Pump corrosion // fertilizer plant TSP/MAP/DAP 3

[OTHMANE001]

Dear colleagues,
I would like to know your opinion about a problem which always persists of our fertilizers plant of the phosphate-enriched fertilizers (TSP) and nitrogenized (DAP/MAP/NPS….).
after 7 months of the commissioning of our centrifugal pumps of washing of gases, we have sudden premature corrosion + abrasion on the the hydraulic part (volute, lid of aspiration and impeller). the material of the pumps is the HA 28.5 (pump FRIATEC) we have immigrant towards a new material 1.4517 without result. knowing that we made the physicochemical analysis of the circulated product: result in the standards (F: 1%, CL 1.5%).
thank you to share me your points of seen on this phenomenon, attachment pictures

 

[EdStainless]

A temperature and pH would be helpful. Any erosion?
I take it that your first alloy is a proprietary version of alloy 28?
And the analysis, 1% Fl and 1.5% Cl and you are not using a Ni alloy?
The Fl level is not out of line, but the Cl is.
If alloy 28 didn't work then most people would move to a "G" (30 or 35) be looking at alloy 59 or 22.

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P.E. Metallurgy, Plymouth Tube

 

[OTHMANE001]

Hello EdStainless,
I would to thank you for your reactivity, moreover, the temperature of the circulated fluid: 65°C-70°C, I want just to rectify information, the problem is a corrosion + erosion (not an abrasion), rate of solid in suspension > 20% for the materiel is 1.4517 GX2CrNiMoCuN25-6-3-3 it comprises Nickel but not much 6%.
And you Know that materials like Alloy 20/28 would be higher chemical resistant, but not higher Erosion, Abrasion.
please, for the material 1.4517 or the duplex in general which are the limiting conditions service with used.
Many thanks.

 

[EdStainless]

You can't judge a duplex based on the Ni content.
And I am sorry but I see abrasion and erosion as the same thing.
You need two things, higher Cr, and higher strength (hardness).
My guess is that the duplex does not have enough corrosion resistance for the hardness to be of value in your application.
In alloy 28 (don't use 20) you may have enough corrosion resistance that erosion alone will not be a significant factor.
There is extensive literature on this subject. Look ut the proceeding from technical conferences.

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P.E. Metallurgy, Plymouth Tube

 

[pradipgoswami]

Hi OTHMANE001,

Following are the extracts from Friatec Pumpen's documents. Both the alloys are Cast duplex stainless steels , with DIN and equivalent ASTM grade explained. The later grade is "Nitrogen" added with additional resistance to pitting corrosion.Friatec is a well known name in pump industry. I would think talking to them for a RCA of failure & then moving forward would be a better idea.Note duplex alloys are proven for similar applications.

I dealt with the similar pumps for phosphate industry many years ago. My understanding is that in phosphate fertilizers abrasion is quite prevalent in addition to corrosion. Hence improvements in casting design + subsequent heat treatments may also help.

According to Flowserve, one of the key players in Pump industry their version, Durcomet 100(

https://www.flowserve.com/sites/default/files/2016-07/bulletin_A7.pdf)

seems to be quite common alloy phosphate fertilizer industry. This alloy is same as DIN Alloy,1.4517,G-X5 CrNilMoCu 25 6 3 3


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HA 28 5, G-X 5 CrNiMoCu 28 5,ASTM-[A 743 CD 4 MCu]
Semi-austenitic, molybdenum and copper alloyed material with a high resistance to pitting and stress corrosion. This material is one of the super duplex steels. It canbe used with crude phosphoric acid, containing solids at up to 100 °C, hot seawater, many solutions containing chloride, FGD suspensions and sulphuric acid at all concentrations at low temperatures.

1.4517, G-X 5 CrNilMoCu 25 6 3 3, ASTM-[A 743 CD 4 MCuN]
Semi-austenitic, molybdenum and copper alloyed material with a high resistance to pitting and stress corrosion. This material is one of the super duplex steels. It can be used with crude phosphoric acid, containing solids at up to 100 °C, hot sea water, many solutions containing chloride, FGD suspensions and sulphuric acid at all concentrations at low temperatures.




Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[OTHMANE001]

Hello colleagues ,
Many thinks for you answers,