Corrosion of Reactor Vessel (SS 316L)

[ukmet]

Dear All,

We made a reactor vessel with a limpard around it for textile chemical plant. It was manufactured in 2010 and now rust had appeared on its surface. Other than analysis of the rusted powder what you suggest to be done to dig the root cause out? Following is its design data:

Shell and Dish Ends : A-240 SS 316L
Coil: A-312 TP 304
Design Pressure: 6Bar
Design max. temp: 200 C
Design min. temp: -29 C
Code : ASME Sec VIII Div. I, 2007 Add. 09

Vessel was not U stamped.


Regards,

Umair

 

[stanweld]

You need to provide more info. What surface - ID or OD? If ID, what is the fluid and its constituents?

 

[gr2vessels]

Rust stain on the surface after years of operation? There must be some sort of iron contamination going on around the reactor. If would have been fabrication contamination and lack of cleaning and passivation, the rust would appear soon after installation. From your post I assume the rust appeared just recently, most likely recent iron contamination and sufficient moisture on the reactor to initiate the oxidation. That brings the question, is the rust under the insulation wrapped on the reactor? Is the reactor long periods out of service, to be covered in condensation and contaminants?
As you see, there are many scenarios where the rust could appear, but first you need to stop the contaminants coming in contact with the reactor, then clean, pickle and passivate again.

 

[cloa]

You need clarify what you mean by rust- a picture would be good.
gr2vessel- he might be using dodgy terminology- he might mean stainless steel corrosion products.

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[ukmet]

Dear Stanweld,

The corrosion product is on the ID. Bottom dish end and shell, though the agitator shaft is not having any sign of corrosion. The customer is not ready to tell the chemical being used in it, as he say its a trade secret.

Dear gr2vessels,

Vessel was in continuous operation. And yes corrosion appeared recently.
Below is the link of rust / corrosion sample we are about to send for analysis.

http://files.engineering.com/getfile.aspx?folder=27818af0-2c04-4690-8cb7-2287a5c46bec&file=5.jpg

 

[stanweld]

There are number of possible reasons: e.g., change in process fluid conditions, development of pitting corrosion with time, contamination (process fluid or on surface during a shutdown), etc.

 

[GenB]

I see no fault on the mfr side the products are corroding the metal. If you recommended the design and materials you may be in trouble because you may have used the wrong as for the job. After passivating scheduled Maintenance through cleaning after each use is needed. Genb

 

[steris]

Is the rust/corrosion occurring all over or is it localized? If it's localized, is it just at one fitting, near/on a weld, on a surface exposed to heat, etc.? Could the customer have put steel into the vessel - is is possible that the corrosion is just a surface stain (rust from something else settling onto the vessel wall) and not vessel itself corroding? As gr2vessles mentioned, there are too many potential causes but as a start get pictures from the customer and try to find out what the chemicals & processes are. If they are allowing halides (fluorides, chlorides, bromides) at elevated temperatures or certain acids to come into contact with the stainless then you will have corrosion.