Duplex for this service.
Any suggestions from Corrosion / Material experts.

 

[SJones]

API Std 610 identifies Material Class D-1, DSS for "sour water". If 316L is not "a preferred option" why wasn't that stated to the Manufacturer, so that they didn't offer it? It would have saved a lot of grief. 60 ppm Cl- isn't really a high chloride if you don't have oxygen problems. SDSS will give you a material more tolerant of operational abuse for not much more money.

 

[EdStainless]

But what is the pH?
And what is the H2S level?
If not too acidic then 2205 would be my go-to for this low Cl application.
If you go with any duplex insist that the castings be annealed and tested per ASTM A923.
Coatings work fine, but not on impellers due to the higher erosion rates.

 

[ShabsRBI]

Thanks very much @SJones and @EdStainless for your valuable input.

 

[ShabsRBI]

Hi @EdStainless

I checked with our Process Engineering and following are the additional details.
Operating Temp : 70 Deg C
pH : 6.0-7.0
H2S Content : <120 ppm

Any additional comments are highly appreciable.

 

[ShabsRBI]

Hi @EdStainless

Based on your recommendations I tried to look ASTM A 923 test and realised the following. Formation of Intermetallic in Duplex SS is result of exposure to 320 to 955 Deg C. Since our requirement is only for 70 Deg C and maximum with 150 Deg C, do you think that there is a possibility of deterioration of DSS with the formation of intermetallic at such a lower temperature and calls for A-923 testing. Only solution annealing will be good enough to minimise this effect.

ASTM A923 - Standard Test Methods for Detecting Detrimental Intermetallic Phase in Duplex Austenitic/Ferritic Stainless Steels​

 

[SJones]

The test is for the material processing quality, not the deterioration by the operating temperature. ISO 17781, and ISO 17782 would be the better standards to deploy from a material quality point of view.

 

[LittleInch]

I must admit I saw 60ppm Cl and thought 316 is probably ok at that level. In the end of the day its a pump body which is usually pretty thick and you get pitting corrosion with SStl so what's the big issue here?

I think you're on the margins and just need to get some costs to find out if all you need is a spare pump body in S stl instead of a duplex one costing 10 times as much. If it only cost 1.5 times as much get a bullet proof Duplex one.

But these guys know much more than me so listen to them.